Soil erosion is one of the most critical environmental problems currently facing Iran, and soil conservation is crucial for managing natural resources. The objective of this study was to investigate the effect of a vetiver cultivation system, known to be a valuable bioengineering technique, and polyacrylamide (PAM) addition on runoff, sediment load (SL) and cumulative water infiltration under field conditions in a loamy soil. The experimental treatments were vetiver cultivation, PAM (applied at 20 and 40 kg ha–1) and a mixture of vetiver and different PAM application rates. Three simulated rainfall intensities of 15, 30 and 45 mm h–1 were applied on the treated soils. Runoff and SL were collected at different time steps. The results showed that vetiver significantly decreased runoff and SL and increased cumulative water infiltration at different rainfall intensities, whereas the effect of PAM on runoff, SL and cumulative water infiltration depended on the PAM level. At the 15 mm h–1 rainfall intensity, PAM application increased the runoff, but decreased SL and cumulative water infiltration. At the 30 mm h–1 rainfall intensity, the 20 kg ha–1 PAM level decreased the runoff and SL. At the 45 mm h–1 rainfall intensity, the higher PAM level was more effective to enhance the cumulative water infiltration and to reduce the runoff and SL. In general, although simultaneous application of vetiver and PAM significantly decreased the runoff volume and SL and increased water infiltration compared with the control, vetiver considerably decreased the runoff and SL. This suggests that vetiver may sufficiently decrease soil erosion and PAM is therefore unnecessary in controlling runoff and soil erosion where vetiver is applied.

Keywords