Comprehensive Benefits Evaluation And Optimization Of Agroforestry In 400-500mm Precipitation Area Of Loess Plateau

By ways of utilizing the theory and methodology of system engineering , several typical agricultural and forestry models located in 400-500mm precipitation area of loess plateau were comprehensively evaluated .In pengyang county ,On the basis of evaluation ,the structure of land used for forestry , agriculture and animal husbandry in agroforestry were optimized. According to the current model of production and management of agriculture ,purposes of comprehensive evaluation were as follows, firstly, assessing and selecting the optimal model of production and management, secondly, using the selected model to aid farmer for getting rid of poor condition ,last ,offering reference and decision service to policy makers. In contrast, purpose of optimization were such as making an overall plan of soil exploitation of this region , drawing up practicable scheme of soil exploitation and offering aid for concrete gain green enforcement.With AHP assessment method, several typical agricultural and forestry models located in 400-5 00mm precipitation area of loess plateau were comprehensively assessed. During the assessment, 14 indexes including output value, net income of labor, profit rate of cost, payout period of investment forestry cover ratio, the amount of soil erosion ,multiple crop index, ecosystem affected rate ,the product abundant degree ,rate of product for commodity and function of demonstrating were used. The result of assessment showed that, the score of the comprehensive benefit of agroforestry was among the highest and its average score is 0.4843,the model of agroforestry is optimal, traditional agricultural model of which the average score was 0.1754 gained the lowest score, the score of the model of forestry of which the average score is 0.4427 was moderately high, but this model was not in harmony with economic , ecological and social benefits, so this kind of model was not optimal.There was obvious difference between various productive model, in agroforestry structure the score of the model of fruit growing combined with medicinal herb was among the highest and its average score was 0.6471,this kind of model is optimal. The scores of comprehensive evaluation of the other models such as forestry incorporating with medicinal herb, forestry associated with herbage, edible kernel of apricot planted in low bank of earth between fields and fruit growing among grain were relatively optimal.For example, in penngyang county , with the method of linear programming, structures of soil used for forestry agriculture and animal husbandry in were optimized .Before optimization ,we analysed the details of current condition of soil utilization ,its major problem and solution. Results showed that, by means of optimization ,the land area used for planting was reduced to 32029ha,the reduced land account for 13% of total land area. The land area in which planted wood was increased to6214ha,the increased land area was amount to 3% of total land area. The land area used for grass was increased to 25865ha,the increased area accounted for 10% of total land area. In the meantime, the inner structures of crop growing , forestry and herbage were regulated .The land area used for cash crops and high yields of economic wood were increased by means of which continually increased farmer's income.The feasibility of optimal scheme was analyzed, in the fields of the utilization of natural resources , the feasibility of society, economic and ecological benefits ,the optimal scheme is practicable. With the aid of optimization , the structures of soil utilization for forestry agriculture and husbandry were more rational.