Integrated Crop Management is published by the Department of Entomology , Iowa State University , Ames, Iowa. Cornfields that have had applications of animal manures or commercially prepared nitrogen fertilizers should be checked in early June for nitrate levels.
Animal manures contain large amounts of nitrogen needed during corn production.
Surveys show, however, that most corn producers do not make adequate adjustments when they purchase and apply commercially prepared N fertilizers. This finding suggests a general lack of appreciation for the potential of animal manure as a fertilizer and as an environmental pollutant. N is to use the late-spring test for soil nitrate after animal manures and commercial fertilizers have been applied. Corn producers usually are surprised by what they learn. The test often shows that nitrate concentrations are two or three times higher than those needed by the crop.