Study On Soil And Water Conservation Benefit Of Different Terrace Types In Red Soil Hilly Region

The red soil hills widely distributed in the areas to the south of the Yangtze River. The Jiangxi province is a typical example of soil and water loss in the red soil hilly regions of South China. Because of the reasonless utilization of land and the destroyed of the natural vegetation, there was a serious problem in the area of soil and water loss which seriousness is next to Loess Plateau for a long time. The hillside was terraced was an important measure of soil and water conservation in slope farmland treatments. A terraced field could remove or slow down the slope, cut short runoff,block the bathed dynamic, enforce the precipitation infiltration and retain amount, conserve water and soil, improve production conditions of slope farmland and create conditions for stable and high agricultural yield and strengthen ecological environment construction. Based on field measured data direct observation in2001-2005, the contrast analysis was carried out between the runoff, sediment, soil moisture, soil nutrient in different kinds of terraced field in the red soil hilly regions by runoff-plot testing method, the following conclusions are reached:(1) The mean yearly rainfall was1451.8mm in the experimental area from2001-2005. The annual rainfall in this area is very asymmetric, the rainfall can reached1808.5mm in2002, contrarily,it only have1164.3mm in2001. The seasonal rainfall was not well balanced and the rain occured most frequently and experienced a long time in spring. The heavy rain or torrential rain often occurred in summer. The amount of rainfall in spring and summer were higher than68%of that of the whole year. Average monthly rainfall was not well balanced and showed a typical bi-model volcanic series. The amount of rainfall on April, May, August respectively were much higher than that of in other months. The annual rainfall centralized on flood season (April to September), the amount of rainfall on flood season were higher than70%of that of the whole year.(2) There was a significantly different in surface runoff that treated by different methods. Because of the annual rainfall centralized on flood season (April to September), the surface runoff of region that treated by different methods centralized on flood season (April to September) too. The surface runoff of region that treated by different methods were91.45%(region10),71.22%(region11),81.98%(region12),89.55%(region13),82.48%(region14),89.68%(region15)respectively. There was a significantly different in surface runoff that treated by different methods on flood season and showed no different the rest time of the year. From the arrangement of benefit of runoff control:region10>region13>region15>region12>region14>region11. The result indicated that the bank and gully of level terrace showed benefit of water reception and runoff reduction, the exposed level terrace showed limited benefit of water reception and runoff reduction, it is showed the importance of grow grass on level terrace preliminary.(3) There was a significantly different in sediment losses that treated by different methods. Because of the sediment losses centralized in spring and summer, the sediment losses could correctly simulate the time of flood season. There was a significantly different in sediment losses that treated by different methods on flood season and showed no different the rest time of the year. From the arrangement of benefit of sediment control: region10region13>region15>region12>region14>region11. The result indicated that the bank and gully of level terrace showed benefit of water reception and runoff reduction. It can be applied to other region in the red soil hilly regions of South China. In addition, the sediment losses of exposed level terrace is next to sloping land orchard and far larger than those in grow grass on level terrace. It further show that the importance of grow grass on level terrace and can be applied to other region in the red soil hilly regions of South China.(4) From the analysis of the improvement of soil physical properties, it showed that it is an effective approach to improve soil moisture Status, soil bulk density, total soil porosity and capillary soil porosity. But the improvement of non-capillary prosity were not markedly obvious. From the analysis of the improvement of geochemical characteristics and nutriment status of soil, it showed that it was not an effective approach to total nitrogen, total phosphorus, total potassium and the rapidly available potassium in the soil and cound not improve the rapidly available phosphorus.