Preliminary Study On The Variation Of Soil Water In Slope Surface With Ephemeral Gullies By Contour Hedgerow

In southern China, there are lots of ephemeral gullies with heterogeneous density distributing on serious erosion slope land, which has seriously restricted the sustainable development of agricultural productivity on slope farmland. Contour hedgerow is a very common and effective technique around the world, which is often employed to revegetate on cultivated slope land and conserve water and soil resources. Contour hedgerows were employed to control ephemeral gully erosion in this thesis. Through measuring soil moisture in ephemeral gully simulation plots, the purpose of this research was to discuss the dynamic variation of soil water in slope surface with ephemeral gullies, and effects of soil and water conservation by contour hedgerows, so that provide scientific basis for controlling ephemeral gully erosion. The main results were as follows:1. Seasonal variation of soil water content of depth 0-45cm in experimental plot agreed with rainfall. Rainfall was the main cause for variation of soil water in slope surface with ephemeral gullies. Seasonal variation of soil water content was divided into three periods. Rainfall was rich for May to August, and exceeded evaporation, so soil water was in accumulating stage; Temperature was high and rainfall was less from September to November, so rainfall was less than evaporation, then soil water was in consumping stage; With temperature descending after November, rainfall equaled to evaporation, then soil water was in steady stage.2. According to the degree of variation of soil water, soil profile was divided into three layers: vertiginous layer (0～15cm), active layer (15～30cm), and sub-active layer (30～45cm).3. The effect on soil water in slope surface with ephemeral gullies by hedgerow was different in different season. In rainy season, soil water content of depth 0-45cm in treatment of ephemeral gullies with contour hedgerow setting was higher than without hedgerow. For instance, soil water content in plots of clay soil and clay loam soil with contour hedgerow setting was 2.2% and 1.2% higher than without hedgerow respectively. While in dry season, soil water content in treatment of ephemeral gullies with contour hedgerow setting was lower than without hedgerow. For instance, soil water content in plots of clay soil and clay loam soil with contour hedgerow setting was 2.6% and 8.9% lower than without hedgerow respectively.4. Under the condition of natural rainfall, soil water content within ephemeral gullies was higher than inter ephemeral gullies. Soil water content within ephemeral gullies in plots of clay soil with hedgerow, clay soil without hedgerow, clay loam soil with hedgerow, clay loam soil without hedgerow was 15.3%, 8,7%, 9.5%. 7.3% higher than inter ephemeral gullies respectively. Moreover, within ephemeral gullies, soil water content of the bottom was higher than that of the top.5. Under the condition of artificial rainfall, in slope surface with ephemeral gullies runoff begun earlier than in slope surface without ephemeral gullies, and the amount was larger, the intensity was greater.6. Contour hedgerows reduced the erosion on slope surface with ephemeral gullies effectively, and the effect of soil conservation was more obvious than the effect of water conservation. Compared with the control, soil erosion for clay soil plot with hedgers reduced 16.92%～43.06%, and runoff reduced 3.59%～25.17%; soil erosion for clay loam soil plot with hedgers reduced 15.04%～37.60%, and runoff reduced 4.05%～24.20%.