A Model for Evaluation of Mulching Effectiveness on Increasing Rainwater Deep Percolation in Shahrkord Plain

One of the most important sources of agricultural water supply in arid areas is groundwater. Moreover, rain water percolation in the soil is the main source of groundwater recharge. Therefore, in this research, the efficiency of various mulches in increasing the percolation depth of rainwater was investigated in Shahrekord Plain. Eight precipitation events from the IDF curves of the study area with 2 and 5 years return periods were selected and the deep percolation of these rainfalls was tested in lysimeters with the same conditions and different mulches including gravel, sand, mixed sand and gravel, and the same soil texture without mulch. A total of 192 data were collected for soil moisture, air temperature and rain percolation. Furthermore, the equations for estimating the depth of rainwater percolation in each rainfall and the estimation of evaporation from soil under each mulch and soil without mulch were derived separately and the efficiency and accuracy of these equations were investigated using the Nash-Sutcliffe index and the coefficient of determination. The results showed that the derived relations had a coefficient of determination in the range of 0.98-0.99 and the Nash-Sutcliff index in the range of 0.98-0.96. Based on these equations and the water balance equation in soil, a soil moisture model was developed. Then, to evaluate the efficiency of mulches in increasing soil moisture and deep water percolation, this model was performed based on one year rainfall and temperature data of the study area. The results showed that the amount of percolation during this period in all studied mulches increased in comparison with the soil without mulch. The highest percolation amount was 17.1% in gravel mulch, which shows 21% increase compared to the non-mulched soil. Therefore, mulching of agricultural land can increase aquifer recharging due to increased percolation of rainwater into the soil as one of the sources for supplying agricultural water. However, considering the positive effects of mulching in saving soil moisture, its implementation issues should be considered broadly when selecting this type of mulch.