SCREENING OF HERBICIDES FOR EFFECTIVE CONTROL OF WEEDS IN SOYBEAN (Glycine max L.).

A two-year field study was accomplished at College of Agriculture experimental site, Sargodha in spring seasons of 2018 and 2019 to evaluate the performance of various herbicides to combat weeds in soybean. The study consisted of 8 herbicide treatments including two pre-emergence herbicides (pendimethalin at 489.1 g a.i. ha-1, pendimethalin + S-metolachlor at 731.1 g a.i. ha-1) which were applied immediately after sowing and six post-emergence herbicides (oxyfluorfen at 237.1 g a.i. ha-1, metribuzin at 518.7 g a.i. ha-1, quizalofop-p-ethyl at 148.2 g a.i. ha-1, acetochlor at 741 g a.i. ha-1, halosulfuron at 37 g a.i. ha-1and topramezone at 21.5 g a.i. ha-1) which were used 25 days after sowing. In contrast to control, all herbicides have shown significant decline in weed density (up to 94%) and dry weight (up to 88%); and caused significant increases in plant height (up to 85%), pod bearing branches (up to 77%), number of pods per plant (up to 83%), 100-seed weight (up to 37%) and seed yield (up to 160%) of soybean. Among herbicides, topramezone at 21.5 g a.i ha-1 gave significantly the highest (1234 and 1272 kg ha-1 in years 2018 and 2019) seed yield of soybean and HEIs (1.28 and 1.03 in year 2018 and 2019, respectively). However, oxyfluorfen at 237.1 g a.i. ha-1, pendimethalin + S-metolachlor at 731.1 g a.i. ha-1, pendimethalin at 489.1 g a.i. ha-1, quizalofop-p-ethyl at 148.2 g a.i. ha-1 followed it. The regression analysis depicted a significant negative moderate relationship of soybean seed yield with weed dry weight (R2 = 0.7074). However, pods per plant was proved to be the main yield component responsible for higher yield of soybean as it had significant positive relationship (R2 = 0.7012) with seed yield. [ABSTRACT FROM AUTHOR]