P. KrishnanBrijesh Yadav2021-07-132021-07-132020-06https://krishikosh.egranth.ac.in/handle/1/5810170445T-10444Studies on the impact of conservation farming practises on improving soil water retention, soil temperature moderation and distribution of soil nitrates in wheat and mustard crops should be given special attention. To understand these processes, field experiments were conducted during 2018-19 and 2019-20 at research farm of ICAR-IARI, New Delhi. Two tillage practices (zero tillage with residue retention, ZT+R and conventional tillage with residue incorporation, CT+R) were followed as main plot factor while two cropping systems (Maize-Wheat- Mungbean and Maize-Mustard-Mungbean) were followed as sub-plot factor in a split plot design. Results clearly showed that adoption of zero tillage with residue retention improved soil physical environment and crop growth parameters. The HYDRUS-2D model simulated soil water content showed significant correlation with observed values in both crops (R2 = 0.72- and RMSE=0.011-0.03 cm3cm-3). HYDRUS-2D simulated soil water balance components in both crops showed that cumulative RWU (CRWU) and cumulative drainage (CD) were higher for ZT+R over CT+R but the magnitudes of cumulative evaporation (CE) was lower due to the residue retention. The HYDRUS- 2D model simulated soil temperature in both wheat and mustard crop showed strong correlation with observed data (R2 = 0.61-0.84 and RMSE = 1.23-3.78 °C). The performance of model to simulate the soil temperature at 2 and 10 cm depths was good but results was less satisfactorily at 20 cm depth. The simulated maximum soil temperature was higher in CT+R than ZT+R while simulated minimum soil temperature was higher in ZT+R. The HYDRUS- 2D model simulated soil nitrate in both wheat and mustard crop showed strong correlation with observed data (R2 = 0.72-0.87 and RMSE = 4.20- 10.43 mg L-1) and simulated nitrate concentration was higher under CT+R as compared to ZT+R for both crops. APSIM model was calibrated during 2018-19 and used for validation during 2019- 20 for both wheat and mustard. APSIM simulated above ground biomass, leaf area index and grain yield showed strong correlation with field measured data. The performance of APSIM model was good to simulate soil water (R2 = 0.66-0.80 and RMSE= 0.017-0.031 cm3cm -3) and soil temperature (R2 = 0.67-0.78 and RMSE= 1.12-1.87 °C) in both wheat and mustard. Performance of HYDRUS- 2D to simulate SWC was highly significant as compared to APSIM. However, HYDRUS-2D simulated ST were significant for 2 and 10 cm depth but performance was less satisfactory at 20 cm depth compared to APSIM. Similarly, performance of HYDRUSEnglishThesis