Effects of rice straw mats on runoff and sediment discharge in a laboratory rainfall simulation

Abstract

The effects of loosely woven rice straw mats on runoff, sediment discharge, and suspended solids (SS) were investigated in laboratory rainfall simulations in an effort to identify conditions that could reduce erosion and improve water quality in farming districts. Small runoff plots of 1×1×0.5m in size were filled with loamy sand. Experimental treatments were rice straw mat cover of 0 (control), 300, 600, and 900gm−2; slopes of 10% and 20%; and rainfall intensities of 30 and 60mm/h. Runoff volume from covered plots was significantly smaller than that from control plots at α=0.05. Runoff reduction by mat treatment varied between 22.1% and 100% of control values. The runoff coefficient varied with runoff volume. Sediment was dramatically reduced by rice straw mat cover. In a 30mm/h rainfall simulation, very little sediment discharge occurred for 10% and 20% slopes. In a simulation of more severe conditions, 60mm/h rainfall and 20% slope, no sediment was yielded if mat cover was 900gm−2. SS concentration from covered plots was significantly lower than that from controls. It was observed that once runoff occurred, even with good mulching, a certain degree of SS was likely to remain because small particulates in suspension were neither filtered nor deposited easily. Rice straw mats were proven to ameliorate runoff, sediment discharge, and SS concentration in laboratory simulations, necessitating their application in the field to validate these results.