| Increasing water-saving function of planting structure by its optimization is an an important part of the crop group water using optimization, which is an important direction for water-saving agriculture development in areas with drought and water shortage. Aim at the problems as high proportion and low water use efficiency of agricultural water as well as the high cost, easy pollution and difficult large-scale promotion of other water-saving measures as conservancy projects, water control and agricultural water conservation, the principle system, division method, optimization, evaluation and regulating policy of Water-Saving Crop Planning (WSCP) were studied systematically according to the data of investigation, statistics and experiment. The planting comprehensive benefits especially water-saving benefit is expected to improve by planting structure optimization. Main results of this paper are as follows:(1)The principles system of the WSCP optimization was established. Based on the existing related theory, the principle system for the optimization is founded, which includes three principles of crop optimum selection, farm product requirement and resource restrict, as well as spatiotemporal crop distribution. The crop optimum selection principle realized the optimum selection of suitable variety and resolved the question of'What to plant'in a region by using crop thermodynamic thresholds and comprehensive adaptability index. The farm product requirement and resource restrict principle solved the question of'How much to plant'in a region by determing the upper and the lower limits for the cultivation area of different crops. The spatiotemporal crop distribution principle answered question of'When and where to plant'in a region by deciding multiple cropping, rotation, continuous cropping, intercropping, interplanting, etc.(2)The division optimization method of WSCP was analyzed and discussed with considering of natural and humanistic factors. 21 division indicators that suitable for Heihe Watershed were selected based on the analysis of affecting factors system for WSCP division. 5 common indicators that were not related with each other but can reflect majority information (93.258%)of original variables were extracted from these 21 ones by using the Factor Analysis (FA), and then each counties in the HeiHe river basin was clustered according to these 5 indicators by using K-Means Clustering Algorithm (KMCA). Based on the clustering results, we divide the basin into 6 subzones as forage grass with dry farming mountain subzone, grain and cash crops with rainfed-irrigation piedmont subzone, grain and cash crops with irrigation of eastern plain corridor subzone, fruits and vegetables with irrigation of western plain corridor subzone, cash crops with irrigation of central plain corridor subzone and cash and forage crops with irrigation desert gobi oases subzone, and finally drafted suitable development programs for each subzone.(3)The model for WSCP baed on Multiple Objective Chaos Particle Swarm Optimization (MOCPSO) was constructed. This model has four target functions: maximum total net output, total grain yield, ecological benefits, and water productivity. The decision variable is the yearly sown area of different crops and its restrictions are the farmland area, the available agricultural water resources and the demands of people and other industries for farming. The results by using this model in the middle portion of the Heihe River basin showed that MOCPSO has the advantages of a high convergence speed and a tendency not easily to fall into a local optimum. After adopting WSCP, economic, social and ecological benefits would be increased under the situation of reducting sown area, besides, irrigation water would be reduced by about 7%.(4)The PPE (Projection Pursuit Evaluation) model for WSCP was put forward by adding RAGA (Real-coding-based Accelerating Genetic Algorithm). By appling this model to evaluate and select an optimal scheme of crop planning in the middle reaches of the Heihe river basin, total 12 optimizing schemes of four kinds which are economic-benefit, food-security, ecological-benefit and water-saving programs in 2006, 2020 and 2030 were evaluated according to 19 indicators which were selected by four criterions as high efficiency of resources use, economic rationality, social equity and ecological security. It showed that the water-saving program is the most optimized scheme in an arid region with water deficiency and fragile ecology in the three chosen years. The evaluated results match up to the development conditions of crop farming in recent years and can objectively and truly reflected the contribution and direction of each evaluating indicator.(5)Regulating measures were discussed based on the survey and analysis for farmers'attitudes towards WSCP adjustment. By using questionnaire survey, the data about farmers'attitudes towards WSCP were investigated and collected and then analyzed by Logit and Logistic model. The study result shows that: the importance orders from strong to weak of influencing factors for WSCP adjustment support ratio were age, whether considering the water-saving effects of planting structure adjustment, whether only regarding capital restraint when adjusting, whether planting is important for family income, the participate of government, education, whether considering the drought-resistant variety has water-saving effects. According to this ordering, we proposed measures to guarantee the smooth implementation of WSCP as establishing demonstration, propaganda and training, economic compensation, government direction and sci-tech investment in agriculture, and then the optimization would be effectively implemented.
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