Effect of sequential application of metribuzin on selectivity and weed control in soybean

Abstract

Post-emergence treatments are often the keys to efficient weed control, and could be a substitute or supplementary to pre-emergence treatment. Accordingly, this study was designed to test the selectivity and efficacy of sequential (pre- + post-emergence) applications of metribuzin on weeds in soybean, and to optimize the dose, volume rate and time of application. We observed that sequential metribuzin treatments were more toxic to soil micro-organisms and caused greater inhibition in photosynthesis, acetylene reduction activity and nodulation of soybean compared to only pre-emergence applications of metribuzin or pendimethalin. The negative effects, however, were mitigated by increased activities of superoxide dismutase and ascorbate peroxidase in soybean. The sequential applications left negligible residues at harvest. A sequential application of metribuzin 0.25 kg ha−1 2 days after sowing and 0.1 kg ha−1 20 days after sowing with 200 Lha−1 of water gave a higher seed yield. This ensured the possibility of sequential application of metribuzin with an optimized dose, volume rate and time of application.