Nitrogen fixation in field beans (Vicia faba) as affected by population density, shading and its relationship with soil moisture

Abstract

N fixation data, estimated by the acetylene reduction technique and by total N content are given for the field experiments reported by Sprent, Bradford & Norton (1977).Maximum potential acetylene reducing activity per plant varied little from year to year. At low population densities a maximum rate of activity was observed shortly after flowering. As density increased this maximum became less pronounced and environmental factors (such as water supply) exerted increasing effects on activity. Shading prolonged activity and delayed nodule senescence.Total plant N continued to increase almost to seed maturation. As plants aged, the acetylene reduction technique progressively underestimated N accumulation. Maximum Nfixed/ha/year was over 600 kg. Itis concluded that the potential for N fixation in this crop is sufficient to sustain high yields.