Water Stress Associated With Crop Cultivation And Optimization Of Wheat-maize Cultivation In Hebei Province

Water scarcity has been a main constraint for the social and economic development in Hebei province.The water footprint theory and related methods were applied to analyze the water stress and water degradation in the main crop production area in Heibei Province in the study. Meanwhile, Wuqiao County was selected as a typical area in Heibei province to specify the major factors that influence crop evapotranspiration, green water productivity and grey water productivity of wheat and maize. In associated with crop production surveys, we discussed how to optimize the crop distribution in Heibei province. The major conclusions are shown below:（1） The water stress index in crop production was much higher in Cangzhou, Handan, Hengshui,Shijiazhuang, Baoding compared to other areas in Heibei plain region, and the high Water Stress Index（WSI） was concentrated on the periods from 1996 to 2005, the annual average WSI was highest in Cangzhou. The annual average irrigation requirements in the plain region of Hebei were 14.62 billion m3,while the total available water resources were 8.89 billion m3. The irrigation requirements in cereal crops production showed declining trend across the province, which was significant in Handan, and the annual average irrigation requirements were largest in Baoding as amount of 2.08 billion m3. The irrigation requirements in economic crops production decreased in six areas except in Langfang, it was highest in Xingtai as amount of 0.52 billion m3Vyear. The irrigation requirements in the production of fruits and vegetables increased in the all 7 selected districts across Heibei Province, which was significant in Shijiazhuang.（2） The potential water pollutions caused by crop planting in Hebei province is worth receiving more attention. Generally, the annual average water degradation footprint （wdf） per unit increased fastest in Qinhuangdao, which increased by 91.7% from 2014 to 1995. The annual average Water Degradation Footprint （WDF） was highest in Shijiazhuang, which indicates the most serious potential pollution, it was among the first level areas in the year of 1995, 2004 and 2014. Zhangjiakou and Chengde was always in the fifth level, and Langfang all in the fourth level, whereas the potential water pollution in crop production was more and more serious in the left areas in Heibei Province, such as Handan and Baoding was in the second level, they respectively changed into the first level in 2004 and 2014. Moreover,Cangzhou fell to the second level in 2014 from the third level in 2004. During the last 20 years, the increase ratio of WDF was largest in Qinhuangdao as 77.4%, while it was smallest in Shijiazhuang as 26.7%.（3） Climate change showed significant impacts on the crop evapotranspiration and water ecological adaptability in Heibei Province. Temperature changed significantly during wheat and maize growing season. The crop evapotranspiration of winter wheat slightly increased in all three growing stages, the average water ecological adaptability in the whole growing season was about 26.63%. Solar radiation,sunshine duration and wind speed have significant positive correlations with the crop evapotranspiration,while the relative humidity has significant negative correlation with the crop evapotranspiration. On the other hand, the crop evapotranspiration of summer maize showed declined trends, and the average water ecological adaptability in the whole growing season was about 68.75%. Similarly, solar radiation and sunshine duration both were significantly positively correlated with the crop evapotranspiration, the mean maximum temperature and mean average temperature were significantly positively correlated with the crop evapotranspiration in the phases of heading-flowering and filling-ripening, while relative humidity was significantly negatively correlated with the crop evapotranspiration in the phases of heading-flowering and filling-ripening.（4） Crop management measures showed significant impacts on Crops’ green water productivity and grey water productivity. Green water productivity of the variety of Jimai-22 was significantly higher than the other five wheat’s varieties, which was 8.14 kg·m^-3. The variety of Zhengdan-958 was significantly highest among all maize’s varieties, which was 3.72 kg·m^-3. The green water productivity of the irrigated winter wheat was highest at the N fertilizer application of 180 kg·hm-2 as the rate of 4.31 kg·m^-3, it was highest for the rain-fed winter wheat at the N fertilizer application of 120 kg·hm-2 as the rate of 2.56 kg- m’3. The green water productivity of maize was highest at the N fertilizer application of 150 kg-hm-2 under rain-fed conditions, which arrived at 7.3 kg·m^-3. Our results in different cropping patterns showed that the potato -maize pattern has the highest green water productivity and green water economic benefit,which were 60.45 kg·m^-3 and 25.7 Yuan·m^-3, respectively. However, the lowest value were existed in wheat-maize pattern, which were 3.92 kg·m 3 and 8.3 Yuan·m^-3, respectively. Under different fertilization disposals, the wheat’s grey water productivity was highest (2.82 kg·m^-3) when N fertilization was 120 kg·hm-2, the maize’s grey water productivity was highest (4.84 kg·m^-3) when the N fertilization was 75 kg·hm-2.（5） The grey GM （1,1） model was used to predict the future water consumption and irrigation proportion in each district in Heibei Province based on the local surveys, and created the optimized strategy of the distributions of wheat and maize planting area in different districts in 2020. The results suggests reducing the wheat planting area by 30000 hm² and 7000 hm² in Handan and Cangzhou,respectively. The current study recommends reducing the maize planting area by 202000 hm², 112000 hm² and 67000 hm² in Cangzhou, Handan and Baoding, respectively.