Long-term tillage and weed management effects on weed shifts, phytosociology and crops productivity

The understanding of the diverse weed flora composition and weed shift in conservation agriculture production system is important to identify weed management component to increase agro-ecosystem sustainability. Hence, in this study, different tillage and weed management practices were assessed to evaluate their impact on diverse weed flora composition and shift in maize-wheat cropping system in North Western Himalaya from 2018-20 in an ongoing longterm experiment being conducted since 2013. Fifteen treatment combinations comprising of five tillage treatments, viz. conventional tillage (CT) in maize-CT in wheat; CT-zero tillage (ZT); ZT-ZT; ZT-zero tillage in combination with residue retention (ZTR) and ZTR-ZTR and three weed management treatments, viz. recommended herbicide (H) in maize-recommended herbicide (H) in wheat; integrated weed management (IWM)-IWM and hand weeding (HW)-HW were evaluated in a strip plot design. In CT, annual weed species were dominant, whereas, perennial weeds dominated in zero tillage (ZT). A shift in weed species with greater dominance of monocots and a marginal decrease in dicots was observed. Parthenium hysterophorus, an obnoxious weed, was observed in the experimental field in maize only during 2018. The monocot weed (Echinochloa colona) had higher relative density (RD), relative abundance (RA), relative frequency (RF) and important value index (IVI) compared to the dicot weeds in maize crop. In Rabi (winter) season, Avena ludoviciana (monocot grass) had higher RD, RF and IVI values, while, Daucus carota (perennial weed) had higher RA when compared to the other annual and biennial weeds. The grain yield of main and intercrop and system productivity were higher in conservation agriculture-based production systems in combination with recommended herbicide (ZTR+H-ZTR+H) in maize-wheat based cropping systems.