Herbicidal effect on weed growth, crop yield and soil microbes in olitorius jute (Corchorus olitorius L.)

Abstract

A field experiment was conducted during 2007-2008 at Barrackpore on Gangetic alluvium soil to find out the effect of pre-emergence (trifluralin and S-metolachlor) and post-emergence (fenoxaprop-p-ethyl, quizalofop ethyl and cyhalofop butyl) herbicides on weed management, growth and fibre yield of olitorius jute, nutrient removal by weeds and effect on soil microbes. The grass and sedges were the dominant weed flora present in the ratio 1: 0.76 on dry weight basis. Trifluralin controlled the grasses but the problem of sedge weeds occurred (97.9 g m-2) and the natural balance of grass:sedge weed complex shifted towards sedge weeds (grass:sedge 1:9). Like trifluralin, the post-emergence grass herbicides (quizalofop ethyl and fenoxaprop-p-ethyl) also allowed sedges to grow. The yield reduction in olitorius jute due to weeds was as high as 47.8%. The field was dominated by sedges (along with grass), so, application of S-metolachlor @ 0.50 kg ha-1 (PE) on soil surface just after jute sowing proved effective in controlling weeds (79.04%), supporting higher jute plant height (252 cm) and achieving higher fibre yield (2.41 Mg ha-1). Weeds in jute field at 45 DAS removed 16.59 kg N, 3.67 kg P2O5 and 33.88 kg K2O ha-1. Nutrient contents were much higher in sedge weeds (1.01% N, 0.34% P2O5 and 2.63% K2O) than the grasses (0.81% N, 0.09% P2O5 and 1.22% K2O). Application of pre and post emergence herbicides in jute affected the total bacteria, actinomycetes and fungi population in soil initially but the microbial population improved gradually and reached to normal level by harvest of jute.