Strategies to Reduce Nitrogen Losses via Leaching and to Increase Precrop Effects when Growing Faba Beans

ABSTRACTIn four year field trials faba bean cultivation techniques were tested with the primary aim to reduce nitrate losses via leaching by increasing crop soil-nitrate uptake. This aim did not generally contradict the aims of gaining high faba bean grain yields, high amounts of symbiotically fixed nitrogen and an increased precrop effect. As a function of poor rooting systems and poor soil-nitrate uptake faba bean pure stands left high amounts of nitrate in the soil before winter, which is suspected to be leached during winter. A more homogenous rooting-distribution via narrow faba bean row distances increased soil-nitrate uptake and slightly reduced residual- nitrate content before winter. Increasing crop rooting-density by intercropping with cereals or undersown non-legumes considerably reduced soil residual-nitrate content. Undersown brassicas like oil-radish or white mustard were more efficient than ryegrass and intercropping with cereals. Undersown crops showed no negative effect on faba bean grain yield and N2-fixation. Intercropping with cereals considerably reduced faba grain yield and N2-fixation. Underseed variety in faba beans and intercropping considerably affected precrop effects to the successive crop oats as a function of different amounts and temporary availability of nitrogen.