Plant biomass nitrogen and effects on the risk of nitrate leaching of intercrops under organic farming in Eastern Austria

Summary

Data on the potential of intercrops to reduce soil nitrate contents, on their N accumulation and biological nitrogen fixation (BNF) are lacking for organic farming in the dry, pannonic region of Eastern Austria. The effect of legumes, non-legumes, and legumes + non-legumes used as intercrops on inorganic soil nitrogen, crop yield and biomass N, and BNF were tested in comparison to bare fallow. Non-legumes and legumes + non-legumes were more efficient than legumes in reducing inorganic soil N contents in autumn and nitrate contents in soil solution from the subsoil in winter. This reduction in inorganic soil N did not last until March of the following year due to an N mineralisation from the mulch. The legume + non-legume mixture contained a larger amount of crop N than both legumes and non-legumes. This was due to the combined effect of soil-N uptake by the non-legumes and BNF by the legumes in the mixture.