Impact of weed control and vermicompost on weed dynamics, yield, and soil microbial activity in fenugreek

An investigation was conducted at Udaipur during the Rabi seasons of 2016-17 and 2017-18 to evaluate weed flora, seed yield, and soil microbial activity in fenugreek (Trigonella foenum-graecum L.). The study comprised thirteen weed management treatments in the main plots and two levels of vermicompost in the subplots (control and 5 t/ha). Results indicated that the application of oxadiargyl at 100 g/ha as pre-emergence followed by hoeing at 40 days after sowing (DAS) resulted in the lowest weed density (13.83 and 16.13 plants/m²) and total weed dry matter (45.89 and 62.51 g/m²) compared to the weedy check (382.77 and 409.22 g/m²), along with the highest weed control efficiency (88.00% and 84.69%) during 2016-17 and 2017-18, respectively. This treatment also recorded the highest seed yield (2779 and 2862 kg/ha) among all weed management practices. In contrast, maintaining a weedy crop throughout the season led to a significant reduction in seed yield by 65.00% and 62.48% during the respective years. Weed management treatments showed no significant effect on soil microbial populations of bacteria, fungi, and actinomycetes at the 50% flowering stage. However, the application of vermicompost significantly enhanced microbial populations, with the highest counts recorded for bacteria (119.86 × 10⁶ cfu/g soil), fungi (150.85 × 10⁴ cfu/g soil), and actinomycetes (173.24 × 10⁵ cfu/g soil), compared to the control (90.26, 118.27, and 134.44 cfu/g soil, respectively). Based on the findings, it is concluded that for optimal seed yield, effective weed control, and enhanced soil microbial activity, the application of oxadiargyl at 100 g/ha as pre-emergence followed by hoeing at 40 DAS is the most effective strategy for fenugreek cultivation in southern Rajasthan.