Nodulation and nitrogen fixation of Phaseolus vulgaris L. grown in minesoil as affected by soil compaction and N fertilization

Abstract

Abstract The objectives of this growth chamber study were to assess the influence of three soil compaction levels, as determined by bulk density, and four N fertilizer treatments on growth, nodulation and N2 fixation of P. vulgaris in minesoils. Shoot and root growth was severely retarded and nodulation essentially absent in N unfertilized, uninoculated (control) plants. With inoculated plants, root and shoot mass increased and nodule mass decreased as bulk density was decreased from 1.55 g/cm3 (unamended) to 1.40 g/cm3 (amended with 50% by volume sand). Root and shoot mass increased as N fertilizer rates increased from 0 to 100 kg N/ha. Nodule mass increased at 25 kg N/ha, but higher N rates decreased nodule mass compared to unfertilized plants. There was no significant correlation between bulk density and N2 fixation, as measured by the acetylene reduction assay. In general, N2(C2H2) fixation was the greatest at 35 days from seeding; however, at 21 days, unfertilized plants showed high N2(C2H2) fixation rates. Fertilizer N at 25 kg N/ha increased acetylene reduction as compared to unfertilized plants, while at 50 and 100 kg N/ha the rate of N2(C2H2) fixation decreased.