Optimization Of Water Resources Utilization For Cropping System In Beijing

In this paper, the balance between water resource supply and demand for cropping system in Beijing was evaluated and regionalized generally based on GIS. Taking Shunyi County and Yanqing County as cases, by theoretical calculation and field experiment, water ecological adaptation, water use efficiency, economical water use efficiency and other indexes of all crops in irrigated farmland and dry farmland were analyzed in this paper. With this view, water resources sustainable utilization for cropping system in Beijing were comprehensively designed. The results of this study are generalized as follows.1) According to water utilization balance of cropping systems in Beijing, five type regions were divided, and those are serious, medium, less, balanceable and rich water resources. Water resources in plain area were shorter than mountainous area because of over-extraction of groundwater and utilization in plain area. It was calculated that there was 47.9% of water shortage area in plain area, most of which was serious and medium water shortage area. Most of mountainous area belonged to water balanceable area. In plain area the water resources for cropping system was short of 1.5438xl07m3, and in mountainous area which exceeded 5.9115x107 m3. Based on the analysis of change of cropping structure water consumption, it showed that water utilization for wheat, corn and other crops decreased year by year, while water consumption for vegetable increased promptly. In 2002, Water consumption of vegetable accounted for 52.2% in proportion to that of cropping system.2) Through the analysis on water ecological adaptability index (WEAI), main crops were divided into three types in Beijing irrigated farmland and dry farmland. In irrigated farmland: I .High water ecological adaptation crops: summer soybean, summer peanut, spring soybean, sorghum, millet had higher water ecological adaptation. II .Medium water ecological adaptation crops: spring corn, spring peanut, summer corn and cotton. III. The crops had lower water ecological adaptation such as winter wheat and alfalfa. In dry farmland: I .Spring millet and spring soybean had better water ecological adaptation. II .spring corn had medium water ecological adaptation. III. The crops had lower water ecological adaptation such as alfalfa and potato.3) Based on the investigation and field experiment of water use efficiency (WUE) for main crops in Beijing, the results showed as follows: From the point of crop biomass, the WUE of spring corn was 30.4-31.8kg.hm-2.mm-1.The WUE of the other main crops in irrigated farmland in Beijing was spring peanut, alfalfa, spring soybean in order. For spring peanut and spring peanut, the WUE under CK treatment was the highest. For the spring corn and alfalfa, different irrigation treatments had little influence on WUE. The WUE of the fruit tree and vegetable was 51.5~67.53 kg.hm-2.mmand some 100 kg.hm-2.mm-1. All of them were higher than field crops. There were also differences in the WUE of main crops in dry farmland in Beijing, the order was: spring corn, spring soybean, alfalfa, potato, spring millet. In all the different fertilizer treatments for one crop, the WUE of medium treatment was highest. In general, the economic benefit of water use could be put in order of vegetable, fruit tree, cashcrops, grain crops, forage crops.4) Based on the statistical data oft agricultural production in Beijing for many years, it was concluded that the planting area of vegetable increased rapidly, which had been going against the severe status of water resources in Beijing. Considering the crops with high profit have the characteristic of high water consumption, the price policy should be put forward to restricting more water resources to high water consumption crops. On the basis of the actual status of water use in Beijing, the strategies to agricultural water price polity were also advised in this paper. The structure of cropping system was adjusted by considering the total water resources in Beijing as the maximal limiting factor, increasing planting area of cr...