Nitrogen and Phosphorus Losses from Winter Disposal of Dairy Manure

Abstract

AbstractAn evaluation of surface runoff losses of inorganic nitrogen and total soluble phosphorus from fields receiving winter applications of dairy manure was conducted. Runoff losses, as derived from natural precipitation, were accumulated for the time period 1 Jan. to 31 Mar. for 3 consecutive years. The influence of rate of manure application (35, 100, and 200 metric tons/ha) and climatological variability within and between years was of primary importance. Average runoff values of inorganic nitrogen for the three rates of application were 16, 1, and 0.2 kg/ha for 1972, 1973, and 1974, respectively. Phosphorus values averaged 3.5, 0.7, and 0.01 kg/ha for the 3 respective years. Adverse weather conditions during the winter application in 1972 were largely responsible for increased nutrient discharges in runoff. Results indicated that manure disposal during active thaw periods can result in increased nutrient losses. Losses were minimized when manure was applied and then covered with snow, melting at a later date. The 35 metric tons/ha rate of application, applied on frozen soil and then covered with snow, resulted in nutrient losses that differed little from areas that received no manure.