Analysis of Comprehensive Benefits of Transforming Slope Farmland to Terraces on the Loess Plateau:A Case Study of the Yangou Watershed in Northern Shaanxi Province,China

De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau.There are different views about the defarming method,and also various de-farming patterns have been put into practice.This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces.Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features,soil and land use data of the Yangou Watershed,the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WIN-YIELD.Furthermore,an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed.The results show that:(1) The bigger the topographic gradient is,the more remarkable benefits it has in yield increase and water-soil conservation.(2) Farmland with slope below 5° could be retained,but farmland with slope above 15° should be converted to forest or grassland as soon as possible.(3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of "Relieving and de-farming" in improving agricultural production conditions,safeguarding food security,raising permanent vegetation coverage rate,and preventing soil and water loss.Besides,it is more cost-effective than the policy of "Relieving and de-farming".It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay.

Land use optimization at small watershed scale on the Loess Plateau

At present, land use optimization at small watershed scale is the key measure to control soil erosion, restore the eco-environment and improve the farmers＇ living standard on the Loess Plateau, China. Based on the land use survey maps of 1966, 1988, 1997, 2003 and the digital topographic map of 1984 in Yangou watershed, and assisted by spatial techniques of GIS, the basic characteristics and driving forces of land use change in Yangou watershed are analyzed. According to the summarization of land-use optimization characteristics since 1997, and with the help of continuous monitoring data for years and farmer investigation data, this paper appraises eco-environmental benefits, economic benefits and sustainability of Yangou watershed. We have used sediment reduction benefits, coverage ratio of permanent vegetation, per capita food production and per capita income of farmers as indices. The results show that Yangou watershed project has successfully controlled the soil and water loss and the farmers＇ living standard has been improved markedly by reasonable adjustment to land use structure. The benefit of sediment reduction is higher than 80% and the coverage ratio of permanent vegetation reaches 61.03%. In 2006, the per capita income increased by 1493 yuan compared with the year 1998.The successful measures and experiences of Yan- gou watershed are worth promoting on the Loess Plateau.