Effects of cadmium, nickel, copper, and zinc on nitrogen fixation by soybeans

Abstract

Cadmium and Ni (1, 2.5, and 5 ppm) and Cu and Zn (1, 5, and 10 ppm) applications inhibited N2 fixation by soybeans in sand culture. In general, the degree of toxicity was Cd > Ni > Cu > Zn. Cadmium greatly reduced nodule number, dry weight and N2 fixation. Although nodulation on Ni-treated plants was adequate, N2 fixation was very low. Copper reduced nodulation, but inhibited N2 fixation directly at only 5 and 10 ppm. Zinc reduced nodulation, but only slightly inhibited N2 fixation.