Estimation and Characterization of Deep Percolation from Rice and Berseem Fields Using Lysimeter Experiments on Sandy Loam Soil

Deep percolation from the root zone of water intensive crops reduces irrigation efficiency, minimizes water productivity andbecomes an environmental threat by carrying chemical residues to groundwater systems. Quantification of the percolation process is oftenmade indirectly without actual field observations. In the present case study, simple, locally constructed drainage type lysimeters were utilizedto monitor daily deep percolation from the root zone of unpuddled sandy loam soil throughout the growth periods of rice and berseem foddercrops. Similarly, other water balance components were monitored on daily time steps during the crop growth periods (2013 and 2014). It wasobserved that a large volume of water is returned as deep percolation loss as physically demonstrated from lysimeter measurements. Overall,approximately 82% of the input water volume in rice season and 61.8% in berseem season accounted for deep percolation in unpuddled sandyloam soil of the experimental field. A simple water balance model was employed to compute deep percolation from the crop root zone. Thedeep percolation computed on a daily basis did not agree with the measured values; however, cumulative deep percolation computed on anextended time interval of seven days (weekly basis) for rice and between wetting intervals for berseem seasons agreed well with the modelcomputed cumulative percolation. This could be attributable to the fact that some time is needed for drainage water to arrive lysimeter outletslocated well below the crop root zone. Consequently, it can be concluded that in application of drainage type lysimeter water balance,estimation of deep percolation from a cropped area can be made fairly well in longer time steps than shorter time intervals. Specifically,heavy rainfall events resulted in large percolation losses. This study also proves that locally constructed lysimeters could effectivelybe utilized in water balance studies of a cropped area when used in combination with root zone soil moisture monitoring devices.