| The eco-environment is fragile in semi-arid areas of the Loess Plateau, China. Improper uses of land like unreasonable farming, overgrazing aggravate soil erosion and the shortage of water resource. All of the above influence the sustainable development of ecology, agriculture and eco-safety. In this study, the Zuli River Basin was selected to study the rational use of agricultural and grass land. Combining water harvesting techniques and soil erosion prevention, the suitable areas for agriculture and grass were analyzed. The study includes:suitable areas for silt storage dams; suitable areas for farmlands; suitable areas for the main crops and micro-water harvesting techniques; suitable areas for alfalfa. Overall, the rational land use for agricultural and grass which can improve the productivity and control soil erosion was delineated.1. The silt storage dam has the ability to intercept sediment and harvest precipitation is an effective way to control water and soil losses. Through field investigation, the databases of location, status, year et al were established. The runoff simulated by Soil Conservation Service (SCS) model and verified by the measured data. Then taking150m3/hm2and250m3/hm2as the boundaries, the suitable areas for silt storage dam were divided by200m buffer of gullies. The results show that the most suitable areas for silt storage dam are in Dingxi Bailu country, Shixw country, Chenggy country and so on. Compared with the actual data,93.5%of the dams are built on the most suitable regions and only6.5%of the dams are built on the moderately suitable and unsuitable regions. Through comparison simulation results and actual result, this method is proved to be reliable. Then, according to this result, a plan scheme for the construction of silt storage dams was proposed in Chengguan country Dingxi city, and the years, capacities and areas for dams were also simulated, the results show that the dams could intercept soil effectively under this planning scheme.2. A long-term solution to control soil erosion and improve the ecological environment is to optimize land use and use precipitation rationally. The spatial distribution of soil erosion was simulated and validated by the measured runoff and sediment data in Huining, Chankou, Guochengyi and Jingyuan stations during1989-2000. Select soil erosion, runoff and slope as criteria, the suitable areas for agriculture was divided by the ideal point method into5levels, class4and5were defined as suitable areas for farmlands and calssl was defined as unsuitable regions. According to this result, the reasonable and unreasonable land uses were analyzed comparing with the actual land use, most of which were in the northwest and southeast of the basin.3. The rational distribution of crops is also the key when it comes to rational land use for agriculture. Based on literatures, the crops'demands for environment were collected. Based on the standard of the most suitable environmental conditions for crops, the suitability maps for these chief crops (wheat, corn and potato) were obtained by the Multi-Criteria Evaluation Approach. Considering the basin is in semi-arid areas, the effect of the technology of double ridges and furrows on the suitable areas for crops was also analyzed. The result shows the most suitable areas for this technology are in northeast of the basin. This study delineated the suitable areas for chief crops which offer consults and scientific basis to adjust agricultural production.4. Taking alfalfa as an example, the impact of returning cropland back to grassland on ecological environment was analyzed. Select soil bulk density, soil moisture, soil contents of C, N and yield as the standards, the effect of alfalfa's growth year on environment was analyzed by the Entropy Method in the northern and southern, respectively. The results show that the appropriate year for planting alfalfa in the northern of the basin is9years, and the appropriate year for planting alfalfa in the southern of the basin is6years, after the appropriate year, the composite index decreased significantly. Finally, the distribution of the yield of alfalfa in Zuli River Basin was displayed in the form of map. The method provides reasonable planting years for alfalfa to not only improve the soil environment but also avoid the dried layer of soil that could use for reference in other regions.The entire study centered around the effective use of agriculture and husbandry has highlighted the concept of taking the rational use of land as the foundation, analyzing the rational use of farmland, crop with its technology of double ridges and furrows and alfalfa to achieve the objective of reduce soil erosion, improve water utilization and productivity. |
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