Searching "win-win" solutions for water saving in rice cultivation under different soil textures: Yield, water...

Rice is presently cultivated over 87 % of total kharif area in Punjab. It exhibits the low water productivity with a significant portion of the applied water being prone to unproductive losses, posing a threat to the sustainability of water resources in the state. It is against the sustainable development goals 6.4 (SDG 6.4) which target to substantially increase productivity across all sectors, particularly in agriculture and ensure sustainable withdrawals and supply of freshwater to address water scarcity and substantially reduce the number of people suffering from it. A two-year multi-location field trial was conducted to quantify the water balance of rice under different soil textured soil and optimize the soil textured-based irrigation schedules. The study comprises two crop establishment methods viz. direct seeded rice (DSR) and puddle transplanted rice (PTR). In DSR there were six irrigation schedules viz. first irrigation at 7, 14 and 21 days after sowing (DAS) and subsequent weather-based irrigation scheduling of IW (amount of irrigation water)/CPE (cumulative potential evaporation) ratio of 1.5 and 2.0; and in PTR three irrigation schedules viz. alternate wetting drying (AWD) of 2- and 3-days and continuous flooded (CF). These treatments were tested in sandy loam (SL), sandy clay loam (SCL) and clay loam (CL) soils. The average reduction in grain yield in DSR than PTR varied from 12 to 15 % with maximum in SL soil and minimum in CL soil. CL soil showed 16.7 % higher water productivity than sandy loam soil. Overall, DSR has 56-137 % higher water productivity than PTR. A delay of first irrigation up to 14 DAS in DSR was beneficial, as it allows the roots to reach and access water from deeper layers. The unproductive loss of total water input as drainage into deeper soil layers was less in DSR (20-31 %) than in PTR (50-75 %). Evapotranspiration (ET) losses accounted for 22-65 %, 20-60 % and 25-49 % of the total water input of rice in SL, SCL and CL soil, respectively. Total water footprints (WF_total) of rice production accounted for 35 % green, 59 % blue and 6 % grey. WF_green was 29-35 % higher and 65-76 % lower WF_blue in DSR than in PTR depending on the soil texture. AWD of 3 days in PTR proved as a saving practice particularly in SL and SCL soil by reducing blue WF by 18 % and 24 %, respectively. DSR can be an water-saving option with a modest yield penalty, particularly in medium to heavy textured soils. These results could significantly impact the development of policies to minimize water losses in rice production while maintaining agricultural productivity.