Effects of fumigation and fertilizer on growth, yield, chemical composition, and Mycorrhizae in white bean and soybean

Plant dry weight of samples taken during the 1984 growing season, and seed yield of white bean (Phaseolus vulgaris L.) in 1986, increased with an increase in N fertilizer. Soybean (Glycine max (L.) Merr.) did not respond to N level except for a depression of nodule weights with increase in fertilizer N, which also occurred in white bean. Soybean had a greater weight of nodules, which formed a higher proportion of plant dry weight than in white bean, especially at high N levels. Soil fumigation reduced nodule weights of both species at 38 d after seeding (DAS) and of soybean at 64 DAS. Fumigation also reduced vesicular arbuscular mycorrhiza (VAM) in both species. Fumigation lowered P concentration in leaf tissue of both species in −PK plots but not in +PK plots. Fumigation increased seed yield in +PK plots, but lowered yield in −PK plots. Reduction of competition from other soil micro-organisms by fumigation did not improve nodulation. The effects of fumigation on yield could be explained by destruction of the VAM, which were beneficial in −PK plots (by aiding uptake of P), but were not beneficial in +PK plots.Key words: Soybean, bean (white, common), nitrogen, phosphorus, mycorrhiza, nodulation