Lack of suitable machinery is a major constraint to direct drilling into combine-harvested rice residues due to the heavy straw load, and the presence of loose tough straw deposited by the harvester. Therefore, most rice stubbles are burnt in the mechanised rice–wheat systems of south Asia and Australia, as this is a rapid and cheap option, and allows for quick turn around between crops. As well as loss of organic matter and nutrients, rice stubble burning causes very serious and widespread air pollution in the north-west Indo-Gangetic Plains, where rice–wheat systems predominate. A novel approach with much promise is the Happy Seeder, which combines the stubble mulching and seed drilling functions in the one machine. The stubble is cut and picked up in front of the sowing tynes, which engage bare soil, and deposited behind the seed drill as mulch. Evaluation of the technology over 3 years in replicated experiments and farmers’ fields in Punjab, India, showed that establishment of wheat sown into rice residues with the Happy Seeder was comparable with establishment using conventional methods (straw burnt followed by direct drilling or cultivation before sowing) for sowings around the optimum time into stubbles up to 7.5 t/ha. For late sowings, plant density declined significantly at straw loads above 5 t/ha. The mulch also reduced weed biomass by ~60%, and reduced soil evaporation. Yield of wheat sown around the optimum time into rice residues, using the Happy Seeder, was comparable with or higher than yield after straw removal or burning, in replicated experiments and farmers’ fields, for straw loads up to 9 t/ha. In farmers’ fields there was an average yield increase of 9 and 11% in 2004–05 and 2005–06, respectively, compared with farmer practice. For sowings after the optimum time, yield declined significantly at straw loads greater than 7.5 t/ha. The Happy Seeder offers the means of drilling wheat into rice stubble without burning, eliminating air pollution and loss of nutrients and organic carbon due to burning, at the same time as maintaining or increasing yield.

Rice-wheat (RW) cropping system of the Indo-Gangetic Plains has played a significant role in the food security of India. However, sustainability of this important cropping system is at risk due to the deterioration of soil health, mounting pressure on natural resources and emerging challenges of climate change. Conservation agriculture involving zero-or minimum-tillage and innovations in crop residue management (CRM) to avoid straw burning should assist in achieving sustainable productivity and allow farmers to reduce nutrient and water inputs, and reduce risk due to climate change. High yields of the irrigated RW system have resulted in production of huge quantities of crop residues (CRs). Burning of rice straw is common in north-western parts of India causing nutrient losses, and serious air quality problems affecting human health and safety. Mulch is a good option for rice residue management during the wheat crop, especially with no tillage. Mulch can increase yield, water use efficiency, and profitability, while decreasing weed pressure. Surplus residue from the previous wheat crop can be incorporated into the paddy fields with no adverse effect on rice yield. Residue decomposition in anaerobic flooded soil substantially increases methane emission relative to residue removal. Long-term studies of the residue recycling have indicated improvements in physical, chemical and biological health of soil. Since CRs contain significant quantities of plant nutrients; their continuous application will have positive effect on fertilizer management in RW system. Other plausible option of CRM lies in utilizing a potion of surplus residue for producing biochar (and co-production of bioenegy) for using as soil amendment to improve soil health, increase nutrient use efficiency and minimize air pollution. In this review authors have discussed current concerns and possible options for with efficient management of CRs in the RW cropping system.

A study was conducted to design productive, profitable, irrigation water¸ nitrogen and energy use efficient intensive cereal systems (rice-wheat; RW and maize-wheat; MW) in North-West India. Bundling of conservation agriculture (CA) with sub-surface drip irrigation termed as CA+ were compared with CA alone and conventional tillage based and flood irrigated RW rotation (farmer’s practice; ScI). In contrast to conventional till RW rotation which consumed 1889 mm ha−1 irrigation water (2-yr mean), CA+ system saved 58.4 and 95.5% irrigation water in RW and MW rotations, respectively. CA+ practices saved 45.8 and 22.7% of irrigation water in rice and maize, respectively compared to CA with flood irrigation. On a system basis, CA+ practices saved 46.7 and 44.7% irrigation water under RW (ScV) and MW (ScVI) systems compared to their respective CA-based systems with flood irrigation (ScIII and ScIV). CA+ in RW system recorded 11.2% higher crop productivity and improved irrigation water productivity by 145% and profitability by 29.2% compared to farmers’ practice. Substitution of rice with maize (MW system; ScVI) recorded 19.7% higher productivity, saved 84.5% of irrigation water and increased net returns by 48.9% compared to farmer’s practice. CA+ RW and MW system improved energy productivity by 75 and 169% and partial factor productivity of N by 44.6 and 49.6%, respectively compared to ScI. The sub-surface drip irrigation system saved the fertilizer N by 20% under CA systems. CA+ in RW and MW systems recorded ~13 and 5% (2-yr mean) higher profitability with 80% subsidy on installing sub-surface drip irrigation system and similar profitability without subsidy scenario compared with their respective flood irrigated CA-based systems.

Intensive tillage, removal or burning of crop residues, limited organic manure use, declining irrigation water resources and scarcity of labour are the major causes of soil degradation and unsustainability of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system (RWS) in South Asia.Resource conservation technologies (RCTs) such as zero tillage (ZT), dry direct seeded rice (DSR) and crop residues retained as mulch have shown promise to increase the productivity and profitability of RWS in South Asia. Effects of RCTs on soil biological parameters are unclear and contradictory. We evaluated the effects of conservation agriculture practices on changes in soil biochemical properties at different growth stages of wheat grown as the fifth crop in RWS. Twelve treatment combinations of tillage, crop establishment and crop residue management included four main plot treatments in rice: (1) conventional tillage (CT)-DSR,(2) ZT-DSR, (3) DTR, ZT machine transplanted rice and (4) PTR, conventional puddled transplanted rice. The three subplot treatments were: (i) CTW-R, CT wheat with both rice and wheat residues removed, (ii) ZTW-R, ZT wheat with residues of both the crops removed and (iii) ZTW+R, ZT wheat with rice residue retained as surface mulch in subsequent wheat. Irrespective of rice establishment methods, mean wheat grain yield under ZTW+R was 6% and 10% greater than CTW-R and ZTW-R respectively. Soil enzyme activities increased (5–18%) under ZTW+R compared with ZTW-R and CTW-R at different growth stages of wheat. The residual effect of rice establishment methods was significant on soil enzyme activities during wheat cropping, which were highest under ZT-DSR followed by CT-DSR, DTR and PTR. Soil organic carbon content in the 0–7.5 cm layer was significantly higher (7–9%) under the ZTW+R treatment compared with all the other treatments. Principal component analysis (PCA) identified three enzyme activities (dehydrogenase, fluorescein diacetate and phosphatase), and soil organic carbon content as the most sensitive indicators for assessing soil quality for RWS based on conservation agriculture. The PCA discriminated rice establishment systems with rice residue as surface mulch from rice establishment systems without rice residue and the maximum tillering stage from the other stages of wheat. The present study provided reliable biochemical indicators to monitor soil biological quality changes in response to conservation agriculture practices in RWS.