INTERACTION OF MANURE AND NITROGEN OR STARTER FERTILIZER IN NORTHERN CORN PRODUCTION

Nutrient availability of applied manure may be reduced under the cool early season climatic conditions found in the far northern corn (Zea m ays L.)-growing environments. This study evaluated the effectiveness o f combining applications of starter and N fertilizers with manure on i mproving corn growth and soil nutrient levels in northern Wisconsin fr om 1979 to 1981. Residual effects of treatments also were evaluated fr om 1982 to 1983. Main treatments of five rates of manure (0, 19, 33, 6 0, and 121 tons/acre on a wet weight basis) were arranged in a split-s trip plot design with split plot treatments of four rates of N fertili zer (0, 40, 80, and 120 lb N/acre) and strip plot treatments of two st arter fertilizer rates (0 and 150 lb/acre of 6-24-24). Although applic ation of manure and N fertilizer consistently increased silage dry mat ter yields, application of starter fertilizer affected yields in only 1 of the 3 yr in which treatments were applied. Climatic conditions al one were not sufficient to explain crop response to starter fertilizer . No interactions between manure and starter fertilizer or manure and broadcast N fertilizer applications were observed.