Soil water dynamics, water productivity and radiation use efficiency of maize under multi-year conservation agriculture during contrasting rainfall events

Increasing resource degradation (soil) and resource scarcity (water) in Indo Gangetic Planes (IGP) had popularized the concept of conservation agriculture (CA). CA practices can alter the soil hydraulic properties by improving soil physical environment and hence water productivity (WP). Since CA practices are highly sites-pecific in nature, its worthiness under different cropping systems, soil types and agro-climatic zones must be studied. In the context of above-mentioned scenario of crop management practices, Hydrus-2D model was used to evaluate most suitable CA-based practice for north western (NW) IGP to understand the process of water transport. The experiment had 3-tillage and crop establishment practices [ZT-zero tillage; PB-permanent raised bed and CT-conventional tillage] in main plot and 4-cropping systems [MWMb-maize-wheat-mungbean; MCS-maize-chickpea-Sesbcrnia; MMuMb-maize-mustard-mungbean and MMS-maize-maize-Sesbania] in sub-plot. The validation of Hydrus-2D showed that nRMSE was observed between 0.19-0.25 and R2 value between 0.80-0.87 at P < 0.01. This indicates model is performing efficiently. The R2 value (0.87) was observed highest and RMSE ,(0.03) and nRMSE (0.15) was observed least in the CA-based PB plots. CA-based plots had 23%-37% less evaporation than CT plots. Cumulative root water uptake (CRWU) under PB was 11% and 15% lower, whereas CRWU under ZT was 20% and 30% higher than CT plots in 2012 and 2013, respectively. Cumulative deep drainage (CDD) in 2013 in PB was higher by 3.64 and 5.88 cm than ZT and CT, respectively. With 10-cm higher rainfall during 2013, variability in the soil water content (SWC) was increased by 22% in CT and 2% in ZT plots. PB had 14-35% and 30-36% higher water productivity than ZT and CT plots, respectively. Radiation use efficiency (RUE) for dry-matter was observed higher under CA based plots. However, RUE for grain yield was observed similar among CA and CT plots during 2012, but in 2013, ZT outperformed than CT plots. The outcome of this study is, the higher rainfall during 2013 mainly contributed to more CDD. Highly variable SWC was observed in the CT plots. With lesser deep drainage in ZT, root water uptake (RWU) was higher and WP was lower, whereas PB plots had comparatively less-moist soil profile and per unit of RWU + evaporation, a proportionately higher dry-matter was produced. In a well-drained soil profile of PB plots frequent and light irrigation may be advocated, whereas in ZT with better profile storage and lesser variability of SWC during both the year irrigation may be required less frequently. Therefore, adoption of CA-based practices leads to higher crop productivity and resource use efficiency, because of favorable soil hydrological property with less fluctuation in soil water content in maize under diversified cropping systems of IGP of south Asia.