Investigating the effect of cultivated furrow length on rill erosion and eroded grain size in a rainfed field

Rill erosion rate and particle size of eroded material can be affected by rill length. This study was conducted investigated the effect of furrow length on the rill erosion rate and sediment grain size. Field experiments were done in a rainfed field with a 10% slope gradient with six furrow lengths (2, 6, 10, 14, 18, and 22 m) in a randomized complete block with three replications. The experiments were performed in the furrows with 20 cm width and 5 cm depth using a simulated flow with 3 l min-1. The initiation time of rill erosion and sediment grain size were determined in each furrow/rill at 5-min intervals for 60 min. Based on the results, rill erosion varied in the furrows over time and mainly increased to 45 min. Rill erosion didn’t occur the 22-m furrow, which is related to water infiltration along the rill and the loss of flow power. Rill erosion in furrows with 2, 6, 10, 14, and 18 m were 0.02136, 0.003232, 0.00225, 0.0150, and 0.00235 mg m-2 s-1, respectively. A decreasing linear relationship was found between rill erosion rate and furrow length (R2= 0.54). The grain size distribution of sediment was significantly affects by furrow length. With increasing furrow length, the selectivity of silt increased, whereas the selectivity of sand was limited in the long rills. The selectivity of clay didn’t affect by furrow length. Application of conservation tillage in rainfed lands can increase water infiltration and control rill erosion in the furrows.