When should you sample hog manure to get the most accurate analysis?

Iowa State University experts say that samples taken at application, or as close to it as possible, offer the best results. That’s because those samples are usually well mixed and are representative of the manure. Taking samples long before application can reduce the representation due to nutrient losses during storage and handling or incomplete agitation of the manure.

Of course, collecting samples at application means you won’t have results in time to provide immediate manure-application recommendations. However, they can be used for subsequent applications, and they allow you to adjust commercial-fertilizer application. The results help create a sampling history for your manure-management plan.

Here are some tips for taking samples:

  • Take samples annually for three years in new facilities.
  • Follow up by taking samples every three to five years, unless regulations require more frequent sampling. The same plan applies if you dramatically change feed rations or manure-handling and storage practices from your present methods. 
  • When you apply the bulk of the manure. If you apply equal amounts in the spring and fall, take samples each time. That’s because temperature levels do affect manure’s nutrient composition.