Study On The Laws Of Rainfall Infiltration Runoff And Erosion Sediment On Slopeland Treated With PAM

PAM, as a new efficient soil amendment, can significantly increase soil infiltration rate , reduce runoff and erosion. But PAM were dissolved into the water and sprayed on the face of soil, or used in furrow irrigation water, at the same time, the slope less than 8 gradient. In the Loess plateau, slope is steep and water is poor, so the methods of PAM and results need be studied. Rainfall simulator was used and the granule of PAM was covered on the face of soil in this study to investigate the laws of rainfall infiltration runoff and erosion sediment and the effect of PAM on soil critical shear stresses , for sloped land at different slope degree, different slope length, different rain intensity and different coverage of PAM. The experiment is designed to have 3 levels of rain intensity: 50 mm h "', 100 mm h"1 and 150 mm h "'; 4 slope degree: 5?, 10?, 20?and 25? (8.74%, 17.63%, 36.4% and 46.63%); 4 equivalent slope length: 8 m, 16 m, 24 m and 40 m; and 5 treatments: control, straw coverage, 3 PAM coverage- 40%,, 60% and 80%. The results show:1. Treated with PAM, can enhance soil infiltration capacity, reduce overland flow, delay the commencement of runoff, and increase infiltration time. With the PAM coverage increased, infiltration rate and stable infiltration rate are also increased. With slope degree increased, stable infiltration rate is reduced for 3 PAM coverage. With rain intensity increased, stable infiltration rate is increased.2. With slope degree increased, erosion sediment is also increased for different treatments. But erosion sediment is reduced at slope degree 25, it shows'that there is a critical slope degree from 20 to 25. Erosion sediment for PAM coverage is far lower than that of control. The more PAM coverage, the little erosion sediment. The bigger slope degree, the better effectreducing erosion sediment. With rain intensity increased, erosion sediment increases for 3 PAM coverage and control.3. The effect of slope length on erosion sediment is different at different rain intensity. With slope length prolonged, erosion sediment increases little at low rain intensity, but increases significantly at high rain intensity. When rain intensity exceeds one intensity, and slope length prolongs the critical slope length, rill erosion is caused. It is one important aspect of slope length on erosion sediment. The effect of slope length on erosion sediment is different at different PAM coverage. The critical slope length increases when covered with PAM, and the bigger PAM coverage, the longer the critical slope length. Effect of slope length on erosion sediment is little at low slope degree, but increases when slope degree increases. At the same time the critical slope length reduces .4. A direct calculation method of the critical shear stresses was established through observing initial place of slope erosion arising and the characteristic of runoff. At the same time, effects of slope degree and PAM coverage on the critical shear stresses were analyzed. The results show, the critical shear stresses decline with slope degree increase; the critical shear stresses increase when treated with PAM and increase with PAM coverage increase.