Deep tillage and irrigation impacts on soil water balance and water productivity of direct-seeded rice-wheat cropping system in north-west India

Direct-seeded rice (DSR) is a potent option for north-west India considering the current shortages of labour and water. The formation of a subsurface compact layer in medium to coarse textured soils due to continuous puddling used for commonly grown puddled, transplanted rice hampers the root growth of DSR and wheat crops. It is thus imperative to study the deep tillage effects on water balance and water productivity of the DSR wheat cropping system. A two-year field experiment was conducted during 2016-17 and 2017-18 in a sandy loam soil to study the soil water dynamics in relation to tillage and irrigation regimes in a DSR-wheat cropping system. There were two irrigation regimes both in DSR (irrigation at 4-day and 8-day intervals) and wheat (based on irrigation water to pan evaporation ratio of 1.0 (I-1.0) and 0.5 (I-0.5)) in main plots; with three tillage treatments in subplots: (1) conventional tillage for both DSR and wheat (DSRCT-WCT), (2) deep tillage before sowing of DSR during the first season + conventional tillage in wheat (DSRDT1-WCT) and (3) deep tillage before sowing of DSR during both seasons + conventional tillage in wheat (DSRDT2-WCT). The irrigation water input was lower by 325 nun under 8-day, I-0.5 compared with 4-day, I-1.0 irrigation regimes during both years. The evapotranspiration (ET) was significantly higher in plots with the 4-day compared to 8-day irrigation regime by 22.8% and 17.2% during 2016 and 2017 respectively. In wheat, ET was significantly higher in plots with I-1.0 than I-0(.5) by 42.7% and 34.8% during 2016-17 and 2017-18 respectively. The ET was significantly higher in DSRDT2-WCT and DSRDT1-WCT than DSRCT-WCT in DSR. The water productivity was higher in less frequently (8-day and I-0.5) than in frequently irrigated (4-day and I-1.0) plots. Deep tillage during both seasons (DSRDT2-WCT) had no significant influence on the soil water balance components and water productivity in comparison to deep tillage only once in two years (DSRDT1-WCT). However, the ET and water productivity were significantly higher in plots with deep tillage compared to conventional tillage.