Best Management Practices (BMPs) to Efficiently Use Swine Manure as Fertilizer

Alan Sutton
Brian Richert
Purdue Univ. Dept. of Animal Sciences

Don Jones
Purdue Univ. Dept. of Agricultural and Biological Engineering

Brad Joern
Purdue Univ. Dept. of Agronomy

Environmental concerns and devastating prices have forced pork producers to look for ways to reduce costs. Manure is often considered a liability to be disposed of. It has received considerable publicity as a contributor to water and air pollution, and in some locations, excessive application of manure onto cropland has caused nutrient buildup in soil and contamination of water. Management strategies that minimize manure nutrient excretion and maximize manure nutrient use efficiency in cropping programs can significantly improve the "bottom line" for most pork producers, especially pork producers who have crop acreage.

The following are examples of best management practices (BMP's) for controlling nutrient flow from the swine operation and for improving the effectiveness of manure as a nutrient resource.

Nutrient Management

  • Evaluate diets and reduce excess feed nutrients. Adding phytase in low P diets will enhance P, N, Cu, Zn and Ca use, and reducing the crude protein and balancing amino acids can reduce N excretion.

  • Reduce water spillage or use wet-dry feeders to reduce manure volume and increase manure nutrient concentrations in liquid pit systems.

  • Consider phase feeding, split-sex feeding, grinding, and pelleting feeds to enhance nutrient use and reduce nutrient excretion.

  • Keep records on each field where manure or commercial fertilizer are applied; on crop information; on soil and manure test results; and on pesticide and herbicide applications. Good records improve your ability to evaluate how your crop management strategies are working on a field-specific basis.

  • Maintain regular manure and soil test programs to determine the optimum application rate and priorities for spreading manure on a field-specific basis.

  • Take samples of manure while emptying the storage. If possible, agitate manure before removal to improve manure nutrient content consistency.

  • Use an on-farm quick test for available N content every 10 or so loads or every food of pit depth, and adjust application rate if necessary. If test results indicate that manure nutrient values change in a consistent pattern when emptying the storage, you may be able to significantly reduce your sampling frequency.

  • Apply manure uniformly with calibrated equipment. Check calibration routinely.

  • Use the nutrients carried in runoff that has contacted manure. Treat runoff from feedlots, animal exercise, or handling areas as manure. Provide a settling basin to greatly reduce the solids suspended in the water.

  • Maintain grassed buffer areas to filter out solids and absorb nutrients at points where field and feedlot runoff may occur.

  • Use nitrification inhibitors in liquid manure-injection systems to reduce nitrogen losses from applications made in the fall or early spring when N loss potential between application and crop uptake may be significant.

  • Apply manure as a way to quickly "build up" soils low in phosphorous or potassium.

  • To prevent excessive P and K build-up, rotate manure applications to different fields and apply to the lowest testing fields.

  • In the Spring, use the pre-side dress N test in fields that received manure the previous Fall to determine whether supplemental commercial fertilizer N is needed.

    Crop Factors

  • Base the crop fertilizer needs on realistic yield goals and then take N credits from last year's legume crop (30 lbs. N/acre for soybeans). Use commercial fertilizer only when manure does not meet crop needs.

  • Apply fertilizer with proper timing and placement for maximum plant utilization.

  • Incorporate manure to reduce N loss and manure runoff.

  • Put manure on non-legume crops to better utilize manure nitrogen.

  • When necessary, only surface-apply manure on fall cover crops or surface residues rather than tilled soil to minimize runoff.

  • During the summer, broadcast manure on pastures or hay fields where nutrients can be used immediately. If manure must be applied to harvested wheat fields, incorporate the manure to reduce nutrient runoff potential.

    Soil Factors

  • ; Apply manure to fields with the lowest P and K soil test values.

  • Avoid applying manure to wet soils to reduce compaction, runoff, denitrification, and leaching.

  • Apply manure in the fall (possibly with a nitrification inhibitor) if compaction appears to be a prevalent problem with spring applications.

  • Apply manure to sandy soil near planting time to minimize nitrate leaching.

  • Delay fall manure applications until the soil has cooled to 50oF or less, or add a nitrification inhibitor.

    Which Manure Where?

  • Apply manure with the highest N content in the spring or fall. Apply the lowest N manure in summer.

  • Haul the highest nutrient content manure to the farthest fields. Apply lowest nutrient content manure to closest fields.

  • Apply the highest nutrient content manure to corn silage or other crops with high nutrient demands.

  • Apply manure with a high N content to legumes, only if you have no better use for the N since legumes produce their own N if none is provided.

  • Avoid N leaching to ground water. Limit N fall manure applications on sandy soils and avoid summer applications of manure to harvested wheat fields if no crop is present.

  • Do not apply more N than the crop needs.

  • Apply high-P manure to fields with lowest P soil test levels. Alternate each year between high-nutrient and low-nutrient manure if manure is applied to the same fields every year.

    Site and Environment Factors

  • Inject manure, or incorporate solid manure, the same day as surface spreading to minimize N losses, odors, and runoff potential.

  • Delay manure applications and tillage on erosive soils until spring.

  • Incorporate liquid manure applied in karst areas.

  • Incorporate manure on nonerosive soils in fall to retain nutrients.

  • Apply manure on frozen or snow-covered soil only if the field is not subject to flooding, and if the slope is less than 2%, or erosion control practices are in place

  • Surface apply manure in highly erodable land only to cover crops, residue cover, or consistent with erosion control practices.

  • Use good conservation practices with manure application.



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