Nitrogen fixed by red clover in lbs /acre High fertility field Med fertility field

1. Table 1. Legumes growing in mixtures show a greater reduction in the amount of nitrogen fixed in fields with higher nitrogen fertility. Data show total nitrogen fixed for one year of red clover growth including estimates of root biomass in pounds of nitrogen/acre from two organic grain fields. Red clover growing alone in monoculture fixes 20% less nitrogen in the field with higher soil fertility. However, when grown in a mixture with orchard grass, the red clover in the high fertility field has dramatically reduced nitrogen fixation compared to the medium fertility field. As the grass takes up soil nitrogen, clover growth is suppressed due to competition and shading by the grass. Nitrogen fixed by red clover in lbs/acre High fertility field Med fertility field Red clover 65 80 Clover/grass 38 70