LAND IMPRINTING AS AN EFFECTIVE WAY OF SOIL SURFACE MANIPULATION by

LAND IMPRINTING  AS AN EFFECTIVE WAY OF SOIL SURFACE MANIPULATION by

LAND IMPRINTING AS AN EFFECTIVE

WAY OF SOIL SURFACE MANIPULATION

TO REVEGETATE ARID LANDS by

Awad Osman Mohmed Abusuwar

A Dissertation Submitted to the Faculty of the

DEPARTMENT OF PLANT SCIENCES

In Partial Fulfillment of the Requirements

For the Degree of

DOCTOR OF PHILOSOPHY

WITH A MAJOR IN AGRONOMY AND PLANT GENETICS

In the Graduate College

THE UNIVERSITY OF ARIZONA

1986

THE UNIVERSITY OF ARIZONA

GRADUATE COLLEGE

As members of the Final Examination Committee, we certify that we have read the dissertation prepared by Awad Osman Mohmed Abusuwar entitled Land imprinting as an effective way of soil surface manipulation to revegetate arid lands and recommend that it be accepted as fulfilling the dissertation requirement

Doctor of Philosophy

ItTr;

Date

Date

Date

Final approval and acceptance of this dissertation is contingent upon the candidate's submission of the final copy of the dissertation to the Graduate

College.

I hereby certify that I have read this dissertation prepared under my direction and recommend that it be accepted as fulfilling the dissertation requirement.

A-erti g6:

Dis ertation

Director

Date

STATEMENT BY AUTHOR

This dissertation has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED

C

ACKNOWLEDGMENTS

The author wishes to express sincere thanks to his major advisor, Dr. M. H. Schonhorst, and to his minor advisor, Dr. R. M. Dixon, for their support, patience, and expert guidance during the course of this study.

Grateful appreciation is extended to the members of the committee, which included Dr. R. E. Briggs, Dr. R. E. Dennis, and

Dr. V. Marcarian, for their valuable suggestions during the course of the study and for reviewing this manuscript. Special thanks are extended to Dr. P. G. Bartels who served on my committee as a substitute both during the preliminary examinations and the final oral examination.

Appreciation and respect are due to my family for their encouragement and support, and to my loving wife, Samia, for her patience, sacrifice, and support without which this study could not have been completed. The presence of my fifteen-month-old daughter, Areij, encouraged me and gave me the motivation to continue.

The Government of the Sudan paid my expenses for transportation, tuition, books, food, lodging, and other costs. This assistance made my studies at the University of Arizona possible, and for this I will always be grateful.

Thanks are extended to Mr. Paul Johnson of the Statistical

Consulting Unit, who helped with the analysis of this study, and to

Ms. Anna McKew who typed the thesis.

A debt of gratitude is due to all who helped in any way to make this dissertation possible.

iv

TABLE OF CONTENTS

Page vii

LIST OF TABLES

LIST OF ILLUSTRATIONS

ABSTRACT

1.

INTRODUCTION

2.

LITERATURE REVIEW

Land Shaping and Types of Seedbeds

Soil Mulching

Artificial Revegetation

Competition

Adapted Species and Suitable Planting Tools

Grass-Legume Mixture

3.

MATERIALS AND METHODS

Treatments

Parameters Measured

4.

RESULTS AND DISCUSSION

30

Meteorological Data

Soil Moisture

30

32

Plant Population 46

Physiological Data (Legumes)

52

Transpiration

Leaf Diffusive Resistance

Plant Height (Grass)

Canopy Cover

52

55

60

63

Biomass

Individual Harvests

Overall Means of the Different Cutting Dates

66

66

78

5. SUMMARY AND CONCLUSION 82 x i

11

12

13

16

9

7

20

21

26

1

7

vi

TABLE OF

CONTENTS--Continued

Page

APPENDIX A: EFFECTS OF TREATMENTS ON PLANT HEIGHT AT THE

ORACLE AGRICULTURAL CENTER FOR THE DIFFERENT

SAMPLING DATES 85

APPENDIX

B: EFFECTS OF TREATMENTS ON PLANT HEIGHT AT THE

CAMPUS AGRICULTURAL CENTER FOR THE DIFFERENT

SAMPLING DATES

90

APPENDIX

C: EFFECTS OF TREATMENTS ON PERCENT CANOPY COVER

AT THE ORACLE AGRICULTURAL CENTER FOR THE

DIFFERENT SAMPLING DATES

APPENDIX D: EFFECTS OF TREATMENTS ON PERCENT CANOPY COVER

AT THE CAMPUS AGRICULTURAL CENTER FOR THE

DIFFERENT SAMPLING DATES

LITERATURE CITED

97

102

109

LIST OF TABLES

Table

Page

1.

Monthly average temperature (C) at the Oracle and Campus

Agricultural Centers

2.

Monthly average relative humidity

(%) at the Oracle and

Campus Agricultural Centers

34

3.

Effects of treatments on percent soil moisture at the Oracle

Agricultural Center

37

4.

Effects of treatments on the percent soil moisture at the

Campus Agricultural Center

38

-2 -1,

5.

Effects of treatments on transpiration rates

(11.g cm

s

) at the Oracle Agricultural Center (Overall means of 8 sampling dates

53

-2 -1,

6.

Effects of treatments on transpiration rates

(11g cm

s

) at the Campus Agricultural Center (overall means of 8 sampling dates)

54

7.

Effects of treatments on leaf diffusive resistance

(S cm)

8 sampling dates)

8.

Effects of treatments on leaf diffusive resistance (S cm

-1

) at the Campus Agricultural Center (overall means of

8 sampling dates)

33

56

.57

9.

Effects of treatments on leaf temperature (C) at the

Oracle Agricultural Center (overall means of 8 sampling dates)

10.

Effects of treatments on leaf temperature

(C) at the

Campus Agricultural Center (overall means of

8 sampling dates)

58

59

11.

Effects of treatments on grass height (cm) at the Oracle

Agricultural Center (overall means of 4 sampling dates) .

12.

Effects of treatments on grass height (cm) at the Campus

Agricultural Center (overall means of 6 sampling dates)

61

62 vii

viii

LIST OF

TABLES--Continued

Table

13.

Effects of treatments on percent canopy cover at the

Oracle Agricultural Center (overall means of 4 sampling dates)

14.

Effects of treatments on percent canopy cover at the

Campus Agricultural Center (overall means of

6 sampling dates)

15.

Effects of treatments on forage dry matter production (kg/ ha) at the Oracle Agricultural Center (First harvest on

9/29/84)

Page

64

65

67

16.

Effects of treatments on forage dry matter production

(kg/ha) at the Oracle Agricultural Center (Second harvest on

5/25/85)

17.

Effects of treatments on forage dry matter production

(kg/ha) at the Oracle Agricultural Center (Third harvest on 8/5/85)

18.

Effects of treatments on forage dry matter production

(kg/ha) at the Oracle Agricultural Center (Fourth harvest on 10/12/85)

19.

Effects of treatments on forage dry matter production

(kg/ha) at the Campus Agricultural Center (First harvest on 5/15/84)

20.

Effects of treatments on forage dry matter production

(kg/ha) at the Campus Agricultural Center (Second harvest on

6/28/84)

21.

Effects of treatments on forage dry matter production

(kg/ha) at the Campus Agricultural Center (Third harvest on

8/20/84)

22.

Effects of treatments on forage dry matter production

(kg/ha) at the Campus Agricultural Center (Fourth harvest on 10/24/84)

23.

Effects of treatments on forage dry matter production

(kg/ha) at the Campus Agricultural Center (Fifth harvest on

5/22/85)

68

69

70

71

72

73

74

75

ix

LIST OF TABLES—Continued

Table

24.

Effects of treatments on forage dry matter

(kg/ha) at the Campus Agricultural Center production

(Sixth harvest on 8/5/85)

25.

Effects of treatments on forage dry matter

(kg/ha) at the Oracle Agricultural Center of 4 harvesting dates) production

(overall means

26.

Effects of treatments on forage dry matter

(kg/ha) at the Campus Agricultural Center of 6 harvesting dates) production

(overall means

Page

76

80

81

LIST OF ILLUSTRATIONS

Figure

Page

1.

The imprintation pattern of land imprinter . .

2.

The hand imprinter

3.

The land imprinter

4

22

23

4.

Precipitation at the Campus and Oracle Agricultural

Centers: Long term average vs. study period average

. . . 31

5.

Neutron probe calibration curves for the Oracle and

Campus Agricultural Centers

6.

Response surface plots showing the effects of surface treatments on soil moisture at the Oracle Agricultural

Center

35

41

7.

Response surface plots showing the effects of surface treatments on soil moisture at the Campus Agricultural

Center

42

8.

Response surface plots showing the effects of cover treatments on soil moisture at the Oracle Agricultural

Center

43

9.

Response surface plots showing the effects of cover treatments on soil moisture at the Campus Agricultural

Center 44

10.

Plant population count at the Oracle Agricultural

Center (Pilot Study)

47

11.

Plant population count at the Oracle Agricultural

Center (Second Study) 49

12.

Plant population count at the Campus Agricultural Center 51

X

ABSTRACT

Research was conducted over a 2-year period at the University of Arizona Campus and Oracle

Agricultural Centers to evaluate the effectiveness of surface imprintation in revegetating arid lands.

Introduction of forage leguminous species into arid rangelands through land

imprintat ion was another objective of this study.

The soil at the Campus Center is a Brasito, mixed thermic, typic torripsamment with a sandy-loam texture. This was compared with a White House, fine mixed thermic, Ustollic haplargid with a sandyloam texture at the Oracle

Center. Natural rains were the only source of irrigation at Oracle. At the Campus Center, however, a sprinkler irrigation system was installed to match rains with that at the

Oracle

Center.

Three cover treatments together with four surface treatments were used at both sites. The cover treatments included a pure stand of grasses, a pure stand of legumes, and a mixture of both grasses and legumes. The surface treatments were imprinted, mulched, imprintedmulched, and an untreated surface as a check. Surface imprintation was performed by a land imprinter at Oracle and by a hand imprinter at Campus.

The imprinted surface significantly increased soil moisture retention, number of plants per unit area, plant height, plant cover, and biomass compared to the untreated surface. At the Oracle Center, the imprinted surface improved legume germination by 800% over the x i

xii untreated surface, and by 367% over the mulched one. Corresponding percentages at Campus were 48 and 4% over the untreated and the mulched surfaces, respectively. Increases in biomass production achieved through surface imprintation were 102% over the untreated surface and 35% over the mulched surface at the Oracle Center. Corresponding increases at Campus were 63 and 33% over the untreated and the mulched surfaces, respectively. Plants grown on imprinted surfaces exhibited higher transpiration rates, lower diffusive resistance, and cooler leaf temperature compared to those grown on the untreated surfaces.

Addition of mulch to the imprinted surface made no significant differences with respect to the parameters measured when compared to the imprinted surface without mulch. When mulch was used as a separate treatment, however, it significantly increased the parameters measured over the untreated surface.

The effect of cover treatments on growth parameters and biomass production was masked by seasonality. Grasses tended to be superior over legumes in samples taken during the fall and the opposite was true during the summer. Mixing legumes with grasses, however, resulted in significantly taller grasses compared to grasses grown as a pure stand.

CHAPTER 1

INTRODUCTION

Arid lands cover one-third of the earth's land surface and they support an estimated 1.5 billion humans. Furthermore, about 70% of the

15 million humans who die of starvation each year live in arid and semi-arid zones. The world needs to develop these areas to contribute more to global agricultural production particularly as the global population continues to expand. Better use and protection of the limited soil and water resources in these areas become a necessity in the light of these facts.

In the United States, approximately 90% of the crop land is farmed without irrigation. Water is the factor most limiting to crop production. Under such conditions of limited water supply, practices that will increase yield per unit of precipitation will be of great help. The practices which should receive major emphasis include those which are directed toward manipulating the soil surface to catch more of the limited available rainfall and retaining more runoff water resulting from intense monsoon thunderstorms, trap snow in cold areas, maximize infiltration, and minimize evaporation, along with crop selection for ease of establishment and high water use efficiency.

Historically, cropland tillage implements have been modified and redesigned in an attempt to revegetate dryland areas. The resulting

2 implements are referred to in the literature as the eccentric disk pitters, brushland disk plows, moldboard plows, land rippers, land furrowers, brush cutters, and shredders. Most recently, in the seventies, a 3-scalpers interseeder was developed in San Dimas, California and the so-called overhead conveyer which was developed at New Mexico State

University.

The seedbed that is produced by any of these implements is usually not good enough to insure vegetative establishment in arid and semi-arid regions. These implements generally require a large amount of energy to perform each tillage function. Tillage functions for each of the above implements are often too few in number, inappropriate in kind or intensity, and conflicting in purpose. Consequently, both the durability and the initial suitability of the seedbed are diminished.

Even when these implements are used in combinations, vegetative establishment is highly erratic. All of these implements operate unsatisfactorily in brushy, steeply sloping, deeply gullied, and rocky terrain.

The surface geometries that are produced by these implements may be characterized as irregular, imprecise, and highly unstable. Very little control over point infiltration, runoff, and surface evaporation is provided by any of these implements even though such control is essential for revegetation and efficient use of both soil and water resources, especially in arid regions. Moreover, many of the traditional methods for revegetation destroy the existing protective cover and increase soil detachability, therefore rendering the land more susceptible

3 to erosion. These hazards are especially pronounced whenever the seeding effort is followed by weather extremes of either drought or intense rainstorms.

In an attempt to overcome the limitations of traditional tillage implements, Dr. R. M. Dixon of the U.S.D.A. developed what is known now as the "land imprinter." The land imprinter was constructed in 1976 after 20 years of research under a wide range of edaphic and climatic conditions. The invention of the land imprinter is based on concentration and conservation of rainwater by applying an infiltration concept, called the air-earth-interface concept, which establishes the principle underlying infiltration control (Dixon, 1966, 1975, and 1977).

The land imprinter converts the smooth, closed soil surface into a rough open one. It increases soil macroporosity - (directly by breaking up the sealed soil surface and indirectly by increasing the activity of soil burrowing macroorganisms through the litter provided) - and microroughness. Consequently, land imprinting establishes high infiltration rates needed to replenish the soil water reservoir, and in turn revegetates the soil. The land imprinter creates a geometric design in such a way that half of the implement forms seedbed strips along its path whereas the other half forms strips perpendicular to its path to direct water runoff into seedbed strips and in effect double the amount of water available for seed germination and establishment (Fig. 1).

In a preliminary test of the imprinter, Dixon (1980) reported significant increases in forage yield of Lehmann's lovegrass 10

Fig. 1. The imprintation pattern of land imprinter.

4

months after planting near Fort Huachuca, Arizona. A yield of 3,248 kg of grass/ha was produced on the imprinted land area compared to only

56 kg/ha on the unimnrinted adiacent land area. Eight months later, the imprinted area p roduced 4,592 kg/ha compared to 325 kg/ha on the unimprinted land. These results have been compared with grass production of 1,568 kg/ha in the lush Kansas Flint Hills. The Kansas region has an average rainfall of 30" per annum while the average rainfall at

Fort Huachuca is only 14" per annum. From these results, it appears that the land imprinter should have a promising future in the arid

Southwestern region of the U.S. and similar dry areas of the world.

These promising results encourage further testing of this implement. Consequently, one of the objectives of this study was to test the land imprinter with and without mulch in conserving soil moisture and enhancing germination and establishment of some grasses and legumes under rainfed conditions. Another objective of the study was to test the possibility of introducing important leguminous forage species such as sweet clover (Melilotus spp.) and spreading types of alfalfa

(Medicago sativa L.) into predominantly grass vegetation of arid rangelands. Results of previous studies, in Canada and other areas of the

United States, indicated that creeping rooted alfalfa varieties are available and have great potential for use in arid rangelands. These alfalfas are aggressive (have sufficient vigor for establishment and more compatible with grasses and other vegetation), hardy, persistent, drought resistant, and withstand grazing (Kilcher and Heinrichs, 1966;

Heinrichs, 1971; Rauzi et al., 1974; Townsend et al., 1975; Cooper,

1977; Rumbaugh and Pederson, 1979).

5

A third objective of this study was to evaluate the relative performance of legumes and grasses as a pure stand and as a mixture under rainfed conditions. It is well known that grasses benefit when grown in mixture with legumes which fix atmospheric nitrogen and increase soil fertility under favorable conditions of soil water.

Furthermore, legumes when present with grasses in a mixture increase forage quality as well as quantity and thus improve animal performance

(Heinrichs, 1963; Wilton et al., 1978;

Lorenz et al.,

1983).

6

CHAPTER 2

LITERATURE REVIEW

Land Shaping and Types of Seedbeds

Land shaping and types of seedbeds have received major emphasis in revegetation studies of dry lands. The National Academy of Sciences

Study Committee on the Potential for Rehabilitating Lands Surface Mined for Coal in the Western United States (N.A.S., 1974) emphasized that seedbed preparation should create a planting medium which will provide moisture, nutrients, and the protection needed by the particular species to insure vegetative establishment. Hodder (1979) stated that surface manipulation to roughen the surface traps precipitation, encourages infiltration, minimizes runoff, and reduces erosion.

Contour furrowing is a land surface treatment that has been used to increase herbage production and reduce runoff and erosion on Western rangelands of the United States (Wight et al., 1978a, 1978b; Lacey et al.,

1981; Kartchner et al., 1983). On sloping lands, with scant precipitation and poor infiltration, contour furrowing has been effective. In studies that covered sixteen arid land range sites in Southern Montana

(U.S.D.A.,

Agric. Info. Bull.

447, 1982), contour furrowing increased forage production by 123%, soil water recharge by

157% on saline upland sites and 162% on pan spot sites. On a well-levelled area in India; however, Ali and

Prasad (1974) found that flat beds were significantly

7

8 more effective in conserving soil moisture than ridged or furrowed beds.

Neff (1980) found contour furrowing was effective in snow trapping in cold areas of Northern United States.

Pitting and ripping have been used extensively on northern plain rangelands of the U.S.A.

Rauzi (1968) reported that pitted pastures supported a 25% heavier stocking rate than moderately flat pastures over a 24-year period. Tromble (1976), in a study conducted in Cochise

County, Arizona to evaluate the effect of root plowing and pitting treatments on surface runoff, concluded that surface roughness of the root plowed and pitted plots provided detention storage for averagesized storms and the pitting treatments significantly decreased runoff as compared to the untreated control.

Furrow diking or basin tillage (the practice of putting miniature dams in the furrow designed to obstruct the flow of water) is used to reduce runoff and increase moisture storage for crop production in the high plains of Texas (Bilbro and Hudspeth, 1977; Hudspeth, 1978;

Lyle and Dixon, 1977; Jones and Clark, 1982; Gerard et al., 1984).

Jones (1981), in a study conducted at Bushland, Texas, concluded that mini-bench, conservation mini-bench, wide contour furrows and Orthman contour furrows are conservation land forming systems that can be used to control erosion, runoff, and increase sorghum yield on drylands in the Southern Great Plains of the United States.

Water harvesting and microwatershed systems have been used in an attempt to redistribute and confine precipitation to small crop

9 areas, (Gardner and Gardner, 1969; Frasier and Myers, 1983). This will reduce cumulative evaporation with time and increase the amount of soil water available for plant use. Fairbourn and Gardner (1974) reported that microwatersheds with vertical mulching reduced water evaporation, increased infiltration and increased grain yield of sorghum from 37 to

150% above the control. They also concluded that vertical mulched microwatersheds have the potential for increasing and stabilizing annual yields in semi-arid regions.

Soil Mulching

The practice of soil mulching is effective in reducing evaporation, conserving soil moisture, and regulating soil temperature. Mulching regulates soil temperature due to the lower thermal conductivity of the mulching material compared to that of the soil (Hanks et al., 1961;

Ali and Prasad, 1972). The usual effect of mulching is to lower soil temperature during summer and increase it during winter (McCalla and

Duley, 1946; Isenberg and Odland, 1951) for the same conductivity reason.

Researchers have reported positive results for various types of mulches. Beneficial effects of mulching on moisture conservation and crop yield have been reported for stubble mulch (McCalla and Army,

1961; Schuman et al., 1980), for plastic mulch (Waggoner et al., 1960;

Lavin et al., 1981), for encap mulch (Yowell, 1963), for straw mulch

(Greb et al., 1967; Raghavula and Singh, 1982), and for gravel mulch

(Corey and Kamper, 1968). Wheat straw, pearl millet husk, and other

organic mulches of crop residues have been reported to be effective in

10 increasing soil moisture storage, increasing yield, and reducing erosion

(Mannering and Meyer, 1963; Moody et al., 1963; Singh et al., 1967;

Greb et al., 1970; Patil et al., 1972; Saxton et al., 1981).

Lavin et al. (1981) reported that mulching with plastic films, cinders, or Juniper slash; deep furrowing; and fallowing increased water penetration and retention of soil moisture, delayed soil surface crusting and lowered seeding zone temperatures in tests at five different pinyon juniper (Pinus edulis Engelm and Juniperus spp.) range locations in Arizona.

Raghavula and Singh (1982) concluded that straw mulch maintained a higher moisture status both in soils and plants by controlling Evaporation losses and increased water use efficiency and yield of grain sorghum under dry land conditions in Northwestern India. Increases in yield of grain sorghum due to mulching under dry conditions have also been reported by Ravindranth et al. (1974) and Umarani et al. (1973). Jones et al.

(1969) found that straw mulching reduced runoff, increased soil water content, and yield of corn. The differences in soil moisture content with and without mulching were significant to a depth of 30 cm. In addition, they found that mulch treatments gave significantly taller corn plants, greater infiltration rates, and less runoff than the unmulched treatments. Ries and Power (1981) reported that grass stubble was effective in trapping snow for overwinter storage of soil water and the subsequent increase in forage production the following season in

North Dakota.

Artificial

Revegetation

Most arid lands have deteriorated to the degree that natural revegetation through enhancement of secondary succession has become difficult if not impossible. Thus, the only way to bring these lands back into production will be through artificial revegetat ion or

1

1 seeding.

Artificial revegetation can be achieved by till or no-till practices and each approach has its supporters and critics. Tillage practices such as deep plowing, contour cultivation, and bounding have been effective in moisture conservation with various dry farming systems in India (Kanitkar, et al., 1960). Moody et al. (1963),

Shanholtz and Lillard (1968) reported that conservation tillage practices have shown that runoff and evaporation losses from the soil surface can be reduced. In addition, they showed that no-till or sod-seeding provided greater protection against short-duration droughts by contributing to a more efficient water use as well as more effective erosion control during severe storms.

No-till seedings are becoming increasingly popular as a soil conservation practice. In addition to conserving valuable top soil, no-till methods save the producers time, labor, machinery and fuel costs. No-till practices for many crbps are well established and widely acceptable. However, no-till establishment procedures for small-seeded legumes, such as alfalfa

(Medicago sativa

L.), are only being developed (White et al., 1982; Sperow, 1983; Hinish, 1983;

Mueller and Chamblee, 1984; Rechcigl et al., 1985).

The no-till principle has shown promise in several geograph-

12 ical regions under a wide range of conditions (Free et al., 1963;

Spain and Klingman, 1965; Triplett et al., 1968). However, in a study on infiltration and runoff in the Northern Corn Belt,

Lindstorm et al. (1984) concluded that soil surface conditions under no-till systems were vulnerable to runoff and their recommendation was that caution should be taken in assuming that no-till farming byitself will solve water runoff problems.

Competition

One common problem with no-till or sod-seeding is the competition from the already existing vegetation. Groya and Sheaffer

(1981) stated that competition between a grass sward and a legume seedling is one of the most important growth-limiting effects encountered when sod-seeding legumes into perennial grass sods. Effective suppression of grass competition by physical or chemical means during the establishment of legumes sod-seeded into grass enhances legume establishment (Taylor et al., 1969; Fairbourg et al., 1978).

Fairbourg et al. (1978) reported that seeding legumes into an undisturbed tall fescue sod resulted in poorer stands than when tillage or chemicals were used for sod suppression.

A combination of suppressant herbicides and no-till seeders have been used successfully to introduce legumes into grass sods

(Vogel et al., 1983; Taylor and Allinson, 1983; Taylor et al., 1969;

Waddington and Bowren, 1976; Oleson et al., 1981), yet there is

13 evidence that sward improvement can be accomplished without the use of herbicides.

Decker et al. (1964, 1969), indicated some success in seedings of birdsfoot trefoil (Lotus

corniculatus L.) and crown vetch

(Coronilla varia

L.) into Kentucky blue grass

(Poa pratensis L.) pasture without herbicide sod suppression. Oleson et al.

(1981) found no significant differences in stand counts, plant heights, and, in most years, legume and legume-grass dry matter yields between red clover (Trifolium pratense L.) seeded in tall fescue

(Festuca arundincea Schreb.) with and without chemicals.

Adapted Species and

Suitable Planting Tools

For artificial revegetation or seeding to be successful, the right selection of adapted species and a suitable tool to plant these adapted species are of prime importance. Cox et al. (1984) stated that artificial seeding has been going on for the past 92 years in the Southwestern United States and Northern Mexico. More than 300 forbs, grasses, and shrubs have been tested. Of the grasses tested, the most widely adapted species within the Sonoran and Chihuahuan deserts of North America, are Boer lovegrass (Eragrostis curvula var.

conferta

Nees.),

Lehmann lovegrass (Eragrostis lehmanniana

Nees.), and

Cochise lovegrass (Eragrostis lehmanniana Nees. X-Eragrostis tricophera

Coss. and Durr.).

Moreover, Cox and Jordan (1983) showed that the establishment of lovegrasses appears to be more influenced by rainfall distribution rather than by total summer rainfall.

14

Judd and Judd (1976) tested 48 exotic species in semi-desert shrub, chapparal, semi-desert grassland, and pinyon juniper at the

Tonto National Forest, AZ. Their results showed that 13 species were able to survive for 20 years; and seven species for 30 years. Among those surviving for 30 years were Lehmann lovegrass and Boer love grass.

The selection of a suitable tool to plant the adapted species, on the other hand, is of equal importance. Over the years, arid land seeding equipments have been in continuous change and modifications to create more favorable conditions for seedling establishment in the harsh conditions of arid environments. The latest generations of these implements include the overhead conveyor developed at New

Mexico State University (Abernathy and Herbel, 1973), the 3-scalpers interseeder machine developed at San Dimas, California by the Forest

Service Equipment Development Center (Steven et al., 1981), and the land imprinter developed by R. M. Dixon of the USDA-ARS at Tucson,

AZ (Dixon, 1977).

In drier regions, overgrazing and short-duration droughts create a vicious cycle of decreasing soil micro-roughness and macroporosity, decreasing water infiltration, increasing surface runoff and evaporation, and increasing land barrenness (Dixon and Simanton, 1977).

Barren lands characteristically possess low infiltration rates which are often only one-tenth of that for woodlands and grasslands (Dixon,

1966; Dixon et al., 1978; Wadleigh et al., 1974). Consequently, barren soils shed most of the rain water from intense thunderstorms,

whereas litter-covered soils infiltrate most of the water where it falls. Bare soils shed water readily since they possess well developed surface drainage patterns and are sealed tightly by rain drops impacting on their surfaces. The small amount of water that does in-

15 filtrate barren land areas penetrates the soil so superficially that most of it is lost by surface evaporation. Thus, a vicious cycle begins that is responsible for desertification, increasing aridity, and irreversible deterioration of vital soil and water resources and loss of vegetation.

The fabrication of the land imprinter takes into account all of the above facts and is based on the concentration of rainwater by applying an infiltration concept, called the air-earth-interface concept, which establishes the principles underlying infiltration control

(Dixon, 1975; and 1977). The land imprinter converts the smooth closed soil surface into a rough open one without inverting the fertile top soil. Thereby, higher water-infiltration rates are established which are needed to replenish the soil water reservoir; in turn, required to revegetate the soil. Thus, the vicious cycle is converted into a virtuous one.

About this machine,Anderson (1981, 1982), among others, wrote

"The land imprinter appears to be the long-sought answer to semi-arid grass land revegetation. The imprinter does not need to operate on the contour for, wherever it goes, it leaves downslope imprints for collecting rain water and across slope imprints for receiving water.

Erosion is reduced and infiltration of rainwater is greatly increased.

Since potential drought is the major risk in revegetation projects, it

is this characteristic of retention of rainwater where it falls which allows germination and plant growth to occur even under conditions of less than normal rainfall."

16

Grass-Legume Mixture

The seeding of legumes into primarily grasslands has the potential of becoming a useful practice for range improvement as compatible species and interseeding technology become available. Millions of acres of rangelands in Western United States and in other countries could be improved by the successful establishment of legumes in their existing grasslands (Kneebone, 1959; Atkins, 1962; Bleak et al., 1965;

Rumbaugh et al., 1965; Mueller-Warrant and Koch, 1980; West et al.,

1980; Taylor and Allinson, 1983; McGinnies and Townsend, 1983). Cox et al. (1984), indicated that there are approximately 2.5 million acres of abandoned irrigated farm lands in the Southwestern U.S. that might be developed into a valuable forage base if such areas were seeded with adapted range grasses, legumes, and shrubs.

Among the legumes suited for interseeding in these areas and other grassland areas is alfalfa

(Medicago sativa

and M. falcata)

as reported by Rumbaugh et al. (1981), Rumbaugh (1982), and Taylor and

Allinson (1983). Hewitt et al. (1982) reported that alfalfa appeared to have the greatest potential for reseeding on arid rangeland sites, of 15 legume species tested.

Introduction of legumes, particularly alfalfa, into grass pastures has the following merits: 1) The legume itself will be a major contributor to forage yield and quality. 2) The legume will

17 fix additional atmospheric nitrogen for the grasses in the plant community. 3) The fixed nitrogen would result in increased productivity and protein content of the associated grass, and 4) The increased quality and quantity of forage would increase livestock production.

The ability of alfalfa in fixing atmospheric nitrogen, increasing crude protein, and forage yield is well documented. Gomm

(1964) observed that mixtures of either sweet clover or 'Ladak' alfalfa with 'Nordan' crested wheat grass produced more forage than either legume or grass alone. Furthermore, protein content of grass grown in mixtures with legumes was higher than when grown in pure stand. The leguminous forage itself contributed directly to both the quality and quantity of feed produced.

Dubbs (1971) found that the percentage crude protein of crested wheat grass increased when it was grown with alfalfa. Similar results were reported by Comstock and Law (1948), Peterson and Bendixon (1961),

Van Riper (1964), and Wedin et al. (1965). Dubbs (1971) also found that grasses grown

with a legume, especially alfalfa, grew taller, produced more forage, and usually contained a higher percentage of crude protein. Hervey (1960) reported that lamb gains increased after alfalfa and crested wheat grass were interseeded into native sod in

Wyoming. Lee and Rothwell (1966) and Norman (1968) successfully used alfalfa pastures to supplement native pastures for sheep and cattle in

Australia.

18

The value of alfalfa as a legume component is commonly recognized. Its contribution to livestock production in dry land pastures and modified rangelands of semi-arid areas is well-documented. Attempts have been made to introduce these species into more arid situations to supplement range vegetation for some usages. Townsend et al. (1975) regarded alfalfa as one of the most promising forage legumes for dryland seedings in the Great Plains. Vallentine et al.

(1963) recommended the use of alfalfa in sagebrush zone range sites in

Utah where annual precipitation averages 30 cm or more.

The merits of using alfalfa for supplementary native pastures or for interseeding would depend on the longevity of the plants and the ability of the species to reseed itself in a drought environment while subjected to grazing. Kilcher and Heinrichs (1966), Pearse

(1965), and Rumbaugh and Pederson (1979), presented evidence that alfalfa survived up to 23 years in an environment that received 20 to

30 cm average annual precipitation. At the end of that time period, the alfalfa yielded 121% as much oven dry forage as the crested wheat grass in an adjacent planting.

The legume-grass mixture can be achieved either by mixing the seeds of both species before sowing or by seeding each in separate alternating rows. Gomm (1964) found that there was no significant effect on yield from mixing legume and grass seeds before seeding or seeding legume and grass in alternate rows.

Persistence of alfalfa in pastures and in hay fields is a very important requirement in dry regions for maximum production, as

19 was noted by Campbell (1963), Clark and Heinrichs (1957), and Kilcher and Heinrichs (1958). They reported that alfalfa varieties which exhibited the creeping root character were superior in persistence to most other non-creeping types, and would therefore be more reliable and productive in dry climates. Rumbaugh (1982) seeded eight alfalfa populations in dryland pastures in Northern Utah and found that the higher rate of seedling survival for populations that primarily originated from Medicago sativa rather than Medicago falcata. In a

6-year study conducted on a strip mineland at Southeastern Montana,

Holecheck et al. (1982) reported that spreader alfalfa was superior to ranger alfalfa with respect to establishment, survival, canopy cover, and productivity characteristics.

CHAPTER 3

MATERIALS AND METHODS

Three field experiments were conducted at the University of

Arizona Oracle Agricultural Center and Campus Agricultural Center during the period July 83 to October 1985. Two of the three experiments were conducted at the Oracle Agricultural Center, 30 miles north of Tucson, AZ. at an elevation of 1125 meters (3688 ft.). The third experiment was conducted at the University of Arizona Campus

Agricultural Center in Tucson. The first experiment at the Oracle

Agricultural Center was intended to serve as a pilot study to gain site specific information.

The soil of the site at the Oracle Agricultural Center is classified as a White House, fine mixed thermic, ustollic haplargid soil with a sandy loam texture. The average annual precipitation for the area during a 41-year period (1931-1972) reported by Sellers and Hills (1974) was 35 to 40 cm.

On the other hand, the soil at the Campus Agricultural Center is classified as a Brasito, mixed thermic, typic torripsamment soil with a sandy loam texture. The average annual precipitation at the Campus

Agricultural Center is 20 to 25 cm (8 to 10"). Natural rain was the only means of irrigation at the Oracle Agricultural Center. Since the average annual rainfall at the Campus Agricultural Center is lower

20

21 than that at the Oracle Agricultural Center, a pivot sprinkler system was installed at the Campus Center experiment to simulate rain to match that at the Oracle Center. Irrigation with the sprinkler system was scheduled on a weekly basis to deliver the difference in rain between that at the Oracle and that at the Campus Center. If it rained at Campus but not at Oracle, the amount of rain would be subtracted from the difference between the two sites supposedly to be delivered by sprinkler the following week. Furthermore, a hand imprinter

(Fig. 2) rather than a land imprinter (Fig. 3) was used at the

Campus Agricultural Center due to experimental area limitations.

Treatments

Three lovegrasses (Lehmann lovegrass (Eragrostis lehmanniana

Nees.), Boer lovegrass (Eragrostis curvula var. conferta Nees.), and

Cochise lovegrass (Eragrostis lehmanniana Nees. X Eragrostis trichophera

Coss and Cur.)) and three legumes (spreader alfalfa II, white sweet clover (Melilotus

alba),

and yellow sweet clover (Melilotus officinalis) were used in these experiments. The three grasses and the three legumes were sown together to form the mixture, the three grasses together to form the grass pure stand, and the three legumes together to form the legume pure stand. Thus, three cover treatments of a pure stand of grasses, a pure stand of legumes, and a grass-legume mixture were established. The three cover treatments were used together with four surface treatments which consisted of an imprinted surface, a mulched surface, an imprinted-mulched surface, and an untreated surface to

Fig.

2.

The hand imprinter.

22

U.S. DEPARTMENT OF AGRICULTURE

23

Fig. 3. The land imprinter

24 serve as a control (check). The three cover treatments together with the four surface treatments produced a combination of 12 treatments as follows:

1.

A grass pure stand on an imprinted surface.

2.

A grass pure stand on a mulched surface.

3.

A grass pure stand on an imprinted-mulched surface.

4.

A grass pure stand on an untreated surface.

5.

A grass-legume mixture on an imprinted surface.

6.

A grass-legume mixture on a mulched surface.

7.

A grass-legume mixture on an imprinted-mulched surface.

8.

A grass-legume mixture on an untreated surface.

9.

A legume pure stand on an imprinted surface.

10.

A legume pure stand on a mulched surface.

11.

A legume pure stand on a mulched-imprinted surface.

12.

A legume pure stand on an untreated surface.

Three blocks (replications) were used in each experiment.

Each block consisted of 12 plots (experimental units). The size of the plot was 5 by 20 meters at the Oracle Agricultural Center and

5 by

6 meters at the Campus Agricultural Center. A randomized complete block design was used in both sites.

Barley straw was used as a mulch at a rate of 2000 kg/ha

(2 tons/ha) for the mulched treatments and at a rate of 1000 kg/ha for the imprinted-mulched treatments. The straw was spread evenly with a hand rake on the soil surface after broadcasting the seeds.

25

Seed sources were Northrup King Co., Woodland, Calif., for the spreader alfalfa, and Valley Seed Co., Phoenix, AZ. for the lovegrasses and the sweet clovers. The recommended seedling rates for the six species used in the experiments, as reported by Dennis (1966) are:

Species Pure Stand

Lehmann lovegrass 03.36 kg/ha

Boer lovegrass 03.36 kg/ha

Cochise lovegrass

Spreader alfalfa

White sweet clover

Yellow sweet clover

Mixture

01.68 kg/ha

01.68 kg/ha

03.36 kg/ha

28.00 kg/ha

01.68 kg/ha

14.00 kg/ha

16.80 kg/ha

08.40 kg/ha

16.80 kg/ha 08.40 kg/ha

Since each species represented one-third of the mixture in the pure stand form and one-sixth in the mixed form, the following seeding rates were used:

Species Grass Mixture Legume Mixture Grass-legume Mix.

Lehman lovegrass

01.12 kg/ha -

00.56 kg/ha

Boer lovegrass

Cochise lovegrass

01.12 kg/ha

01.12 kg/ha

-

-

00.56 kg/ha

00.56 kg/ha

Spreader alfalfa

White sweet clover

- 09.33 kg/ha

05.60 kg/ha

04.67 kg/ha

Yellow sweet clover

-

-

05.60 kg/ha

02.80 kg/ha

02.80 kg/ha

In each of the experiments, four rain gauges were installed, one at each corner of the experiment. In addition to the rain gauges, a

26 catch can was installed in each treatment at the Campus Agricultural

Center to determine the distribution pattern of the sprinkled water over the treatments. This made it possible to assure that all treatments received equal amounts of water.

Results of the pilot study conducted during the first year at the Oracle Agricultural Center showed that competition from natural grasses and heavy grazing by jackrabbits were the main limiting factors in the establishment of legumes in that area. As a result of those problems, an adjacent experimental area was ripped to reduce the existing natural vegetation and a poultry wire fence was established to exclude jackrabbits and other animals.

Meteorological data including precipitation, atmospheric temperature, and relative humidity were monitored throughout the course of the study at both sites (Atmospheric temperature and relative humidity at the Oracle Center were provided by Sheri Musil, Dept.

Soil and Water Sciences, University of Arizona).

Parameters Measured

Percent soil moisture (on a volume basis) was measured at both sites during the study period. Aluminum access tubes were permanently installed at the center of each treatment for moisture determinations using a Campbell Pacific Neutron Moisture Meter, Model 503 (Manufactured by Campbell Pacific, San Francisco, California). Soil water content was determined at the following depths from the soil surface: 15, 30, 45,

60, and 75 cm for each treatment. At the beginning of each experiment,

27 soil samples were taken from the same depths for gravimetric determinations of moisture content and for field calibration of the neutron probe (Nakayama and Reginato, 1982). Measurements of soil moisture were taken at an interval of 15 days for 10 consecutive months at the Oracle

Agricultural Center and for 12 consecutive months at the Campus Agricultural Center. Regression analysis was applied to the soil moisture data and then a response surface plot (Neter and Wasserman, 1974) was established. The response surface plot is a form of a 3-dimensional graph with the X-axis representing time (months), the Y-axis soil depth (cm), and the Z-axis representing the percent soil moisture.

Germination, seedling establishment and survival were monitored throughout the course of the study. Two, one-square-meter areas, were permanently marked in each treatment at one-third and two-thirds of the plot length at the beginning of each experiment. Seedling emergence and plant count were made on the above-mentioned areas two weeks after the first rain at each site and at 1-month intervals up to the third count. Then a fourth, and final, count was done later in the growing season.

A one-square-meter frame was used in sampling for plant biomass, plant height, and estimation of the percent canopy cover. Three random samples were taken from each treatment using this one-squaremeter frame. Five Lehmann lovegrass plants were randomly selected from each sample area to measure grass height both in the pure grass stand plots and the grass-legume mixture plots to determine the effect of legumes

28 when grown with grass in a mixture. Plant height was measured from the soil surface to the tip of the tallest stem. Lehmann lovegrass was selected for plant-height measurements because it was the dominant grass at both sites.

Canopy cover was estimated by standing near the frame and visually estimating the percent of the ground inside the frame that was covered by vegetation.

After measuring plant height and estimating the percent ground cover, the forage inside the frame was harvested, oven dried at 76 C for 48 hrs until a constant weight was obtained. Then oven-dry weights were recorded for the biomass. Data were collected on four sampling dates for plant height, percent cover, and biomass at the

Oracle experiment, and on six sampling dates for the Campus experiment.

Physiological data for transpiration (pg cm

-2 s

-1

),leaf diffusive resistance (S

-1

), and leaf temperature (C) were taken for the legumes in the grass-legume mixture and in the pure legume stand plots using a Licor model LI-1600 Steady State Porometer (manufactured by

Licor Inc. Lincoln, Nebraska). Spreader alfalfa was the dominant legume at the Campus experiment whereas white sweet clover was the dominant one at the Oracle site. Therefore, spreader alfalfa and white sweet clover were selected for the physiological measurements at the Campus and at the Oracle sites, respectively. Three plants from each treatment were randomly selected and the two upper fully expanded growing leaflets from each plant were used for the measurements. Eight sampling dates were used in each experiment.

29

Analysis of the data was conducted by the Statistical Package for the Social Sciences (SPSS) in a Cyper 175 computer HP 41-CV at the University of Arizona Computer Center. The percent canopy cover, however, was transformed using the arc sin transformation technique before the final analysis. The rest of the data were analyzed using the standard analysis of variance. Means were compared using the

Student-Newman-Keul's test as described by Little and Hills (1978).

CHAPTER

4

RESULTS AND DISCUSSION

Meteorological Data

Although the two sites of Oracle Agricultural Center and Campus

Agricultural Center are only

48 kilometers apart, they have quite different growing conditions due to elevation. The Oracle Agricultural Center is located at an elevation of 1125 meters (3688 ft) above sea level

* whereas the Campus Center is located at an elevation of 710 meters

(2330 ft.).

Average monthly precipitation for a 30-year period

(1952-1982) versus the study period is shown in Fig. 4 for both sites. The annual average precipitation at the Oracle Agricultural Center during the study period was

514 mm.

This is compared to 393.4 mm which was the annual average of 30 years for the same site. At Campus Agricultural Center, on the other hand, the annual average precipitation during the study period was

392.3 mn compared to

300.2 mm long term average. Since the rainfall at the Campus Farm experiment was supplemented by a sprinkler system to deliver the difference in rainfall between the two sites, the total amount of water received by treatments in each location was equal.

With respect to rainfall distribution, both sites show a similar pattern of distribution both for the long-term average and the

30

LONG TERM AVE.

(30

YRS.)

----.

STUDY PERIOD AVE.

(2

YRS.)

31

150

120

90

60

30

0

I s

MAR

1

APR s - -

J

Time (months)

t

SE

CAMPUS AGRICULTURAL CENTER

t

OCT NOV DEC

150

120

90

60

30

0

JA

I

N FEB MAR APR MAY

JUN

JUL

Time (months)

AUG

ORACLE AGRICULTURAL CENTER

SEP OCT NOV DEC

Fig. 4. Precipitation at the Campus and Oracle Agricultural Centers:

Long term average vs. study period average.

32 study-period average (Fig. 4). In both locations, the winter rains for long-term and study-period were more or less equal. For summer rains, however, the study-period in both sites exceeded the long-term average.

The average monthly atmospheric temperature for both sites is presented in Table 1. With the exception of February and November 1984 and January 1985, the monthly average temperature at Oracle was always less than that at the Campus site. This difference was anticipated since the elevation at Oracle was 414 meter (1358 ft.) higher than that at the Campus site.

The percent relative humidity at both locations is presented in

Table 2. On an overall average monthly basis, relative humidity at the

Campus site was higher than that at Oracle in 1984 and 1985. In 1983, though, the opposite was true when relative humidity at Oracle exceeded that at the Campus site.

Soil Moisture

Neutron probe soil moisture calibration curves for the Oracle and Campus Agricultural Centers are shown in Fig. 5a and b, respectively.

These figures represent the regression of volumetric moisture content on count ratio for the probe used to estimate soil moisture at both sites

(Nakayama and Reginato, 1982). The correlation coefficient 'R' was 0.91

and 0.90 at Oracle and the Campus centers, respectively. Calibration curves for both sites were very highly significant (P < 0.00001).

Table

1.

Monthly average temperature (C) at the Oracle and Campus

Agricultural Centers.

33

Year

Site

Month

Oracle

1983

Campus

Jan.

Feb.

March

April

May

June

July

August

Sept.

Oct.

Nov.

Dec.

Overall

Monthly

Average

26.9

25.7

25.3

18.1

10.9

08.8

19.3

22.0

30.1

28.8

28.6

20.1

13.2

11.4

Oracle

1984

Campus Oracle

1985

Campus

08.4

11.0

13.5

15.1

24.3

25.8

25.8

24.8

21.5

15.8

16.7

07.2

17.5

09.8

10.3

14.6

16.8

25.4

27.9

28.1

27.9

27.2

18.7

13.5

09.7

19.2

13.9

08.6

11.9

18.1

21.9

25.9

27.6

26.7

21.9

18.1

11.6

10.5

18.1

09.3

10.8

14.0

19.3

23.5

28.4

30.4

29.9

23.7

20.3

13.7

12.6

19.7

34

Table

2. Monthly average relative humidity

(%) at the Oracle and

Campus Agricultural Centers.

Year

Site

Month

Jan.

Feb.

March

April

May

June

July

August

Sept.

Oct.

Nov.

Dec.

Overall

Monthly

Average

Oracle

1983

Campus Oracle

1984

Campus Oracle

1985

Campus

58.12

61.61

58.44

72.17

72.03

71.07

65.50

30.08

35.55

36.63

39.69

40.33

39.27

36.93

57.14

26.75

20.17

27.19

15.72

21.17

51.86

57.12

43.60

37.05

18.64

31.18

33.96

39.03

28.15

26.07

28.02

23.97

37.32

45.62

46.95

39.87

46.67

44.12

53.15

38.25

16.86

42.33

46.55

28.61

20.83

15.87

38.68

41.96

48.45

48.86

55.22

56.30

38.38

29.93

39.69

38.25

41.83

50.55

59.10

60.11

50.46

47.44

41.80

38.48

32.82

44.21

35.50

28.40

21.30

14.20

7.10

a) Oracle

Y= 0.13 +0.03 X

R=0.91

Sig.= (0.00001)

1.36

1.70

35.5

28.40

ca

21.3

14.20

ILl

Ci a

7.10

°/1*

/

41( b)Campus

Y= -4.81+ 29.63X

R =0.90

Sig

=

(0.0000 1)

0 34 0 68

1.02

COUNT RATIO

1.36

1.70

Fig.

5.

Neutron probe calibration curves for the Oracle and

Campus Agricultural Centers.

35

36

Soil surface manipulation had a significant effect on soil moisture conservation and storage. At both sites soil surface imprinting, mulching, or the combination of both resulted in significantly higher soil moisture compared to the untreated surface (Tables 3 and 4).

At the Oracle Center the imprinted-mulched surface significantly increased soil moisture over the mulched and the untreated surfaces

(Table 3). In contrast to the results at the Oracle site, the imprinted surface without mulch at the Campus site had significantly more soil moisture than the mulched and the untreated surfaces (Table 4). The addition of the mulch to the imprinted surface in both sites had no effect, yet the mulch added separately without imprinting significantly increased soil moisture over the control (untreated surface). This might be due to the fact that the land imprinter in its path chops the above-ground vegetation which acts as a mulch. Therefore, the addition of more mulch to the imprinted surface had no increased benefit. The imprinted surface increased soil moisture over the untreated surface by 33% at Oracle, and by 54% at the Campus Center. This substantial increase in soil moisture as a result of imprintation might have been due to the stable angular pockets (imprints) formed by the imprinter.

These angular pockets serve as reservoirs to hold rainwater which is in excess of the infiltration capacity of the soil. The excess water that is held in these reservoirs will be infiltrated later after the rain ceases; therefore increasing the soil moisture. Compared with the imprinted surface, the untreated surface lacks these water pockets, and having a relatively sealed surface, will shed most of the rainwater.

37

Table

3.

Effects of treatments on percent soil moisture at the

Oracle Agricultural Center.

Surface

Tr

Cover

Tr Grass

Mixture Legumes

Row

Means

1

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

26.57

2

20.72 bc

23.19

24.46 cd ef de

24.19

19.23

24.42

27.76 f de ab de

24.57

16.92

23.72 de a d

25.76 def

Column

Means 3 23.73

23.89

22.74

NS

1

Surface treatment means

2

Individual treatment means

3

Cover treatment means

-

Figures followed by the same letter(s) within the row means, the column means, or the individual treatments means are not significantly different at the 5% level according to the SNK method.

25.11 bc

18:95 a

23.77 b

25.99 c

Table 4.

Effects of treatments on the percent soil moisture at the

Campus

Agricultural Center.

38

Grass

Mixture

Legumes

Row

1

Means

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

19.75

2

13.07 abc

16.95 def

20.09 f f

18.30 ef

11.87 ab

14.48 bcd

14.22 abcd

17.47 def

11.08 a

15.33 cde

19.96 ef

Column

Means

3

17.47 b

1

Surface treatment means

3

Cover treatment means

14.72 a 15.46 a

2

Individual treatment means

18.51 c

12.01 a

15.59 b

17.42 bc

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the

5% level according to the

SNK method.

39

The land imprinter, beside creating these angular pockets, also breaks the smooth, sealed soil surface into a rough open one. Dixon, 1966;

Dixon et al., 1978; and Wadleigh et al., 1974 stated that barren lands characteristically posses low infiltration rates which are often only one-tenth of that for woodlands.

The effect of cover treatments on soil moisture is shown in the column means of Table 3 for the Oracle Center and Table 4 for the

Campus Center. Both tables show higher soil moisture under grass treatment compared to legume treatment. This increase in soil moisture under the grass treatment was only significant at the Campus Agricultural

Center. The presence of more soil moisture under grass treatment compared to legume treatment could be explained on the basis of consumptive use for each group. The annual consumptive use for alfalfa is about

139 ancompared to about 38 cm for lovegrasses. Therefore, legumes depleted most of soil moisture available to satisfy their water requirements, whereas the soil moisture avaialble for grasses was more than enough for their water requirements.

With regard to individual treatments, at the Oracle Center a maximum soil moisture of 27.8% was recorded for the grass-legume mixture on imprinted-mulched surface, and a minimum of 16.9% was recorded for legumes on an untreated surface (Table 3). This is compared to a maximum of 20% for grass - imprinted-mulched and a minimum of 11% for legumes on an untreated surface at the Campus Center (Table 4).

When plotting soil moisture data in a response surface to show the effect of treatments on soil moisture through time and depth, it

40 is clear that treated soil surfaces remained wetter over time at different depths compared to the untreated surface (Figs.

6, 7, 8, and

9).

The general trend of soil moisture, over time in all treatments at both sites, was that soil moisture dropped during summer months and then increased to reach a peak during fall and winter months. This is not unusual since rainfall distribution in southern Arizona, as represented by Fig. 4, follows the same pattern. Moisture in soil is a reflection of the seasonal rainfall distribution pattern. Moreover, grasses are dormant during winter and legumes are partially dormant during this period. Therefore, moisture extraction from soil by plants will be minimal.

Soil moisture tended to increase with soil depth in all treatments at both sites. Minimum values were always at or near the surface, whereas maximum values were found at the deepest soil layer measured

(75 cm). Root activity in the upper layers plus surface evaporation losses could be the explanation for this trend. At the Oracle

Agricultural Center, a maximum of 35 to

39.9% soil moisture at 75 cm depth was recorded for the treated surfaces compared to

30 to

34.9% on the untreated surface for the same depth (Fig. 6). In the upper surface layer, however, a maximum of 15 to 19.9% was recorded for imprinted surfaces with and without mulch,

10 to

14.9% for mulched surface, and only

0 to

4.9% for the untreated surface.

In comparison with Oracle, soil moisture in the deepest soil layer of

75 cm at Campus reached a maximum of 35 to 39.9% for imprinted surfaces with and without mulch, 30 to 34.9% for the mulched surface,

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J/84FM

I 1

I

AMJ

1

J

1 1

AS

I I I

OND/84

1

Z- Scale

(Vo soil moisture)

TIME (Months)

0=0- 4.9 2=10-14.9

4:20.24.9 6=30- 34.9

1=5 -9.9 3=15-19.9 5:25_29.9 7=35-39.9

Fig. 9. Response surface plots showing the effects of cover treatments on soil moisture at the Campus Agricultural Center.

4

4

45 and only

25 to 29.9% for the untreated surface (Fig. 7). When mulching was combined with imprinting, it affected maximum soil moisture by shifting it upward to the upper soil layers compared to imprinting without mulch (Fig.

7a and d). Generally, the surface treatments affected soil moisture mostly in the upper soil layers. This should have been an advantage in seed germination, seedling survival, and plant growth since the major portion of the root system, especially in grasses, is confined to that region. A maximum of 20 to 24.9% soil moisture was recorded in the upper soil layer on the imprinted-mulched surface, followed by

10 to 14.9% on mulched, and imprinted surfaces.

The upper soil layer of the untreated surface was obviously the driest one (0 to

4.9%).

The dry condition extended down to deeper layers in the untreated surface (Fig. 7b).

Response surface plots of soil moisture for cover treatments at the Oracle Center (Fig. 8) show that the grass-legume mixture treatment resembled that of the grass treatment, whereas at the Campus Center

(Fig.

9), it resembled that of the legumes. It was observed that the mixed treatment was dominated by grasses at Oracle and by legumes at the

Campus site. This seems natural since the Oracle site is basically a grassland region whereas campus site is not. Furthermore, there was more soil moisture in the grass treatment compared to the legume treatment, especially in the deep layers, at both experimental sites. Differences in water requirements and root habits between legumes and grasses could provide an explanation for this phenomenon. Legumes have

46 a higher water requirement than grasses and have deep tap roots that extract soil water from deep layers. Unlike legumes, grasses possess a fibrous root system that is restricted to the upper soil layers, and their water requirement is less than that of legumes.

Plant Population

Results of germination, seedling establishment and plant survival for the pilot study conducted at the Oracle Center are shown in

Fig. 10.

Grasses on imprinted surface with or without mulch outnumbered other surface treatments throughout the three observation periods

(Fig. 10a). The imprinted surface exceeded the imprinted-mulched surface during the first and second counting dates. However, by the final count this trend was reversed. This might have been a result of mulch degradation that released nutrients to benefit the plants.

The legumes, on the other hand, presented quite a different story. No legumes germinated on the untreated surface (Fig.

10b).

Possibly absence of a suitable seedbed resulting from no-till seeding and the uncovering of seeds had something to do with this germination failure. Even those legumes which did germinate on the treated surfaces disappeared by the third count. It was noted that heavy grazing on

_legumes by jackrabbits and competition with natural vegetation already present accounted for their disappearance. Groya and Sheaffer (1981) stated that competition between a grass sward and a legume seedling is one of the most important growth-limiting factors encountered when sodseeding legumes into perennial grass sods. Similar observations were made by other researchers (Taylor et al., 1969;

Fairbourg et al.,

1978).

50 la 45

;

40

2

35

0

a

) co ci

30

O c cn

n

25

0

'a'

20

611

i5

0

b) s

47

\1

Imprinted surface

',...!

Untreated surface

7

Mulched surface

Imprinted-mulched surface

9/83

12/93

Counting

Dates

5/84

•=••

_

Imprinted surface

OVIV

'A

7

Untreated surface

_..z.

Mulched surface

Imprinted-mulched surface

9/83

12/ 83

Counting

Dates

5/84

Legumei

}Grass

0

9/83 12/83

Counting

Dates

5/84

Fig.

10.

Plant population count at the Oracle

Agricultural

Center (Pilot

Study).

48

The trend of the mixture was similar to that when each group was sown as a pure stand (Fig.

10c).

Grass in the mixture that was planted on the imprinted surface outnumbered other surface treatments up to the second count. By the third count, grass on imprinted surface with mulch exceeded that on imprinted surface without mulch. As was observed in legumes grown as a pure stand, legumes in the mixture disappeared by the third count.

The result of the pilot study, which was aimed at gaining site specific information, led us to rip an adjacent area. Ripping was intended to reduce competition by subduing the growth of natural vegetation. In addition, a poultry wire fence was established around the perimeter to exclude jackrabbits from the treated area.

After ripping the area and establishing a fence, we were able to get legume plants established successfully in all treatments (Fig.

llb and c).

At the Oracle Agricultural Center, the imprinted surface without mulch increased grass germination by

126% over the untreated surface, and by 87% over the mulched one (Fig.

11a).

In comparison to grass, the imprinted surface increased legume germination by

800% over the untreated surface, and by 367% over the mulched surface (Fig. 11b). When grasses and legumes were grown together as a mixture, the increase was 295% over the untreated surface and 190% over the mulched surface for the grass; 123% over the untreated surface and 109% over the mulched surface for the legumes (Fig. 11c).

49

150 cc, 135 cp 120

• 105

• 90 co

• 75

co

a) 60

2

0

.

45

o •

Z 15

0

7/18/84

50

6

, 40

• 35

Ci 30

O CO

0 g

25

20 b)

0

—t

0

15

ô

1

o

5

7/18/84

8/18/84

9/30/84

12/30/84

Counting Dates

Imprinted surface

I w

Untreated surface

Mulched surface

Imprinted— mulched surface

Imprinted surface

P a y"

Untreated surface

Mulched surface

Imprinted—mulched surface

Legume{ lim

n

••

1

n

11

/Grass

7/18/84

8/8/84

9/30/84 12/30/84

Counting Dates

Fig.

11.

Plant population count at the Oracle Agricultural

Center (Second Study).

50

The imprinted surface planted with legumes outnumbered all other surface treatments except during the final count when the imprinted surface with mulch took the lead. As suggested earlier, this might have been due to degradation of mulches which released nutrients upon decomposition.

At the Campus Agricultural Center, substantial increases in germination as a result of surface imprinting were also noticed (Fig.

12). The imprinted surface without mulch resulted in the highest number of grasses over other surface treatments except during the final count when imprinted surface with mulch outnumbered imprinted surface without mulch (Fig. 12a).

The imprinted surface with or without mulch substantially increased the number of legumes over other surface treatments (Fig. 12b).

The same increasing pattern in seed germination and seedling establishment as a result of surface imprinting that is observed in Figs. 12a and b was repeated when both legumes and grasses were grown as a mixture (Fig. 12c). Within the leguminous species planted, it was observed that white sweet clover was the dominant species at Oracle whereas spreader alfalfa dominated the Campus experiment.

It is obvious from the soil-moisture data that soil surface imprinting had resulted in a significant increase in soil moisture compared to other surface treatments. Therefore, the substantial increase in germination, seedling establishment and survival was a reflection of this increase in soil moisture in the imprinted treatments. This

51

a)

b)

225

k..200

,

4

1; 175

2

150

6

'125

œ cts

E

c 75

CS

4

0

Z.

50

6

25

0

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50

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Z120

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CO

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4f.

1

60

45 a

30

0

15

0

/10/84

2/10/84 3/10/84

11/23/84

Counting dates

1/10/84 2/10/84 3/10/84

Counting dates

11/23/84

0

6.

160

!!140

2

120 c) e

_ Igo cn

".• o

c

60

1 aS el

)

Z. 40

6

20

Z

0

In11

.11n11

•• n

• n

WOMM

. • n • n •=1, via n ol

411n111n

111=n1,

41nn•

2/10/84 3/10/84 11/23/84

Counting dates

Imprinted surface

•••

Untreated surface

Mulched surface t

:

Z3

Imprinted—mulched surface

Imprinted surface

Untreated surface

7

Mulched surface

Imprinted—mulched surface

G ras s{

••••

n

nn

Fig.

12.

Plant population count at the Campus Agricultural Center.

52 is especially true under arid conditions where soil moisture is by far the most important factor limiting plant growth and crop production.

Moreover, as noted by Dixon

(1977, 1980), the seedling cradles created by'the imprinter provide a good protection for the young seedlings against desiccating winds, hot sun, and early morning frosts. This would be of particular significance to these seedlings since they are most vulnerable at this age.

Physiological Data (Legumes)

Transpiration

The treated surfaces - (whether imprinted, mulched, or the combination of both) - significantly increased transpiration over the untreated surface both at Oracle (Table 5) and at the Campus Center

(Table 6). The treated surfaces retained more soil moisture for plant growth compared to the untreated surface which represented the dry treatment in this case. The higher soil moisture level in the treated surfaces was reflected in higher transpiration rates. These results are consistent with the results of Singh and Misra (1985), who reported that leaf water status and transpiration rates decreased as soil moisture stress increased in a field study with some

C

3 and

C

4 grasses in a seasonal dry tropical region in India.

on the other hand, were not significant. Transpiration rates of legumes, whether grown as a pure stand or as a mixture, were similar at both sites.

Table

5.

Effects of treatments on transpiration rates cm

-2 s at the Oracle Agricultural Center (Overall means of

8 sampling dates).

-1

)

53

Surface

Tr

Cover

Tr

Legumes

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

33.28

2 b

17.43 a

25.95 ab

32.26 b

Column Means

3

27.23

Legume

Grass Mixture

28.08

19.06

26.86 ab a ab

32.78 b

Row Means

30.68 b

18.25 a

26.41 b

32.52 b

26.70

NS

'

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatments means are not significantly different at the 5% level according to the SNK method.

1

-2 -1,

Table 6. Effects of treatments on transpiration rates .,ÇY cm s) at the Campus Agricultural Center (overall means of 8 sampling dates).

54

Surface

Tr

Cover

Tr

Legumes

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

30.00

2 b

14.05 a

24.42 ab

29.91 b

Column Means

3

24.60

Legume

Grass Mixture

29.14 b

15.46 a

23.78 ab

29.34 b

24.43 NS

Row Means

29.57 b

14.75 a

24.10 b

29.63 b

1

Surface treatment means

3

Cover treatment means

.2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

55

Leaf Diffusive Resistance

The sane trend observed with transpiration was duplicated for leaf diffusive resistance in a reciprocal way for both sites (Tables 7 and 8). Plants grown on treated surfaces showed significantly lower diffusive resistance compared to the untreated surface. Stomates of plants grown under stress conditions (untreated surface in this case) close. This reduces water losses through transpiration and enables them to survive. Consequently, this would result in an increase in leaf dif-

• fusive resistance. This would explain why plants grown on treated surfaces showed significantly higher transpiration rates and lower diffusive resistance than those plants grown on untreated soil surface.

This was a reflection of water status in the soil. There was adequate soil water in the treated surfaces and plants on those treatments transpired normally.

Unlike plants grown on the imprinted surfaces, those on the untreated surface (water stress) had to close their stomates and increase their leaf diffusive resistance in order to cope with the limited water supply available in the soil.

No significant differences were recorded between treated and untreated surfaces regarding leaf temperature at both sites (Tables 9 and 10). However, plants grown in the treated soil surface areas maintained lower leaf temperature than those in the untreated surface areas.

This is due to the cooling effect of transpiration. Plants grown on the treated surfaces, as reported earlier, had a significantly higher transpiration rate which lowered their leaf temperature.

Table

7. Effects of treatments on leaf diffusive resistance

(s cm

-1

) at the Oracle Agricultural Center (overall means of

8 sampling dates).

56

Surface

Tr

Cover

Tr

Legumes

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

0.59

2 a

1.56 b

0.85 a

0.63a

Column Means

3

0.91

Legume

Grass Mixture

0.68

1.41 b

0.81

0.57

0.87 a a a

NS

Row Means

0.64

0.83

0.60

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the

5% level according to the SNK method.

a

1.43 b a a

1

Table 8. Effects of treatments on-leaf diffusive resistance (S cm

-1

) at the Campus Agricultural Center (overall means of 8 sampling dates).

57

Surface

Tr

Cover

Tr

Legumes

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

0.97

2 a

3.60 b

1.21 a

0.91a

Column Means

3

1.67

Legume

Grass Mixture

0.88 a

3.37 b

1.47 a

1.08 a

Row Means

1

0.92 a

3.49 b

1.34 a

1.00 a

1.70 NS

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the indivi4ua1 treatment means are not significantly different at the 5% level according to the SNI( method.

Table 9. Effects of treatments on leaf temperature (C) at the Oracle

Agricultural Center (overall means of 8 sampling dates).

58

Surface

Tr

Cover

Tr

Legumes

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

26.20

2

26.10

25.87

26.05

Column Means

3

26.05

Legume

Grass Mixture

25.73

26.05

25.76

25.68 NS

Row Means"

25.96

26.07

25.82

25.86 NS

25.80 NS

1

Surface treatment means

3

Cover treatment means

2

Individual treatment,means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

59

Table 10. Effects of treatments on leaf temperature (C) at the

Campus Agricultural Center (overall means of 8 sampling dates).

Surface

Tr

Cover

Tr

Legumes

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

Column Means

3

30.15

2

32.04

30.54

30.79

30.88

Legume

Grass Mixture

29.76

31.87

30.79

30.87 NS

Row Means

30.82 NS

1

Surface treatment means

3

Cover treatment means

2

IndividuaL treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

29.95

31.95

30.66

30.83 NS

1

60

Similar to transpiration and leaf diffusive resistance, no significant differences with respect to leaf temperature were reported for the cover treatments.

Plant Height (Grass)

Overall means of plant height at the different sampling dates are shown in Table

11 for the Oracle Agricultural Center and in

Table

12 for the Campus Agricultural Center. At both sites the imprinted surface with and without mulch resulted in significantly taller plants than those grown on either the mulched or the untreated surface.

The mulch had no detectable impact on plant height within the imprinted surfaces since no significant differences were recorded between imprinted surface with mulch and imprinted surface without mulch. It did have an impact, however, when the mulch was used as a separate treatment.

Plants grown on the mulched surface were significantly taller than those on the untreated surface.

Planting legumes with grasses significantly benefited the grass component and resulted in taller grass plants compared to those grown in a pure stand at both sites (Tables

11 and

12).

Apparently the legumes benefited the grass through atmospheric nitrogen fixation that became available for the grass. These results are in line with the results reported by Dubbs (1971), who reported that grasses grown with legumes, especially alfalfa grew taller, produced more forage, and usually contained a higher percentage of protein. At both sites the tallest plants were recorded for the mixture grown on an imprinted surface.

Table

11.

Effects of treatments on grass height (cm) at the Oracle

Agricultural Center (overall means of

4 sampling dates).

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

097.0

2 d

072.3 a

Mulched Surface

081.5 b

Imprinted-Mulched

093.8 cd

Surface

Column Means

3

085.1 a

Grass

Legume Mixture

108.4 e

089.0 c

097.3 d

108.3 e

Row Means

100.8 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

102.7 c

080.6 a

089.4 b

101.0 c

1

61

Table 12. Effects of treatments on grass height (cm) at the Campus

Agricultural Center (overall means of 6 sampling dates).

62

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

096.6

2 c

074.4 a

086.0 b

090.8 bc

Column 11eans

3

085.9 a

Legume

Grass Mixture

108.9 d

077.6 a

092.11 bc

111.0 d

097.4 b

Row Means

102.8 c

076.0 a

089.1 b

100.9 c

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

63

The effects of surface treatments and cover treatments on plant height at each sampling date are shown in Appendix A for Oracle and Appendix B for the Campus site. The same trend shown in the overall means of the different sampling dates was repeated for each sampling date.

Canopy Cover

Overall means of percent canopy cover for the different sampling dates are shown in Table

13 for the Oracle Center and Table 14 for the

Campus Center. The same effects of surface manipulation observed in plant height were repeated on percent canopy cover. The treated surfaces resulted in a significantly higher percent cover compared to the untreated surface. The imprinted surface with or without mulch had a higher percent cover over the mulched and the untreated surfaces at both sites. Adding mulch to the imprinted surface did not increase canopy cover, since no significant differences were observed between imprinted surfaces with or without mulch. Yet, the mulch applied separately significantly increased the percent cover over the untreated surface.

Mixing legumes with grasses resulted in a significantly higher percent cover over the grass grown as a pure stand at the Campus site

(Table 14). The same trend of a higher percent cover with the mixture was observed at Oracle (Table

13), although it did not reach the statistical significance level.

The effects of cover and surface treatments on percent canopy cover during each sampling date are shown in Appendix C for the Oracle experiment and in Appendix D for the Campus experiment.

Table 13. Effects of treatments on percent canopy cover at the Oracle

Agricultural Center (overall means of 4 sampling dates).

64

Grass Mixture Legumes Row 1

Means

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means

3

92 2 c

47a

72 ab

85c

74

94c

48a

78b

92c

78

91c

53a

68 ab

90c

76 NS

89c

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

92c

50a

72b

65

Table

14. Effects of treatments on percent canopy cover at t'le

Campus Agricultural Center (overall means of 6 sampling dates).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means

3

Grass

2

81 bc

67

74

80 b

75 a a a

Mixture

97 ef

83 b

91 de

95 ef

91b

Legumes

98 ef

84 bc

90 cd

94 ef

91b

Row

Means

92 c

78 a

85 b

90 c

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

66

Biomass

Individual Harvests

Surface treatments significantly affected biomass production both at Oracle and at Campus throughout the different harvesting dates

(Tables 15 to 24). The only exception to that was at the Campus site during the first harvest (Table 19). Though no significant difference in forage production was observed among surface treatments at that time, yields were substantially greater than forage production from the untreated surface. At the Oracle Agricultural Center, no significant differences in forage production between the treated surfaces were recorded for the first cutting date (9/29/84), but they were significant over the untreated surface (Table 15). From the second cut onward

(Tables 16, 17, and 18), the imprinted surfaces with or without mulch significantly outyielded both the untreated and the mulch treatment.

At Campus, the highest biomass throughout the different harvesting dates was recorded for the imprinted surfaces with and without mulch. The imprinted surface scored the highest biomass among the treated surfaces at the first, second, third, and final (sixth) harvests (Tables 19, 20, 21, and 24). On the other hand, the imprintedmulched surface outscored the imprinted surface at the fourth and fifth harvests (Tables 22 and 23). No significant differences were reported between imprinted surface with mulch and imprinted surface without mulch except during the third harvest (Table 21).

Table 15. Effects of treatments on forage dry matter production (kg/ ha) at the Oracle Agricultural Center (First harvest on

9/29/84).

67

Grass Mixture Legumes

Row

Means

1

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

2126.7

1846.7

2366.7

2400.0

2185.0

2

2203.3

1670.0

2000.0

2373.3

2061.7

2363.3

1386.7

2043.3

2126.7 NS

1980.0 NS

2231.1 b

1634.4 a

2136.7 b

2300.0 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Table 16. Effects of treatments on forage dry matter production

(kg/ha) at the Oracle Agricultural Center (Second harvest on 5/25/85).

68

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means3

Grass

2

3673.3bc

• 1426.7 a

2326.7 ab

3213.3 bc

2660.0

Mixture

Legumes

Row

Means

1

4033.3 c

1503.3 a

2543.3 ab

3960.0 c

1343.3 a

2810.0 bc

3888.9 d

1424.4 a

2560.0 b

2950.0 bc 3250.0 bc

3137.8 c

2750.0

2840.8 NS

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

69

Table 17. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Third harvest on 8/5/85).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Grass

2

2850.5de

1380.0 a

1673.3 abc

2623.3 bcde

Column

Means 3

2131.7 a

Mixture

Row

Means

1

3230.0 e 3266.7 e 3115.6 c

1836.7 abcd 1606.7 ab 1607.8 a

2486.7 abcde 2196.7 abcde 2118.9 b

3243.3 e

2699.2 b

Legumes

2770.0 cde 2878.9 c

2460.0 ab

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

70

Table 18. Effects of treatments on forage dry matter production (kg/ha) at the Oracle Agricultural Center (Fourth harvest on 10/12/85).

Grass

Mixture Legumes

Row

Means

1

Imprinted

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

2 d

2266.7 abc

3176.7 bcd

3666.7 cd

Column

Means 3

3337.5

4250.0 d

1606.7 a

3913.0 d

2000.0 ab

4134.4 c

1957 8 a

3216.7 bcd 2926.7 bcd 3106.7 b

3550.0 cd

3155.8

3860.0 d

3175.0 NS

3692.0 c

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

71

Table 19. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (First harvest on 5/15/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

0317.0

2 ab

0167.0 a

0277.0 ab

0417.0 abc

0294.0 a

Mixture

1333.0 c

0787.0 abc

0580.0 abc

0627.0 abc

0832.0 b

Legumes

1327.0 c 0992.0

0843.0 abc 0599.0

0970.0 abc

0609.0

1183.0 bc

1081.0 b

Row

Means

1

0742. ONS

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

72

Table 20. Effects of treatments on fprage dry matter production (kg/ha) at the Campus Agricultural Center (Second harvest on

6/28/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

1757.0

2 ab

1163.0 ab

0683.0 a

1743.0 ab

Mixture Legumes

2780.0 b

2100.0 ab

1933.0 ab

2633.0 b

2057.0 ab

2037.0 ab

2390.0 b

1773.0 ab

1551.0 a

2007.0 ab 2550.0 b

Row

Means

1

2100.0 ab

1337.0 a 2205.0 b

2319.0 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

73

Table 21. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Third harvest on 8/20/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

5550.0

2 b

3483.0 a

3450.0 a

3977.0 a

4115.0 b

Mixture

2987.0 a

2910.0 a

2877.0 a

3277.0 a

3012.0 a

Legumes

3667.0 a

2860.0 a

2507.0 a

2710.0 a

2936.0 a

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Row

Means

1

4068.0 b

3084.0 a

2944.0 a

3321.0 a

74

Table 22. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Fourth harvest on 10/24/84).

Surf ac

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

3967.0

2 b

2497.0 ab

3490.0 ab

3833.0 b

3447.0 b

Mixture Row 1

Means

3140.0 ab

2340.0 a

2503.0 ab

2717.0 ab

2287.0 a

2503.0 ab

3274.0 bc

2374.0 a

2832.0 ab

3397.0 ab 3397.0 ab 3542.0 c

2845.0 a

Legumes

2726.0 a

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

75

Table 23. Effects (..f treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Fifth harvest on 5/22/85).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means3

Grass

2903.3

2 ab

1350.0 a

1600.0 a

2143.3 a

1999.2 a

Mixture

4440.0 bcd

2130.0 a

3873.3 bc

5820.0 d

4065.8 b

Legumes

Row

Means

4696.7 bcd 4013.3 c

1750.0 a 1743.3 a

4166.7 bcd

3213.3 b

5573.3 cd

4512.2 c

4046.7 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

76

Table 24. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (Sixth harvest on 8/5/85).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

4790.0

2 c

2490.0 ab

4266.7 c

4850.0 c

4099.2 b

Mixture

4383.3 c

2183.3 ab

3466.7 bc

4616.7 c

3662.5 b

Legumes

4310.0 c

1916.7 a

2266.7 ab

3860.0 c

3088.3 a

Row

Means

1

4494.4 c

2196.7 a

3333.3 b

4442.2 c

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

77

The effect of cover treatments on biomass production seemed to be affected by the time of cutting (seasonal variation). At the Campus

Center, harvests that were made during the summer (1st, 2nd, and 5th cut), legume plots were always dominant and significantly outyielded the grass plots (Tables 19, 20, 23). This trend was reversed during the fall which coincided with the peak growth period of the lovegrasses. In cuts that were made during the fall (3rd, 4th, and 6th cut), the grasses significantly outyielded the legumes (Tables 21, 22, 24).

This same trend of seasonal variation was observed at the Oracle

Center. Harvests that were made during the fall (1st, 3rd, and 4th cut), the grasses outyielded the legumes (Tables 15, 17, 18). In cuts that were made during the summer (2nd cut), however, the opposite was true (Table 16). This observation of seasonal change could be explained by the fact that lovegrasses remain dormant throughout the winter, start regrowth in summer, and reach their peak of growth during the fall which coincided with the maximum rainfall. Legumes, on the other hand, are partially dormant during the fall.

With respect to individual treatments (the combination of cover and surface treatments) - at Campus, the highest biomass of 8520 kg/ha was recorded for the grass-legume mixture on the imprinted-mulched surface during the summer of 1985 (5th cut, Table 23). This is compared to 5550 kg/ha recorded for the grass on imprinted surface during the fall of 1984 (3rd cut, Table 21).

At the Oracle Center, on the other hand, the highest biomass of 4033 kg/ha was recorded for the legumes on imprinted surface during

78 the summer of

1985 (2nd cut, Table

16). This is compared to 4240 kg/ha recorded for the grasses on imprinted surface during the fall of 1985

(4th cut, Table

18).

Overall Means of the Different

Cutting Dates

Soil surface manipulation through imprinting and mulching significantly increased biomass production in both sites as seen in the overall means of the different harvesting dates (Table 25 for Oracle and Table 26 for the Campus Center). Imprinted surfaces with or without mulch significantly increased biomass production over mulched and untreated surfaces. The mulch alone significantly increased biomass production over the untreated surface. The imprinted surfaces, however, were not affected by mulch addition. This could be related to the fact that only half of the mulch added in the mulched treatment was added to the imprinted-mulched surface treatment. Furthermore, the imprinter by itself breaks the above-ground vegetation to serve as a mulch, and this could have masked the effect of the additional mulch

added in the imprinted-mulched treatment.

It is worth mentioning here that similar effects of surface treatment on biomass production were observed for plant height and percent cover. Since biomass production is largely determined by both plant height and the percent of the ground that is covered by vegetation (plant cover), it seems logical to observe the same effects for plant height and cover on biomass production. The imprinted surface without mulch increased biomass production by 102% over the untreated surface, and by

35% over the mulched surface at the Oracle Center

79

(Table 25). In comparison to Oracle, at the Campus Center, the imprinted surface increased biomass production by 63% over the untreated surface, and by 33% over the mulched surface (Table 26).

The substantial increase in biomass production due to surface imprintation at both sites reflects the importance of this technique for retaining a higher amount of natural rainfall for plant growth in a desert environment. These results are in agreement with the results reported by Dixon (1980) at Fort Huachuca, Arizona. He reported a substantial increase in Lehmann lovegrass herbage production from an imprinted surface compared to forage production in an adjacent untreated but seeded area.

The seasonal variation, reported earlier in the discussion of individual harvesting dates, masked the effects of cover treatments on biomass production for the overall means of the different cutting dates.

No significant differences were recorded for cover treatments on the overall means of the different cutting dates at both sites (Tables 25 and 26). However, both at Campus and at Oracle Centers the grass-legume mixture treatment scored the highest biomass, followed by legumes, and then grasses.

S O

Table

25.

Effects of treatments on forage dry matter production

(kg/ha) at the Oracle Agricultural Center (overall means of 4 harvesting dates).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprintad-

Mulched

Surface

Column

Means

3

Grass

2

3222.5bc

1730.0 a

2385.8 ab

2975.8 bc

2578.5

Mixture

3429.2 c

1654.2 a

2561.7 bc

3029.2 bc

2668.5

Legumes

Row

Means

1

3375.8 bc

3342.5 c

1584.2 a

1656.1 a

2494.2 bc 2480.6 b

3001.7 bc 3002.2 c

2614.0

NS

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the

5% level according to the

SNK method.

81

Table 26. Effects of treatments on forage dry matter production (kg/ha) at the Campus Agricultural Center (overall means of 6 harvesting dates).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

3213.9

2 d

1858.3 a

2294.4 abc

2827.2 cd

2548.5

Mixture

3177.2 d

2075.0 ab

2538.9 bc

3290.5 d

2770.4

Legumes

3225.0 d 3205.4 c

1952.2 ab

1961.8 a

2408.3 abc

2413.9 b

3212.2 d

2699.4 NS

Row

Means

1

3110.0 c

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

CHAPTER 5

SUMMARY AND CONCLUSION

A study was conducted over a

2-year period at the University of Arizona Campus Agricultural Center and the Oracle Agricultural

Center to evaluate surface imprintation and soil mulching as means of improving revegetation of arid rangelands. The study also aimed at testing the possibility of introducing important leguminous forages, such as alfalfa and sweet clover, into arid rangelands vegetated predominantly by grass species to improve forage quality. Moreover, evaluation of the relative performance of legumes and grasses grown as a pure stand and as a mixture was a third objective of this investigation.

Three cover treatments along with four surface treatments were used in this investigation. The three cover treatments included planting grasses as a pure stand, legumes as a pure stand, and a mixture of both grasses and legumes. The surface treatments, on the other hand, included surface imprintation by a land imprinter at the Oracle

Agricultural Center and by a hand imprinter at the Campus Agricultural

Center, mulching the surface, a combination of imprinting and mulching, and an untreated surface to serve as a check.

The imprinted surface significantly increased soil moisture, number of plants per unit area, plant height, canopy cover, biomass, transpiration rate and reduced leaf diffusive resistance. At the

Oracle Agricultural Center during the year

1985, the imprinted surface

82

produced a total of 11,139.7 kg/ha of legume dry matter (a total of three cuts), and a total of 11,513.3 kg/ha dry matter of legume grass mixture. The total annual precipitation at Oracle for that year was

395 mm. Comparing this amount to the consumptive use of alfalfa, which is 1887 mm (74.3"), surface imprintation appeared very impressive.

Mulching the surface substantially improved soil moisture storage, germination of seeds, plant height and cover, and total biomass production. It also increased transpiration rates and reduced leaf diffusive resistance as more soil moisture became available for plant growth. Mulching effects on the different parameters measured, however, were significant over the untreated surface but not over the imprinted surface. The imprinted surface, as a matter of fact, was more effective than mulching in all the parameters measured.

The effect of cover treatments on soil moisture appeared to be influenced by the differences in root systems of legumes and grasses, and by the differences in their water requirements. Relatively less soil moisture was recorded for legumes compared to grasses. The effects of cover treatments on growth parameters and final yield was largely affected by time of sampling. During the summer, legumes outyielded grasses, but the opposite was true in the fall.

It could be concluded from the results of this study that:

1. Surface imprintation by land or hand imprinter has proven to be an effective way of soil surface manipulation to revegetate arid lands.

83

84

2.

Introduction of forage leguminous species, like spreader alfalfa and sweet clovers, into predominantly grass rangelands proved possible. It is worth mentioning, however, that protection of young seedlings from grazing by jackrabbits and other range pests through fencing is essential.

3.

The problem of jackrabbits and other range pests could be minimized by planting larger areas.

4.

The relative performance of grasses and legumes as a mixture is affected by time of sampling. Grasses tend to be superior over legumes in the fall and the opposite is true in the summer.

Differences in growth peaks and dormancy periods for each group accounts for this seasonality. The seasonality pattern should be an advantage to growers and ranchers since it insures forage availability all the year round. Moreover, having grasses and legumes in a mixture insures a more uniform and deeper utilization of water and minerals in the soil profile, improves forage quality through symbiotic nitrogen fixation by legumes which benefit grasses, and reduces the occurrence of bloating of livestock.

APPENDIX

A

EFFECTS

OF

TREATMENTS

ON PLANT

HEIGHT

AT THE ORACLE AGRICULTURAL CENTER FOR

THE

DIFFERENT SAMPLING

DATES

85

Table A.1. Effects of treatments on grass height (cm) at the Oracle

Agricultural Center (First Sampling on 9/29/1984).

86

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Sutface

Mulched Surface

Imprinted-Mulched

Surface

123.7

2 c

091.7 a

103.3 ab

117.0 bc

Column Means

3

108.9 a

Grass

Legume Mixture Row Means

1

126.7 c

113.7 bc

116.3 bc

121.3 c

119.5 b

125.2 b

102.7 a

109.8 a

119.2 b

1

Surface treatment means

2

Individual treatment means

3

Cover treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatments means are not significantly different at the 5% level according to the SNK method.

Table A.2. Effects of treatments on grass height (on) at the Oracle

Agricultural Center (Second sampling on 5/22/85).

87

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

56.0

2 abc

Untreated Surface

43.0 a

Mulched Surface

47.3 ab

Imprinted-Mulched

Surface

53.7 abc

Column Means

3

50.0 a

Grass

Legume Mixture

60.0 bc

43.0 a

59.0 bc

63.3 c

56.3 b

Row Means

1

58.0 b

43.0 a

53.2 b

58.5 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter-Es)-within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Table A.3. Effects of treatments on grass height (an) at the Oracle

Agricultural Center (Third sampling on 8/5/85).

88

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

104.3

2 b

084.3 a

091.7 ab

102.3 b

Column Means

3

095.7 a

Grass

Legume Mixture

122.3 c

105.0 b

106.0 b

122.3 c

113.9 b

Row Means

113.3 b

094.7 a

098.8 a

112.3 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

1

Table A.4. Effects of treatments on grass height (cm) at the Oracle

Agricultural Center (Fourth sampling on 10/12/85).

89

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

104.0

2 c

070.0 a

Mulched Surface

083.7 ab

Imprinted-Mulched

Surface

102.3 c

Column Means

3

090.0 a

Grass

Legume Mixture

124.7 d

094.3 bc

108.0 c

126.0 d

113.3 b

Row Means

114.3 c

082.2 a

095.8 b

114.2 c

1

Surface treatment means

3

Cover treazment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

1

APPENDIX

B

EFFECTS OF TREATMENTS ON PLANT HEIGHT

AT THE CAMPUS AGRICULTURAL CENTER FOR

THE DIFFERENT SAMPLING DATES

90

Table

B.1. Effects of treatments on grass height (cm) at the

Campus Agricultural Center (First sampling on

5/15/84).

91

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

13.2 -

2 ab

07.0 a

13.3 ab

13.2 ab

Column Means

3

11.7 a

Grass

Legume Mixture

37.5 b

31.8

31.7

28.8 ab ab ab

32.4 b

Row Means

25.3

19.4

22.5

21.0

NS

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

1

Table

B.2. Effects of treatments on grass height (cm) at the Campus

Agricultural Center (Second sampling on

6/28/84).

92

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

076.0

Untreated Surface

065.0

Mulched Surface

075.0

2

Imprinted-Mulched.

Surface

077.0

Column Means

3

073.3

Grass

Legume Mixture

095.3

957.3

077.3

106.7 NS

084.2 NS

Row Means

035.7

061.2

076.2

091.8 NS

1

Surface treatment means

3

Cover treatment means

2

Individua3. treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNI( method.

1

Table

B.3. Effects of treatmants on grass height (cm) at the Campus

Agricultural Center (Third sampling on

8/20/85).

93

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

120.7

2 bc

100.0 ab

114.3 bc

115.0 bc

Column Means

3

112.5

Grass

Legume Mixture

125.0 c

086.0 a

092.0 a

127.3 c

107.8 NS

Row Means

122.8 b

093.3 a

103.2 a

121.2 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the

5% level according to the SNI( method.

1

Table B.4. Effects of treatments on grass height (cm) at the Campus

Agricultural Center (Fourth sampling on 10/24/84).

94

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

Mulched Surface

Imprinted-Mulched

Surface

133.0

2 bc

109.3 ab

126.7 bc

127.3 bc

Column Means

3

124.1

Grass

Legume Mixture

144.3 bc

089.0 a

130.0 bc

156.3 c

129.9 NS

Row Means

138.7 b

099.2 a

128.3 b

141.8 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

1

Table B.5. Effects of treatments on grass height (cm) at the Campus

Agricultural Center (Fifth sampling on 5/22/85).

95

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

102.0

2 b

Untreated Surface

073.0 a

Mulched Surface

080.0 a

Imprinted-Mulched

Surface

076.0 a

Column Means

3

082.8 a

Grass

Legume Mixture

Row Means

1

113.0 b

086.0 a

108.0 b

115.0 b

105.5 b

107.5 c

079.5 a

094.0 b

095.5 b

1

Surface treatment means

2

Individual treatment means

3

Cover treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Table

B.6. Effects of treatments on grass height (cm) at the Campus

Agricultural Center (Sixth sampling on 8/5/85).

96

Surface

Tr

Cover

Tr

Grass

Pure Stand

Imprinted Surface

Untreated Surface

134.6

2 c

Mulched Surface

092.0 a

106.7 b

Imprinted-Mulched

Surface

136.0 c

Grass

Legume Mixture

138.3 c

115.0 b

113.7 b

131.7 c

Row Means

136.5 b

103.5 a

110.2 a

133.8 b

Column Means

3

117.3 a 124.7 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

.

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

1

APPENDIX

C

EFFECTS OF TREATMENTS ON PERCENT CANOPY

COVER AT THE ORACLE AGRICULTURAL CENTER

FOR THE DIFFERENT SAMPLING DATES

97

98

Table C.I. Effects of treatments on percent canopy cover at the

Oracle Agricultural Center (First sampling on 9/29/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Lmprinted-

Mulched

Surface

Grass

2

89c

55 ab

71 abc

78 abc

Mixture

88 c

45a

73 abc

80 abc

Legumes

81 bc

45a

71 abc

88 c

Means

3

73

1

Surface treatment means

3

Cover treatment means

2

72 72 NS

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual trEatment means are not significantly different at the 5% level according to the SNK method.

Row

Means

1

86 c

48a

72 b

82 c

99

Table C.2. Effects of treatments on percent canopy cover at the Oracle

Agricultural Center (second sampling on 5/22/85).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Grass

90

2 fg

92 g

36 ab 28a

70 d

82 def

Mixture

75 de

90 fg

Legumes

85 efg

48 bc

55 c

89 d

38a

Row

Means

1

67 b

82 def 84c

Column

Means 3

69 ab

1

Surface treatment means

3

Cover treatment means

71b

67a

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

100

Table C.3. Effects of treatments on percent canopy cover at the Oracle

Agricultural Center (Third sampling on 8/5/85).

Grass

Mixture Legumes

Row

Means

1

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

092

2 abc

048 a

067 a

087 abc

095 bc

060 a

080 ab

097 bc

100 c

061 a

073 ab

093 bc

096 b

Column

Means 3

073

1

Surface treatment means

3

Cover treatment means

2

083

082 NS

Individual treatment means

Figures followed by the same letter(s) witnin the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

057 a

073 a

092

D

Table C.4. Effects of treatments on percent canopy cover ac the

Oracle Agricultural Center (Fourth sampling on 10/12/85).

101

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means

3

Grass

098

2 b

050a

078a

093b

080

Mixture

100 b

060a

083a

100 b

086

Legumes

099 b

057a

072a

098b

081 NS

'

Surface treatment means

3

Cover treatment

.

means

2 Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual =eatment means are not significantly different at the 5% level according to the SNI( method.

Row

Means

099 c

055a

078b

097c

1

APPENDIX D

EFFECTS OF TREATMENTS ON PERCENT CANOPY

COVER AT THE CAMPUS AGRICULTURAL CENTER

FOR THE DIFFERENT SAMPLING DATES

102

103

Table D.1. Effects of treatments on percent canopy cover at the Campus

Agricultural Center (first sampling on 5/15/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

32 2 a

40 ab

25a

43 ab

Mixture

84b

72 ab

71 ab

74 ab

Legumes

89b

75 ab

81 ab

66 ab

35 a 75b

78b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Row

Means

1

69

63

59

61 NS

104

Table D.2. Effect of treatments on percent canopy cover at the Campus

Agricultural Center (second sampling on 6/28/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface.

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

2

076 a

068 a

075 a

060a

070a

Mixture

100 b

100 b

100 b

096b

099b

Legumes

100 b

100 b

100 b

100 b

100 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Row

Means

1

092

089

092

085 NS

105

Table

D.3. Effects of treatments on percent canopy cover at the

Campus

Agricultural Center (third sampling on 8/2/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

100

2

100

100

100

100

Mixture

100

100

100

100

100

Legumes

100

100

100

100 NS

100 NS

1

Surface treatment means

.

3

Cover treatment means

2

Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the

5% level according to the

SNK method.

Row

Means

1

100

100

100

100 NS

106

Table D.4. :ffects of treatments on percent canopy cover at the Campus

Agricultural Center (fourth sampling on 10/24/84).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

2

100 b

070 a

091 b

096 b

089 a

Mixture

100 b

092 b

100 b

100 b

098b

Legumes

100 b

100 b

100 b

100 b

100 b

1

Surface treatment means

3

Cover treatment means

2

Individual treatment means

Figures followed by th a same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the

SNK method.

Row

Means

1

100 b

087 a

097 b

099 b

Talde D.5. Effects of treatments on percent canopy cover at the

Campus Agricultural Center (fifth sampling on 5/22/85).

107

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means 3

Grass

078

2 ab

058 a

068 ab

078 ab

071 a

Mixture

100 c

076 ab

098 c

100 c

094b

Legumes

100 c

075 ab

086 b

100 c

090b

1

Surface treatment means

3

Cover treatment means

2 Individual treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Row

Means

1

093 c

070 a

084 b

093c

108

Table

D.6.

Effects of treatments on percent canopy cover at the Campus

Agricultural Center (sixth sampling on 8/5/85).

Surface

Tr

Cover

Tr

Imprinted

Surface

Untreated

Surface

Mulched

Surface

Imprinted-

Mulched

Surface

Column

Means

3

Grass

100

2 b

063 a

085 a

100 b

087

Mixture

100 b

055 a

076 a

100 b

083

Legumes

100 b

053 a

071 a

100 b

081 NS

1

Surface treatment means

2

Individual treatment means

Cover treatment means

Figures followed by the same letter(s) within the row means, the column means, or the individual treatment means are not significantly different at the 5% level according to the SNK method.

Row

Means

1

100 c

057 a

078 b

100 c

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