Continuing Education and
Communication Services
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
10/25/01
Contacts:
Antonio Mallarino, Department of Agronomy, (515) 294-6200, apmallar@iastate.edu
John Creswell, Nutrient Management Education Project, (515) 727-0656,
creswell@iastate.edu
Del Marks, Continuing Education and Communication Services, (515) 294-9807,
delmarks@iastate.edu
FOR IMMEDIATE RELEASE
Fall Soil Tests Make a Difference
AMES, Iowa -- Farmers who are wrapping up fall harvest should consider soil testing to determine crop nutrient needs before they apply commercial fertilizer, lime, or manure. Antonio Mallarino, Iowa State University associate professor of agronomy says, "Managing soil fertility is important economically as well as environmentally. Under-apply nutrients, and yield and profitability may suffer. Over-apply nutrients, and money may be wasted. And, it may also cause surface water quality problems," says Mallarino.
Since reliable soil test data depends on sampling consistency, Mallarino recommends that farmers develop a reliable soil testing routine -- every two to four years, at the same time of year and following the same crop.
"Also, plan a sampling program using the county's soil survey, which is available at ISU county Extension offices, Soil and Water Conservation District offices, or public libraries. Use the map to find out what soils are on your farm, then take soil samples that best represent your soils and different field areas. Management zone sampling, using farming history, aerial photographs, and yield maps can be used in addition to soil survey maps to delineate soil sampling areas."
Mallarino says that getting an accurate, consistent and representative sample will provide the most accurate analysis. "Use an established protocol, and keep in mind that sample depth is critical -- soil test calibrations are set with a 6 to 7-inch sample depth. Take multiple cores per sample and don't soil sample right after lime or fertilizer applications. Limestone dust from gravel roads can affect soil tests, so be careful when sampling in field areas near these roads."
"Use the results to formulate nutrient and limestone applications. And remember that the 'optimum' category is the most profitable category. The low and very low categories indicate deficient soil test levels, while the high and especially the very high categories indicate levels testing higher than required for crop production. The very high soil test category indicates that further additions of that nutrient will very seldom produce a profitable yield response."
For more detailed information, call your ISU county Extension office, and ask for a copy of PM 1688, "General Guide for Crop Nutrient Recommendations in Iowa."
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Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.