Predicting Nutrients From Winter Cover Crop Biomass.

An ultimate goal of a grower using cover crops as a green manure is to predict the amount of nutrients in the cover, the percentage that will decompose that summer, and then reduce accordingly the soil test recommendation of fertilizer for the following summer crop.  This prediction normally requires three measurements:  the amount of biomass (dry weight), the elemental composition of the cover crop, and the decomposition rate of the cover crop during the summer for release of the nutrients.  This paper predicts amount of potential plant nutrient available from a decomposing cover crop. Winter cover crops consisting of both legume and small grains were analyzed for nutrient content. Accruement of nitrogen, phosphorus, potassium, calcium, and magnesium were calculated for each nutrient, and predictive equations established. Ratios of each element were then calculated. Hairy vetch winter cover had a N,K,P,Ca,Mg ratio of 1: 0.96: 0.12: 0.39: 0.08 ratio while rye winter cover had a ratio of 1: 1.3: 0.20: 0.25: 0.10.