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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.

The experiment consisted of 12 treatments (weed interference until 15, 30, 45, 60, and 75 days after emergence (DAE), weedy until crop maturity, and weed-free until 15, 30, 45, 60, 75, and a weed-free until crop maturity) and the treatments were arranged in a randomized complete block design (RCBD) with three replications. This study indicated increased weed interference period reduced the pod yield by 6.5–36 and 0.7–32%, and haulm yield by 6.4 – 34 and 6.5 – 34% during rainy and winter season respectively. Further, reduction in total biomass production by crop due to weed interference declined the total nutrient uptake by crop, i.e. nitrogen by 7.8–52.1 and 9.6–54.5%, phosphorus by 4.8–45.4 and 6–47.5%, potassium by 6.9–43.7 and 6.3–44.4%, sulphur by 18.4–53.3 and 18.8–53.9%, during rainy and winter season respectively. However, weed-free until crop harvest increased RUE by 293% and 314%, chlorophyll content by 8.7 and 10.7%, respectively, during rainy and winter seasons. This study indicated critical duration for crop-weed interference under 5% relative yield loss (RYL) was 16 to 66 DAE in rainy and 15 to 63 DAE in winter. Similarly, at 10%, RYL were 23 to 62 and 21 to 61 DAE, respectively, during the rainy and winter seasons. As a result, farmers should keep their groundnut crop weed-free between 15 and 66 DAE during the rainy and winter seasons.

Abstract In the Indo-Gangetic Plains (IGP), rice–wheat cropping system (RWCS) predominates, producing large quantity of crop residue and its management is major concern. Farmers usually burn the residue to clear the field for succeding crop, and burning damages soil microbes, resulted in loss of soil organic matter. Hence, current study was conducted to assess the impact of different Happy seeder based residue management options on changes in microbial dynamics, enzyme activities and soil organic matter content and also to know that alternative method for attaining sustainable wheat productivity in sandy loam soils of Haryana, India. Results revealed that Zero tillage wheat (ZTW) with partial and full residue retention treatments sown with Happy seeder (after using chopper and spreader), and ZTW with anchored stubbles significantly enhanced soil microbial count by 47.9–60.4%, diazotropic count by 59.0–73.1% and actinomycetes count by 47.3–55.2%, grain yield by 9.8–11.3% and biomass yield by 7.4–9.6% over conventional tilled (CT) residue burning and residue removal plots. ZTW sown with surface retention of rice crop residue increased the organic carbon by 0.36–0.42% and the soil moisture content by 13.4–23.6% over CTW without residue load. Similarly, ZTW sown with Happy seeder with full residue enhanced alkaline phosphatase activity from 95.3 µg TPF g−1 soil 24 h−1 in 2018–2019 to 98.6 µg TPF g−1 soil 24 h−1 in 2019–2020 over control plots. Likely, microbial population and enzymatic activity showed strong positive correlation under variable residue retention practices. However, increased microbial population reduced the soil pH from 7.49 to 7.27 under ZTW with residue retention plots. The wheat yield enhanced by 9.8–11.3% during 2018–2019 and 2019–2020 under ZTW with Happy seeder with full residue load over residue burning and residue removal plots. ZTW sown with Happy seeder under full residue retention, achieved maximum net return 43.16–57.08 × 103 ₹ ha−1) and B-C ratio (1.52 to 1.70) over CTW without residue. Therefore, rice residue needs to be managed by planting wheat using appropriate machinery under ZT for sustaining higher productivity in RWCS and improve soil health and environment under IGP regions.