| Based on the typical double cropping of winter wheat and summer maize in the north China plain and aimed at water resource sustainability, calibrated and validated the Agricultural Production System Simulator(APSIM) for its application to North China by use of data from the 1999-2001 field experiments of the Yucheng Experiment Station under Academia Sinica in conjunction with data on the water amount supplied by the water and fertilizer measured in 2002-2003. Based on the daily meteorological data of Beijing and Jinan from 1961 to 1999, APSIM model was used to analyze the photo-temperature productive potentiality, rain-fed yield and the water content ratio. Three different precipitation year styles (PYS) were divided by rainfall guarantee rate curves. According to the wet, normal dry year style and water consumption of different growing time of crops and water sensitive index, high, low and normal treatment were set up, each of them has seven different irrigation schedules (four schedules in dry year). Based on the concept of the irrigation water use efficiency (IWUE) and the economic sustainable IWUE, optimum the "ecological efficiency first"and "economic efficency first"irrigation schedule eventually. It can make sure to minimize yield reductions and maximize water use efficiency and also can refer a water-saving and yield-increasing technology when the environment becomes dryer and dryer.The adjustment and validation show that in the Yucheng 1999-2000 (2000-2001) field experiments the averaged errors across simulations are 27.61, 24.59 and 7.68% (32.65, 35.95 and 10.26%), respectively for leaf area index (LAI), biomass and soil moisture content. On the other hand, the mean errors over simulations are 17.03 and 15.42% (20.10 and 23.00%), respectively, for LAI and biomass from higher (low) moisture content of soil in 2002-2003. It is found that a good fit is produced between simulations and measurements for biomass, the coefficients acquired are larger than 0.85, indicating that higher usefulness of the APSIM in modeling biomass and soil moisture of wheat-maize growing in rotation with exclusion of somewhat bigger bias of the simulated vs measured LAI.Analysis of yield of winter wheat and summer maize in Beijing and Jinan were done by the APSIM model which has been evaluated, and theresults show that the average potential yield is respectively 24600.33 kg'hm-2 and 22901.90 kg·hm-2, the coefficient of variation is 8.48% and 7.98% respectively. The average rain-fed yield is respectively 12415.65kg·hm-2 and 11456.79kg·hm-2, which CV is 34.09% and 33.48% respectively.The WCR of Beijing and Jinan is 0.511 and 0.504, CV is 35.51% and 33.25% respectively.The best irrigation pattern of three different hydrological years is presented. In the dry year, three times of irrigation should be given to winter wheat (jointing+heading+milking)with 80mm per one time, meanwhile, two or three times for summer maize (jointing+heading or jointing+heading+milking) with 50mm per one time. The "ecological efficiency first" irrigating quota is 340-390mm: Four times for winter wheat (base water+jointing+heading+milldng) with 80mm per oΠe time, and three times for summer maize (jointing+heading+milking) with 50mm per one time as the "economic efficiency first" irrigation schedule which quota is 470mm。In the normal year, two or three times of irrigation should be given to winter wheat (jointing+heading or jointing+heading+milking) with 60mm per one time, meanwhile, two times for summer maize(jointing+heading)with 30mm per one time. The "ecological efficiency first" irrigating quota is 180-240mm: Three times for winter wheat (jointing+heading+milking) with 60-70mm per one time, and two times for summer maize (jointing+heading) with 30-40mm per one time as the "economic efficiency first" irrigation schedule which quota is 240-290mm。In the wet year, there is no irrigation during the winter wheat and summer maize stage because the IWUE can't reach the economic sustainable criterion.
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