Water And Nutrient Use Efficiency In Winter Wheat-Summer Maize Rotation System Under Different Culitivation Pattern On Semi-Dryland Farming

Nutrient and water is two major limiting factors on semi-arid and arid farming. Water stress own to the lack of water resources and the uneven spatial and temporal distribution is one of the main limiting factors to increase food production in northern China. The key issue of sustainable agriculture is the efficient use of water and fertilizer. Therefore, combination of supplemental irrigation method on semi-dryland farming by different cultivation methods, is an option for the utilization of limited water resource in the summer maize/winter wheat rotation system in the northern China.Therefore, a field continuous experiment was conducted in Guanzhong region of Shaanxi Province to study the effects of different cultivation methods and amount of N on grain yield of winter wheat and summer maize, water use efficiency, the accumulated amount and distribution of nitrate N in soil profiles after harvesting and nitrogen accumulation and transportation in the different growing seasons of summer maize and winter wheat. The experiment was aimed to provide a secientific theary basis for increasing grains yield and resource using effiency in the summer maize/winter wheat rotation system. The main conclusions included as follows:1. The average yield of crop in the past 6-years showed the straw mulching and furrow planting cultivation patterns significantly increased the grain yields of summer maize, and had little effect on the yields of winter wheat compared to the conventional cultivation pattern. Water-controlled pattern decreased the yields of summer maize and winter wheat. The total grain yields of summer maize and winter wheat in the past 6-years decreased in the following order: furrow planting > straw mulching > conventional > water-controlled. Furrow planting pattern significantly increased water use efficiency of winter wheat and summer maize. Straw mulching and water-controlled patterns significantly increased the water use efficiency of summer maize, but had little effect on that of winter wheat. Total water use efficiency under winter wheat/summer maize rotation system decreased in the following order: furrow planting > straw mulching > water-controlled > conventional. Nitrogen rates at 120 kg/ha and 240 kg/ha significantly increased the yields and water use efficiency of winter wheat and summer maize compared to the no nitrogen fertilizer treatment, but the differences between nitrogen rates at 120 kg/ha and 240 kg/ha was not great.2. After 5 years of planting, the organic matter and total nitrogen increased in the order: straw mulching > furrow planting > conventional > water-controlled, and straw mulching significantly increased the amount of organic matter and total nitrogen. The nitrogen application had significant impact on the organic matter and total nitrogen. After the 6 year of maize-wheat rotation cropping, the residual nitrate N in the 0~200 cm soil profiles increased as: furrow planting > water-controlled > straw mulching > conventional, and the accumulated nitrate N in the furrow planting and water-controlled treatment was higher than that in the conventional treatment. As the duration of the cultivation and the increases of nitrogen application, the accumulated nitrate N increased in the 0~200 cm soil profile; and the accumulated nitrate N in the N240 treatment was higher than that in the N120 treatment. The trend of nitrate N distribution was different in the different amount of nitrogen application. Contrary to the N120 and N0 treatment, the nitrate N content in the N240 treatment below 120 cm depth increased as the depth increased.3. By the study of crop N on 11th and 12th season, the results showed that the furrow planting pattern significantly increased the N accumulation in summer-maize mature stage, whereas no effects of other treatments occurred on the N accumulation in the maize and winter wheat. At the same time, the N accumulation of different organs in maize was enhanced in the furrow planting treatment, and that of leaf section was significantly influenced by the different cultivation patterns. The N mobilization of different organs and their contributions to grain N increased in the order: furrow planting > conventional > straw mulching > water-controlled. Comparing with the control treatment, fertilizer applying (including 120 kg/ha and 240 kg/ha)raised the crop N accumulation. The N accumulation was significantly elevated in the higher fertilizer treatment in comparison with that of the lower fertilizer amount. However, no differences showed in the N contributions and partition processes between the two fertilizer treatments in the anthesis stage of winter wheat. The N use efficiency and N agronomic efficiency all appeared the fall- trend as the fertilizer amount increased.