Effects Of Hedgerows On Soil And Water Conservation Of Sloping Land In Loess Hilly Areas

Sloping land is one of the basic factors of production to meet the local demand for foodas one of the main types of basic farmland in loess hilly region. And so it is the main areacausing soil erosion. Research and implementation of the effective measures controlling soiland water loss are the effective ways to solve the contradiction between local agriculturalproduction and ecological environment. Taking the alfalfa and sainfoin as the main researchobjects, the soil anti-erodibility, soil anti-scourability and soil anti-shear strength were testedwith hydrostatic disintegrating method, undisturbed soil trough scouring method anddetermination of undisturbed soil shear resistance. And the variation characteristics wereanalyzed along with the influence factors of soil erosion resistance. In addition,we analyzedthe effects of hedgerows on runoff and sediment on the sloping land. The main conclusionswere as follows:(1) The hedgerows can improve the soil anti-erodibility. In the first year the hedgerowsplanted, soil disintegration rate decreased with time and then stabilized. In the sloping landbetween hedgerow bands and nudation plot, soil disintegration rates were determined by soilbulk density, and had negative correlations with it. In hedgerow bands, soil disintegrationrates were determined by root length density, and had negative correlations with it.Soilanti-erodibility in hedgerow bands was stronger than that in nudation. In later period(T5), soildisintegration rates in sainfoin hedgerow bands were59.62%lower than that in nudation, and25.0%lower than in alfalfa hedgerow bands. The soil disintegration rate in alfalfa hedgerowbands was46.15%lower than that in nudation.(2) The hedgerows can improve the soil anti-scourability. In the first year the hedgerowsplanted, soil anti-scourability in hedgerow bands increased with time. Soil bulk density wasthe main factor to influence soil anti-scourability in nudation and sloping lands betweenhedgerow bands, and there was a positive correlation between them. Soil anti-scourability inhedgerows was determined by root length density, and there was a positive correlationbetween them, too. Because of the plants, soil anti-scourability in hedgerows was strongerthan that in nudation. In later period (T5), soil anti-scourability in hedgerows of alfalfa andsainfoin were2.76times and3.39times higher than that in nudation. And soil anti-scourability in sainfoin hedgerow bands could be stronger than that in alfalfa hedgerowbands ranging from2.09%(T2) to22.45%(T5).(3) The hedgerows can improve the soil anti-shear strength. Soil anti-shear strength inhedgerow bands increased with time. Soil bulk density was the main factor to influence soilanti-shear strength in nudation and sloping lands between hedgerow bands, and there was apositive correlation between them. Soil anti-shear strength in hedgerows was determined byroot length density, and there was a positive correlation between them, too. Because of theroots, soil anti-shear strength in hedgerow bands was higher than that in nudation. In laterperiod(T5)，the soil anti-shear strength in alfalfa hedgerow bands was35.84%higher than thatin the nudation, which showed48.75%in sainfoin hedgerow bands. And the soil anti-shearstrength in sainfoin hedgerow bands was9.50%higher than that in alfalfa hedgerow bands.(4) Hedgerows can reduce the runoff on sloping lands. The runoff in plots which hadplanted hedgerows was significantly less than the nudation plot. The hedgerow showed abetter effect of reducing runoff with a narrower distance between hedgerow bands. Under thesame precipitation condition, both in alfalfa hedgerow and sainfoin hedgerow, the runoffvaried with distance between hedgerow bands as the following order:3m<4m<5m<CK. Therunoff did not varied significantly with different plants.(5)Hedgerows can play a positive role in reducing the sediment on sloping lands. Thesediment in plots which had planted hedgerows was significantly less than the nudation plot.The hedgerow showed a better effect of reducing sediment with a narrower distance betweenhedgerow bands. Under the same precipitation condition, both in alfalfa hedgerow andsainfoin hedgerow, the runoff varied with distance between hedgerow bands as the followingorder:3m<4m<5m<CK. The sediment did not varied significantly with different plants.