Pramila AggarwalVIKAS KUMAR RAI2018-08-142018-08-142017http://krishikosh.egranth.ac.in/handle/1/5810064275t-9644The studies on effect of conservation agricultural practices on moderation of soil temperature and distribution of soil water in the profile during crop growth need special attention for understand changes in water and energy balance components, which are crucial components of crop improvement programmes. In current study, both water balance and energy balance components of soil under different conservation agriculture (CA) practices were analyzed using the Hydrus-2D model during the pigeonpea growth. The treatments were: conventional tillage (CT), zero tillage (ZT), permanent narrow beds (PNB), permanent broad beds (PBB), ZT with residue (ZT+R), PNB with residue (PNB+R) and PBB with residue (PBB+R). Results on soil physical environment changes after 7 years of continuous adoption of different CA practices showed that both permanent broad bed and narrow bed with and without residue retention and zero tillage with residue retention reduced bulk density (BD), increased field saturated hydraulic conductivity (Ksat) and improved soil water retention significantly over CT. Ksat values obtained as the output of Rosetta Lite model could not be used as hydraulic input parameter as they were very low and hence, measured value of Ksat and α and n parameter obtained as output of Rosetta Lite model were optimized through inverse modeling and were used as hydraulic inputs of the model which predicted daily change in SWC of profile with reasonable accuracy (R2= 0.78; RMSE= 0.012). Soil water balance simulated from the model showed higher cumulative transpiration, lower cumulative evaporation and higher soil water retention in most of the CA practices as compared to CT. Computed values of Thermal conductivity (λ) obtained from observed soil temperature (ST) data at different soil water contents showed good correlation with the optimized values of thermal conductivity obtained through inverse modeling. Hydrus 2D predicted ST variation of 0-20 cm soil profile using optimized values with reasonable accuracy (R2=0.91) for a simulation period of 10 days, although it slightly over predicted ST values. Both observed and simulated results of ST as function of depth and time, revealed that fluctuation of peak magnitude of temperature wave between 5 and 20 cm was more in 138 CT than in PBB+R. Simulated Value of ST at hourly interval for 5 cm depth showed more variation and occurrence of peak was 2-3 hours earlier than those of ST values at 15 and 20 cm. Among different energy balance components, computed ground heat flux was lower and Latent heat flux was more in PBB+R as compared to CT. Hence it was concluded that PBB+R and PNB+R practices should be adopted for pigeon pea cultivation, as these practices modified soil hydrothermal regimes, enhanced root growth and improved radiation interception, LAI and biomass production. The Hydrus-2D can satisfactorily simulate the temporal changes in water balance components as well as ground heat flux (G) and latent heat flux (LE) components of energy balance during the crop period; hence it may be adopted for evaluating different management practices in terms of improvement in water and radiation use by them.en-USnullThesis