Analyzing Manure Test Outcomes
Applying manure to farmland can provide a valuable source of nutrients for crops, but it's crucial to ensure that the application is well-managed to avoid potential issues such as nutrient runoff and excesses. Here's a step-by-step guide on how to determine the appropriate manure application based on manure test results, soil nutrient status, and crop nutrient needs.
Step 1: Obtain a Manure Nutrient Analysis
To begin, obtain a manure nutrient analysis to measure the actual content of key nutrients such as nitrogen (N), phosphorus (P), potassium (K), and micronutrients in the manure. This analysis should be recent, typically within 60 days of application.
Step 2: Conduct a Current Soil Test
Conduct a current soil test on the field to assess existing nutrient levels and avoid potential nutrient excess or toxicity, especially for P, K, zinc (Zn), and copper (Cu).
Step 3: Determine the Crop Nutrient Requirements
Determine the crop nutrient requirements based on realistic yield expectations and the type of crop to be planted. For example, for crops like soybeans that fix their own nitrogen, P- or K-based manure rates are more relevant than N-based rates.
Step 4: Calculate the Correct Manure Application Rate
Calculate the correct manure application rate by using the manure test to find the amount of available nutrients per unit of manure. Match manure nutrient supply with crop nutrient demand, often prioritizing the most limiting nutrient for the crop to avoid over-application. Adjust for nutrient availability and losses by accounting for application method.
Step 5: Account for Nutrient Credits and Environmental Considerations
Account for nutrient credits and environmental considerations, including residual soil nutrients, previous fertilizer applications, and nitrogen credits (e.g., from legumes).
Step 6: Calibrate Application Equipment
Calibrate application equipment to ensure uniform application of the target manure rate across the field to prevent localized over- or under-fertilization.
A practical formula example used in feedlot manure management includes calculating the total manure N available, calculating crop N removal, and dividing manure N by crop N removal per acre to find the required acreage for application. This approach minimizes nutrient runoff and accumulation issues such as P or Zn toxicity caused by repeated manure applications at N-based rates.
For instance, if the Tri-State Fertilizer Recommendation for nitrogen for corn following soybeans with a yield goal of 180 bushels per acre is 190 pounds per acre, supplemental nitrogen will be needed. Similarly, the Tri-State Fertilizer Recommendation for potassium for corn with a yield goal of 180 bushels per acre, 25 ppm and a 20 CEC, is 220 pounds per acre, so supplemental potassium will also be needed.
The manure contains 13 pounds per 1,000 gallon of KO. The total nitrogen in 1,000 gallons of manure, taking into account both ammonium and organic nitrogen, is approximately 9.5 lbs. To meet the phosphorus requirement for corn with a yield goal of 180 bushels per acre, approximately 9,400 gallons/acre of manure need to be applied.
Nutrient levels in manure samples are often reported in pounds per 1,000 gallon for liquid manure and pounds per ton for solid manure. The availability of nitrogen depends heavily on when the manure is applied and how quickly it is incorporated into the soil. The remaining organic nitrogen must be broken down before becoming available, which usually occurs over a three-year period.
Manure test results include moisture, total nitrogen (N), ammonium N, organic N, phosphorus as PO, and potassium as KO. Phosphorus and potassium are reported on test results as PO and KO, respectively, and their nutrient levels can be compared to the crop's nutrient needs from the Tri-State Fertilizer Recommendations.
Incorporation of manure into the soil provides protection from the sun and runoff loss from rain, and affects nitrogen availability. The application of this amount of manure would result in approximately 89.3 lbs/acre of total N.
By following these steps and considering the unique characteristics of your farm and manure, you can ensure a balanced and environmentally friendly manure application for optimal crop growth.
- The manure analysis reveals the nutrient content, including nitrogen (N), phosphorus (P), potassium (K), and micronutrients, which are essential for supporting the health-and-wellness of crops and livestock.
- To establish the optimal application rate of manure, first, factor in the crop's nutrient needs, such as the Tri-State Fertilizer Recommendation for nitrogen for corn following soybeans, which is 190 pounds per acre.
- By proper manure management, including scientifically determining manure application rates during the agriculture process, it contributes to a sustainable and nutritious environment conducive to crop growth and livestock health.
