The rice–wheat cropping system (RWCS) has substantially contributed in making India self-sufficient in food grain production; however, rice residue management is of great concern, threatening the sustainability of this system. Rice residue is invariably disposed of by farmers through open burning. In addition to environmental pollution, residue burning of rice also leads to loss of soil nutrients. One of the alternatives to overcome these problems and sustain the RWCS is managing the rice residues in the field itself. Rice residue retention has variable effects on agricultural pests (namely, weeds, insect pests, diseases, and rodents) in the RWCS. High weed infestation in the RWCS results in high consumption of herbicides, which leads to several ecological problems and evolution of herbicide resistance. The shift from intensive tillage to conservation tillage causes major changes in weed dynamics and herbicide efficacy. Incorporation of rice residue reduces weed density and helps in improving soil physical, chemical, and biological properties. Rice residue retention on the surface or mulching reduces weed density and the biomass of both grass and broadleaf weeds in wheat crop as compared to its removal. Long-term field studies involving the use of rice residue as a component of integrated weed management strategies are needed to be done in the RWCS.

Evolution of multiple herbicide resistance in Phalaris minor in wheat has resulted from the repeated use of herbicides with a similar mode of action which could threaten the sustainability of the rice-wheat cropping system in North-West India. In this context, field studies were conducted at Research Farm, Department of Agronomy, Punjab Agricultural University, Ludhiana during 2011–12, 2012–13 and 2013–14 in randomized block design replicated four times and at farmer's field during 2016–17 and 2017–18 with the objective to evaluate the efficacy of herbicide with alternative mechanism of action for the control of resistant P. minor in wheat. The treatments included pyroxasulfone 85, 102, 127.5 g/ha, pendimethalin 750 g/ha as pre-emergence (PE), sulfosulfuron 25 g/ha, clodinafop 60 g/ha as postemergence (PoE) and unsprayed control. However, the treatments during 2013–14 included pyroxasulfone 85, 102, 127.5 g/ha, pendimethalin 750 g/ha and unsprayed control with pendimethalin 1125 g/ha as PE at farmers’ field instead of pendimethalin 750 g/ha. The results indicated that pyroxasulfone at 127.5 g/ha recorded effective control of P. minor and its biomass and gave the highest wheat grain yield (4.87, 4.80 and 5.43 t/ha) during 2011–12, 2012–13 and 2013–14, respectively At farmer's field, pyroxasulfone 127.5 g/ha has been found effective against the resistant populations of Phalaris with 5.37 and 5.42 t/ha grain yield. The current study demonstrated that PE application of pyroxasulfone at 127.5 g/ha would be a suitable option for the control of resistant populations of Phalaris in wheat in Punjab.

The escalating scarcity of irrigation water, transplantation of rice on light-textured soils and labour cost acted as major drivers for the transition towards direct-seeded rice (DSR) cultivation from the conventionally flooded transplanting system. Despite these advantages, DSR is a challenge in light texture soil due to heavy weed infestation and a slight decline in crop yield. The weeds compete for nutrients and have an adverse effect on the growth and yield of crops. Hence, to assess the removal of macro and micronutrients by weeds and direct-seeded rice, a field experiment was carried out on sandy loam soil for two consecutive Kharif seasons (2018 and 2019). Three treatments from rice, namely: DSR under zero tillage (DSR-ZT), DSR under conventional tillage (DSR-CT) and DSR under reduced tillage (DSR-RT) were taken as main plots with three tillage treatments in wheat, namely: Conventional tillage without rice straw (CTW-R), Zero tillage without rice straw (ZTW-R) and Zero tillage with straw as mulch using Happy Seeder (ZTW+R) as subplots, replicated thrice. Among the rice establishment methods, DSR-RT showed an edge in terms of rice grain and straw yield (6.18 and 8.14 Mg ha⁻¹, respectively) as well as macro- and micronutrient uptake by rice. Under management practices, ZTW+R proved as an efficient strategy in terms of yield and nutrient uptake by crops. The contribution of weeds towards biomass production was maximum under the ZTW-R (9.44%) treatment followed by DSR-ZT (7.72%). The nutrient budgeting showed that macro- and micronutrient removal by weeds was minimum under reduced tillage (24.51 and 50.35%, respectively), whereas it was 21.88 and 44.87% when wheat was grown under conventional tillage without rice straw. In overall, the research study concluded that weeds on an average remove 25.65 % macronutrients (N, P, K) and 51.47% of micronutrients (Zn, Cu, Fe and Mn) in DSR under rice-wheat cropping system.