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Based on 560 stations across the country from 1961 to 2008, weather data and production of different crops (winter wheat, maize, cotton and soybean), soil moisture, irrigation amount of data, based on the principle of water balance, combined with crop yields - water relations, crop water deficit lack of sensitivity index to analyze the relationship between crop water deficit rate in different developmental stages, the amount of water deficit and cut the rate to build water-saving irrigation of different developmental stages of winter wheat, maize, cotton and soybean the Meteorological level indicators. Coupling risk principle to construct the sequence of the long era of water deficit, calculated by the soft histogram method based on information diffusion crop developmental stages Ⅰ ~ Ⅲ grade water deficit rate risk probability of different water deficit, draw under natural conditions winter wheat, maize, cotton and soybeans, water-saving irrigation meteorological grade risk zoning map, analysis of the risk of the water deficit of the crop development period to provide a theoretical basis for the optimization of agricultural irrigation, to guide agricultural production. The conclusions are as follows: 1) based on the FAO-1979 crop yields - water function to study the relationship between the rate of crop water deficit and cut the rate to establish a fitting function equation can be used to measure irrigation costs and increasing production efficiency, optimize the irrigation system; 2) revealed four kinds of crop water deficit doesnot space distribution: severe winter wheat water deficit is mainly distributed in China's north, southwest and the Xinjiang region; Guangxi - Hunan - Hubei - Henan - Hebei region, summer corn moisture loss The vacancy rate in the 0 to 40%; Cotton moisture deficit rate distribution Huanghuai area north and Xinjiang regions; Northeast spring soybean average water deficit rate is generally 20% to 60%; 3) based on the farmland water deficit and cut The rate of correspondence between meteorological grade indicators of water-saving irrigation of crops. Growth of winter wheat water-saving irrigation meteorological level indicators (%): 15, 35), [35, 50) and ≥ 50; sowing - jointing: [20,40), [40,60) and ≥ 60; jointing - heading : [15,30), [30,45), and ≥ 45; heading - mature: [15,30), [30,50) and ≥ 50. Maize growing level indicators (%): 10, 25), [25,45) and ≥ 45; sowing - jointing: [15,30) [30,45) and ≥ 45; jointing - heading: [15, 25), [25,45) and ≥ 45; heading - mature: [15,30), [30, 40) and ≥ 40. The cotton growing level indicators (%): 15, 30), [30, 50) and ≥ 50; sowing - squaring: [20,40), [40,60) and ≥ 60; budding - flowering: [ 20,35), [35,45) and ≥ 45; flowering - boll opening: [20,35), [35,50) and ≥ 50. Soybean growth period level indicators (%): 15, 35), [35, 50) and ≥ 50%; sowing - branching: [20,40), [40,60) and ≥ 60; branches - pod : [20,30), [30,45), and ≥ 45; pod - mature: [15,30), [30,45) and ≥ 45 4) preparation of crops natural state of water deficit risk mapping the distribution of different irrigation weather rating of risk, risk maps of integrated risk distribution and the amount of water deficit. Quantify the the Irrigation risk and provide theoretical support for optimizing the irrigation system to improve water use efficiency.
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