| This study was to further illuminate the water-nitrogen coupling effect on the dynamic variation rule of the establishment of super high-yield rice population and optimizing the source,sink and stream for the better yield formation.(1)The effects of water-nitrogen management patterns on yield formation and nitrogen utilization of hybrid rice F you 498.Two irrigation patterns,basin irrigation(W1)and controlled intermittent irrigation(W2),combined with nitrogen management were conducted in 2015.Nitrogen application rates were 5 levels(0,90,135,180 and 225 kg/hm2).The nitrogen application methods were different between W1 and W2,where the ratio of basal fertilizer,tillering fertilizer and panicle fertilizer was 5:3:2 and the panicle fertilizer was applied at the stage of 4th leaves emerged from the top under W1,while the ratio of basal fertilizer,tillering fertilizer and panicle fertilizer was 3:3:4 and the panicle fertilizer was applied at the stage of 4th and 2nd leaves emerged from the top under W2.(2)The effects of nitrogen application rates on yield formation and nitrogen utilization of hybrid rice with different nitrogen use efficiency in controlled intermittent irrigation.Based on controlled intermittent irrigation and the ratio of basal fertilizer,tillering fertilizer and panicle fertilizer of 3:3:4,two rice cultivars F you 498(PI,High nitrogen use efficiency)and Yixiang 3724(P2,low nitrogen use efficiency)with 5 nitrogen application rates(0,90,135,180 and 225 kg/hm2)were used to study the yield formation rule of hybrid rice in 2016.In this two years experiments,we compared the grain yield,dry matter accumulation,photosynthetic characteristics,leaf area and lodging resistance of culm in different irrigation conditions.Meanwhile,the root traits of hybrid rice cultivars with different nitrogen use efficiency under controlled intermittent irrigation were also studied to further illuminate the effects on water use efficiency and nitrogen use efficiency.Finally,we proposed the optimal nitrogen management under different irrigation conditions and optimized nitrogen application rate in controlled intermittent irrigation combined with hybrid rice with different nitrogen use efficiency.The main results are as follows.1.Effects of water-nitrogen managements on grain yield and its componentsThere was significant difference in grain yield and its components affected by irrigation ways and nitrogen managements.The higher grain yield could be reached when the nitrogen application rate was 180 kg/hm2(the ratio of basal fertilizer,tillering fertilizer and panicle fertilizer was 5:3:2)under basin irrigation conditions while 135 kg/hm2(the ratio of basal fertilizer,tillering fertilizer and panicle fertilizer was 3:3:4)under controlled intermittent irrigation.Compared with basin irrigation,the grain yield in W2 increased by 3.22%.There had a large difference in grain yield components under different irrigation ways.The effective panicle number in W1 was 4.90%higher than that in W2.However,compared to W1,the spikelet number per panicle and total spikelet number in W2 were increased by 7.89%and 2.89%,while the seed setting rate and 1000-grain weight were increased by 1.07-1.65%and 2.01-3.73%,respectively.Meanwhile,there had the significant difference in grain yield between the two rice cultivars due to the difference in yield components.There was no difference in effective panicle number affected by rice cultivars.However,the spikelet number per panicle,the total spikelet number and seed setting rate in F you 498(high nitrogen use efficiency)were 18.32%,14.77%and 11.88%higher than that in Yixiang 3724(low nitrogen use efficiency),respectively,whereas,the 1000-grain weight was decreased by 9.02%.These results showed that the controlled intermittent irrigation might be beneficial for the harmonious development of effective panicle number and spikelet number per panicle,which improved the total spikelet number and further increased the grain yield.2.Effects of water-nitrogen managements on nitrogen utilization characteristicsAlthough there had no difference in total nitrogen accumulation amount of rice between basin irrigation and controlled intermittent irrigation,the latter could avail the nitrogen accumulation in organs at the later growth stage,which facilitated effectively the nitrogen translocation from stem and sheath to the panicle.However,the high nitrogen conditions suppressed the nitrogen translocation of leaves in two irrigation ways,which resulted in nitrogen residual quantity in nutritive organs especially leaves were very high.The nitrogen use efficiency in controlled intermittent irrigation was higher than that in basin irrigation.The nitrogen agronomy use efficiency and physiological use efficiency in the controlled intermittent irrigation were increased by 13.74%and 7.68%to basin irrigation,respectively.Furthermore,there had the significant difference in the nitrogen accumulation amount between hybrid rice cultivars in the controlled intermittent irrigation conditions.The high nitrogen use efficiency rice cultivar had the higher nitrogen accumulation amount at maturity stage and a higher nitrogen use efficiency than low nitrogen use efficiency rice cultivar,Compared with low nitrogen use efficiency rice cultivar yixiang 3724,nitrogen partial agriculture productivity,nitrogen utilization efficiency and nitrogen harvest index of high nitrogen efficiency hybrid indica F you 498 significantly increased by 7.62%,6.89%and 3.19%respectively.In addition,the high nitrogen efficient hybrid indica rice leaf nitrogen transfer capacity,transport rate and n contribution rate on average increased by 45.64%,23.58%and 45.64%respectively.and it was also beneficial to nitrogen translocation of leaves of high nitrogen use efficiency rice cultivars and of stem-sheath of low nitrogen use efficiency rice cultivars under controlled intermittent irrigation conditions.The controlled intermittent irrigation combined with reasonable nitrogen management could balance the nitrogen supply at the whole rice growth stage,facilitate the nitrogen uptake,which improved nitrogen accumulation amount at later growth stage and the translocation amount from stem-sheath and leaves to panicle after heading,and improved nitrogen uptake and nitrogen utilization efficiency.3.Effects of water-nitrogen managements on growth quality of hybrid rice population.From the views of irrigation methods,the controlled intermittent irrigation could enlarge the sink and improve the source,which further enhanced dry matter accumulation and grain yield by gaining more spikelet number per panicle and the total spikelet number where there had enough effective panicle number.However,the rice plants were grown in flooding conditions for a long time under the basin irrigation,which resulted in increasing the ineffective tillering number at the earlier stage and died out quickly at the later stage,and deteriorating the group growth quality to cause the adverse effects on dry matter accumulation,nitrogen uptake and grain yield.Compared with basin irrigation,dry matter accumulation under the intermittent irrigation at heading stage was significantly increased by 11.53%,to mature period is increased by 4.89%.Compared to basin irrigation,it could significantly improve the configuration of leaf area of population under the controlled intermittent irrigation,which enhanced the leaf area index and high effective leaf area index.Leaf area index,effective leaf area index under the controlled intermittent irrigation average increased by 20.65%and 22.81%respectively than flood irrigation mode.Meanwhile,the root-shoot ratio at rice growing stage and the root system architecture at the heading stage in the controlled intermittent irrigation were superior to those in basin irrigation.The net photosynthetic rate and lodging resistance capability of culm also had been improved in the controlled intermittent irrigation.Furthermore,there had a large difference in root system architecture between the two rice cultivars under the controlled intermittent irrigation.The cultivar with high nitrogen use efficiency had the better root system architecture than the other one.Especially,the root senescence of high nitrogen efficiency rice cultivar was slower than that of low nitrogen efficiency rice cultivar,which could ensure the higher root activity at the later growth stage to provide more nutrient and water for plant growth and contribute to improving the grain yield.In summary,For this experiment it is concluded that based on different soil fertility conditions under the condition of intermittent irrigation with n application rate,135-180 kg/hm2(basal:tillers fat:caring fertilizer=3:3:4)was the best water and nitrogen management mode.which could significantly enhance the production efficiency and irrigation water productivity of water and provide different nitrogen efficiency hybrid indica each growth period with comparative balance of nitrogen supply,advantageous to realize the synchronization of rice yield and nutrient use efficiency improved effectively. |
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