Ecological approaches to sustainable soybean production with sequential herbicide applications and their impact on weed dynamics and crop yield

Soybean is an important legume crop which is adversely affected by prolonged weed infestation.With the objective to combat this issue over two consecutive years (2022 and 2023), field experiments were conducted at the Agronomic Research Farm, Department of Agronomy, University of Agriculture Faisalabad.The study contains 11 treatments, sole and sequential application of pre-emergence and post-emergence herbicides including s-metolachlor + pendimethalin; s-metolachlor; fluazifop-p-butyl; haloxyfop-p-ethyl; s-metolachlor + pendimethalin and fluazifop-p-butyl; s-metolachlor + pendimethalin and haloxyfop-p-ethyl; s-metolachlor and fluazifop-p-butyl; s-metolachlor and haloxyfop-p-ethyl; weed-free; weedy check and two hand hoeing (at 30 and 45 days after sowing) replicated three times in a randomized complete block design.Growth parameters, weed-related factors and crop yield were meticulously assessed using standard procedures.The study showed that sequential application of herbicide s-metolachlor + pendimethalin as PRE and fluazifop-p-butyl as POST resulted in increased crop vigor scores (7.70 and 7.83), cumulative leaf area duration (197.86 and 195.86 days), net assimilation rate (2.79 and 2.75 gm -2 day -1 ), leaf area index (4.75 and 4.78 m 2 m -2 ), total dry matter (531.492022 and 544.65 gm -2 ), reduced weed cover scores (2.40 and 2.10), lower weed counts (35.67 and 28.67), higher plant population (32.00 and 32.33 m -2 ), taller plant height (45.00 and 47.00 cm), higher number of pods plant -1 (42.60 and 43.37), improved seed yield (1784.84 and 1784.84 kgha -1 ), harvest index (36.12%and 37.04%), higher protein content (35.78% and 36.97%),oil content (20.33% and 20.90%), oil yield (386.96 and 402.08 kgha -1 ) and effective weed control percentage (44.59% to 75.65% at 45 days after spray), with weed control efficiency (88.62% and 89.16%), weed index showed that it reduced minimum (11.43% and 7.19%) soybean yield, herbicide efficiency index (8.83%and 11.38%) in 2022 and 2023 respectively.So, it is recommended that sequential application of s-metolachlor + pendimethalin as a pre-emergence followed by fluazifop-p-butyl as a post-emergence herbicide optimize soybean growth parameters, yield attributes and quality parameters.