Impact of nutrient management in rice-maize-greengram cropping system and integrated weed management treatments on summer greengram productivity

Nutrient and weed management in crops and especially cropping system play an important role to enhance productivity and sustainability in different cropping systems. A field experiment was conducted for two consecutive years to evaluate the effect of nutrient management in preceding crops and integrated weed management practices in summer greengram on weeds growth and greengram productivity. The nutrients were applied in previous rice and maize crops and greengram was grown under residual soil fertility. The inorganic nitrogenous (N) fertilizer (25% of recommended dose) was substituted with bulky organic manures [farm yard manure (FYM) and vermicompost] and concentrated organic manures [Brassica seed meal (BSM) and neem cake]. The weed management treatments comprised of: herbicide use alone [post-emergence application (PoE) of imazethapyr 100 g/ha at 25 days after sowing (DAS)] and integrated weed management approach [pre-emergence application (PE) of pendimethalin 750 g/ha at 2 DAS followed by (fb) hoeing at 25 DAS]. The addition of concentrated organic manures (BSM and neem cake) effectively reduced the germination and overall growth of the weeds probably due to released allelochemicals. The N supplementation using neem cake and BSM decreased the weed biomass and reduced the nutrient uptake by weeds, and enhanced the nutrient uptake of greengram crop which ultimately enhanced the greengram growth and seed yield. This effect was more pronounced in the second year of study due to repeated application of organic manures. In comparison to use of herbicide alone (imazethapyr), the integrated weed management (pendimethalin PE fb hoeing) reduced the weed density and biomass accumulation by ~50 and 80%, respectively. The integrated weed management also enhanced the greengram seed yield by 12 and 9% compared to herbicide usage alone during 2015 and 2016, respectively.