Losses of soil, organic carbon, phosphorous and potassium due to interrill erosion influenced by different levels of wind velocity and plant residue coverage

Interrill erosion is one of the most important forms of soil erosion in agricultural lands let to decline in the quality and loss of soil. Despite many studies have been done on interrill erosion, few studies have been conducted on the losses of soil, organic carbon (OC) and nutrients due to wind-driven interrill erosion. Therefore, the purpose of this study is to investigate the effects of different percentages of wheat straw coverage and wind velocities on the losses of soil, OC, phosphorus (P) and potassium (K) following to wind-driven interrill erosion on two contrasting cropland soil samples.

the experiment was conducted as factorial in a completely randomized design using three factors. Two soil samples with maximum aggregate sizes of 2 and 4.75 mm covered by four levels of wheat straw mulch including 0 (as control), 30, 60, 90% (equal to 800, 1650, and 3300 kg ha-1) were examined at different wind velocities (0, 6 and 12 m s-1), each at three replicates under simulated rain and wind. Therefore, a constant intensity rainfall of 40 mm/h was generated for 40 minutes and the amount of soil losses, as well as OC, P and K losses were measured. Finally, the relationship of wind-driven interrill erosion rate with the OC, P, and K losses was evaluated.

The results showed that the loss of soil, OC, P, and K In the studied soils ranged from 8.1 to 134.9, 0.02 to 1.28, 0.03×10-3 to 1.45×10-3, and 0.007 to 0.160 mg m-2 s-1, respectively. With increasing the percentage of mulch, the losses were reduced significantly as nonlinear trends. In contrast, higher wind velocities increased the losses of soil and the nutrients. In the absence of wind and coverage, fewer losses were found in the soil containing coarser aggregates. The OC loss in the soils was higher than the P and K losses. The relationship of soil loss with OC and P losses was closer than that with the K loss.

The findings of this study showed that blowing of erosive winds during a rainfall can intensify the loss of soil and nutrients. However, wind velocity enhances stream power; the presence of surface mulch can reduce the losses by enhancing the surface roughness and conserving the soil surface from the direct impact of raindrops. Moreover, the presence of larger aggregates at the soil surface has an effective influence on the interrill erosion control. Based on the findings of this study, 60% was determined as the optimal coverage of wheat straw to control soil loss due to interrill erosion. Therefore, keeping this amount of plant residue coverage on agricultural soils can considerably constrain the losses of soil and nutrients due to interrill erosion.