Studies On The Techniques For Controlling Soil Erosion From Economic Forests And Nutrient Runoff Losses From Rice Fields In West Tiaoxi Watershed

Developing economic forests is a main path to increase farmers’ income. Planting rice is the foundation to safeguard food security. The processes of economic forest and rice production have become the one of important sources of agricultural non-point pollution on account of inappropriate fertilization and other agronomic measures. The control of soil erosion and nutrient losses is significant to cut non-point pollution load. In this paper, the characteristics of soil erosion in economic forests with different vegetation management were investigated. Meanwhile, rice growth responses and nutrient losses as affected by the application of coated slow-release urea with appreciate fertilization techniques were studied under field conditions. The results were as follows:1. The results of the observational experiment indicated that the cumulative runoffs of the treatments with planting economic forests were reduced by 39% to 96%, comparing with the treatment of non-planting, as well as the cumulative amounts of sediments were reduced by 39% to 96%. For planting white tea, the cumulative amounts of runoffs and sediments with contour planting manner were reduced by 5% and 22%, as well as the cumulative losses of total nitrogen and total phosphorus in sediments both were reduced by 30%. For planting pears and bamboos, the cumulative amounts of runoffs were reduced by 89% and 52% respectively. And the cumulative sediments were reduced by 98% and 48%. When planting pears, the cumulative losses of total nitrogen and phosohorus were reduced by 89% and 92% in runoffs respectively with vegetation mulching.; And those both were reduced 98% and 98% in sediments. When planting bamboos, the cumulative losses of total nitrogen and phosphorus were reduced by 52% and 48% in runoffs respectively with vegetation mulching.; And those were reduced 64% and 26% in sediments respectively. Vegetation mulching can control soil erosions of economic forests and reduce the losses of nitrogen and phosphorus efficiently.2. The results of the observational experiment with Phyllostachys Edulis showed that the cumulative runoffs, the cumalative losses of the total nitrogen, nitrate nitrogen, organic nitrogen and losses of various phosphorus forms in runoff of the treatments with vegetation mulching and chemical weed control were significantly lower than those of the treatment of manual weed control (P< 0.05). When planting Phyllostachys edulis, the cumulative runoffs were reduced by 24% to 29% of the treatments with contour planting Adinandra milletii. And the cumulative losses of nitrogen, phosphorus and potassium were reduced by 37% to 46%,14% to 27%,26% to 35% respectively. That indicated contour planting Adinandra milletii can trap runoffs step-by-step, and absorb a few nutrients carried by runoffs. The cumulative runoffs and the cumalative losses of the total nitrogen, phosphorus and potassium of the treatment with contour planting Adinandra milletii in the condition of vegetation mulching were reduced by 57%,70%,52% and 73% comparing to the treatment of manual weed control without planting Adinandra milletii. The cumulative runoffs and the cumalative losses of the total nitrogen, phosphorus and potassium of the treatment with ontour planting Adinandra milletii in the condition of vegetation mulching were reduced by 29%,37%, 21% and 38% respectively comparing to the treatment of vegetation mulching alone. The cumulative runoffs and the cumalative losses of the total nitrogen, phosphorus and potassium of the treatment with ontour planting Adinandra milletii in the condition of vegetation mulching were reduced by.26 to 41%,33% to 45%,25% to 44% and 21% to 38% comparing to the treatment of contour planting Adinandra milletii alone That indicated that contour planting Adinandra milletii in the condition of vegetation mulching can reduce the cumulative runoffs and the losses of soil nitrients of Phyllostachys Eduli efficiently3. The field experiment with five treatments such as CK, UR1, UR2, PU1 and PU2 was conducted. The results indicated the rice grain yields with no irragation were reduced from 17% to 21%, comparing to normal irragation. Under irrigation conditions, the grain yields of the treatments of reduced rates of nitrogen (UR1, UR2) and coated urea (PU1) applied were higher than that of the CK (conventional fertilization). These implied that the formulated fertilization with reduced doses of nitrogen and the application of coated slow-released urea can maintain the grain yields. The loss indexes of total nitrogen and ammonium nitrogen with the treatments of applying coated urea were reduced by 25% and 19%,51% and 55% respectively, with the comparison to the conventional fertilization. At fully tillering stage and booting stage, the concentrations of water-souble total nitrogen and ammonium nitrogen in soil with the treatment of applying coated urea were significantly (P<0.05) lower than these of the control or the treatment with reducd rates of nitrogen. The loss index of the total nitrogen and ammonium nitrogen of the treatment with much lower nitrogen rates were reduced by 7% and 9% comparing to the control. At fully tillering stage and heading stage, the concentrations of water-souble total nitrogen and ammonium nitrogen in soil with much lower nitrogen rates were significantly (P<0.05) lower than the CK. Applying coated urea and formula fertilization of reducing doses not only guarantee the grain yields, but reduce the nitrogen losses efficiently.