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Take soil samples now – crop and animal producers

Here’s a reminder for confinement feeding operation producers who must have a manure management plan (MMP): soil tests are required once every four years. The best times to sample soils are in the fall after harvest and before fertilizer or manure is applied, or in the spring before fertilization.

“Producers should check the age of their soil samples and get samples on fields that need it,” says Jeremy Klatt, DNR Environmental Specialist. “Fields that will be added to the manure plan must also be sampled.”

Crop producers who accept manure from confinements may also want to discuss with their manure provider how the P index could affect manure application on their cropland and if they need to have soil samples taken.

Producers must take at least one sample for every 10 acres of field, following Iowa State University Extension’s soil sampling recommendations. Please see ISU publication PM 0287 “Take a Good Soil Sample to Help Make Good Decisions” or NCR 13 Report 348 “Soil Sampling for Variable-Rate Fertilizer and Lime Application” for information on sampling procedures. Another good reference is PMJ 1688 “A General Guide for Crop Nutrient and Limestone Recommendations in Iowa.” Find even more information on the ISU Soil Fertility page.

Producers must submit the phosphorus or P index to DNR as part of a complete MMP once every four years. The P index takes into consideration the lay of the land, the distance from a stream and the phosphorus that is available in the soil. Running the P index requires soil test results, erosion calculations using the revised universal soil loss equation 2 (RUSLE 2) to see whether manure can be land applied based on N crop uptake rates or P crop uptake rates.

Find detailed requirements for soil sampling, testing and the P index in the Iowa Administrative Code Chapter 65.17(17) and 65.17(18)