SOIL CHEMICAL PROPERTIES AND REMOVAL OF NUTRIENTS BY CORN RESULTING FROM DIFFERENT RATES AND TIMING OF LIQUID DAIRY MANURE APPLICATIONS

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Abstract
Liquid dairy cattle manure was applied at three rates (224, 560 and 879 kg/(ha∙yr) of manure nitrogen (N)) and four different times: in the fall after harvest of silage corn, before seeding, half in the fall and half before seeding, or in winter to continous corn grown on sandy clay loam for 5 yr. Two other plots were included: one received chemical N-P-K fertilizer at recommended rates, and one received neither fertilizer nor manure. Over the 5-yr study, soil organic carbon increased in the surface layer of the high-rate plots, but decreased in the chemically fertilized plot. Soil inorganic N contents measured at harvest in the 0- to 120-cm layer of the manured plots were related to both cumulative and annual N inputs. Bicarbonate extractable phosphorus in the 0- to 15-cm layer increased each year in the medium- and high-rate plots and exceeded 90 μg/g in the high-rate plots after 5 yr. Exchangeable potassium levels increased singificantly in the plow layer of the medium- and high-rate plots. Smaller accumulations occurred in the winter-applied plots than in the fall- and spring-applied plots. Uptake of nutrients by the corn crop increased with manure rate, but generally was not affected by time of application.