Rates & Methods
Manure rates should be based on the nutrient requirement of the crop being grown to ensure efficient use of manure nutrients and to minimize the chances of nutrient loss by leaching and through surface runoff. Soil testing, manure analysis and proper estimation of yield goal are necessary to calculate proper agronomic application rates of manure and fertilizers. Manure Application Rate Calculation Worksheet illustrates the steps of calculating the proper amount of manure needed.
Manure application rates are limited by state regulations:
- Not to exceed crop N requirement
- Certain soil P test levels
- Other field conditions
The Soil Test Interpretation and Fertilizer Decision Support
Program allows you to calculate the value of manure nutrients based on prices of commercial fertilizers, and to calculate the application rates based on yield goal and soil tests on line. The actual value of manure is more just nutrients. It also has liming effects for acid soils, and adds organic matter to improve soil quality.
Manure can be applied to land by surface broadcasting using a manure spreader, irrigation system, or tank wagon followed by plowing or disking, by broadcasting without incorporation, or by knifing under the soil surface. Maximum nutrient benefit is realized when manure is incorporated into the soil immediately or soon after application. Immediate incorporation of solid manure minimizes nitrogen loss to the air and allows soil microorganisms to break down the organic fraction of the manure. Injecting, chiseling, or knifing liquid manure beneath the soil surface reduces nitrogen losses by volatilization and potential runoff. Incorporation of either solid or liquid manure also reduces odor problems. Nitrogen loss by ammonia volatilization from surface applications is greater on dry, warm, windy days than on days that are humid and/or cold. To prevent local high concentrations of ammonium or inorganic salts which can reduce germination and affect yields, manure should be applied uniformly (See Classification of Irrigation Water Quality and Reclaiming Slick Spots and Salty Soils for salinity related information).
Phosphorus and potassium are not as mobile as nitrogen, so incorporation of manure will minimize phosphorus and potassium losses due to runoff, and increase their agronomic values.