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Using manure as a resource is goal of ISU scientists
Iowa
In just a few short weeks, Iowa's farmers will have harvested another bumper crop of corn and soybean. For many, their next step will be to apply liquid swine manure to their fields to meet some of the nutrient needs of next year's crop. However, environmental concerns could arise if nutrients in manure aren't adequately accounted for or application timing isn't best for crop use.
A four-year demonstration project conducted by Iowa State University scientists has shown that corn responds well to liquid swine manure nitrogen and phosphorus and that manure applied using sound methods can successfully provide needed crop nutrients. The goal of the project was to increase producer confidence in swine manure's nutrient availability and consistency relative to commercial fertilizers.
"Using liquid swine manure as a reliable source of nitrogen and phosphorus for crop production takes effort, but can be done," says John Sawyer, associate professor of agronomy.
Sawyer and Antonio Mallarino, agronomy professor, led the project that was part of the Integrated Farm/Livestock Management demonstration program, funded by the Iowa Department of Agriculture and Land Stewardship, the U. S. Department of Agriculture's Natural Resources Conservation Service and ISU's Leopold Center for Sustainable Agriculture.
The project had nearly 40 on-farm demonstrations with 16 cooperators in 12 Iowa counties. At each field site, soil samples were collected to determine phosphorus, potassium and pH. Liquid swine manure also was sampled and analyzed for nitrogen, phosphorus and potassium content.
Manure was applied in field-length strips at three rates based on its nutrient content to monitor crop responses and its nutrient availability. Application equipment was carefully calibrated to make sure the desired rates were applied.
Several methods were used to monitor the nutrient status in each field. Aerial photos, leaf chlorophyll meter readings, soil phosphorus tests, late-spring soil nitrate tests, end-of-season cornstalk tests and post-harvest profile nitrate provided an assessment of plant response to manure nutrient application, plus the soil nitrogen and phosphorus status. Finally, crop yields were checked, with comparisons done between the field-length manure rate strips and strips where commercial fertilizers were applied.
"This project documented it is possible to accurately set manure application rates based on crop nitrogen and phosphorus needs," Sawyer says. "It takes effort and proper equipment, but can be quite successful." Sawyer and Mallarino have a similar project underway using poultry manure. Producers interested in cooperating in that project can contact Mallarino at 515-294-6200 (apmallar@iastate.edu) or Sawyer at 515-294-1923 (jsawyer@iastate.edu).
Date: 8/25/04
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