Manure Application Considerations

The use of livestock manurers in cropping systems has many advantages.  Animal manurers can reduce the cost of fertilizer inputs.  Manure can help build or maintain soil fertility, increase water holding capacity, and improve soil tilth.  In addition to major plant nutrients of nitrogen, phosphorus, and potassium, manure also contains many micronutrients such as calcium, sulfur, zinc, boron, copper, magnesium, and manganese.  However, application of manure in excess of needs can reduce the following crop yield, create surface and groundwater pollution and reduce the economic returns that are desired.

Land application of manure should always be applied at proper rates and soil conditions to eliminate or reduce erosion and runoff possibilities.  The longer that manure is on the soil prior to crop uptake, the more possibilities exist for nutrient losses through mineralization, volatilization, denitrification, leaching, and erosion.  Uniform application or spread should take into consideration timing so plants can efficiently uptake nutrients and reduce any negative environmental impact.

Fall manure applications are often necessary.  This management practice allows for increased storage capacity for manure accumulations during the cold wet winter months.  The least desirable application is during the winter when the soil is frozen and nutrients are not able to bind with the soil.  Manure lying on the surface of frozen ground therefore is more apt to be lost from the system.  While recent warmer winters have stretched the application window, producers should consider potential negative environmental impacts of winter applications. It is always recommended that a manure sample be submitted for analysis prior to application so that the producer is applying adequate quantities for crop need but not in excess for environmental interference.  This should be matched with an appropriate soil testing program. Both soil and manure testing is available through the MU Soil Testing and Plant Diagnostic Service.  Samples can be submitted through your local MU Extension center.

The nutrient needs of the crop to be grown should be also taken into consideration so that proper manure application rates are utilized. Table 1 lists a few of the values for above ground portion of the plants when only grain is removed.  A complete listing is in the Midwest Plan Service Livestock Waste Facilities Handbook.

 

Table 1.  Crop Nutrient Needs (note: Soybean and alfalfa are legumes and get most of their N from the nitrogen fixing association utilizing air)

Crop

Yield Unit

N

P2O5

K2O

Corn grain

100 bushel

160

60

215

Soybean grain

40 bushel

180

45

80

Wheat grain

60 bushel

125

50

110

Fescue

3.5 ton

135

65

185

Alfalfa

4 ton

180

40

180

 

It should be noted that waste handling systems can affect the nutrient composition.  Moisture content and bedding type can result in less available nutrients per pound of product. Ammonia nitrogen can be lost to the air and open lot or stockpiles can lose nitrogen to leaching.

As good stewards of this land, it is imperative that producers develop a good manure management plan from the feeding of livestock to application of manure on the land. Anything less helps the public create negative stereotypes of production agriculture which affects all producers and generally leads to harsher regulations.

Source:  lorenzt@missouri.eduTodd Lorenz, Agronomy Specialist