NITRATE NITROGEN DISTRIBUTION IN CORN LAND FOLLOWING APPLICATIONS OF DIGESTED SEWAGE SLUDGE

Anaerobically digested sewage sludge was applied to a loam soil at rates of 1.25, 2.5 and 5.0 cm ha−1. Treatments were replicated four times, and all plots were cropped to corn. The soil in the 0- to 90-cm profile under each plot was sampled every month from May to October in 1972 and analyzed for NO3−-N and NH4+. The two highest sludge application rates resulted in significant increases in soil NO3−-N in the 0- to 90-cm soil profile, which persisted until October following crop harvest. Of the N supplied by the sludge, only about 3–12% was recovered by the corn crop. At the conclusion of the experiment, in October, 6–10% of the N supplied by the sludge remained in the soil and on the soil surface in the residual solids. Sludge applications in excess of 1.25 cm ha−1 did not produce significant increases in the yields of grain or stover.