Soil Fertility

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Welcome to the Iowa State University Agronomy Extension Soil Fertility Home Page. Nutrient topics are listed on the left side. Simply click on a topic of interest and you can find information about that topic, including Extension publications, newsletter articles, conference proceedings and reports, presentations, and links to other related sites. Links also provide access to soil fertility decision aid tools, a photo gallery, and the ISU Soil and Plant Analysis Laboratory.

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Runoff Phosphorus Loss Shortly After Applying Fertilizer and Animal Manure without Incorporation Into the Soil

Antonio P. Mallarino, Professor, Department of Agronomy, Iowa State University, Mazhar U. Haq, Assistant Scientist, Department of Agronomy, Iowa State University
November 25, 2009

Fertilizer and manure are needed to supply crop phosphorus (P) requirements when soils are deficient or to maintain an optimal soil-test P level. Recent research on the value of animal manure nutrients resulted in updated guidelines for manure nutrient management. Soil-test P interpretations and P application guidelines are available in Iowa State University Extension publications PM 1688 and PMR 1003 (see complete references below). However, too high P application rates and/or inappropriate application methods can contribute to surface water quality impairment when runoff occurs. Recent research has been investigating P loss with surface runoff as affected by P source and time elapsing between P application and a runoff event. Phosphorus loss from fields is affected by many source and transport factors, most of which are considered in P Indices like the Iowa P Index. The Iowa P Index and some others developed in the Corn Belt region do not account for potential differences between P sources and the probability of a runoff event after P application. These factors might influence P loss, especially during the first few weeks after P is applied to the soil surface without being incorporated into the soil. Read on.

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