Losses of nitrogen and phosphorus under different land use patterns in small red soil watershed
YUAN Dong-Hai1, WANG Zhao-Qian1, CHEN Xin1, GUO Xin-Bo1, ZHANG Ru-Liang2 (1.Institute of Agroecology, Zhejiang University Hangzhou 310029,China;2.Lanxi Water and Soil Conservation Supervision Station Lanxi 321100,China).
Soil erosion is very significantly serious throughout China, which covers 1.80 million km2. In red soil region of southern China, soil erosion also occurred seriously with area of 0.80 million km2. Soil erosion, which causes river silted, floods, nutrient loss, water pollution, soil and land productivity degradation, has negatively impacted on sustainable agriculture development. A lot of reports on soil erosion were presented focusing on simulation based on single factor treatment. Soil erosion research on watershed scale by adopting comprehensive approaches is poor reported. Reports aim to clarify soil erosion process and the approach to develop a comprehensive farming system in some watersheds were little presented. In this paper soil erosion and nutrient loss in Jiangjiatang micro-watershed located in Lanxi City in Zhejiang Province were studied. The micro-watershed is located in west of central Zhejiang Province, at the north of Jinqu Basin and upper Qianjiang River. It is characterized by monsoon climate in a subtropical zone. Annual precipitation there is about 1400~1600mm, mainly occurred in the period during April to August. The annual mean temperature is round 17.7℃ and cumulative temperature of more than 10℃ is around 5600℃. Soil in the micro-watershed belongs to red soil, being zonal soil originating from Q 2, and the land with this soil is mostly sloped with a relative altitude of about 34m. The micro-watershed for the experiment is about 321100m2, and 194900 m2 of it is sloped, 126200 m2 is riverside land. Five experimental catchments were set up according to the naturally canal and gully systems. Each experimental catchment has respectively independent canal and gully system. This micro-watershed with five catchments was exploited and utilized in 1992. The patterns of land utilization were described as follows. Catchment 1, it was an extensive land use area with 43400 m2 where land is nearly barren and covered with few naturally grown brushwood and short bamboo (Bambusa) on the upper part of the slope which accounts for 27%, and 16% of total land in this area respectively. On the middle part of the slope, China fir (Cunnhamia laceolata (Lamb.) Hook.), Chinese chestnut (Castaea mollissima Blume), loquat (Eriobotrya japonica(Thunb.) Lindal.), huyou (Citrus sp.) were cultivated without terraces, which accounts for 31% of total land in this area. Except China fir (Cunnhamia laceolata (Lamb.) Hook.), other fruit trees grew very poor due to no fertilizer application for three years. The denudation was significant on this slope with no grass among fruit trees. The lower part of the slope was constructed into terraces for planting Chinese chestnut (Castaea mollissima Blume) and cole (Brassica napus L.), which accounts for 26% of total land. But the quality of those terraces with different widths ranging from 2m to 4m and 5 to 7 degree gradient was not good enough. The application rate of fertilizer used on those terraces was relatively less. Catchment 2, it was an intensive land use area covering 66700m2. On the upper part of the slope there are little brushwood and even bared resulting into a significant denudation. The open vegetation land accounts for 25% of total area and 12% of that are bared. On the upper and middle part of the slope there were cultivated bamboo (Bambusa) and huyou (Citrus sp.) which accounts for 28% of total land in this area and 16% of that are bamboo (Bambusa). Much organic fertilizer and phosphorus were applied to the bamboo. The middle and lower part of the slope were constructed into terraces whose width range 4m to 5 m, some of them were used for huyou (Citrus sp.) accounting for 22% of total area, others were used for fruit trees intercropping soybean (Glycina max(Linn.) Merr.) and cole (Brassica napus L.) which account for 25% of total area. Only small terraces had grass stripe edges to prevent soil erosion. Fertilizer management was practiced on those terraces as usual. Catchment 3, it is a plant conservation area covering 19000m2. Some of the upper slope were barren with
【Fund】： 国家自然科学基金重点资助项目 ( 30 0 30 0 30 )~~
【CateGory Index】： S158
【CateGory Index】： S158