Agroforestry is a newly developed technique, which includes various fields and is suitable for developing countries. Recently,
the contour hedgerow-crop system has become one of the major forms of
agroforestry on slopeland in developing countries. It was proved intercropping between the contour hedgerows is favorable for controlling erosion, increasing soil fertility and gaining higher benefit of the slopeland by relatively low input. The primary objective of applying hedgerows is to control erosion and non-point pollution on slopeland. The distance between contour hedgerows mainly decides the effect of erosion control and the cultivable area in the hedgerows-crop systems. Therefore, the design of the distance is very important to applying the contour hedgerow techniques. The existing studies have not paid much attention to the hedgerow's control process for erosion and nutrient in the
temperate zone and semiarid region. The present study quantitatively analyzes the rules of various erosion zones on a slope by using plenty of field observed data in hilly loess area of northwest Hebei Province, as well as large-scale artificial rainfall simulation data from sloping field. Taking contour hedgerow-crop system as an example, this paper discusses the major mechanism of soil erosion and nutrient change processes, the design of level spacial structure of typical agroforestry systems in hilly area of northwest Hebei. The results showed that the critical slope length is 10-15m on the condition of rainstorm, which can control the generation of rills and make the erosion amount decrease obviously. The study provides a theoretical basis for the hedgerow plant, and the hedgerow can control the erosion and nutrient loss through changing the erosion process on slopes and control thes generation of rill erosion. The study has a scientific value for the application of the hedgerow-crops agroforestiy system in the temperate zone and semiarid region.