Weed-management and wheat productivity in a conservation agriculture-based maize (Zea mays)-wheat (Triticum aestivum)-mungbean (Vigna radiata) system in north-western Indo-Gangetic plains of India

In this study, a possible weed management has been envisaged in zero-till (ZT) and conventional till (CT) wheat [Triticum aestivum (L.) emend. Fiori & Paol.] with and without residue during 2013–14 and 2014–15 using residue, N and weed-control treatments. It was observed that ZT with 5 t/ha maize (Zea mays L.) residue retention (ZT + R) + 75% N + rest N-based on Green Seeker (GS) caused a considerable reduction in the population of narrow-leaf, broad-leaf and total weeds compared to CT and ZT without residue. Pendimethalin (PMT) followed by sulfosulfuron (SSF) application significantly reduced the weeds population and dry weight than the unweeded control (UWC). Wheat yield attributes were higher in ZT with residue retention (ZT + R) than conventional-tilled treatments. Application of PMT @ 1 kg/ha followed by SSF 25 g/ha combined with ZT with 5 t/ha maize residue retention (ZT + R) + 75% N + rest N based on Green Seeker (GS) resulting in higher wheat yield which was comparable with that in weed-free check (WFC). Zero tillage with or without residue reduced the nutrient uptake by weeds than the conventional tillage which led to the higher uptake of nutrients by crop in zero tillage condition over the years. The sum total amount of N, P and K removed by the crop was higher in ZT + R + 75% N + rest N based on Green Seeker (GS) than CT-R + 100% N (farmer practice) to the tune of 23.8% and 34.6% in 2013–14 and 2014–15, respectively. The sequential application PMT and SSF had an edge over the ready-mix application of SSF+ metsulfuron methyl (MSM) in respect of nutrients uptake by crop which was due to the reduction in nutrients uptake by weeds by the former than the later. The treatment combination ZT + R + 75% N + rest N based on Green Seeker (GS) and sequential application of PMT-SSF secured highest output energy than the CT-R + 100% N with UWC and ready-mix application of SSF + MSM. The interaction between tillage, residue and N management with weed control practices for net benefit: cost ratio revealed that irrespective of residue the zero tillage fetched the higher net benefit: cost than conventional tillage. The partial cost-benefit of sequential as well as ready-mix application of herbicide was on a par under both the tillage condition. Therefore, ZT + R + 75% N + rest N based on Green Seeker (GS) and sequential application of PMT-SSF can be recommended for wheat production in north-western Indo-Gangetic plains of India.