Effects Of Different Nitrogen Rates And Water Control Pattern On Yield, Water And Nitrogen Use Efficiency Of Dryland Winter Wheat

Water shortage and nutrient deficiency are key factors that restricted crop production in arid and semiarid areas. Therefore to improve the utilization efficiency of water and nitrogen have become researching and pursuiting of the goal. At present, combination of straw mulching and supplemental irrigation patterns is an option for the utilization of limited water resource in arid and semi-dryland farming, But more research about single factor or double factors, study considering the N rate, straw mulching, irrigation amount and irrigation time on the yield, water and nitrogen use efficiency was rare.A field experiment was conducted in Guanzhong region of Shaanxi Province to study the effect of different nitrogen application rates and water control patterns on winter wheat grain yield and yield component, water use efficiency and soil water content dynamic change in different growing stages, the accumulated amount and distribution of nitrate N in soil profiles after harvesting and nitrogen accumulation and transportation in different growing stages, and analyze the physiological mechanisms that causes different yield, water and nitrogen use efficiency. The experiment was aimed to provide a scientific theory basis for increasing grains yield and resource using effiency in winter wheat of arid and semiarid areas. The main conclusions included:1. Application of nitrogen fertilizer (N150) can significantly improve the grain yield, effective panicles and grains per spike of winter wheat, and there was not have significant difference between N150 and N225. The yield in MJS(Straw mulch+ jointing stage irrigation (40 mm)) treatment was significant higher than No irrigation (CK) treatment in N0 and N150, there was not have significant difference in N225 of grain yield. Effective panicles and grains per spike in MJS were significant higher than CK. In short, Straw mulch+ jointing stage irrigation (40 mm) were the best treatment under N0, N150 and N225. Correlation analysis showed that the effective panicles made the greatest contribution to the grain yield in yield component.2. Application of nitrogen fertilizer can significantly improve the total population of winter wheat stems (spikes) number, leaf area and chlorophyll content. Application nitrogen fertilizer did not have significant effect on photosynthetic rate, transpiration rate on winter wheat earlier stage, and had significant effect on filling stage. The water control patterns that combination of straw mulching and irrigation can reduce the number of tillers in regreening stage and the total number of stems in jointing stage, however, it reduce the small tillers deaths, straw mulching combined with supplementary irrigation at jointing stage had significantly effect than supplementary irrigation at overwintering stage. Irrigation had little effect on winter wheat total stems (spikes), but it can significantly increase the effective panicles. Irrigation at jointing stage can significantly improve the stomatal conductance and transpiration rate more than irrigation at over-wintering stage. Straw mulch and irrigation delayed the degradation of chlorophyll, extended the period of leaf function.3. At jointing stage, water content in 0 ~ 40 cm soil layer in N150 and N225 was lower than the N0, At filling stage, water content in 40 ~ 120 cm soil layer in N150 and N225 treatments was significantly lower than N0, and with the winter wheat growth, water content in deeper soil layer decreased obviously. There was not haveing significant difference between the N150 and N225 treatments. N150 can significantly improve water consumption and WUE (water use efficiency) than N0. Irrigation can increase the water content in 0 ~ 60 cm soil layer and the total water consumption. The consumption and water use efficiency is not having significant difference between jointing stage irrigation and overwintering stage under No straw mulching condition. In straw mulching condition, jointing stage irrigation can significantly reduced the total water consumption, increased water use efficiency. In short, straw mulching+jointing stage supplementary irrigation (MJS) treatment can significantly reduced total water consumption and increase the WUE than other treatments.4. Application of nitrogen fertilizer (N150, N225) can significantly promote the nitrogen accumulation in shoot and grain. But when nitrogen fertilizer excessively applicated (N225), the residual nitrate N in the 0~200 cm soil profiles significantly increased, and NUE(nitrogen use efficiency) was significantly decreased. Straw mulch+ jointing stage irrigation (MJS) treatment had the highest accumulation of N in shoot, the residual nitrate N in the 0~200 cm soil profiles was also higher. The NUE of MJS treatment was significantly higher than other water control patterns, and N agronomic efficiency did not have significant differences. The amount of nitrogen transfer and contribution rate in No irrigation (CK) treatment were significantly lower than other treatments.