| Controlling agricultural non-point source pollution of drinking water source is not only a question of ecology environment, but also concerns the safety problem of drinking water.However, the study of mechanism and integration and control technology for controlling the agricultural non-point source pollution has been so weak that this paper was put forward in response to the current situation of the non-point source pollution of Yunmeng Lake reservoir area and the drinking water security of1million Linyi people, which was crucial, imperative and imperious.Taking the typical small watershed of the Yunmeng Lake large watershed of Jiepai Town, Mengyin County-Shuangheyu small watershed as the object of study, this research designed and laid out a series of measure system to control nutrient loss in sloping land and conducted a comprehensive benefit evaluation of the sloping nutrient loss of small watershed according to the governance effect of various measures.1. According to the current situation of serious soil and water erosion and incidental non-point source pollution in sloping land, the treatments of different herb layers between ridges at sloping land were laid out, that were:Arachis hypogaea and Bermuda cultivar; Arachis hypogae and Melilotus officinalis; Arachis hypogaea and Ryegrass; Arachis hypogaea and Trifolium; Arachis hypogaea and blank control. Results showed:(1) The grass planting between ridges in Arachis hypogaea land could effectively control soil and water loss with its runoff loss an order of Arachis hypogaea and blank control> Arachis hypogae and Melilotus officinalis> Arachis hypogaea and Bermuda cultivar> Arachis hypogaea and Trifolium> Arachis hypogaea and Ryegrass,which was55.1%-61.3%of that of bare land and the soil erosion3.4%-32.3%of that of bare land, an order of Arachis hypogaea and blank control> Arachis hypogaea and Trifolium> Arachis hypogae and Melilotus officinalis> Arachis hypogaea and Bermuda cultivar> Arachis hypogaea and Ryegrass. The treatment of Arachis hypogaea and Ryegrass was effective in storing water and retaining sediment. Influenced by factors such as rainfall, concentration of sediment loss presented a distinct fluctuation variation during its early establishment and the rate of sediment retention presented to be similar to the control. While the sediment loss continuously decreased and performed more stable in later stage and the rate of sediment retention increased afterwards accordingly. As to nutrient retention, the grass planting between ridges in Arachis hypogaea land effectively controlled output of phosphorus, with its loss of TP52.8%～75.3%of that of bare land and their loss of TP showing a decreasing sequence of Arachis hypogaea and blank control> Arachis hypogaea and Bermuda cultivar> Arachis hypogae and Melilotus officinalis> Arachis hypogaea and Trifolium> Arachis hypogaea and Ryegrass.(2) As a result of grass planting between ridges, the output percentage of PP was reduced to27.5%～67%in comparison of that of bare land; while the output percentage of DP was relatively increased. Arachis hypogaea and Ryegrass was prior in control of phosphorus transportation, with output of TP58.4%of that of bare land and PP27.5%. During the vegetation growth stage, amounts of different forms of phosphorus loss also performed variation from one another, and DIP was the main form of DP transportation during the whole rainy season. Transportation load of various forms of phosphorus in the first rainfall were much higher than that in the maximum intensity rainfall after peanuts were harvested.(3) The grass planting between ridges made soil coarsening index, sand content, total porosity, capillary porosity, capillary moisture capacity, soil organic matter and total nitrogen appears different degree increases, and soil bulk density, clay and silt, total phosphorus showed a trend of decline. Compared with the blank control, the grass planting between ridges evidently improved the soil physicochemical properties, among which the effect of ryegrass was the best, with its grey correlation degree of0.9024.2. Aimed at the serious soil erosion on slide slope of terraced fields resulting from rainfall and gravity, the treatment of planting grass on terrace ridge was laid out with the grass seeds as followed: Melilotus officinalis; Medicago sativa; Bermuda cultivar; Trifolium; Ryegrass; Hemerocallis and blank control. Results showed that:(1) Planting grass on terrace ridge could increase the land cover and decrease the direct blow of raindrop to the surface of sloping land through retention of plant canopies so that the flow velocity of surface runoff and surface wind speed were reduced, the scouring force and wind power decreased and loss of dissolved nutrient carried by runoff diminished. At the same time, the anti-erodibility and anti-scourability of the topsoil were enhanced and the soil performance was improved so that the loss of dissolved nutrient in soil was diminished.(2) Compared with the blank control, planting grass on terrace ridge evidently improved the soil physicochemical properties, among which the effect of Hemerocallis was the best, with its optimal indicators and grey correlation degree of nearly1, indicating that the comprehensive judgement result of its indicators was closest to the decision matrix. The others showed a decreasing sequence of Ryegrass(0.8742)>Trifolium(0.7312)> Medicago sativa (0.6677)> Melilotus Officinalis (0.6614)> Bermudagrass Cultivar(0.6577). As to improvement of the soil physicochemical properties, effect of the blank control was the worst, with its grey correlation degree just0.3749.(3) Hemerocallis, with its luxuriant plant and flourishing root, produces a micoenvironment which is benefical to the development of plant and microorganism and functions well in reducing rainfall kinetic energy, regulating the surface runoff and enhancing the anti-erodibility and anti-scourability of soil at the roots so that its effect of controlling soil nutrient loss and improving soil physicochemical properties is superior to other plants.3. Aimed at the current status of fast infiltration and evaporation and low soil organic matter content, the treatment of planting grass around the trunk was laid out with the grass seeds as followed: Trifolium; Ryegrass; Bermuda cultivar and blank control. Results showed that:(1) Planting grass around the trunk could increase the surface canopy density to avoid the direct sunniness and decrease the surface temperature and the evaporation of soil water. Further more, its development roots and humus layer overground could retent much surface runoff and increase flow infiltration so that a large proportion of water would be conserved and a large "soil reservoir" formed.(2) Compared with the blank control, the grass planting around the trunk evidently improved the soil organic matter and N、P content, among which the organic matter content was increased by23.18%～37.14% than before experiment, TN increased by9.9%～20.7% and TP by11.49%～14.44%.(3) Ryegrass is a kind of gramineous forage grass. With its tough cauline leaf,5～10cm plant height,5tiller number, multi-strains plexus type and high cross degree of cauline leaf, the vegetation coverage was improved. With its flourishing roots underground, Ryegrass is superior to other plants in increasing rainwater infiltration and improving soil physicochemical properties and the effect of improving surface temperature and water is most evident. With its N、P reinforcement function, the concentration of N, P in later stage increases obviously. With its luxuriant plant and flourishing root, the soil organic matter content is higher than others after the Ryegrass withered.4. Aimed at the factual truth of unreasonable land use structure and by means of GIS and linear programming model, the land use spatial optimal allocation of small watershed was conducted based on the risk control of N, P output.(1) Land suitability assessment was conducted through combination of the single-factor evaluation and the comprehensive evaluation method, which applied to meso-and micro-scale systems and made up for the deficiency of a linear programming model. It turned out that the method was easy to operate and had good availability of data, which guaranteed the reliability of the configuration result.(2) Land suitability evaluation was carried out through the method of effective coupling of linear programming model with dominant optimization analysis capabilities and GIS equipped with powerful spatial configuration function. The results showed that:the very combining of linear programming model and GIS not only provided the optimal allocation of land use with sound constraint effect in terms of area, but also matched the configuration information with specific spatial location at the same time, which enhanced the scientificalness and visuality of the optimal results.(3) As taking account of the output of N, P non-point source pollutant into the factors considered by the optimal allocation of land use, the configuration results realized the goal of unifying the economic and environmental benefits through establishing multi-objective linear programming model of minimizing output of the non-point source pollution and maximizing the economic effectiveness.(4) Taking the typical small watershed of the Yimeng mountainous area-Shuangheyu small watershed as the object of study, the optimal allocation of land use structure and the field monitoring experiment in the study area were carried out and results showed that the orchard, with high economic effectiveness, comparatively lower N、P output risk and good flexibility in spatial configuration, was main factor influencing the land use optimal allocation, which should be put priority in optimization scheme.5. With the help of spatial optimal allocation of land use and land use distributed as follows: Ryegrass planting between ridges for sloping land, Hemerocallis growing on terrace ridge for side slope and Ryegrass planting around the trunk for orchard, various sloping treatments were integrated to conduct comprehensive benefits evaluation. As a result, the benefit of the small watershed were increased by561.6m3for water retention,881.4kg for soil conservation,21.391million yuan for economy and N and P output reduce433.61g for ecology, respectively. |
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