Several recent modifications to ISBA land surface scheme in ARPS based on a variety of sources in the current literature were analyzed against OASIS observations. The analyses were done seperately for each modification to see their respective contribution and together to see the synergetic effects on the simulation of soil hydrology. It was found that the parameter retrieval technique using adjoint technique can significantly enhance the forecasting ability of land surface model, if the underlying physics are correctly implemented and the criteria for measuring data-model misfit are suitably chosen.