RICE-WHEAT cropping system occupies over 24 Mha cropped area in Asia with 13.5 Mha area in South and fulfill need of millions of people. There are several conflicts in this production system such as time of sowing, edaphic, and labour etc. The farmers of rice-wheat zone mainly grow basmati rice, which matures late and delays the paddy harvest and planting of subsequent wheat crop. This late harvest of paddy and management of rice residues are the major hindrances in the seedbed preparation for the following crop. Any rainfall at that time may cause further delay in wheat sowing. After the rice harvesting, the puddle soil may require few more days to reach the workable soil moisture. Moreover, delay in wheat sowing after mid-November results in yield reduction by 0.7-1.5% per hectare per day. Anthesis and grain filling stages of wheat are very sensitive to high temperature. Both these stages require optimum temperature ranges from 12 to 22°C. The temperature increases during these stages, time required to capture resources becomes less, and finally grain yield is reduced.
Conservation agriculture is a system with least soil disturbance, enduring soil cover, and planned rotation of crops offer a pragmatic and eco-friendly option to resolve the edaphic conflict in the conventional rice-wheat cropping system thus saving time, labor, water, reducing input costs with increased productivity. To improve the input, efficiency and farm profitability can be used on sustainable basis and to tackle the problems of yield stagnation in rice-wheat cropping system resource conservation technologies must be adopted. In order to save labor and water resources conventional production practices for rice needs to be replaced by conservation tillage practices.
Water saving rice production systems includes aerobic rice culture, alternate wetting and drying (AWD), system of rice intensification (SRI), raised beds, and ground cover rice production system (GCRPS). In aerobic rice culture, rice is sown directly in non-puddled, non-saturated, and well- drained soil in the absence of pounded water. Cultivation of aerobic rice provides a best alternative of transplanted rice because water requirement is substantially reduced in aerobic rice. Aerobic rice can save 35 to 60 % water as compared to transplanted rice. Direct seeding may allow earlier wheat planting as direct seeded rice matures 7-15 days earlier than transplanted rice.
The practice of withholding irrigation for several days after the vanishing of ponded water is known as alternate wetting and drying (AWD) that can save irrigational water and enhance water productivity without yield penalty. This can save 7-30 % water as compared to conventional puddling method. Water saving of above 50% has been observed in AWD as compared to flooded rice in areas having deeper ground water table. Alternate wetting and drying can minimize evaporative losses from 2-33% as compared to flooded rice.
System of rice intensification (SRI) can substantially boost the production and profitability of rice farmers accomplished with reduction in water requirement. Rice planted in SRI can save 12.6-70% water than continuous flooded rice. The rice crop grown by SRI method matures 5-20 days earlier.
Conservation tillage (CT) allows earlier wheat planting, reduces production costs, helps in water conservation and can increase wheat yield from 6-10%. The conservation tillage practices improve soil water storage capacity, soil organic carbon, improve soil quality and reduce soil erosion.
Conservation tillage also increases various soil enzymes activity, soil respiration and soil microbial biomass carbon (SMBC). Zero tillage enhanced soil respiration by 81.1%, SMBC by 104 % and soil dehydrogenase activity by 59.2% as compared to conventional tillage.
Zero tillage (ZT) is defined as sowing of crop directly into unplowed fields. Sowing of wheat by ZT is the most successful resource conservation technology. Cost saving of almost 5-16% has been reported in ZT of wheat as compared to conventional tillage. Zero tillage and other resource conservation technologies may also help to improve irrigation efficiency at field level through saving in irrigational water. Zero tillage of wheat can save 10-35% of the irrigational water. Zero tillage and reduced tillage can increase wheat yield from 0.09 to 1.5 t ha-1. Zero tillage wheat following ZT direct seeded rice produced more yield than conventional tillage. To abridge, it is clear that, these conservation techniques are not only beneficial for improving the production of the crops but also improving the soil health on sustainable basis.
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