Continuing Education and
Communication Services
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
9/27/01
Contacts:
Palmer Holden, Animal Science, (515) 294-2240, pholden@iastate.edu
John Sawyer, Agronomy, (515) 294-1923, jsawyer@iastate.edu
Del Marks, Continuing Education and Communication Services, (515) 294-9807,
delmarks@iastate.edu
Reducing Phosphorus in Swine Manure Aids Environment
AMES, Iowa -- Animal feeding operations can provide a significant source of nutrients for crops through manure. However, supplying manure that provides crops with balanced amounts of nitrogen (N) and phosphorus (P) requires reducing the phosphorus content of manure, without compromising the performance of the livestock, according to two Iowa State University researchers.
Optimizing nutrition while minimizing production costs and impact on the environment can be complementary goals in swine feeding operations, according to Palmer Holden, ISU Extension livestock specialist, and John Sawyer, extension agronomist. Successful strategies include matching recommendations and requirements when selecting available phosphorus sources, and using additives to enhance phosphorus availability.
Supplementing swine feed with the phytase enzyme, or feeding low-phytate corn varieties that have a much higher available P content, reduces P levels in manure without sacrificing performance or carcass characteristics, Holden said. The economics of phytase additions can vary as prices of inorganic P sources fluctuate, but generally production costs are not affected by replacing dicalcium phosphate with phytase.
To effectively use this new technology, producers need to sample the manure and have it analyzed for nutrient content, Sawyer said. Then, they should use current soil test data and crop nutrient requirements to decide how to best-apply this low P manure to the land. Producers need to remember that potassium (K) is often not applied at high enough rates when manure applications are made based only on N or P requirements, Sawyer said.
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