Organic Fertilizer Alternatives - Hamilton County Soil and Water

Storm Water District
ORGANIC FERTILIZER ALTERNATIVES By Holly Utrata-­‐Halcomb, Administrator Hamilton County Soil & Water Conservation District pH pH is the most critical aspect of soil fertility. If pH is too low (acidic) or too high (alkaline) vital macro and micro nutrients may be present in the soil but nor available to plants. Most vegetable crops prefer a slightly acidic soil with a pH around 6.5 – 6.8. This range makes for happy worms and microorganisms and generally supports an abundance of readily available soil nutrients. Your soil fertility test results will list a target pH. To lower pH, elemental sulfur or iron sulfate may be applied. It is recommended that these products be applied in the fall as it will take several months to be effective. This application must be applied every fall because the soil pH will tend to migrate back to its original level. One downside of using iron sulfate is that it could also tie up phosphorus, particularly in this case where the phosphorus soil test is on the low side. Aluminum Sulfate is immediately effective after application, but the Aluminum can be toxic to ericaceous (acid loving) plants such as Rhododendron, Azalea and Blueberries. Peat Moss and coffee grounds will help to moderate pH, but the amount of coffee grounds required to lower pH by 1 point would prove to be toxic to the plants. To Decrease pH: Apply 2 to 3 pounds of sulfur per 100 square feet to lower soil pH 1 point. Always read package directions To increase pH: Apply 5 pounds of lime per 100 square feet to raise soil pH by 1 point. Always read package directions Organic Matter Incorporate organic matter into your soil with a locally available compost material. Mulching gardens with 2-­‐3" of organic material annually will increase soil organic matter and reduce the amount of commercial fertilizer you need to apply. This organic material will feed the microorganisms, help to moderate soil temperature and pH, loosen compacted soil and help to retain moisture during dry periods. After 3 years, the rate of fertilizer could possibly be reduced by 1/2. This is one reason why soil fertility tests should be run every 4-­‐5 years. It is advisable to add organic matter prior to pulling samples for a soil fertility test, not afterward. Nitrogen (N) Total N Concentration in Common Organic Sources Organic Source Total N (%) Poultry manure 1.5-­‐3.0 Pig, horse, cow manure 0.3-­‐0.6 Green manure 1.5-­‐5.0 Compost 0.5-­‐2.0 Seaweed meal 2.0-­‐3.0 Sewage sludge 1.0-­‐5.0 Fish waste 4.0-­‐10.0 Blood (slaughter house) 10.0-­‐12.0 Human urine/night soil 1.0-­‐1.5 Synchronization. The need for N fertilizers would be reduced significantly if the crop's N requirement can be timed closely to the nitrogen release from organic sources. Plants require different amounts of N at different stages of growth: seedlings and senescing plants definitely require much less N than flowering or fruiting plants. We also have known that different organic manures have different N releasing patterns. For example, the below chart shows the N release patterns three organic sources. Nitrogen from poultry manures (non-­‐composted) is more quickly available than N in manure from cow, and sheep. This is because poultry manure contains significant amounts of uric acid, which is readily decomposable. Also, roughage in cattle diets results in manure that is less readily decomposed due to lignin and cellulose. Horse manure is the least desirable type of manure due to the high rate of viable weed seed. Presence of bedding or litter lowers N content by dilution, but its effect on N availability cannot be easily predicted. Moist manure, when exposed to the air, undergoes significant loss of N as volatile NH3. Fresh manure can also burn plants. Nitrogen losses after spreading can be significantly reduced by incorporating the manure -­‐-­‐even shallow incorporation is adequate. Nitrogen in composts is a more stable form than N in manures. Thus, there is a decreased likelihood of losing compost N from the system. On the other hand, composts containing less than 1.5% total N and supply little or no N to crops during the first few weeks after application. Green manures are fast growing catch crops like clovers, mustard, rye, radishes and vetches that are incorporated into the soil while they are still green in order to improve the soil and to supply N to the associated/subsequent crop. A properly managed legume cover crop can fix up to 3 – 4 lbs. of N/1,000ft.sq. in 3 to 6 months. (Bugg and Miller, 1991). Phosphorus (P) Total P concentration in organically acceptable sources Source Total P (%) Rock phosphate 17-­‐26 Bone meal 20-­‐30 Fish meal 5-­‐10 Wood ash 2-­‐5 Poultry manure 0.5-­‐1.5 Green manure 0.2-­‐0.5 Compost 0.2-­‐0.5 Sewage sludge 0.4-­‐2.5 The above table shows P content of selected sources that are acceptable to organic farming community in most states. Among these, the first two, rock phosphate and bone meal, have reasonably high total P content: between 20 and 30%. However, P in these two sources is very insoluble, thus much less plant available than P in treble superphosphate. More specifically, P in rock phosphate and bone meal has the formula: Ca5(OH)(PO4)3 which is hydroxy apatite or apatite for short. This is the same material that our bones and teeth are made of. As our teeth can attest to it, apatite is quite durable; is very hard to dissolve in water, meaning that it provides very little phosphate to your crop in the short term. A couple of things should be mentioned about rock phosphate. First, it is a source of P for long-­‐
term soil improvement, don’t t expect any noticeable effect from it within weeks or months, unless you use huge amounts of it. Second, its solubility, and thus plant availability, depends strongly on soil pH and particle size. It is more effective in acid soils than in calcareous or alkaline soils; more effective when it is fine than coarse, and more effective in the presence of mycorrhiza than without mycorrhiza. By contrast, P contents of chicken manure, compost, and sludge are relatively low, usually below 3%. Thus, large amounts would be needed to meet P requirement of the crop. Yet, pound for pound, P from these organic sources is quite available to plants; sometimes even more effective than treble superphosphate. Our recent work has shown that organic matter from the manure interacts with clay minerals and reduces P sorption by the soil, thereby enhancing P availability to plants (Hue, 1990; 1991). POTASSIUM (K) In plants, potassium is required for maintaining osmotic potential of cell. That is, K makes plants look turgid. Since K regulates the osmotic potential of cells, and the close or open conditions of stomata, it plays an important role in water relations in the plant. Potassium is involved in water uptake from the soil, water retention in the plant tissue, and long distance transport of water in the xylem and of photosynthates in the phloem. Potassium affects cell extension. With adequate K, cell walls are thicker, thereby improving plant resistance to lodging, pests and disease. Fruits and vegetables grown with adequate K seem to have a longer shelf life in the grocery store. Total K concentration in selected organically acceptable sources (Adapted from
Nick and Bradley, 1994; and personal data)
Total K, %
Sul-Po-Mag [Mg, K, SO4]
Polyhalite [Ca, K, SO4]
Wood ash
Green sand
Green manure
Seaweed meal
Quick Tip Guide Table 7. Average Plant Food Content of Natural and Organic Fertilizer Materials (Percentage on a Dry-­‐Weight Basis.) Organic Materials % N % P % K Availability Acidity Fish Scrap 5.0 3.0 0 slowly acid Fish Meal 10.0 4.0 0 slowly acid Guano, Bat 10.0 4.0 2.0 moderately acid Sewage Sludge 2.0-­‐6.0 1.0-­‐2.5 0.0-­‐0.4 slowly acid Dried Blood 12.0 1.5 0.8 mod. slow acid Soybean Meal 7.0 1.2 1.5 slowly v. sl. acid Tankage, Animal 9.0 10.0 15.5 slowly acid Tobacco Stems 1.5 0.5 5.0 slowly alkaline Seaweed 1.0 -­‐-­‐-­‐ 4.0-­‐10.0 slowly -­‐-­‐-­‐ Bone Meal, Raw 3.5 22.0 -­‐-­‐-­‐ slowly alkaline Wood Ashes -­‐-­‐-­‐ 2.0 4.0-­‐10.0 quickly alkaline Cocoa Shell Meal 2.5 1.0 2.5 slowly neutral Cotton Seed Meal 6.0 2.5 1.5 slowly acid Ground Rock Phosphate -­‐-­‐-­‐ 33.0 -­‐-­‐-­‐ very slowly alkaline Green Sand -­‐-­‐-­‐ 1.0 6.0 very slowly -­‐-­‐-­‐ Basic Slag -­‐-­‐-­‐ 8.0 -­‐-­‐-­‐ quickly alkaline Horn and Hoof Meal 12.0 2.0 -­‐-­‐-­‐ -­‐-­‐-­‐ -­‐-­‐-­‐ Milorganite 6.0 2.5 -­‐-­‐-­‐ -­‐-­‐-­‐ -­‐-­‐-­‐ Peat and Muck 1.5-­‐3.0 0.25-­‐0.5 0.5-­‐.10 very slowly acid Spent Mushroom Compost 2.0 .74 1.46 moderately 6.4 To determine % of nutrient to lbs./1,000ft square use this quick calculation.
_______________ Divided by ____________ = _____________________
Amt. of Nitrogen
% of Nitrogen
# lbs Needed
Needed in lbs.
Example – My soil test shows the need for 1 lb. of Nitrogen and 4 lb of
Potassium/1,000ft. sq.
I will use composted Poultry Manure with an analysis of 3-1-1. The percentage of N is
______1______ Divided by __.03_______ = _______33_______
Amt. of Nitrogen
% of Nitrogen
# lbs Needed
in manure
I divided 1 by .03 = 33lbs of composted poultry manure needed/1,000ft. sq.
This amount of Composted Poultry Manure also contains.33 pounds of Potassium.
______33________ Times ______.01_________ = ____.33____
# pound being used
% of Potassium
# lbs supplied
I arrived at this number by multiplying the number of pound I will be using – 33 - times
the percentage of Potassium available in composted chicken manure .01 = .33
I still need 3.67 lbs. of Potassium to make up the rest of the Potassium I need, I will use
Green Sand with an analysis of 0-1-6. The percentage of each element is 0-.01-.06
____3.67___________ Divided by _____.06_______ = __61.16________
Amt. of Nitrogen needed
% of Nitrogen
# lbs Needed
Needed in lbs.
This calculation shows I will need 61.16 lbs of Green sand to make up the need for the
rest of the Potassium. Note, these materials also will provide some Phosphorus, which I
don’t need, but it is the minimal amount from the choice of materials.
•­‐calculator/ Fertilizer calculator. References
1. Bugg, R. L. and P. R. Miller. 1991. Grasses/legumes:Dream team. Sustainable
Agric. News 3(4):1-4. UC Davis, CA.
2. Caplan, B. 1992. Organic gardening. Headline Book Publ., London, UK.
3. Hue, N. V. 1990. Interaction of Ca(H2PO4)2 applied to an Oxisol and previous
sludge amendment:soil and crop response. Commun. Soil Sci. Plant Anal. 21:6173.
4. Hue, N. V. 1991. Effects of organic acids/anions on P sorption and
phytoavailability in soils with different mineralogies. Soil Sci. 152:463-471.
5. Hue, N. V., H. Ikawa, and X. Huang. 1994. Predicting phosphorus requirements
of some Hawaii soils. Fact Sheet no. 2. CTAHR.
6. Hue, N. V. 1995. Sewage sludge. pp. 193-239. In J. E. Rechcigl (ed) Soil
amendment and environmental quality. Lewis Publ., Boca Raton, FL.
7. Nick, J. and F. Bradley. 1994. Growing fruits and vegetables organically. Rodale
Press, Emmaus, PA.
8. Tamimi, Y., J. A. Silva, R. S. Yost, and N. V. Hue. 1994. Adequate nutrient levels
in soils and plants in Hawaii. Fact Sheet no. 3. CTAHR.
9. Today's Chemist. 1995. May issue. Am. Chem. Soc.
10. WSARE. 1995. The basic principles of sustainable agriculture. URL: (the internet).
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