Influence of Nitrogen Fertilizer Applied in Winter on Alfalfa Yield at the First Cutting in Spring

Abstract

Some growers feel that nitrogen (N) fixing nodules found on the roots of the alfalfa plant are ineffective in cold soil during the winter and early spring. Thus, starter N fertilizer is commonly applied in late winter to established alfalfa to enhance growth until spring when the soil warms up and alfalfa begins actively fixing atmospheric N₂. Established alfalfa normally does not benefit from applications of N fertilizer since it is a leguminous crop that is capable of fixing its own N from atmospheric N₂. Afield experiment was conducted to determine the effect of N fertilizer applied in winter on alfalfa hay yield at the first cutting in spring. Two treatments consisted of an unfertilized check plot and UAN 32 water run at a rate of 35 lbs. N/acre to three year old 'CVF 101' alfalfa grown on a silt loam soil testing deficient in nitrate-N. Maximum alfalfa hay yield (J ton/acre) was obtained at the first spring cutting without N fertilizer application. However, since the field has a known yield potential of 1.5 ton/acre, factors other than fertility influenced the alfalfa hay yields observed in this study.