Stop or reduce importing poultry manure
Case study: dairy operation
The purpose of this case study is to demonstrate the economic and environmental value of reducing imports of manure into farms where farm phosphorus imports exceed exports and soil test phosphorus is very high.
Manure stacking slab
This dairy farm in Central Minnesota has 110 head of Holstein cows with a DHIA Rolling Herd Average of 26,000 pounds on 2X milking. The milking cows and replacement heifers average 268 Animal Units (A.U.). The milking cows housing is a tie-stall barn using straw bedding. The balance of the animals are on conventional bedding packs. Manure is stored on a permanent stacking slab. This dairy farm has 335 harvested and 315 tilled acres for harvested acres to animal unit ratio of 1.3. This farm purchases some grass hay and bedding but raises all other grains and forages, selling rye and some hay and corn. Center pivot irrigation is used on all but 50 acres of these Loamy Sand soils. Dry shell corn yields routinely exceed 220 bushels/acre.
Phosphorus import-export analysis:
The dairy purchases feed supplements and the total phosphorus (P) in the lactation ration is .34 to .36%. The only P fertilizer used is 130 pounds/acre of a 16-3-28 corn starter. This farm has been annually importing around 432 tons of poultry manure averaging 3.43% N and 2.73% P. Field application of all farm produced and imported manure is based on nitrogen (N) needs of the crops. The farm P imports exceed exports by 21 lbs./acre and 27 lbs./A.U. annually, building soil test P above 80 Bray 1-P.
|Animals||0||886||Harvested Acres||Animal Units||Ratio|
|Protein/Minerals||3512||0||Excess P (lb.)||Harvested Acres||Ratio|
|Manure||10,143||0||Excess P (lb.)||Animal Units||Ratio|
Dilemma of long-term application of manure based on nitrogen needs:
Field nutrient imbalance with manure
Manure can provide valuable nutrition to our soils in N, P, potassium (K), sulfur, trace minerals, and organic matter. Analysis of manure varies by animal species: type of production (growing vs lactation), bedding used, and manure storage system. Sampling the manure and submitting it to a certified laboratory for testing is necessary to determine the nutrient analysis. However, the N: P ratio in manure usually does not match the relative N: P ratio needs of common agriculture crops. If application of manure is continuous to corn ground based on N need, the soil P level will usually increase over a period of years. The following diagram illustrates this long-term phenomenon with dairy manure and corn. Typical poultry manure has a closer N: P ratio than dairy manure. With a typical dairy farm's crop rotation of corn grain/silage and alfalfa, the alfalfa will utilize most if not all of the K. Alfalfa has about the same P needs as corn.
Discontinue importing poultry manure:
If poultry manure imports were to cease on this dairy farm, the P balance would swing from positive to negative. In other words, the farm would then export more P than it imports. In referring to the chart, the new P balance would be -2939 rather than a +7204. Obviously only a partial reduction of poultry manure is necessary to balance P imports with exports. If the goal were to reduce field P levels, a period of more P exports than imports would be necessary.
|Excess P (lb.)||Harvested acres||Ratio|
|Excess P (lb.)||Animal units||Ratio|
By using worksheets available on the University of Minnesota Extension website1 along with a manure analysis, the N, P, and K value of manure can be determined based on the replacement cost of commercial fertilizer. Whatever the form of the manure, it is usually more expensive to purchase commercial fertilizer and the aforementioned worksheet accounts for this. In this case study, the only realized current value of manure is N since P and K in the soils of this farm are more than adequate for crop production. At $6.00/ton for application and $15/ton purchase cost of the poultry manure, the total cost of the 432 tons of this manure would be $9072. The total N value of the poultry manure is $14,949. The net savings of utilizing the manure instead of commercial fertilizer is $5,8771,2, realizing a positive return to purchasing poultry manure over commercial fertilizer. However, persistent importation of poultry manure will continue to escalate the already high P levels in the soil and continue to pose a risk for P in runoff.
- Manure can provide significant nutrient contributions for crop production.
- The relative level of N and P in most manure does not match the relative needs of conventional crops.
- Importing manure to meet corn N needs can cause an excess P balance on a livestock farm.
- Reduction of manure imports is a viable option when most fields on a farm have excessive soil test P. This is creating a risk of runoff to surface waters.
- Discontinuing importation of manure and purchasing commercial N fertilizer may have an economic cost.
- Spreadsheets for calculating the economic value of manure.
- Commercial fertilizer values used in economic comparison: Urea (46-0-0) $/490/ton, DAP (18-46) $595/ton, and Potash (0-0-60) $525/ton.