The Effect of Wheat Straw on Flow Characteristics and Rill Erosion in Wheat Rainfed Field

Rill erosion is one of the most important reasons of the soil lost in the plowed rainfed fields alongside the slope. Increasing infiltration rate in the soil and decreasing the erosivity of flow is essential for controlling rill erosion as well as increasing crop yield. This research was carried out to find out the effect of wheat straw on hydraulic characteristics of the flow and rill erosion in the wheat rainfed field in semi-arid region in Zanjan. The experiment was performed at seven straw mulch levels (0, 25, 50, 75, 100, 125 and 150 %) using the randomized complete block design with three replicates under the field conditions with plowing alongside the slope. At 100% level, 0.5 kgm-2 equivalent to five tons per hectare of straw mulch was applied into the soil. The results indicated that the effects of wheat straw on flow velocity, flow power and rill erosion was significant (p< 0.05), while its effect on the hydraulic radius and shear stress wasn’t statistically significant. These results were associated with a low depth of flow as affected by straw mulch in the furrow rills (p> 0.05). By increasing the wheat straw mulch level, the flow velocity, flow power and rill erosion decreased about 19, 23 and 55% respectively, as compared to the control treatment. There was a high correlation between the rill erosion and the flow velocity (r=0.71). The 100%-level of wheat straw mulch which decreased the flow power (34%) and the rill erosion (71%), was the most appropriate amount for decreasing rill erosion in rainfed wheat field. Generally, it can be concluded that the application of wheat straw mulch is a biological and proper practice for reducing erosivity of flow and controlling rill erosion in rainfed fields.