Plant nutrient losses were measured in tile drainage effluent varied with season with N, drainage effiuent from three cropping systems P, K and Ca concentration tending to be on a Brookston clay soil over a 7-year period. lower in the spring. The amount of water that Highest losses of N, P and K occurred with flowed through the soil of a particular cropcoln and lowest with bluegrass sod. Addi-ping system was the predominant factor intions of N-P-K increased average losses of N, fluencing nutrient loss.

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.

A 6-year study was conducted to determine the effects of rate and time of liquid manure application, chemical fertilizer application, and no fertilizer, on the chemical composition of surface and subsurface water and on crop yield. Liquid manure was applied at three rates of 224, 560 and 897 kg/(ha•yr) of N in accordance with four application schedules (i.e. spring, fall, split rates in spring and fall, and winter). In all cases except winter application, manure was incorporated by plowing at time of application. During spring snow-melt, surface runoff concentrations of inorganic N, P, and K from winter-applied manure increased approximately in proportion to increased application rate. Also, they were much higher than concentrations from spring, fall, spring-fall, and chemical fertilizer treatments. In contrast to spring snowmelt surface runoff, tile drain effluent NO 3-N concentrations from the plots receiving manure at nearly 900 kg/(ha•yr) of N appeared to be little different from the plot chemically fertilized with 134 kg/(ha•yr) of N. However, at and above the 560 kg/(ha•yr) of N (140 kg/(ha•yr) of P) rates of manure the drain effluent PO 4-P concentrations tended to be higher than the concentration resulting from chemical fertilizer applications. Most of the nitrogen and phosphorus in surface runoff during June storms was associated with suspended sediment that resulted from erosion. Neither the amounts of sediment nor their total N and total P contents were affected by manure or fertilizer applications. Although the concentrations of inorganic N and PO 4-P in the water portion of June storm runoff were small (<3 percent) compared to those in the sediment, plots with higher rate spring-applied manure tended to have higher concentrations of inorganic N, PO 4-P and K. No significant differences in silage corn yields were observed amongst any of the manure and the chemical fertilizer treatments. ___________________

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