Temporal changes of runoff and soil loss under different flow discharges in furrows of rainfed wheat

The variety of factors affecting soil properties leads to temporal changes in the soil erosion process. This research was conducted to assess short-term changes in runoff and soil loss in rainfed wheat furrows under fallow conditions. To this end, three rainfed lands with 15% slope gradient were selected in south west of Kermanshah Province. In each land, furrows with five m in length and 30 cm in width were created using sowing set. Runoff and soil loss were measured using simulated flows with a discharge of 0.5, 1, 1.5 and 2 L.min-1 at intervals of five minutes to 60 minutes 60 minutes in three replications. Results showed that the lowest soil loss was recorded in flow discharge of 0.5 L.min-1 (2.66 g.m-2) and the highest of soil loss was produced in flow discharge of 2 5 L.min-1 (85.33 g.m-2). Also, the lowest runoff was recorded in flow discharge of 0.5 L.min-1 (0.47 L) and the highest of soil loss was produced in flow discharge of 2 5 L.min-1 (7.65 L). The effect of time on runoff and sediment variables was significant in all flow discharge (p<0.01). Runoff production was low at the beginning of the experiment and increased over time. The pattern of temporal changes in soil loss was different from runoff production, amount of soil loss at the beginning of the experiment was higher values ​​than the final test times, which associated with to supply of erodible soil particles in the rills in the beginning of the experiment. With starting the experiment to 25 minutes, the rate of soil loss changes drastically and then until the end of the experiment, it followed a uniform reduction pattern and in the final stages, it is almost constant. The results showed that rill erosion is strongly influenced by flow intensity and its value changes over time and these changes are independent of flow production and depended on the transmittance of soil particles transferable in the rill.