NITRATE DISAPPEARANCE IN SOIL-WATER PERCOLATES by Bassam Saad Nimry

NITRATE DISAPPEARANCE IN SOIL-WATER PERCOLATES by Bassam Saad Nimry
NITRATE DISAPPEARANCE IN
SOIL-WATER PERCOLATES
by
Bassam Saad Nimry
A Thesis Submitted to the Faculty of the
DEPARTMENT OF AGRICULTURAL CHEMISTRY AND SOILS
In Partial Fulfillment of the Requirements
For the Degree of
MASTER OF SCIENCE
In the Graduate College
THE UNIVERSITY OF ARIZONA
1967
STATEMENT BY AUTHOR
This thesis 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 thesis are allowable without
special permission, provided that accurate acknowledgement 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 judgement 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:
APPROVAL BY THESIS DIRECTORS
This thesis has been approved on the date shown below:
GORDON R. DUTT
Assistant Professor
Agricultural Chemistry and Soils
THOMAS H. McINTOSH
Assistant Professor
Agricultural Chemistry and Soils
-Qr-Date
/57
ACKNOWLEDGEMENTS
The author wishes to express his gratitude to Dr. Gordon R. Dutt
and Dr. Thomas H. McIntosh for their guidance and encouragement throughout
the course of the investigation and also for their patient review and
helpful criticism of the manuscript.
The author is grateful to USAID and the Jordan government for
the financial aid which made this study possible.
Appreciation for the grant-in-aid which helped support this
investigation is extended to the Phillips Petroleum Company and Arizona
Agricultural Experiment Station.
The author wishes to thank Mr. Michele Capacchione for the
analysis of the Organic-N fraction in one of the experiments.
Special appreciation is expressed to the author's wife, Ferouz,
for her sacrifice and constant encouragement.
111
TABLE OF CONTENTS
Page
INTRODUCTION
1
LITERATURE REVIEN
3
MATERIALS AND EXPERIMENTAL PROCEDURES
8
Materials
8
Experimental Procedure
13
Analytical
13
Short Column Studies
13
Percolation Studies
14
16
RESULTS
Nitrate Movement
16
Soil Moisture Potential
21
Nitrate
Recovery
21
Oxygen and Nitrogen
25
Redox Potential and p[i Values
30
DISCUSSION
34
SUNNARY AND CONCUJSION
46
LITERATURE CITED
4
APPENDIX A
51
Calculation of Irrigation and Fertilizer Need
52
53
APPENDIX B
Tables
54
iv
LIST OF TABLES
Table
Page
Treatments Employed in Short Column Studies
14
Recovery of Nitrate Percolating Through Columns Without
Sugar Addition
23
Disappearance of NO3-N as Related to the Incubation Time
and the Amount of Sugar and NO3-N Added
24
Nitrate Used in the Decomposition of Added Sugar
43
Redox Potential, pH and Tension Values in the One-Layer
Short Column During the Various Treatments
54
Redox Potential, pH and Tension Values in the One-Layer
Long Column During the Two Treatments
57
Nitrate Recovery in the Effluent Water of the Two Long
Columns During the Two Replicates of Treatment 7
.
.
62
Nitrate Recovery in the Effluent Water of the Two Long
Columns During the Two Replicates of Treatment 8
.
.
63
.
.
Nitrate Recovery in the Effluent Water of the Short OneLayer Column Treatments
64
02/N2 Peaks in Long Columns (cm) During Treatments 7 and
8
65
V
LIST OF ILLUSTTION3
Figure
Page
Experimental Design of Columns U5ed in the Study
10
Instrumentation of the Mohave Soil Layer
12
Nitrate Recovery From the Two Long Columns During the
Incubation and Leaching Periods of Nitrate Alone
.
17
Volume of Effluent Water From the Two Long Columns During
the Incubation and Leaching Periods of Nitrate ± Sugar
.
18
Nitrate Recovery From the Two Long Columns During the
Incubation and Leaching Periods of Nitrate ± Sugar
.
.
19
Breakthrough Curves for Nitrate in the Two Long Columns.
.
20
.
7,
.
.
Soil Moisture Tension Above and Below the Mohave Soil
Layer During the Incubation and Leaching Periods of
Nitrate + Sugar
22
The Ratio of 02 in Column in the Long Sand Column During
02 in Air
the Incubation and Leaching Periods of Sugar + Nitrate
The Ratio of 02 in Column in the One-Layer Long Column
02 in Air
During the Incubation and Leaching Periods of Sugar +
Nitrate
12.
26
27
The Ratio of N2 in Column in the Sand Column During the
N2 in Air
Incubation and Leaching Periods of Sugar + Nitrate
28
The Ratio of N2 in Column in the One-Layer Long Column
N2 in Air
During the Incubation and Leaching Periods of Sugar
+ Nitrate
29
Redox Potential Values at Platinum Electrodes 1-4
One-Layer Long Column During the Incubation and
Leaching Periods of Sugar + Nitrate
31
.
11,
.
vi
in the
vii
LIST OF ILLUSTRATIONS- -Continued
Figure
13
14
Page
Redox Potential. Values at Platinum Electrodes 5-8
in the One-Layer Long Column During the
Incubation and Leaching Periods of Sugar + Nitrate
32
The Relative Concentration of Sugar and Nitrate in the
Effluent Water
41
ABSTRACT
The objective of this study was to evaluate potential denitrification in nitrate-containing waters percolating through the soil.
Laboratory studies were conducted in 5bil columns.
The extent of deni-
trification was studied under two different soil conditions, 1.
sand, and 2.
Pure
Pure sand interbedded, at one location, with 15 centimeters
of a finer texture soil material.
The treatments included the addition
of nitrate alone, sugar (sucrose) alone and sugar + nitrate.
Under the conditions of the experiments performed, no nitrate
disappeared without the presence of an energy source.
Based on this find-
ing, the nitrate loss was attributed to respiratory nitrate reduction
and immobilization by microorganisms during the oxidation of the added
sugar.
In the treatments with different combinations of sugar and nitrate
the total amount of NO3-N that disappeared varied between 14 and 37 percent.
The amount of NO3-N that disappeared depended on the concentrations
of both NO3-N and sugar added.
It was concluded from the gas analyses, redox potentials and
pH values, that the distribution of sugar and nitrate when added with
water took place above the anaerobic zone that developed beneath
the soil layer.
This conclusion meant that the major nitrate utilization
by microorganisms took place in an overall aerobic condition, where only
the small anaerobic pores exerted the most influence on nitrate loss.
INTRODUCTION
The continuous increase in irrigated areas and use of nitrogenous
fertilizers have enhanced the possibility of contamination of ground
water with nitrate.
When nitrates begin to exceed a concentration of
fifty milligrams per liter in domestic water, a health hazard exists (26).
The fate of large amounts of nitrogenous fertilizers applied
under irrigated conditions is largely unknown.
Of particular interest,
was an observation by Dutt1- that drainage waters from an intensively
fertilized and irrigated area near Yuma, Arizona were very low in
nitrates.
The low nitrate content of the drainage water in Yuma, Arizona
may be attributed to one or more of the following reasons:
(1)
Nitrates
are diluted in irrigation and ground waters to such an extent as to make
them undetectable.
(2)
Nitrates are retained within the soil.
(3)
Nitrates are, at least, partially lost through denitrification processes.
Under natural conditions in the Southwest, the soil surface dries
rather quickly after the addition of water,
Microbial activity at the
surface becomes restricted, allowing soluble organic material and nitrate
to accumulate.
In addition, plant residues may also accumulate at the
surface either through natural leaf fall or artificial addition.
Upon
wetting by rain or irrigation, appreciable amounts of soluble organic
materials may percolate downward through the soil profile.
If nitrate,
Agricultural Chemistry
Gordon R. Dutt, Associate Professor.
1.
and Soils, University of Arizona, Tucson, Arizona.
1
2
organic energy sources, and restricted 02 supply occur together, then
denitrification is possible.
The above conditions could act solely or in combination to
reduce the amount of nitrates reaching the ground water table.
Laboratory studies were conducted using conditions similar to
those at Yuma, with the objective of evaluating denitrification as one
of the major factors that might influence the amount of nitrate reaching
ground water.
LITERATURE REVIEW
Loss of nitrate by leaching or denitrification is an important
economic factor in crop production on one hand, and the possible contamination of ground water with nitrates is an important health factor
on the other hand.
The movement of nitrates in soils has been investi-
gated by a number of workers (17, 19, 31, 32).
Their findings, experi-
mentally and theoretically, point that nitrates are very mobile, move
readily with the advancing water front, and have little affinity for
soil colloids.
Dyer (17) working with Panoche soils in the San Joaquin
Valley, California found that the maximum concentration of nitrates
occurred at 4.6 meters and 9.2 meters in unirrigated soil and associated
irrigated soils respectively; however, nitrates were present in appreciable
quantities to a depth of 15 meters,
Wetselaar (32), working in tropical
soils under 61 centimeters per year of rainfall, found that the maximum
concentration of nitrate was at a depth of 61 to 122 centimeters in
nearly all soils investigated.
He also found that during drying phases,
nitrate increased in the surface layers and decreased in the sub-surface
layers.
The rainy period resulted in a reverse effect.
Maximum accumu-
lation during the drying phase occured in the 0 - 5 centimeters layers.
Wetselaar (31) concluded that the high nitrates content generally found
in the surface of tropical soils after a dry period was due to upward
capillary movement of nitrates formed biologically in the sub-surface
during periods of adequate water content.
3
The nitrates accumulated under
4
the zone where the physical continuity of the soil was broken.
Jewitt
(19) working on Gezira soils in Sudan found an unusual accumulation of
nitrates at 1.8 meters depth.
The upper 1.2 meters contained low
nitrate concentration of 1 ppm while a significant accumulation ranging
from 14 to 40 ppm NO3 was found at depths of 1.5 to 1.8 meters.
The nitrate status in the soil is complicated by biological
activities which vary markedly with soil conditions.
nutrient under normal soil conditions.
Nitrate is a plant
Under anaerobic microbial oxi-
dation of an organic substrate, NO3 then becomes the terminal electron
acceptor.
Janssen and Metzger (18) investigated the fate of nitrates
under flooded and unflooded conditions using manure as a source of energy.
In the unflooded soil there was an accumulation of nitrates while in the
flooded soil nitrates rapidly disappeared.
Cady and Bartholomew (12)
found the N2 accounted for 83 to 95 percent of the isotopically labelled
nitrates added to a soil maintained under anaerobic conditions.
Broadbent
and Stojanovic (9) found under anaerobic conditions that negligible
amounts of nitrates were converted to ammonia.
Allison and Klein (2)
showed in laboratory experiments using sucrose as a source of energy, that
in two days the microorganisms immobilized 3.7 to 4.4 percent nitrogen.
The readily available source of energy for microbial activity under
field conditions depends mainly on agricultural practices in an area, and
on natural vegetation if the area is uncultivated.
Brown, (10) investi-
gating the water solubility of plant residues, found that the water
soluble fraction depended not only on the type of plant but also on the
part of plant extracted.
The water-soluble fraction was 24.4 and 11.6 per-
cent for whole soybean plant and for soybean straw respectively.
The water
,oluble fraction, it was found, contained an average of 3.5 percent nitrogen.
'talcoia and McCraken (20) investigating the organic matter content of a
simulated canopy drip of evergreen forest, found that approximately 100
lb per acre per year of organic matter were contributed to the soil as
canopy drip.
Of this amount, approximately 5 to 20 lb per acre per year
are in the form of polyphenols and reducing sugars.
The rate at which denitrification takes place is usually very
rapid.
Breinrier and Shaw (4) reported that in the presence of an energy
source and under anaerobic condition, 1,000 ppm of nitrate nitrogen were
lost in three days.
Broadbent (7) also found that NO3-N was lost at the
rate of 56 ppm per day where clover was used as an energy source.
Cooper
and Smith (14) showed that a decrease in temperature has a great influence
on denitrification.
fold.
A drop of 100 C increased denitrification time two-
A decrease in initial concentration of NO3 did not change the
overall rate of denitrification.
Bremner and Shaw (5) demonstrated that
the critical moisture level above which denitrification occurred and below
which practically none occurred was about 60 percent of the water holding
capacity of the soil.
They also found that denitrification was greatly
affected by the P11 value of the soil with maximum occurring at a neutral
to alkaline reaction.
The true mechanism of denitrification remains a matter for speculation.
Nitrite, nevertheless, is an intermediate in the process.
Smith and Clark (29) investigating volatile losses from soils containing
nitrite and ammoniuta ions found that in the presence of oxygen, the
tendency for nitrite to convert chemically to nitrate was three to four
times as strong as for it to react with awmoniuin ion.
The conversion
6
to nitrate was even more rapid in aerobic soil.
They believed that the
reduction of nitrite to nitrogen gas is accomplished by some component
(probably chemical) of the soil complex.
These results were supported
by the findings of Wullstein, et al (33) and also by Reuss and Smith (27).
The former investigators believe that the break down of nitrite in soils
is due to an oxidation-reduction mechanism whereby exchangeable heavy
metals may reduce nitrite to nitric oxide.
The latter investigators
observed an increase in NO3 when NO2 was added to an acid soil.
Little work has been done on the relationship between denitrification and oxidation-reduction potential of soils.
Patrick (23),
working with submerged soils, found that nitrate reduction rates were
dependent on the redox potential of the soil.
Decreasing the redox
potential resulted in an increase in nitrate reduction.
He also
demonstrated that the redox potential at which nitrates became unstable in the soil was +338 millivolts at a pH value of approximately
5.1.
Above this potential nitrates accumulated and below this nitrates
disappeared.
De Gee (16) working in rice fields near Boger (Java) found
that in the uppermost layers of flooded soils, redox potential reached
+510 to +570 millivolts; somewhat deeper at 7 to 16 centimeters it fell
to 60 millivolts; in deeper layers the potential rose again.
unirrigated soil the redox potential was +600 millivolts.
In a similar
It was also
found in the Fergana Valley (30) that sharp changes occur in the redox
potential due to furrow irrigation.
The potential which reaches +420
to +460 millivolts prior to irrigation, dropped to +230 millivolts one
day after irrigation.
Improving soil aeration after drying restored the
redox potential to its previous value, but only after 13 to 15 days.
7
Pearsalls' data (25) pertaining to British soils shows that peaty soil
horizons are more acid (pH 3.7-3.45) when well aerated (+595 to +500
millivolts) and become less acid (P11 5.51) when aeration is poor (+165
millivolts) due to excessive moistening.
Patrick and Wyatt (24) investi-
gating soil nitrogen losses as a result of alternate submergence and
drying under laboratory conditions found that the redox potential rapidly
decreased and reached very reducing values of -300 millivolts when the
soil was submerged for the first time.
After the soil was dried to
optimum moisture and then submerged again, the potential did not decrease
as rapidly or reach as low a value as when first submerged.
The results of these thvesigators regarding the movement and
disappearance of nitrate indicate that the change in redox potential and
p11 is dependent upon the initial soil conditions, the soil type, and the
treatment.
All the results, nevertheless, point to the fact that in the
presence of an energy source under anaerobic conditions, part of the
nitrates are lost in the form of gases,
The terms aerobic and anaerobic
were not defined and thus became an estimated condition.
How much
denitrification takes place under natural condItions is still open to
question.
MATERIALS AND EXPERIMENTAL PROCEDURES
Materials:
The two soil materials used were 60 mesh sandblasting quartz
sand, obtained commercially2 and Mohave soil taken from tne top 6 inches
of a virgin site (11).
The quartz sand was selected for this study
because of its similarity in texture to the soils of the Yuma area, and
the absence of organic matter which could supply energy for denitrification
or result in mineralization of organic nitrogen.
The particle size frac-
tions of the Mohave soil material were 77 percent sand, 15 percent silt
and 8 percent clay.
The organic matter content was 0.22 percent and
the P11 value as a 2:1 paste was 6.9.
sand fraction was 3.19 percent (ibid).
The heavy mineral content in the
The particle size fractions of
the quartz sand were 60 percent, 0.25 ram; 41.3 percent, 0.15 mm; 7.0
percent, .05 mm; and 1.2 percent, .05 ram.
The soil was packed into columns of different lengths.
of experiments were conducted.
In the preliminary set of experiments,
a Plexiglas column 30.5 cm long and 8.6 cm I.
used.
Two sets
D.
(inside diameter) was
A P.V.C. (Polyvinyl Chloride)columnl33Cm long and 8.6 cm I.
was employed in the simulated soil percolation studies,
The columns were
sealed at one end with a Plexiglas plate having a 3/3 inch 0. D.
(outisde
diameter) threaded hole into which a 1/4 inch 0. D. copper tube was
2.
Crystal Silica Company, Oceaside, California.
D.
9
fitted through a 3/8 inch 0. D. compression tubing connector.
The 1/4
inch 0. D. copper tube which provided the outlet was bent into a U shape
to restrict air entry into the column and also to establish atmospheric
pressure at the bottom of the column.
The quality of water used in these experiments was comparable
to that of the Colorado River.
As made up in the laboratory it had the
following composition in milliequivalents per liter: 3.42 Ca, 5.50 Na+,
1.2 Mg, 3.00 HC0. 2.56 C1
and 5.04 SOZ.
Nitrate added to the soil columns was in the form of Ca (NO3)2.
4H70.
Sugar (sucrose) was added as the energy source,
The columns utilized in this study were provided with gas
sampling probes, calomel reference electrodes, glass electrodes and
platinum electrodes (Fig. 1).
The gas sampling probes, the glass elec-
trodes, and the porous cups were inserted into the soil through rubber
stoppers.
The gas sampling probes were similar to those made by Ritchie (28).
Beckman #39167 glass electrodes were used.
The platinum electrodes were
5 cm in lengths of 16 guage platinum wire.
The platinum electrodes were
inserted 3.75 cm into the column and sealed with epoxy cement.
The calomel electrodes were constructed in the following manner.
A saturated KC1 solution in 5 percent agar agar was prepared and kept in
a 45°C temperature bath to prevent it from solidifying.
Glass tubes
4 mm I. D. and 15 cm long with a capillary tip were then half-filled with
this solution by suction.
Upon solidification of the solution within
the tubes, a saturated mixture of mercurous chloride, mercury and KC1
in asbestos fibers was carefully packed into the tubes to within 1 cm of
Figure 1.
Experimental Design of Columns
Ussd in the Study.
10
COL. I
COL. 2
5m
-
SHORT COLUMN
0
I0
0
aD
z
(I)
0
ci)
Mohave
1E
0
0
_i
_LQD
I
#2
Lt)_#3
!Q
T5
-t---- E
0
U)
See Fig. 2
'I
c'J
tI2
D Glass Electrode ; 0 Reference Electrode;
- Platinum Electrode; ® Gas Sampling Probe)
Figure 1
11
the top and pressed firmly against KC1 saturated agar agar.
The top 1 cm
was then filled with mercury and a wire inserted and the tube sealed.
The tubes were immersed in water and left for a week to develop a constant
potential.
These calomel calls were used as reference electrodes for
measurements of
H vué and redox potential.
Contact between tue soil and the reference electrode was accomplished through a Pharmaseal 352 plastic "T" tubing connector.
end of the plastic !tTP
soil.
One
was connected to a porous cup imbedded in the
The reference electrode was inserted through a rubber tubing that
acted as a seal into another opening o
the 'T.
Suction was then applied
to the third opening of the connector and water drawn from the soil,
thus establishing contact with the soil.
was then connected to the third
TTt
A 1/3 inch 0. D. plastic tubing
opening and employed as a "U" tube
manometer to measure soil moisture potential.
(Fig. 2).
Measurements of pH value and redox potential were made with a
Beckman Expanded Scale
H meter.
To avoid continuous standardization,
the instrument was arbritarily set to 0 at zero EMF and measurements
were made from this point.
At the completion of the experiment, the
glass electrodes were taken out of the column, standardized, and the
necessary corrections made.
A Microtek gas chromotographic unit4 type DSSO 171 DPT with a
thermal conductivity bridge and W-2 type detector filaments was used
Pharmaseal Laboratories, Glendale 1, California.
Microtek Instruments, Inc., P. 0. Box 15409, Baton Rouge,
Louisiana.
Figure 2.
Instrumentation of the
Mohave Soil Layer
12
'f0
12
2-6. Platinum Electrodes; 7. Porus Cupsj 8. Rubber Tubing;
9 "T' Tubing Connector) 10. Reference Electrode;
II. 00 Rubber Stopper 12. v8 Nylon Tubing; 13. Glass
Electrode; l4.O Rubber Stopper) 15. Gas Sampling
Probe
Figure 2
13
for gas analysis.
The chrouzotographic column consisted of a 1/4 inch O.D.
10 foot copper tube.
Two feet of the column was packed with 30/60 sieve
silica gel and the other 8 feet with Linde 5A molecular sieve.
The gas
was drawn from the soil column through the gas probes with a gas tight
one milliliter #1001 Hamilton syringe5 and needle #72822.
for the gas analysis were as follows:
The conditions
carrier gas-Helium; flow rate
60 cc/mm; attenuation 128; oven temperature 90°C; inlet temperature
200°C; bridge temperature 250°C; bridge current 170 milliamperes; volume
of sample 300 microliters.
Experitnenta 1 Procedure:
Analytical:
Two sets of experiments were conducted using two
different column lengths.
In both sets of experiments measurements were
made of redox potential and pH.
NH2-N and (N0
± N0) -N.
The effluent water was analyzed for
In the long column experiment, gases within
the columns were analyzed for 02 and N2, by gas chromotography.
For determination of N114-N, (N05 ± N0)-N and organic - N, the
inicrokjeldahl method described by Bremner (3) was used.
Sugar was determined using the anthrone method (6).
Short Column Studies:
The short column was used during
development of the instrumentation.
The treatments of the short column
are outlined in Table 1.
5.
The Hamilton Company, P. 0. Box 307, Whittier, California.
14
Table 1.
Treatment
Treatments Employed in Short Column Studies.
Water Applied
ml
NO3-N Added
Sugar Added
Incubation Period
mg
mg
Hr.
0
2000
0
0
5
1
670
255.5
0
24
2
670
0
272.6
24
3
670
255.5
272.6
24
4
670
257
272.6
48
5
670
130
272.6
24
6
670
130
545.2
24
In each experiment, the solution containing nitrate and/or
sugar was added to the column and permitted to drain freely.
After a
specified time (incubation time) the column was leached with simulated
Colorado river water continually until N0
was no longer detectable in
the effluent.
Percolation studies:
mesh quartz sand (column 1).
One P. V. C. column was packed with 60
The other column (column 2) was similarly
packed with 60 mesh sand except that a 15 cm long layer of Mohave soil
tuaterial was placed at a depth of 120 cm from the top column (Fig. 1).
The columns were first leached with 5 liters of synthetic Colorado river
water. After the precondition leaching, two experiments were performed.
Each experiment was repeated using the same columns.
In the first experiment (treatment 7), nitrate alone was added
to the columns while in the second (treatment 8), nitrate and sugar were
15
added together.
The experiments consisted of two phases.
The first phase
consisted of adding 670 ml of treatment solution and allowing the solution
to percolate and freely drain from the columns for three days (incubation
Mter that, the columns were leached (second phase) with 500 ml
period).
increments of synthetic Colorado river water added every 12 hours for
three days.
The effluent was collected in an ice bath to restrict biological
activity.
The effluent collected during each 12 hr period was measured
and analyzed for organic - N, (NOj + N0) - N and NH-N.
The organic -
N in the sand column effluent was determined only during the second
experiment.
Redox potential and
were measured every four hours.
Gas
samples were taken every twelve hours prior to the addition of the
water increments
RESULTS
Nitrate Movement:
The nitrate recovery when nitrate alone was added to the two long
columns is shown in Figure 3.
The volume of effluent water and the
nitrate recovery for the same columns, when sugar and nitrate were added
simultaneously, are shown in Figures 4 and 5.
It is noted that the
shape of the nitrate recovery curves in both Figures 3 and 5 are similar
except the peaks decreased in height when sugar was incorporated.
This
decrease in peak heights corresponded to the disappearance of nitrate
that took place when sugar was included.
The first effluent water resulting from the addition of the
treatment solution contained no nitrate.
The initial flow rate of water
in the sand column was always higher than that of the one-layer column.
This difference in the flow rates of water retarded the elution of the
nitrate twelve hours in the one-layer column as compared to the sand
column (Fig. 3).
In Figure 6, the breakthrough curves are plotted for nitrate in
the two long columns.
Comparing the two curves, one can see that the
concentration ratio does not build up as fast in the effluent solution
of the sand column as in the one-layer column.
Because of the disappear-
ance of nitrate in the layered column, the curve did not reach unity.
16
Figure 3.
Nitrate Recovery From the Two Long
Columns During the Incubation and
Leaching periods of Nitrate Alone.
0
ir()
E
0
10
20
30
Solution added
Treatment N0
I
2
3
4
p
0
,
5
I
I
I
7
8
Figure 3
9
Treatment N0
Solution added
67OmI
11ME - DAYS
6
HH
500 ml Water Increment
added at each arrow
10
II
I
I
I
I
I
I
12
- Col. I (Sand)
*
13
14
--0-- CoI.IE (One Layer)
-
0
I
I
I
I
I
I
I
I
I
HH
added at each arrow
500 ml Water Increment
Figure 4.
Water From the Two
Long Columns During the Incubation and
Leaching Periods of Nitrate + Sugar.
Volume of Effluent
LU
UU-
J
LU
F-
>
J
0
E
100
20
300
400
500
600
ii,
added
Sugar - N0
7
8
Figure
4
TiME- D4YS
6
Solution added
670 ml
500 ml Water Increment
added at each arrow
Sugar + N0
9
10
N
H
12
13
14
--0-- One-Layer Cal.
-- Sand Col.
500 ml Water Increment
added at each arrow
Figure 5.
Nitrate Recovery From the Two Long
Columns During the Incubation and
Leaching Periods of Nitrate + Sugar
2:
rN)
0
2:
E
LU
LL
LL.
-J
LU
20
0
1
F-3°
LU
added
Sugar N0
I
2
3
4
i
I
5
6
7
8
Figure 5
TIME -DAYS
0\\
9
500 ml Water Increment
added at each arrow
Sugar + N0
Solution added
670 ml
10
:
II
II
12
13
14
I S Sand Col.
-J D
,,/
/
1
H
500 ml Water Increment
added at each arrow
Figure 6.
Breakthrough Curves for Nitrate
in the Two Long Columns
20
0
o.9
O.8
zIJJO.6
0z
0Q5
0
ir()
/
/
/
/
/
/
/
,0
/
/
/
A
0.4
0
02
LiJ
/
/
/
/
-A -A- Sand Col.
00 One-LayerCol.
J
uJ
0
200
600
1000
1400
1800
VOLUME of EFFLUENT (ml.)
Figure 6
2200
21
Soil Moisture Potential:
The soil moisture potential in centimeters during the incubation
and leaching periods of sugar ± nitrate above and below the Mohave soil
layer in the one-layer column are plotted in figure 7.
At the start of
the experiment, the soil moisture potential in both columns was about
-30 cm,
During the incubation periods, the soil moisture potential became
less negative and ranged between -30 and -3 cm.
Immediately after the
addition of the treatment solution the potential changed to about
-12 cm.
3 to
At the end of the three days incubation period the moisture
potential returned to about -30 cm.
Tue most significant increase in
the potential took place during the leaching period reaching maximum
value of +13 cm.
It was mentioned earlier that the initial flow rate of water in
the sand column was always greater than the one-layer column.
With
further addition of water the flow rates in both columns approached each
other.
The head build-up above the Mohave soil layer increased the flow
rate and made it comparable to that of the sand column.
Nitrate Recovery:
From 95 to 98 percent of the nitrate introduced into columns
without sugar was recovered in the effluent water (Table 2).
Figure 7.
of Sugar +
Nitrate.
Below the Mohave Soil Layer During
the Incubation and Leaching Periods
Soil Moisture Tension Above and
-30
-35
0
Sugar t N0
added
I
2
3
4
5
HH
7
8
Figure 7
9
Sugar + NO
Solution added
670m1
TIME - DAYS
6
500 ml Water Increment
added at each arrow
H
12
13
14
- .- Tensiometer above Soil Layer
----o--Tensiometer below Soil Layer
tO
HU
added at each arrow
500ml Water Increment
23
Table 2.
Recovery of Nitrate Percolating Through Columns
Without Sugar Addition.
Column
Added
tug
Short
255.5
NOl - N
Recovered
Average Loss
tug
7.
247.1
3
Long, Sand
68
67
1.2
Long, One-Layer
68
65
4.5
These results indicate that in the absence of sugar neither
physical retention nor chemical or biological transformation contributed
appreciably to nitrate loss in the systems studied.
The recovery of nitrate in the presence of sugar in both the
short and long columns are presented in Table
3.
It can be seen from
this table that holding the amount of sugar and nitrate constant (272.6
did not
tug sugar and 255 tug NO3-N) and doubling the time of incubation
materially alter the recovery of nitrate in the short column (treatments
3 and 4).
The equivalent NO3-N that disappeared was 61 Kg/Ha (54 lb/A)
in treatment 3 and 67 Kg/Ha (59 lb/A) in treatment 4.
NO3-N added to each was 220 Kg/Ha (192 lb/A).
The amount of
When sugar was increased
hrs.)
from 272.6 tug to 545.2 tug while holding the incubation time (24
of NO3-N
and nitrate (130 tug) constant, treatments 5 and 6, the amount
lb/A).
that disappeared increased from 35 to 57 Kg/Ha (31 to 50
Less
NO3-N disappeared when NO3-N was decreased from 255.5 tug to 130 tug
while holding the amount of sugar constant (272.6 tug).
The NO3-N that
disappeared dropped from 61, in treatment 3, to 35 Kg/Ha in treatment
5 (54 to 31 lb/A).
43
24
24
72
72
Short Layered
Short Layered
Short Layered
Long, Sand
Long, 1 Layer
4
5
6
81
811
545.2
545.2
545.2
272.6
272.6
68.0
68.0
130.0
130.0
257.0
255.5
mg
mg
272.6
Addedb
Sucrose
Addeda
42.6
51.6
96
109
217
219
rag
Recovered
NO3 -N
37
24
26
16
15
14
7o
Lost
To convert Kg/Ha to lbs/A multiply by 088.
Addition of 63 rag, 130 rag and 255.5 rag NO3-N was equal to 114 Kg, 218 Kg
and 426 Kg/Ha NO3-N.
Addition of 272.6 rag and 545.2 rag sucrose was equal to 455 Kg and 900 Kg/Ha
respectively. This amount of material would equal the 20, water soluble
fraction of a 2000 lb and 4000 lb/A addition of fresh plant residue
respectively.
24
[irs
Incubation
Time
Short Layered
Column
Type
Disappearance of NO3-N as Related to the Incubation Time and the
Amount of Sugar and NO3-N Added.
3
No
Treatment
Table 3.
42
27
57
35
67
61C
Kg7Ha
25
Oxygen and Nitrogen:
The relative oxygen and nitrogen content of the soil atmosphere
during the incubation and leaching periods in the two long columns
are
plotted in figures 8-li and tabulated in Appendix Table 10.
During the
incubation and leaching periods of nitrate alone, the oxygen and nitrogen
values remained constant and in the same proportion as that of atmospheric air with the exception of the gas sampling site located 10 cm
below the Mohave soil layer.
At this site the column/air oxygen and
nitrogen ratios became approximately 0.38 and 1.1 respectively.
During the incubation period of sugar
nitrate in the sand column
(Fig. 8), the column/air oxygen ratio decreased to 0.70 at the three
sites of measurements.
During the leaching period, the column/air
oxygen ratio increased to unity.
In the one-layer column, Figure 9, the
column/air oxygen ratio decreased at site #1 located 90 cm from the top
of the column during the second incubation period reaching a value of
0.70.
No major change took place in oxygen status at site #2, located
in the Mohave soil layer.
At site #3 located 10 cm below the Mohave
soil layer, the oxygen level was low as in the previous nitrate treatment.
Tue oxygen completely disappeared during the incubation period.
It reappeared during the first leaching period and the column/air oxygen
ratio became 0.06.
After the sixth day the oxygen disappeared and
remained so until the termination of the experiment.
The measured nitrogen values in both columns, with the exception
of sampling site #3 in the one-layer column, remained fairly constant.
(Fig. 10 & 11).
At this site the high nitrogen status remained as in
the previous nitrate treatment.
99Z nitrogen,
The soil atmosphere was approximately
Figure 8
The Ratio of 02 in Column in the Long
02 in Air
Sand Column During the Incubation and
Leaching Periods of Sugar + Nitrate
I
incubation Period
Sugar + NO added
Figure 8
added
Incubation Period
Sugar t NO
T ME- DAYS
Hilt
Leaching Period
Leaching
-3
128
153
90
Gas Probes Depth (cm)
Period
Figure 9.
The Ratio of 02 in Column in the One-Layer
02 in Air
Long Column During the Incubation and
Leaching Periods of Sugar + Nitrate.
0
c'J
0
0.l
0.7
0.8
0.9
1.0
1.2
1
Sugar t N0 added
Incubation Period
1.
.
7
I
S
10
a
9
8
Figure 9
11
II
S
12
13
1H
Period
_o_#2
153
128
90
Gas Probes Depth (cm)
Leaching
a. a
Sugar t N0 added
Incubation Period
TIME- DAYS
J,1rL1
Leaching Period
Figure 10.
The Ratio of N2 in Coluflin in the Sand
N2 in ir
Column During the Incubation and Leaching
Periods of Sugar + Nitrate.
o
c.j
z
('J
C
c
C
0
0
-J
0
0.9
1.0
'I,
0
Sugar+ NO added
Incubation Period
2
3
4
5
6
Period
7
Figure 10
8
9
Sugar i- NO added
Incubation
TI MEDAYS
HH
Leaching Period
0
12
13
H
Period
__#3
128
153
90
Gas Probes Depth (cm)
II
Leaching
Figure 11.
Leaching Periods of Sugar + Nitrate.
The Ratio of N2 in Column in the One-Layer
N2 in Air
Long Column During the Incubation and
Period
Sugar tNO added
Incubation
Incubation Period
Sugart NO added
Figure 1]
TIME -DAYS
Leaching Period
to
H
13
__#I
128
153
90
Gas Probes Depth(cm)
12
H
Leaching Period
30
Two rather important findings stand out from the results of the
gas analysis.
First, the systems studied were mainly aerobic during
both the incubation and leaching periods.
Second, the Mohave soil layer
acted as a barrier to oxygen movement inducing an anaerobic environment below it.
Redox Potential and PH Values
The most significant decrease in redox potential in the short
column experiments occurred immediately after the addition of sugar
alone.
The redox potential decreased from +300 to -500 millivolts in
10 hours at the two electrodes within the Mohave soil layer located at
a depth of 17 and 23 cm.
56 hours.
The potential remained at -500 millivolts for
There was no change at the other electrode during the same
treatment, and the potential remained at +250 millivolts.
When nitrate
+ sugar were added, the redox potential at the 17 and 23 cm deep electrodes decreased from +300 to -60 millivolts within 10 hours.
Further
addition of sugar and nitrate did not produce any appreciable decrease
at any of the electrodes but remained within +300 millivolts which was
below the redox potential of +380 millivolts below which the nitrates
are unstable (23).
The redox potential in the long column did not fluctuate during
the addition of nitrates alone but remained within +200 to +500 millivolts.
The redox potential, after the addition of sugar and nitrate in the
long column, is plotted in Figures 12 and 13.
The lowest potential of
-170 millivolts occurred at 123 cm depth (electrode #5).
at electrodes
1
and 2
remained near +500
millivoltS.
The potential
At
Figure 12.
Redox Potential Values at Platinum
Electrodes 1-4 in the One-Layer Lang
Column During the Incubation and
Leaching Periods of Sugar + Nitrate.
a:
uJ
0
><
400
0
*100
+200
*300
1-
*500
-i-600
0
1
I
Sugar s N0 added
Incubation Period
2
3
i
'1
4
i
5
6
7
'I,
Figure 12
8
9
Incubation Period
Sugar i- N0 added
TIME- DAYS
Leaching Period
L?
II
lrJP
12
4
13
1
14
--2
-D-#3
-0-1
117
120
123
127
Platinum Electrode Depth (cm)
10
1,
Leaching Period
Figure 13.
Redox Potential Values at Platinum
Electrodes 5-8 in the One-Layer Long
Column During the Incubation and
Leaching Periods of Sugar + Nitrate.
0
I
2
Incubation Period
Sugar + NO added
3
4
5
Leaching Period
DAYS
7
Figure 13
TIME
6
Incubation Period
8
9
Sugar -i- NO added
II
12
13
14
-0-
-.-A-
5
6
7
8
181
135
138
132
Platinum Electrode Depth (cm)
-0-
10
Leaching Period
33
electrodes 3 and 4, the potential dropped but remained above +100
millivolts, while at electrodes 5,6,7 and 8 the potential dropped and
then climbed again.
The p11 in the long one-layer column did not change appreciably
during the incubation and leaching periods of sugar + nitrate (see
Appendix table 6).
At glass electrode #2 located at the middle of the
Mohave soil layer the p11 remained fairly constant, at about 7.4.
At
glass electrode #3 located 2 cm. from the bottom of the column, the
H fluctuated between 7.0 and 7.8.
The p'1 of the simulated Colorado
river water that was used for leaching was 7.8.
DISCUSSION
The objective of this study was to evaluate
denjtrjfjcacion as
a major factor contributing to the partial elimination of nitrates in
nitrate-containing waters percolating through the soil.
The extent of
denitrification was studied mainly under two different soil conditions;
(1) pure sand, and (2) pure sand interbedded with a different
texture
soil material.
This phenomenon of stratification is a natural one and
occurs in a multitude of combinations,
In this study a condition of one
stratum ivaand column was employed.
The results of denitrification
in the two columns should give an indication of the effect of a physical
discontinuity in a soil.
The physical discontinuity would produce
differential soil moisture content above and below this layer.
a
An
increase in moisture content or a decrease in moisture movement should
retard oxygen diffusion and induce more denitrificatjon to take place
when nitrate and energy source are present.
Under field conditions in the Southwest, the soil surface dries
rather quickly after the addition of water.
Microbial activity at the
surface becomes restricted, allowing soluble organic materials and
nitrate to accumulate.
In addition, plant residues may also accumulate
at the surface either through natural leaf fall or artificial application.
Upon wetting by rain or irrigation, appreciable amounts of soluble
organic materials may percolate downward through the profile.
If nitrate,
organic energy source, and restricted oxygen supply occur together, then
denitrjfjcatjon is possible.
It was estimated that the yearly amount
34
35
of NO3-N that would be added to a soil under irrigated agriculture would
It was also estimated
range between 114 and 426 Kg/Ha (100 to 375 lb/A).
that the yearly amount of organic matter that would be added to an agricultural land, either through leaf fall or artificial application would
Assuming the organic
range between 455 and 900 Kg/Ha (1 to 2 tons/A).
matter contains 20 percent readily available energy source, the equivalent amount would be
91 and 109
Kg/ha of sucrose.
These amounts of
NO3-N and sugar were used in different combinations to evaluate the
extent of denitrification in the column studies.
The process in which nitrates are utilized by microorganisms
nitrate assimilation or assimila-
falls into two general classes:
(1)
tory nitrate reduction, and (2)
nitrate respiration or dissiniilatory
nitrate reduction.
In nitrate assimilation the nitrate is biologically
reduced to the ammonium form and the products used for the biosynthesis
of nitrogen containing cellular constituents.
In
nitrate respiration,
nitrate is used as the terminal electron acceptor in place of oxygen by
a variety of microorganisms in the absence of oxygen.
Under complete
aerobic conditions, oxidation of sugar by microorganisms leads to the
formation of CO2 and 1120:
C6H12O5 + 602 *6CO2 +
61120
Oxygen in this reaction acts as the electron acceptor.
[i
If oxygen
will replace
diminishes for any reason and nitrates are present, they
oxygen as the electron acceptor.
In the complete absence of oxygen
takes place:
and in presence of nitrate, the following reaction
C6H1206 ± 4NO
,.6C09 ± 61120 + 2N2
[2]
36
For the complete oxidation of 180 mg sugar, 192 mg 02 or 56 tng
of NO3N are required for reactionsjl]
and
respectively.
[21
In a dynamic system, such as the soil, these two reactions could
occur concurrently, if the energy source, nitrate and/or oxygen, are
present.
The rate at which denitrification occurs in soils is governed
by a number of environmental factors.
It has been well established
that denitrification occurs only when the supply of oxygen required by
the denitrifying microorganisms is restricted, generally by excessive
moisture.
In this respect, the critical moisture level has been found
Below this level
to be about 607e of the water-holding capacity (5).
practically no dentrification takes place; above this level denitri-
fication increases rapidly provided an adequate energy source is
present.
Assuming the number of microorganisms during the oxidation
of an energy source does not diminish, but, increases logarithmicallY,
and
the rate of oxidation increases with the increase of microorganisms
As the metabolic
then decreases as the organic matter is exhausted.
activity increases so will the oxygen demand.
If nitrate is present
high, the
and °2 is limited during oxidation and the oxygen demand is
microorganisms will utilize the nitrate instead of 02.
This relation-
mentioned, is subject to
ship is quite a complex one, and as previously
the influence of a number of environmental factors.
In a recent review of
denitrificatiOfl by Broadbent and Clark (8),
a number of significant points were brought out.
The above authors have
regarding "aerobic" and
found a large number of conflicting results
"anaerobic" denitrificatiOn.
They attributed these results to the ill-
under which the
definition of the terms "aerobic" and "anaerobic"
37
experiments were performed.
Nevertheless, with this conflict on the
condition under which dentrification takes place, the results of many
workers were shown to be quite consistent, and the percentage N loss
ranged from 1 to 35 percent.
In the experiments conducted here, the
percentage N denitrified ranged between 8 and 21 percent.
This loss is
in good agreement with the findings of a number of workers as reported
by the above authors.
Under our experimental conditions, in the absence of sugar and
in the presence of nitrate, there was no appreciable change in the
redox potential and pH.
There was, however, a change in the soil
atmosphere below the Mohave soil layer in the one-layer column.
At
this lower depth a marked decrease in the oxygen level and a marked
This change in the soil
increase in the nitrogen level took place.
atmosphere was probably due to the movement of soluble organic matter
from the Mohave soil layer and its subsequent utilization by microorganisms.
The microbial activity produced a drop in the oxygen level
and an increase in the nitrogen level.
and high 1itrogen persisted
This
condition
of low oxygen
without appreciable change in nitrogen but
with the complete disappearance of oxygen as the experiment progressed
and sugar was included. (See Fig. 9 and 11).
When sugar was included with the nitrate, a change in the soil
envirotunent took place.
This change, with the exception of pH values,
of nitrate and sugar
was not detected inunediately after the addition
or during the incubation period.
During this period the redox potentials
did not change from their initial values.
There was, however, a slight
38
change in the pH during this period at the glass electrodes located at
120 cm and 181 cm depth, innediately above the Mohave soil layer and at
the bottom of the column respectively (glass electrodes 1 & 3).
The
pH value dropped from the initial 8.75 at electrode 1 to 7.55 within
48 hours of the first incubation period.
The pH value at the same
site dropped during the second incubation period from the initial 8.10
to 7.6 at the end of this period.
Th*s change in pH indicated that a
chemical or biological reaction took place in which an acid was
produced.
A chemical reaction was excluded on the basis that nitrate
alone did not produce any change in the environment
Although the
decrease in pH value was slight, it indicated that biological oxidation
of sugar took place at this site which could have
led to the production
of CO2 and the formation of carbonic acid or to the formation of organic
acids.
At the glass electrode located within the Mohave soil layer the
pH did not change from its initial value of 7.4.
This stability of the
of the soil
pH value in this region could be due to the buffering action
layer.
column,
At the glass electrode located 2 cm from the bottom of the
the change in pH value took place at the end of the leaching period
Appendix
where it decreased from its initial value of 7.7 to 7.0. (See
Table 6).
This delayed change in pH value indicated that sugar and
nitrate were present above the Mohave soil layer during the incubation
period when, probably, most of the sugar was oxidized.
As more water
down into the anaerobic
was added, the sugar and nitrate moved further
zone below the Mohave soil layer.
This conclusion was further supported
by redox potential measurements which are discussed below.
39
The redox potentials at the different electrodes did not change
from their initial readings during the first incubation period.
With
the exception of the two electrodes above the soil layer which did not
change in potential, the remaining electrodes indicated a signific*nt
drop from their intiial readings only after the addition of second
500 ml portion leaching water.
coitained only 1 mg of NO3-N.
The first 500 ml of effluent water
The appearance of nitrate in the effluent
water coincided with the marked decrease in the redox potentials.
This drop in redox potentials indicated that the sugar and nitrate
reached and were passing through the Mohave soil layer.
It could be
concluded that the sugar and nitrate were distributed above the soil
layer during the time o
added sugar.
the major microbiological oxidation of the
The quantity of sugar that moved with the nitrate to
the anaerobic zone below the Mohave soil layer was not determined.
The depth at which nitrate and sugar were distributed within the
columns could be approximated from volume of water present in the pores
of the soil material.
When the columns were first leached with 2 liters
of water, 1,120 ml and 1,320 ml were retained by the sand and one-layer
columns respectively.
Assuming this quantity of water was equal to
volume of pore space filled with water and assuming uniformity of
distribution, the 670 ml of treatment solution will only move 121 cm
and 91 cm in the sand and one-layer columns respectively.
This approx-
measurements.
imation agreed quite well with pH, redox potentials and gas
distributed within
The manner in which sugar and nitrate were initially
of the
the columns was not determined and in future work modification
experimental set-up should be made to investigate their initial distribution.
40
It was found that the breakthrough curves of sugar and nitrate
were the same (meaning that both were moving together in the column)
as seen in Figure 14.
Although the concentration of added sugar was
750 ppm only 11 ppm appeared in the effluent water.
This low recovery
of sugar indicated that practically all the sugar was utilized.
In
the short column treatments it was found that nitrates disappeared
within the first 24 hours.
On this basis, we can reasonably assume
that the major oxidation of sugar and utilization of nitrate took place
at the same time and long before they were leached below the anaerobic
If this was the case the anaerobic zone
zone of the Mohave soil layer.
did not materially influence the amount of nitrate utilized by microorganisms.
The main effect the soil layer produced was to increase
the moisture content above it and to reduce the movement of oxygen
in such a way as to induce more nitrate utilization by microorganisms.
This condition could have possibly induced more nitrate utilization in
the one-layer column than in the sand column, which will be discussed
in the coming section.
From the above discussion and from the gas
analysis, one could conclude that the major part of the nitrate was
utilized under overall aerobic
conditions.
The utilization of nitrate
could have taken place mainly in the small pores into which oxygen
movement was slower than the biochemical oxygen demand.
Under the conditions of the experiments performed, no nitrate
disappeared without the presence of an energy source.
Based on this
nitrate
finding, the nitrate loss would be attributed to respiratory
reduction and immobilization by
microorganisms during the oxidation of
Figure 14.
The Relative Concentration of
Sugar and Nitrate in the
Effluent Water.
0
0
0
0.2
0.4
0.6
0.8
LO
0
500
1000
1500
2500
Figure 14
VOLUME - ml.
2000
3000
NITRATE
3500
X
SUGAR
42
sugar when sugar was added.
In the different treatments with different
combinations of sugar and nitrate levels, the total amount of NO3-N that
disappeared varied between 14 percent and 37 percent (See Table 3).
The
amount of NO3-N that disappeared depended on both amounts of NO3-N and
sugar.
The least amount of NO3-N disappeared in the long sand column
amounting to 27 Kg/Ha.
The highest amount of NO3-N disappeared in the
short column when the sugar to NO3-N ratio was 1:1, amounting to 61 Kg/Ha.
The length of the column did not have an effect on the amount of NO3-N
that disappeared.
On the basis of reaction [2]
,
Table 4 was prepared to illus-
trate the extent of biological nitrate utilization under the experimental
conditions.
The unrecovered NO
in the effluent water was partitioned
between potential immobilization and possible denitrification as seen
in Table 4.
The potential immobilization was based on 2 parts N per
100 parts organic carbon utilized (1).
This assumed value was substan-
sand column.
tiated by organic-N analysis in experiment 3 of the long
The determined organic-N was 7.3 mg.
The discrepancy between the
either a
calculated and determined values could be attributed to
displacement of microorganisms
high assumed value of N or incomplete
in the columns.
NO3-N, which
The potential immobilized fraction of
added, ranged from 5.5 to 11 nzg.
was proportional to the amount of sugar
varied from 68 to 257 mg.
The amount of added NO3-N
In treatuients3and 5
than the maximum NO3-N demand for complete
the added NO3-N was greater
sugar oxidation.
acceptor
In treatments 6 and 8 the potential electron
added.
demand was greater than the amount of NO3-N
In either case, only
satisfied through reduction of NO3.
part of the electron acceptor demand was
25
68.0
170
545.2
13.5
3.0
8.3
18.0
8.0
21.0
5
14
11.0" 16.0
16.0
11.0
11.0
23
36.5
8.0
11.8
18.0
31
I
155 11.8
2.2
tug
V
III - IV
Used to
satisfy
reductive
demand
x 100
4.2
5.5
5.5
tug
IV
Possible
Potential
Immobilization Denitrification
NO3-N
Effluent contained 7.3 tug organic - N and 7 tug free sugar.
'4J Calculated assuming 2 parts N immobilized in microbial tissue per 100 parts organic
carbon utilized (I).
Calculated from the reaction: C6111206 + 4 N0-. 6 Co2 + 6U20 + 2N2
1 layer
long,
811
16
68.0
170
545.2
long,
sand
81
34
545.2
short,
1 layer,
6
130.0
85
272.6
170
37
21
255.5
85
tug
III
Unrecovered
130.0
272.6
tag
II
tug NO3-N
short,
1 layer
1 layer
short,
tug
I
Sucrose Maximum
Added Reductive
Added
Demand
Nitrate Used in the Decomposition of Added Sugar.
5
3
No
Column
Treatment Type
Table 4.
44
The reductive demand that was satisfied ranged from a lowest value of
3.0 percent in treatment 8-1 to a highest value of 36.5 percent in
treatment 3.
Although the electron demand satisfied by NO3-N was
independent of the potential reductive demand, it was related to the
amount of NO3-N added.
This relationship between NO3-N added and
utilized may be noted in treatments 3 and 5.
As the nitrate amount
added decreased from 255.5 to 130 mg, while holding the sugar constant
(272.6 mg), the satisfied reductive demand decreased proportionally
from 36.5 to 13.0 percent.
When the sugar was increased from 272.6
to 545.2 while holding the amount of nitrate constant, 130 tag (treatnients 5 and 6), the satisfied reductive demand decreased slightly from
18.0 to 13.5 percent.
The reason for this decrease was due to a greater
immobilization of NO3-N induced by the increase in the amount of
sugar added.
As the amount of NO3-N added was further reduced from
130 tag to 68 mg while holding the sugar constant, 545.2 tag, only 3
and 8.3 percent of the potential reductive demand of 170 tag was
satisfied in treatments 8-1 and 8-lI, respectively.
The satisfied
reductive demand was approximately 3 times greater in the one-layer
than in the sand columns.
These results indicate that the sand column
was relatively more aerobic than the one-layer column in which the
Mohave soil layer impeded the movement of water, and consequently air,
into the column.
The results also indicate that the systems studied
were aerobic and oxygen was the main electron acceptor during the
oxidation of added sugars.
This situation was further supported by
the results of gas analysis discussed earlier.
45
In the short and long one-layer column treatments, the nitrate
loss was the same and proportional to the sugar and nitrate added.
This
finding suggested that probably the most important site for the micro-
biological interaction of sugar and nitrates was in the top 12 inches
of the soil.
Ii this region the organic matter and nitrate are
more likely to come in contact with each other.
Once the sugar is
decomposed, the oxygen and/or nitrate demand becomes negligible.
The
remaining nitrate, if no further addition of organic matter takes
place, moves with the water front and eventually with more water
addition, will reach the ground water.
The movement of nitrate through the two long columns had the
same characteristics although one of the columns had a Mohave soil layer.
The effect of the Mohave soil layer was to retard the movement
of nitrate by 12 hours as compared to the sand column.
This retar-
dation in nitrate movement could possibly be due to the initial
slow rate of water movement in the one-layer column that affected the
initial distribution of nitrate.
The shape of the elution curves for
nitrates in both columns were similar to a normal Gaussion distribution
and agree with the findings of Day (15).
The breakthrough curves
also agree with the findings of Bigger and Nielson on miscible displacement (22).
Neither physical retention nor chemical action occurred
when nitrate alone was added to the columns.
SU}IMARY AND CONCLUSION
The objective of this study was to evaluate potential denitrification in nitrate-containing waters percolating through the soil.
Laboratory studies were conducted in 30 and 183 eta long columns.
The
extent of denitrjficatjon was studied under two different soil conditions,
1.
Pure sand, and 2.
Pure sand interbedded, at one location, with
15 centimeters of a finer texture soil material.
The two conditions
should give an indication of the effect of a physical discontinuity in
a soil upon denitrification.
The treatments included the addition. of nitrate alone, sugar
(sucrose) alone and sugar + nitrate.
ranged from 272.6 to 545.2 milligrams.
The amount of sucrose added
These amounts of sucrose would
equal the 20 percent water soluble fraction of a 2,250 Kg/Ha and 4,550
Kg/Ha addition of fresh plant residue respectively.
as Ca(NO3)2.
Nitrate was added
The amount of NO3-N added to the column ranged between 68
milligrams and 355,5 milligrams which was equivalent to 114 Kg and 426
Kg/Ha respectively.
During the course of the experiments, redox potentials, pH, soil
moisture potential and oxygen and nitrogen were measured at different
levels in the columns.
Under the conditions of the experiments performed, no nitrate
disappeared without the presence of an energy source.
Based on this find-
ing, the nitrate loss was attributed to respiratory nitrate reduction
and immobilization by tuicroorganisnus during the oxidation of the added
46
47
sugar.
In the treatments with different combinations of sugar and nitrate
the total amount of NO3-N that disappeared varied between 14 and 37 percent.
The amount of NO3-N that disappeared depended on the concenttations
of both NO3-N and sugar added.
The least amount of NO3-N disappeared
(27Kg/Ha) in the long (183 cm) sand column.
The highest amount of
NO3-N disappeared (61Kg/Ha) in the short (30 cm) column when the sugar
to NO3-N ratio was 1:1.
The length of the column did not materially
affect the amount of NO3-N that disappeared.
It was concluded from the gas analyses, redox potentials and
pH values, that the distribution of sugar and nitrate when added with
670 nil water took place above the anaerobic zone that developed beneath
the soil layer.
This conclusion meant that the major nitrate utilization
by microorganisms took place in an overall aerobic condition, where only
the small. anaerobic pores exerted the most influence on nitrate loss.
LITERATURE CITED
1961.
Introduction to Soil Microbiology.
Alexander, M.
Chapter 15 and 17.
and Sons, Inc. New York.
John Wiley
1962.
Rates of Immobilization and
Allison, F. E. and C. J. Klein.
Release of Nitrogen Following Additions of Carbonaceous Material
Soil
ci.
93: 338-386.
and Nitrogen to Soils.
Bretuner, J. M.
Agron., Inc.
Methods of Soil Analysis. Part 2.
Madison, Wisconsin. pp. 1179-1254.
1965.
Am. Soc.
Denitrification in Soils.
1958.
Bremner, J. N. and K. Shaw.
51: 22-52.
J. Agr. Sci.
Methods of Investigation.
I.
II.
Denitrification in Soil.
1958.
Bremner, J. M. and K. Shaw.
Factors Affecting Denitrification. J. Agr. Sci. 51: 40-56.
1960.
Measurement
Brink, R. II. Jr., R. Dubach and D. L. Lynch.
of Carbohydrates in Soil Hydralyzates with Anthrone. Soil
89: 157-166.
Sci.
Denitrification in Some
1951.
Broadbent, F. E.
72: 129-137.
Soil Sci.
California Soils.
In
Denitrification,
1965.
Broadbent, F. E. and F. E. Clark.
Am.
Soc.
Soil
Nitrogen.
Bartholomew, W. V. and F. E. Clark ed.
Agron. 10: 347-362.
The Effect of Partial
1952.
Broadbent, F. E. and B. F. Stojanovc.
Soil
Transformations.
Pressure of Oxygen on Some Soil Nitrogen
16:
359-363.
Sci. Soc. Am. Proc.
Nitrogen and Carbon Transformations in a Soil
1963.
Brown, J. R.
Ph.D. Thesis.
Additions
of Crop Residues.
as ]nfluenced by
pp. 35-38.
Science
and
Technology.
Iowa State University of
A Genesis Study of a Mohave
1964.
Buol, S. W. and N. S. yesilsoy.
28: 254-256.
Soil
Sci.
Soc.
Am.
Proc.
Sandy Loam Profile.
sequential Products of
1960.
Cady, F. B. and W. V. Bartholomew.
Soil Sd.
Soil
Material.
Anaerobic DenitrificatiOn in Norfolk
24: 477-482.
Am. Proc.
48
49
LITERATURE CITED - - (continued)
1962.
Absorption of Nitrate by Corn as Related to
Calvert, D. V.
Movement of Nitrate and Water in Soil. Ph.D. Thesis..
Iowa
State University of Science and Technology.
Sequence of Products Formed
1963.
Cooper, G. S. and R. L. Smith.
Soil Sci.
During Denitrification in Some Diverse Western Soils.
27:
659-662.
Soc. Am. Proc.
Dispersion of a Moving Salt-Water Boundary
1956.
R.
Advancing Through Saturated Sand. Trans. Am. Geophys. Union.
37: 595-601.
Day, P.
Preliminary Oxidation Potential Determination
1950.
De Gee, J. C.
Trans. 4th Int. Cong.
in a uSawanu Profile near Bogor (Java).
1: 300-303.
Soil Sd.
Interpretation of Chloride and Nitrate Ion
1965.
Dyer, K. L.
Distribution Patterns in Adjacent Irrigated and Nonirrigated
29: 170-176.
Panoche Soils. Soil Sci, Soc. Am. Proc.
1923.
Janssen, G. and W. 1-i Metzger.
in Rice Soils. J. Am, Soc. Agron.
Transformation of Nitrogen
20: 459-476.
Field Nitrate in Gezira Soil II.
Jewitt, T. N. 1956.
47: 461-467.
Sci.
J.
AgE.
Canopy Drip; a Source of
1966.
Malcom, R. L. and R. J. McCraken
Mobile Soil Organic Matter for Mobilization of Iron and Aluminum.
Agron. Abstracts 1966, p. 67.
Symposium on Metabolism of Inorganic Compounds. II.
1962.
Nason, A.
Enzymatic Pathways of Nitrate, Nitrite and Hydroxylamifle
Metabolism. Bacteriol Rev. 26: 16-36.
Miscible Displacement:
1963.
Nielson, D. R. and J. W. Biggar.
26: 222-227.
Soil
Sci.
Soc.
Am. Proc.
Mixing in Glass Beads.
Nitrate Reduction Rates In a Submerged Soil
1960.
Patrick, w. H.
Soil
Trans. 7th mt. Cong.
as Affected by Redox Potential,
2: 494-500.
Sd.
Soil Nitrogen Loss as a Result
1964.
Patrick, W. ii. and R. Wyatt.
Proc.
of Alternate Submergence and Drying Soil Sci. Soc. Am.
28: 647-653.
50
LITERATuRE CITED - - (continued)
Pearsall, W. H.
Significance.
1952.
The pH of Natural Soils and its Ecological
J. Soil Sci,
3: 41-51.
Pruel, H. C.
1964.
Travel of Nitrogen Compounds in Soils.
Thesis, University of Minnesota.
pp. 3-8.
Ph.D.
Reuss, J. 0. and R. L. Smith.
Chemical Reaction of Nitrites
1965.
in Acid Soils. Soil Sci. Soc. Am. Proc.
29: 267-270.
Ritchie, J. T.
1964.
Soil Aeration Characterization Using Gas
Chromatography. Ph.D. Thesis. pp. 18-25.
Smith, D. H. and F. E. Clark.
1960.
Volatile Losses From Acid
or Neutral Soils Containing Nitrite and Arnmonium Ions.
Soil
Sci.
90: 86-92.
Volobuev, V. R. Ecology of Soils. 1964.
Inc.
New York. Chap. 9 and 10.
Daniel Davey and Co.,
Nitrate Distribution in Tropical Soils. II.
Wetselaar, R. 1961.
Extent of Capillary Accumulation of Nitrates During a Long Dry
15: 121-133.
Period.
Plant and Soil.
Nitrate Distribution in Tropical Soils. III.
1962.
Wetselaar, R.
Downward Movement and Accumulation of Nitrate in the Subsoil.
16: 19-31.
Plant and Soil.
1963.
Gaseous
Wulistein, L. H., Gilmour, C. M., and Bollen, W. B.
Loss of Soil Nitrogen by Chemical and Microbial Pathways. Agron.
Abstracts 1963.
p. 34.
APPENDIX A
51
52
CALCULATION OF IRRIGATION AND FERTILIZER NEED
Irrigation
Need
3.41 x r2 x h
Volume in cc/inch
3.41 x (4.32)2cm x 2.54 cm/in
.49 cc/in.
the
If each irrigation is equal to 4.5 in then
total
volume per
irrigation is:
149 cc/in x 4.5 in/irrig
= 670 cc/irrig.
Fertilizer Need
Area of Column = 0.7854 d2, d = 3.45 in
0.288 ft.
= 0.7354 x 0.2882 ft
= 0.0652 ft2.
If each acre receives 200 lb-N
200 lb/ac
0.0046 lb/ft2
43,560 ft2/ac
0.0046 lb/ft2 x 454 gm/lb = 2.09 gm/ft2
2.09 gm/ft2 x .0652 ft2
The fertilizer to
Contains 28-N
Gram
be used is
of Fertilizer required
0. 1363 gut
Ca (NO3)2.4H20, Formula wt.
0. 1363 x 236.16
28
= 1.15 gut.
236.16,
APPENDIX B
53
54
Table 5.
Hrs Accum
Rrs
1
Redox Potential, pH and Tension Values in the OneLayer Short Column During the Various Treatments.
Redox Potential
3
4
2
Tension
pH
5
R-1
R-2
8.80
8.35
9.00
7.80
7.38
7.93
7.42
7.12
6.75
6.80
6.80
7.39
7.41
7.42
7.40
7.31
7.36
7.33
7.43
7.87
7.60
7.60
7.44
7.51
8.30
8.25
8.25
7.20
7.19
7.30
7.30
7.20
7.06
7.00
7.09
7.54
7.01
6.96
7.08
6.97
6.96
6.91
6.89
6.89
6.80
6.85
6.96
6.86
Treatment 0
00
00
22
22
24
46
58
12
6
72
78
93
99
6
13
2
2
6
4
1
5
19
8
13
10
13
4
8
16
20
105
118
120
122
128
132
133
138
157
165
178
188
201
205
213
229
249
14
6
15
+168
+158
+153
+152
+100
+200
+219
+200
+260
+262
±242
+242
±180
±205
+200
+172
+188
+155
+135
+190
+225
+210
±220
+230
-20.
-100
-160
+7
00
+250
+295
+305
+320
+330
+309
+290
+285
+308
+288
±290
+290
+280
+292
+300
+340
+330
+340
+360
-220
-500
-500
-160
-220
-260
+18
+140
+52
+115
±190
+212
+232
+230
±150
+220
+242
+230
+160
+5
-100
+150
+150
1-130
+210
+220
+220
+222
+275
--23O
±233
+ 60
+ 22
- 20
-200
- 20
- 35
± 42
±330
±30
-10
-270
-50
-20
-2o
-10
+300
±340
+250
+168
+103
+263
±290
+68
+295
+212
+250
+291
+230
+260
+245
+260
+253
+248
+242
+220
+240
+238
+230
+242
+270
+250
Treatment 1
1 250
4
19
1
5
6
13
254
273
274
279
285
298
+240
+220
+220
+390
+360
+250
+360
+343
+240
+330
+240
+100
±250
+240
+233
7.32
7.10
7.25
6.60
6.60
6.58
+230
+230
+230
+360
+345
+342
+220
+320
+238
±210
+120
+ 40
+260
+245
+213
7.28
7.40
7.55
6.88
6.85
6.93
7.23
7.02
6.88
6.79
Treatment
3 301
5 306
-225
+240
+325
+340
+320
+ 95
+100
-410
+200
+240
2
T1
55
Table 5.
Redox Potential
lirs Accum
lirs
(continued).
1
2
4
3
Tension
p11
5
R-1
R-2
Ti
T2
Treatment 2--continued
8
307
310
322
323
325
332
349
357
13
370
1
3
12
1
2
7
17
+210
+240
+230
+245
±240
+240
+260
+260
±240
+340
+338
+360
+330
+360
+365
+330
+380
+380
± 60
- 40
-500
+190
-500
470
-500
-500
-500
-500
-500
-500
-500
-500
-500
-500
-500
-500
+220
+240
+240
+220
+240
+240
+260
+250
+240
7.13
7.37
7.11
7.12
7.03
7.00
7.05
7.20
6.78
7.32
6.67
6.95
6.93
7.00
6.96
6,92
7.00
6.93
6.50
6.43
6.46
6.99
6.93
7.17
7.03
7.31
7.32
7.40
6.52
6.47
6.40
6.38
6.34
6.67
6.65
6.65
6.81
6.75
6.72
6.70
6.73
6.73
6.51
6.55
6.64
6.74
6.83
6.38
6.92
6.95
7.00
6.93
6.38
6.33
6.35
6.27
6.26
6.29
6.31
6.37
6.39
6.43
6.43
6.41
6.43
6.41
6.83
Treatment 3
1
3
7
12
3
2
7
13
11
22
18
21
371
374
381
393
396
398
405
418
429
451
469
490
+280
+240
+260
+280
±260
+260
+260
±260
+260
+260
+230
+230
±340
+360
+360
+400
+380
+330
+380
+330
+380
+370
+360
+360
±300
+240
- 60
+ 70
± 50
+300
+110
- 80
+300
-100
+300
360
-500
+ 80
- 60
- 20
- 40
+ 70
+200
+230
+250
+260
+260
+280
+230
+250
+240
+240
+220
+240
+240
+240
+240
±240
±230
+240
-41.5
-27.5
-15.0
-23.0
-28.5
-29.6
-30.2
-31.5
-33.0
-33.4
-35.2
-35.2
-36.0
-34.0
-34.0
-23.0
-16.6
-16.6
-17.0
-18.5
-18.7
-20.5
-20.3
-22.3
-36.4
-37.3
-23.0
-22.7
-24.0
-29.0
Treatment 4
1
5
4
12
4
9
12
4
8
2
9
5
7
14
5
+250
+250
+250
+260
+260
+260
537 +250
541 +250
549 +250
551 +240
560 +250
565 +240
572 +240
586 ±250
590 +250
491
496
500
512
516
525
+390
+360
+380
+380
+380
+330
+380
+370
+370
+330
+370
+370
+370
+370
+360
+370
4360
±330
±330
+330
+380
+380
+370
±380
+330
+380
±380
+370
+380
+340
+270
±200
+160
+160
+160
+200
+230
+240
+260
+260
+270
+230
+280
+300
+310
±240
+240
+240
+240
±260
+300
+330
+330
4330
±340
+330
+340
+340
+340
+290
7.07
7.03
7.07
56
Table 5.
Redox Potential
Hrs Accuzn
Hrs
(continued).
1
2
4
3
Tension
pH
5
R1
R-2
T1
T2
Treatment 4--continued
5
12
12
39
1
9
13
34
13
595
607
619
628
629
638
651
685
698
+260
+260
+260
+380
+380
+375
+340
+160
+260
+240
+240
+250
+260,
+360
+360
±360
+360
+360
+280
+230
-100
-500
-500
-500
+290
+30Q
+300
+270
+280
+260
7.07
7.1].
6.94
6.85
+310
+290
+150
+300
+230
+270
±290
+280
7.08
7.00
7.01
7.24
7.33
6.70
6.93
6.89
6.87
6.60
6.90
6.33
6.12
6.87
6.79
6.89
7.14
7.51
6.52
6.40
6.37
6.55
6.97
6.90
6.77
7.14
1.14
6.43
7.12
7.16
6.74
6.52
6.90
7.05
00
- 10
-14.3
-27.5
-23.8
-44.5
-17.3
-15.5
-26.5
-31.5
-32.2
-14.0
-18.3
-19.4
-15.2
-22.5
-32.0
-14.0
-21.6
-15.0
-29.5
-29.5
-26.2
-16.5
Treatment 5
1
o99
12
711
722
726
735
748
11
4
9
13
31
0
779
+260
+280
+280
+280
+280
+290
+260
+250
+360
+380
+400
+380
+400
+400
+380
+340
+190
- 10
- 10
-160
-500
-500
-500
+310
+ 80
+120
+120
+ 80
+200
+ 70
- 40
+370
+280
+250
+230
+200
+280
+240
+250
+310
Treatment 6
3
3
20
23
6
29
33
4
+240
+280
+250
+300
+340
+350
+380
+390
+290
±300
+320
+350
+340
+200
+240
+340
+290
±200
+240
+280
2
3
5
6
8
11
14
1
3
2
1
12
12
ii.
5
2
2
1
3
1
9
3
3
30
35
37
48
60
72
27
28
23
24
1
2
00
1
firs
Accum
O
firs
±480
+480
+490
+470
+480
-
+470
-
-
+470
±470
+470
+480
1
+480
+470
+500
-
+470
+470
+460
-
+460
-
+470
-
+450
-
+480
2
+460
+490
+500
-
+300
+320
-
-
+340
-
±460
-
+480
-
+480
-
-
+510
3
Table
5
6
7
+350
+490
+480
+130
+110
+160
-
-
+280
-
+340
-
+370
-
+460
+410
±450
±460
-
+400
±400
-
-
+330
-
+140
-
+320
+350
-
+420
±500
+500
+490
-
+500
+500
-
-
+500
-
±500
-
+500
+490
-
+510
+500
+490
+490
-
+490
+500
+490
+490
-
+490
-
+480
-
-
+500
Treatment 7 - Replicate 1
4
Redox Potential
+480
+480
+470
-
+480
+480
-
+480
-
+480
-
+470
-
+460
-
-
+485
8
1
Redox Potential, pH and Tension
Values in the One-Layer Long Column
During the Two Treataents.
2
P11
3
-14.0
-14.8
-17.0
-17.8
-19.0
-22.5
-23.5
-29.0
-32.0
-33.6
-5.3
- 3.0
-1.3
- 3.1
-5.2
-10.3
-10.7
-11.6
-12.0
-12.6
-15.3
-16.4
-22.7
-25.5
-27.3
-6.9
- 6.2
-5.1
- 5.6
-l.4
-6.5
-19.0
-18.8
-15.7
Tension
-23.0
-26.9
-21.0
-14.0
T1
+440
-
84
96
98
2
+490
+480
6 108
12 120
-
±490
+490
6
2
+500
-
+460
-
11
12
24
25
26
1
11
1
1
-
10
4
1
+490
+490
-
-
+480
+500
+500
-
-
1
1
-
+500
-
±490
+440
00
o
34
+510
-
±57fl
-
crn
+500
±510
+500
-
-
+490
-
+480
6
7
8
+490
+490
+500
±500
±500
-
+500
+500
-
-
-
+490
±490
+490
+480
±460
±490
+490
+420
+460
7.60
7.70
-
8.40
-
-
-
-
7.50 7.60
-
-
7.50
8.40
-
7.70
-
-
-
7.70
7.70
-
-
7.50
7.50
-
4.0
+1.5
+
+15.5
-23.0
-23.6
-24.3
- 4.5
- 3.5
- 0.4
- 1.5
-20.5
- 5.6
-21.0
7.40 7.70 + 6.5
-
7.40 7.70
6.0
6.5
+
+
+10.0
+11.4
±4.2
-12.0
- 4.0
-20.7
1.3
-
6.6
-11.8
-22.4
-23.0
-23.7
-11.3
-10.3
- 9.6
-20.5
-12.2
-20.6
-
-9.0
1.8
- 7.5
-
- 5.0
- 5.5
2.0
-
-5.3
- 9.0
-12.0
-27.1
-18.0
T2
Tension
-33.3
Ti
7.60
-
3
8.40
+460
-
-
-
+450
-
-
±490
±490
+490
+490
+420
+450
±460
+500
8.70
8.40
+460
+500
8.70
-
-
-
-
-
7.50
-
-
-
-
-
2
p11
8.90 7.50
8.70 7.40
-
8.90
-
-
-
-
1
+490
+480
-
-
±480
+480
+460
-
+480
-
-
+500
-
±500
+500
-
+490
-
±500
-
-
Treatment 7 - Replicate 2.
±510
-
+460
+5fl
-
-
+LLLLO
±440
+3.Sfl
-
+/' ..
-
-
4-S1l
-
+510
+490
+480
-
-
Leaching, 500 ml water added every 12 hrs.
3
+430
-
+490
+510
±430
+490
+490
-
-
-
2
(continued).
Redox Potential
5
4
2 146
12144
8 132
-
-
2102
4124
+490
2 100
-
-
78
4
6
12
-
74
1
2
Hrs Etccum
Hrs
Table 6.
±530
+520
+520
+520
±530
+520
+520
+520
±530
5
6
9
24
28
1
1
1
12
4
4
2
0
10
11
12
3
1
0
2
2
1
±530
+550
+570
+510
±510
±420
+420
96
84
72
+520
+530
+550
+520
+500
+500
+500
+500
±510
+510
±490
±490
+500
+500
+510
+490
51
60
+500
+500
+500
+490
27
28
30
48
12 108
2 110
10 120
12 132
12
12
3
9
12
18
2
1
1
2
lIrs
Hrs Accum
±470
+460
±500
+465
+400
+500
+360
+440
+490
+490
±490
±490
+390
±440
+490
+490
±490
+490
+425
+410
+370
±420
±400
+340
+370
+370
8
+480
±470
+480
±470
±440
+410
+450
±450
+410
+410
±420
+450
+460
+440
±300
±280
+470
+460
±440
+420
±390
±340
+280
+250
±460
+450
+440
+420
+380
+330
+300
+190
±180
+300
+190
±230
+230
+250
±320
+210
±200
+220
+230
+220
+220
+220
+180
+170
+160
+180
+190
±180
+180
±l&0
+240
+230
+150
+160
+200
+250
+250
+250
+420
+340
+460
+440
+450
+470
+430
+430
water added every 12 hr S.
+430
+420
Treatment 3 - Replicate 1.
+530
+530
+440
+440
+520
+530
+530
+510
7
- Replicate 2 (continued)
Leaching, 500 ml
+450
+400
7
6
(continued).
Redox Potential
4
5
Treatment
3
Table 6.
3
-32. 1
-19. 1
7.70
-
7.50 7.75
-29.0
-24.5
-14.5
-11.6
-10.4
8.50 7.45
8.50 7.35
7.70
7.70
-
-18.7
-21.8
- 7.4
-7.5
- 7.8
8.50 7.45 7.70 - 8.2
-
8.60
-
7.30
875 7.40 7.70
3.60 7.40 7.70
8.70 7.50 7.75
8.70 7.50 7.75
8.50
-21.0
- 1c)
U.
-26.3
-22.0
-16.6
-14.5
-13.6
-12.4
-12.5
-12.7
-13.0
- 9.0
-13.7
-11.3
-11.6
-11.0
-11.1
-32.8
-17.9
-12.2
7.70
7.70
7.60
7.50
7.60
7.60
- 3.9
7.30
7.30
7.30
7.30
7.30
7.30
-24.4
-25.1
-26.4
-35.2
Tension
T2
Tl
- 7.2
- 3.0
- 3.5
- 4.2
- 0.5
8.50 7.30 7.60 - 6.3
8.60
8.50
8.50
8.50
8.50
8.40
-
-
2
pH
-25.2
26.0
8.50 7.20 7.70 -27.0
8.70 720 7.70 -36.0
-
1
52
60
72
75
78
84
96
101
106
118
122
124
128
130
131
142
145
147
155
4
3
3
6
12
5
5
12
4
2
4
2
1
11
3
2
8
12
8
48
11
4
+53k
+540
+540
+530
+520
±515
+510
+510
+510
±510
±510
+500
+510
±510
+510
+540
+540
+550
+520
+510
+510
+520
+520
+520
+520
+520
+510
±520
+520
+520
+520
±210
+220
+220
+220
-
+180
+190
Leaching, 500 ml water
+320
+220
+435
+830
+400
+220
+370
±380
+220
±480
+480
+270
±430
+150
+440
+360
+400
±225
+310
+300
+ 60
+290
+100
+10
±290
+210
±0.0
--270
+210
30
+270
+200
30
±260
+200
- 60
+260
+200
- 90
±240
+190
- 90
+240
+190
-100
±220
+180
-110
+430
+440
+460
+460
+560
+560
+535
+530
+370
+400
+580
+560
+550
±540
±320
+320
+320
+310
+370
+340
-
+510
5
Redox Potential
6
7
(continued).
8
+175
+180
+180
+180
+170
+170
+200
+160
+200
+210
-
+220
+220
added every 12 hrs.
+210
+190
+210
+210
+180
+210
+200
+180
+200
+210
+190
+210
+210
+190
+200
±210
+190
+210
+190
+170
+140
+190
+160
+210
+130
+160
+120
+170
+140
+200
+160
+130
+190
+170
+130
+190
+120
+ 90
+170
±110
+ 80
±160
+110
± 70
+160
+ 80
+ 60
±160
+210
+210
+200
+200
-
+200
+210
Treatment 8 - Replicate 1 (continued).
3
-
+560
+560
+520
+440
30
36
137
6
2
2
1
firs
firs Accum
Table 6.
-12.8
+ 7.2
-33.5
-29.0
-18.0
- 3.0
-23.0
-26.4
-26.8
-30.2
-31.3
-31.5
-36.8
Ti
+17.0
- 1.3
-12.0
7.30
7.40
7.6
9.7
7.4
2.3
+11.0
+
+
+
+
7.30
7.30
7.30
7.00
8.10
8.10
8.10
8.10
8.10
8.10
7.30
7.30 +17.0
7.35
-29.8
-22.7
-15.0
- 9.0
- 5.6
- 8.3
-10.0
- 7.0
- 7.2
- 8.0
- 9.0
- 8.1
-10.2
-11.4
-12.5
-16.4
-21.8
-24.6
-24.8
-27.8
-28.7
-30.6
-33.0
T2
Tension
7.30 + 5.6
7.72
7.75
7.60
7.60
7.30
7.30
7.70
7.65
7.65
7.75
-
7.70
7.70
3
7.38
7.38
7.38
7.39
7.40
7.32
-
7.45
7.35
7.35
7.38
7.40
7.40
7.40
-
7.40
7.45
7.35
7.48
-
7.40
7.45
2
pH
810 7.38
8.00
o,00
8.00
8.00
7.85
7.85
7.80
7.80
8.00
7.55
7.60
3.00
8.00
8.40
7.75
1
160
167
7
74
78
96
108
114
120
132
134
142
154
72
24
30
36
48
54
60
10
12
5
0.0
3
6
12
8
4
12
6
6
12
8
2
2
12
6
6
12
6
6
12
00
3
2
5
2
lirs
Hrs Accuni
+500
+500
±500
+500
+495
+535
+550
+540
-
±550
+550
+550
+550
+550
+565
+500
+560
±560
+560
+550
+550
+550
+550
+550
+560
+550
+560
+550
+550
+550
+SO0
+500
+500
+500
±500
2
+470
+490
+510
+510
±520
+520
+520
+450
+530
+540
+490
+550
1
+260
+420
±470
+470
+510
+520
±520
+530
±530
+525
-
±240
+ 15
+ 50
- 50
0.0
-125
-150
-140
-150
-160
-170
-190
-150
+ 10
± 30
+ 50
± 60
- 80
- 20
- 50
+ 65
4- 30
+ 50
+ 35
+ 50
+210
+285
+370
±380
+450
+465
+480
+290
+240
+220
4-240
+180
+200
+180
+280
+360
+375
±420
±440
±420
+ 70
±100
+100
+100
+180
+130
+180
±280
±220
+ 60
+ 90
500 ml water added
+ 60 + 60
-
+170
+170
+170
+160
+170
±170
+160
+160
+110
+190
+210
+220
Leaching
-240
+210
+220
+220
+225
±225
+220
+225
+230
±235
+240
+240
6
7
20
30
5
60
+ 10
-
+ 40
+ 35
+
+ 80
+ 90
± 40
+ 70
±125
±110
a
+100
+130
+120
-
+ 65
+ 80
+ 85
+ 85
+ 80
+ 80
+ 80
-130
-5.0
+ 40
+ 10
+ 75
+ 50
+ 80
+ 75
-110
-160
- 20
every 12 hrs.
- 55
+ 70
+ 50
+ 60
+
+ 10
-
+ 40
+ 30
+ 30
+ 30
± 70
+ 10
0.0
Treatment 8 - Replicate 2
Redox Potential
5
4
3
Table 6. (continued).
-
-
- 2.5
-
7.40 7.40 ± 1.3
7.40 7.40 - 0.3
7.40 7.55 -12.3
7.40 7.60 -16.6
7.40 7.60 -21.0
7.40 7.55 -27.0
7.40 7.50 -23.3
7.45 7.70 -29.5
7.50 7.75 -31.6
7.50 -22.0
7.50 - 9.2
6.1
- 9.5
-
-10.6
- 6.3
- 9.0
-11.4
-10.0
- 9.3
-28.2
-23.2
-14.3
-13.0
-21.3
-14.9
-12.5
-12.2
-12.5
-17.7
-18.6
-20.3
-24.0
-25.1
-26.5
-28.5
Tension
T1
-31.5
-25.7
-12.0
7.75
7.75 7.50
7.35 7.50 7.35 - 0.5
8.00 7.50 7.70 +10.0
8.00 7.50 7.75 + 3.0
8.00 7.40 7.80 ± 64
±15.5
8.00 7.40 7.80 + 5.9
8.00 7.40 7.80 + 1.8
8.10 7.40 7.80 +10.5
8.10 7.40 7.80 - 1.6
8.30
8.30
8.30
8.20
8.10
7.90
7.30
7.60
7.60
-
8.10 7.35
8.15 7.45
2
pH
62
Table 7.
Nitrate Recoveryain the Effluent Water of The
Two Long Columns During the Two Replicates
of Treatment 7.
One-Layer Column
Second Trial
First Trial
Elution
Time
Effluent
Volume
NO3-N
Total
NO3-N
Effluent
Volume
NO3-N
hr
ml
Mg/mi
tng
ml
Mg/nil
12
157
396
0.00
1.54
58.52
66.53
6.16
1.23
0.00
0.61
25.16
33.53
3.20
0.63
205
360
485
487
500
503
0.00
3.08
72.38
56.08
6.47
2.46
1.11
35.10
27.23
3.24
1.34
360
467
515
479
500
500
3.08
56.05
70.22
6.73
0.00
0.00
1.11
26.15
36.20
3.25
0.00
0.00
24
36
48
60
72
430
504
518
501
Total NO3-N
tug
0.00
Sand Column
12
299
24
36
48
60
72
510
500
484
475
475
3.10
54.80
69.68
7.40
0.62
0.00
0.93
27.96
34.50
3.58
0,30
0.00
of the treatment solution
a. The effluent resulting from the addition
contained no NO.-N
63
Table 8.
Nitiate ecoverybin the Effluent Water of
the Two Long Columns During the Two Replicates
of Treatment 3.
One-Layer Column
First Replicate
Elution
Time
Effluent
Volume
NO3-N
hrs
ml
12
132
382
24
36
43
60
72
433
450
433
490
Second Replicate
Total
NO3N
Efiluent
Volume
NO3-N
Total NO3N
M/ml
mg
ml
Mg/mi
mg
0.62
2.46
32.65
46.32
6.16
1.35
0.03
0.94
14.30
21.10
3.60
0.91
170
410
435
493
511
1.85
1.85
33.33
47.12
4.62
2.46
0.31
0.76
16.43
23.21
2.35
1.30
2.46
39.42
56.06
5.24
1.23
0,00
0.73
19.42
23.64
2.62
0.62
0.00
523
Sand Column
12
24
36
48
80
72
311
496
490
505
502
485
3.08
39.42
52.36
3.00
0.00
0.00
0.96
19.53
25.66
4.04
0.00
0.00
318
495
511
500
506
485
The effluent resulting from the addition of the treatment
solution contained no NO3-N.
b.
64
Table 9.
Treatment 1
Nitrate Recovery in the Effluent Water
of the Short One-Layer Column Treatments.
Sugar
Added
NO3-N
Added
Effluent
NO3-N
Volume
tug
tug
ml
630
710
0.0
255.5
705
Total
NO3-N
Loss
Mg/mi
mg
70
123
87.04
156.20
4.34
220
6.16
3.1
247.58
Treatment 3
272.6
255.5
690
770
650
105
139
0.0
73.0
146.0
0.0
14
219.0
Treatment. 4
272.6
257.0
645
685
715
99.5
208
14.2
64.1
143.0
10.2
15
217.3
272.6
130
2060
53
109
16
Treatment 5
545.2
130
2190
43.3
95.5
26
Treatment 6
146
168
178
22
10
26
24
60
60
288
348
Leaching -
204
228
120
26
96
24
36
48
72
0
12
24
24
24
0
12
12
12
12
(hrs)
lated
Time
(hrs)
Accumu-
Sampling
Interval
4.80/12.8
4.90/13.0
4.70/12.7
4.30/12.0
4.20/12.0
4.30/12.2
4.90/13.0
4.70/12.7
5.10/13.0
4.70/12.3
4.80/12.4
4.90/13.0
4.30/12.8
4.70/13.0
4.80/12,8
4.90/13.0
4.80/12.8
4.90/12.8
Water in the Gas Probes.
Treatment 7 - Replicate 2.
5.30/13.6
5.30/13.7
5.30/13.7
4.70/12.2
4.70/12.3
4.70/12.3
4.80/12.6
4.80/12.6
4.80/12.6
4.90/13.0
4.90/13.0
4.90/13.0
4.80/12.3
4.90/12.8
4.70/12.6
4.30/12.0
4.40/12.2
4.40/12.4
4.80/12.9
4.80/12.7
1
4.80/12.8
4.90/12.3
4.90/13.0
4. 701 12. 1
5.30/13.5
4.70/12.4
5.00/13.1
5.00/13.1
4.80/12.5
4.70/12.6
4.40/12.1
4.20/11.9
4.40/12.1
4.30/12.6
4.90/13.0
2
One-Layer Column
Gas Probes
ml Water Added Every 12 hrs.
4.90/12.8
4.90/13.0
4.90/12.7
5.00/13.1
5.00/13.1
5.00/13.1
4.80/12.6
4.30/12.9
5.00/12.9
4.30/12.4
9.30/12.6
4.70/12.7
4. 20/ 12.0
4.60/12.7
4.20/11.9
Inability to Sample for 60 hrs.
5.30/13.7
4.70/12.3
4.30/12.6
4.90/13.0
3
Treatment 7 - Replicate 1.
4.50/12.4
4.20/11.9
4.00/12.0
4.30/12.2
4.30/12.9
4.70/12.7
2
Air
02/N2 Peaks in Long Columns (cm)
During Treatments 7 and 8.
Leaching, 500
4.90/12.9
4.90/13.0
5.00/13.2
5.00/13.1
4.80/12.9
4.80/12.9
4.40/12.7
4.00/12.0
4.10/11.9
4.30/12.2
9.80/12.7
4.70/12.7
1
Sand Column
Gas Probes
Table 10.
0.20/15.7
0.15/15.7
0.60/14.9
0.60/15.8
0. 50/ 14. 9
1.30/ 16.3
0.90/15.2
0.70/15.3
0.70/15.1
1.60/14.8
1.10/15.2
1. 20/14.0
1.30/14.4
1.50/14.0
1.40/14.1
3
12
48
12
12
12
14
12
12
6
4
12
12
12
12
12
12
12
12
12
12
528
530
542
554
602
516
432
444
456
468
472
473
492
504
360
372
384
396
408
420
(hrs)
Interval lated
(hrs)
Time
Sampling Accuinu-
3.25/12.20
3.10/11.90
3.40/12.00
3.20/10.30
3.65/11.80
3.65/11.90
4.00/12.50
4.35/12.45
4.40/12.50
4.40/12.60
4.30/12.31
4.20/12.30
4.20/12.15
4.19/11.90
3
Air
(continued).
4.60/12.35
4.45/11.98
4.20/12.00
4.20/11.90
4.10/11.95
4.60/11.45
3.60/12.25
2.90/11.90
3.20/12.00
3.05/10.90
3.60/11.72
3.60/12.25
2.90/12.20
3.10/11.92
3.03/11.05
3.55/11.66
2.
4.30/11.95
4.05/11.60
4.10/11.80
3.90/11.10
4.00/11.72
Treatment 8 - Replicate
500 ml Uater Added Every 12
3.45/11.90 3.40/11.95 4.00/11.32
4.20/12.60 3.95/12.50 4.55/12.32
4.15/12.50 4.19/12.50 4.69/12.35
4.50/12.70 4.30/12.49 4.75/12.50
4.45/12.64 4.20/12.60 4.85/12.50
4.10/12.10 4.15/12.20 4.45/12.00
4.10/12.13 4.20/12.30 4.50/12.00
4.15/12.30 4.10/12.15 4.40/12.20
4.10/12.00 4.00/11.75 4.30/12.05
4.50/12.05
4.20/12.30
3.05/12.30
3.10/12.05
3.10/11.85
4.05/12.60
Treatment 3 - Replicate 1.
4.50/12.30
4.10/11.90
3.15/12.10
3.20/12.20
3.30/11.38
4.05/12.50
2
Leaching,
4.50/12.25
4.10/12.10
3.50/12.20
3.45/12.20
3.59/12.10
9.35/12.70
1
Sand Column
Gas Probes
Table 10.
4.30/11.95
2.90/11.40
3.45/11.55
3.40/10.90
3.70/11.33
4.09/11.36
4.45/11.95
4.50/11.90
4.52/12.15
4.70/12.15
4.50/12.05
4.50/12.00
4.40/12.00
4.25/11.83
Hrs.
4.60/12.30
4.40/12.00
4.20/11.30
4.35/11.90
4.15/11.92
4.70/11.45
1
4.35/12.20
4.05/11.30
4.20/11.80
3.65/10.50
4.00/11.70
4.09/11.90
4.65/12.45
4.60/12.15
4.75/12.50
4.30/12.56
4.49/12.10
4.50/12.00
4.30/11.95
4.30/11.90
4.60/12.30
4.50/12.10
4.40/12.10
4.32/11.95
4.15/11.92
4.70/11.45
2
One-Layer Column
Gas Probes
0.00/15.00
0.00/14.65
6.00/14.65
0.00/13.60
0.00/10.40
0.00/14.85
0. 00/14.50
0.00/15.30
0.00/15.30
0.20/14.95
0.30/15.15
0.30/15.35
0.00/14.80
0.00/14.50
0.30/15.35
0.00/15.00
0.00/14.90
0.00/14.90
0.00/15.00
0.30/18.40
3
12
12
12
12
Time
(hrs)
614
626
638
650
(hrs)
lated
Accumu-
Sampling
Interval
2
3
Air
(continued).
3.60/11.75
3.80/12.00
3.68/11.65
3.65/11.68
3.60/11.85
3.70/11.90
3.68/11.75
3.70/11.70
1
4.00/11.70
4.10/12.00
3.98/11.59
3.90/11.60
2
One-Layer Column
Gas Probes
3.60/11.96
3.68/12.20
3.52/12.00
3.60/11.70
12 firs.
4.05/11.90
4.20/12.00
4.05/11.75
3.98/11.70
Leaching, 500 ml Water Added Every
4.10/12.30
3.90/12.05
3.65/11.56
3.63/11.70
I
Sand Column
Gas Probes
Table 10.
0.00/14.60
0.00/13.40
0.00/14.30
0.00/14.38
3
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