Nitrogen Yields and Biological Nitrogen Fixation of Winter Grain Legumes

Abstract

Grain legumes are valuable sources of protein and contribute to the diversification and sustainability of agricultural systems. Shifting the sowing date from spring to autumn is a strategy to address low yields of spring grain legumes under conditions of climate change. A two-year field experiment was conducted under Pannonian climate conditions in eastern Austria to assess the nitrogen yield and biological N2 fixation of winter peas and winter faba beans compared to their spring forms. The grain nitrogen yields of winter peas and winter faba beans were 1.83-fold and 1.35-fold higher compared to their spring forms, respectively, with a higher value for winter peas. This was mainly due to higher grain yields of winter legumes, as winter faba beans had a 1.06-fold higher grain nitrogen concentration than spring faba bean. Soil mineral nitrate after harvest was similar for all grain legumes, with by 2.85- and 2.92-fold higher values for peas and faba beans than for cereals, respectively. The N2 fixation of winter peas and winter faba beans were 3.90-fold and 2.28-fold higher compared to their spring forms, with winter peas having a 1.60-fold higher N2 fixation than winter faba beans. The negative nitrogen balance of winter peas was smaller than that of winter faba beans as they demonstrated the ability to overcompensate for higher nitrogen removal with grain through higher N2 fixation. The cultivation of winter grain legumes, especially winter peas, can be recommended under Pannonian climate conditions as they achieve high nitrogen yields and high levels of N2 fixation.