Determination of critical crop-weed competition period: Impact on growth, nutrient dynamics and productivity of green gram (Vigna radiata)

The critical period of crop-weed competition (CPCWC) varies by cultivars, management strategies, cropping seasons, soil, and climate. Hence, a study was done to assess CPCWC in green gram under different cropping seasons and its impact on nutrient mining, agro-physiological characteristics, and productivity of green gram during the summer and rainy seasons. The experiment comprised of 12 treatments (weed interference until 10, 20, 30, 40, 50 days after sowing (DAS) and crop maturity, weed-free until 10, 20, 30, 40, 50 DAS and crop maturity). The treatments were placed in a randomized complete block design (RCBD) with three replications. Results revealed that, summer green gram outperformed rainy green gram by boosting nutrient uptake, growth and productivity. Weed interference up to crop harvest lowered the green gram dry matter accumulation by 34.11 %, seed index by 8.98 %, grain yield by 76.21 % and biological yield by 31.06 %. However, weed-free until crop harvest boosted nitrogen content by 50.4 %, phosphorus by 87.7 % and potassium by 42.9 %. Similarly, weed-free environment until harvest of the crop raised chlorophyll-a content by 2.9-6.6 fold and 2.7-7.0 fold, chlorophyll-b by 3.8-5.8 fold and 3.8-6.5 fold over season-long weedy plots during summer and rainy season, respectively. This study suggested that the critical duration for crop-weed competition under 5 % relative yield loss (RYL) was 11-43 DAS in summer and 4 to 36 DAS in rainy. Whereas, critical duration for the crop-weed competition at 10 % RYL was 21-36 DAS in summer and 8 to 27 DAS in rainy seasons.