Response of Lentil (Lens culinaries) to Post-rice Residual Soil Moisture Under Contrasting Tillage Practices

Soil moisture stress and excessive soil wetness are the main abiotic factors limiting lentil (Lens culinaries Medik) growth and productivity in the humid tropics. Field experiments were conducted during the post-monsoon to winter seasons (November-March) of 2012-2013 to 2013-2014 on a clay loam soil (Aeric Haplaquept) of Eastern India to cultivate rainfed lentil, utilizing the carry-over soil moisture and residual soil fertility, in rice fallow during post-rainy season. Our objective was to determine the effects of three tillage treatments, viz. No tillage with standing rice stubbles (NT), minimum tillage with standing rice stubbles (MT) and conventional tillage (CT), imposed on post-rice soil conditions, on the root-zone soil moisture storage, actual evapotranspiration (ETa) of lentil, actual time and intensity of crop stress exposed, as well as growth, seed yield, and water use efficiency of lentil. The soil moisture storage within the root-zone was 17.1-18.6cm for NT and MT and 13.8-14.3cm for CT during the time of sowing and the values declined to 7.5-10.0cm during harvesting of lentil. Treatment CT declined>40% of its readily available water at pod-formation stage. Soil moisture storage depletion from sowing to maturity at 0-40cm depth was found 4.8, 3.4 and 6.9cm under NT, MT, and CT, respectively. The leaf relative water content (RWC), chlorophyll concentration, crop growth rate (CGR) and biomass were significantly (P<0.05) higher in NT and MT than CT. Leaf area, chlorophyll concentration and RWC varied significantly (P<0.05) at critical crop growth periods under different tillage as compared to soil moisture stress. The ratio of CGR to LAI was 1.5 times more under NT and MT than under CT. The ETa was 11.41, 11.16 and 10.28cm, respectively, for CT, NT and MT with a mean seed yield of 938, 1292 and 1225kgha(-1) across both the years. Treatments NT and MT had significantly (P<0.05) higher water use efficiency producing 35.3kgha(-1) more seed yield per cm of water as compared with CT. The increase in yield was primarily ascribed to the favourable soil moisture content, which increased the plant growth rate (96% as compared with CT), thereby helping the crop to overcome the terminal drought during the later stages of the growth of lentil. Contrasting tillage practices modified the crop coefficient (K-c) values by altering evaporation and transpiration coefficients with mean K-c values for initial, development, mid-season and maturity stages were 0.32, 0.43, 1.12 and 0.39, respectively, under post-rice residual soil moisture. Our study concluded that when long-duration puddled-transplanted monsoon rice (150days) was the preceding crop in rice fallow situations, NT and MT are better alternatives to CT for the production of lentil.