CORN Newsletter: 2004-38, November 9, 2004

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C.O.R.N Newsletter 2004-38
November 9, 2004 - November 23, 2004

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Sludge and Waste Application on Production Fields
by Robert Mullen


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Sludges and wastes generated from municipal, agricultural, and industrial activities can be excellent sources of nutrients for crop production, and land application is an excellent way to recycle these materials. Due to the variability of waste materials and their nutrient contents (primarily depending upon how it was treated), lab analysis of the material is extremely important. Typical lab analysis should reveal nutrient concentrations of nitrogen, potassium, and phosphorus as well as some micros and heavy metals.

Nitrogen

Keep the following rules in mind when determining sludge and waste material rates based on nitrogen need. Nitrogen applied as nitrate is readily plant available, so allocate it appropriately in your N budget. If the sludge (or waste) is surface-applied between November and February, assume that 50% of the N applied as ammonium will be available next spring. If the manure is injected below the soil surface or incorporated immediately after surface application, assume that all of the N will be available next spring. Assume that of the organic N applied 30% will be plant available next spring. Below is an example calculation:

Yield potential – 160 bu/acre
N recommendation (Tri-State Guide) – 190 lb N/acre
Sludge analysis (aerobically digested)
Ammonium-N – 683 ppm
Organic N – 18,500 ppm
Moisture – 35%

To determine the amount of ammonium-N available (assuming the waste is surface applied in November), convert from ppm to lb NH4-N/ton of sludge by multiplying 683 by 0.002. Because the material is surface applied only 50% is assumed to be available next spring thus only 0.7 lb NH4-N/ton of sludge will be available (683 * 0.002 *0.5). Convert the concentration of organic-N from ppm to lb organic-N/ton of sludge using the same 0.002 conversion factor. Assuming that 30% of the organic-N applied will be plant available next year, 11.1 lb N/ton of sludge will be plant available from mineralization of the organic-N fraction (18,500 * 0.002 * 0.3). Combining both plant available pools of N (ammonium-N and mineralized organic-N), a total of 11.8 lb N/ton of sludge will be plant available next growing season. Because 190 lb N/acre is needed, 16.1 dry tons of sludge per acre must be applied (190/11.8). The water contained in the sludge must be accounted for when determining the total amount of material to apply. The rate of material that must be applied to provide 190 lb N/acre is 24.8 ton/acre (16.1/(1-0.35)). Estimated mineralization rates for sludges and waste materials differ, so make sure to identify the material you want to apply. For additional mineralization rate estimates consult Ohio State University Bulletin 879-99 at http://ohioline.osu.edu/b879/.

Phosphorus

Assuming the above material was applied at 24.8 ton/acre, how much P was applied? Lab analysis reveals that the sludge material contained 800 ppm P. Converting the concentration from ppm to lb P/ton of sludge is done using the same conversion factor as before, thus there 1.6 lb P/ton of sludge (800 * 0.002). Fertilizer P is typically presented as P2O5, so the P concentration should be converted. Thus the sludge contains 3.7 lb P2O5/ton (1.6/0.436). If 24.8 tons of sludge is applied per acre, 91.8 lb P2O5 is applied per acre (24.8 * 3.7). Depending upon soil test levels this rate may exceed the agronomic rate, so make certain to account for P when making sludge applications.

Lime

Some sludges or waste materials are lime stabilized and actually have some neutralizing power. Care should be taken when applying these materials. Annual applications of such materials can increase soil pH levels well above 7, so make sure to account for the neutralizing ability of the materials that are applied as well as monitoring soil pH levels determined by soil test.

Heavy Metals

Depending upon the source of the sludge or waste material and how it was treated, heavy metal levels may be of concern for land application. Current EPA levels restrict the amount of heavy metals that can be applied to production land. Laboratory analysis should reveal the metal content of the sludge/waste material which can be used for determining application restrictions. For additional information on EPA restrictions regarding sludge materials and heavy metals consult Ohio State University Bulletin 879-99.

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C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.

Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868


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