A valuable resource
by Kris Kohl, extension agricultural engineering field specialist
Manure can be a valuable resource or a liability depending on your point of view. The first step to make it a resource is knowing the nutrient content. While book values can offer a good place to start, only a manure test will allow confidence in applying the proper amount.
No one would order fertilizer from the local dealer without knowing the nutrient content first. Manure should be no different. To convert manure into a valuable resource, sonsider the following actions:
Manure is a mixture of solids and liquid. Solid manure from an open lot is 75% to 80% water; liquid pit manure is 90% to 95% water;and lagoon liquid is 99% to 99.9% water. Solid manure can be collected by scraping across the lot with a scoop shovel to collect an "average" sample, or several samples can be collected to determine the possible range of nutrient contents.
Liquid manure sampling involves collecting manure, making sure that the proper amount of solids and liquids are sampled. The phosphate in manure is mainly in the solid portion, potash is mainly in the liquid, and the nitrogen is split about 50% in liquid and 50% in the solids.
Agitating the pit and collecting a sample, or collecting a sample with a pan in the field are good sampling techniquies. However due to lab processing time requirements, about one week typically is needed before the results are available, making these sampling techniques less desirable for immediate decisions. Commercial probes are available that take a vertical profile sample - similar to a soil core in soil testing. Additional information on taking manure samples for nutrient analysis can be found in the Extension publication (pdf-file) How to Sample Manure for Nutrient Analysis.
Comparing to other similar facilities
Extension specialists have been collecting profile samples over the past two years, 1996 and 1997, to help producers determine the proper application rates on their fields. Approximately 193 pits were sampled across Iowa. Results from the sampling are presented in the tables listed below.
The normal cost for handling manure is about $10 per 1,000 gallons (a penny per gallon) making most pit manure worth the handling cost. The water content makes a big difference - wet/dry feeders conserve water, making the manure "richer." The higher values in our results come from operations using wet-dry feeders.
Many additional manure samples have been collected, but the results are somewhat unique to their farms. When interpreting individual results, if the phosphate is unusually high in comparison to the nitrogen and potassium, the pit probably has an accumulation of solids. Unusually high phosphate readings on an individual sample might indicate poor agitation during hauling. The actual phosphate level that is applied to the field may be lower than average since many of the solids are accumulating in the pit.Properly applying manure to the soil
It is important to uniformly apply the manure to a field so that all of the field receives an adequate level of fertility. Be sure to keep good notes on where the manure was applied to prevent the need for a blanket application of commercial nitrogen to cover up mistakes and light spots.
Taking appropriate credit and doing on-farm research
Once the nutrient value is known, take the appropriate credit, figuring the losses and the amount that will be available for crops. It also is wise to try a few test plots to compare the manure fertilized land to those acres fertilized with commercial sources of fertilizer.
Manure testing it an important tool to make manure a valued resource.
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Page last updated October 5, 2004
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