民勤绿洲种植业结构调整及其对农作物需水量的影响

论文引入虚拟水理论,构建种植业结构调整需水模型,分析近33 a民勤绿洲种植业结构调整对农作物需水量的影响。结果表明：1）民勤绿洲粮食作物、经济作物与其他作物面积比重之比由1978年的84∶12∶4调整为2010年的25∶72∶3。粮食作物播种面积比重的下降主要是由小麦播种面积比重的快速减少所致。2）民勤绿洲农作物需水总量由1978年的2.15×10⁸ m³增加到2010年的2.49×10⁸ m³,粮食作物和经济作物需水总量之比由1978年的88∶12变化为2010年的31∶69。3）民勤绿洲种植业结构调整的生态节水效应在不同时段存在差异,1979—1998年,种植业结构调整对于农作物需水而言,未起到节水作用;1999—2008年,种植业结构调整的节水效果明显;2009—2010年,种植业结构的进一步调整导致需水量的快速增加,未起到节水作用。单位面积需水量较高的蔬菜、小麦、玉米等5种农作物面积比重之和的大小对节水效果起到决定性作用。

Study on the Planting Industry Structure Adjustment and Its Impact on the Water Demand of Crops in Minqin Oasis

Oasis agriculture is not only the leading industry, but also the main water-consumption industry in the Minqin Oasis. The large water consumption of farming is the chief cause of intensifying contradiction between water supply and water demand and continuous deterioration of ecological environment. The optimization of agricultural structure, especially the cropping structure, is the key of sustainable development of agriculture in the Minqin Oasis. In this paper, the impact of cropping structure adjustment on the water demand of crops in the Minqin Oasis in recent 33 years was analyzed by using the theory of virtual water and the water demand models. Three conclusions are drawn. Firstly, the planting industry structure has been experienced great changes. The areal ratio of food crops, economic crops and other crops to the total planting area was readjusted from 84∶12∶4 in 1978 to 25∶72∶3 in 2010. Due to the rapid decreasing of wheat area, the proportion of food crops decreased, while the proportion of cotton, oil crops, cucurbits, fruits and vegetables area increased during this period. Secondly, the water demand of crops increased from 2.15×10⁸ m³ in 1978 to 2.49×10⁸ m³ in 2010. The water demand ratio of food crops to economic crops changed from 88∶12 in 1978 to 31∶69 in 2010. Thirdly, the ecological water-saving effect of planting structures adjustment at different times in Minqin was different. From 1979 to 1998, there was no water-saving effect; during 1999-2008, planting structure adjustment showed obvious water-saving effect; during 2009-2010, there was no water-saving effect due to the increasing water demand caused by further adjustment of planting structure. The total proportion of five kinds of high water demand crops played a decisive role in the water-saving effect. These results would provide scientific basis for the cropping structure adjustment and the rational utilization of water and soil resources in the Minqin Oasis.