Study On High Yield And High Efficiency Cultivation Measures Of Super Rice And Its Hormone Regulation Mechanism

Super rice has high yield potential,but its nitrogen use efficiency(NUE)is low.Large-scale planting of super rice plays an important role in solving the world food crisis.At the same time,a large amount of water and fertilizer resources have been invested and wasted,which has caused a huge crisis to the natural environment.The key to solve the above problems is to develop green high-yield cultivation methods of super rice and to understand its physiological mechanisms of high-yielding and high-efficiency.In this paper,two super rice varieties,an indica/japonica hybrid Yongyou 2640 and a japonica inbred Wuyunjing 24,were used.Compared with the local farmers'practice,nine kinds of cultivation and management patterns were set up,includig no N application(ON),local farmer's practice(LFP,control),reduction of N(RN),increase in plant density and decrease in N rate(IDRN),precise irrigation(PI),application of rapeseed cake fertilizer(ACF),deep plowing(DP),application of silicon and zinc fertilizer(ASZF),and application of earthworm manure(AEM).Based on Yield and NUE,the effects of cultivation patterns on physiological processes such as rice growth and development,nitrogen fertilizer absorption ang partitioning,canopy photosynthesis and cytokinin synthesis were analyzed in order to elucidate physiological mechanisms of high yielding and high nitrogen efficiency management practices on super rice.The main results are as follows:1.Grain yield,population growth and development characteristicsThe grain yield of Yongyou 2640 under IDRN,PI,ACF,DP,ASZF and AEM was 12.52t hm-2,13.25 t hm-2,13.64t hm-2,14.18 t hm-2,14.74 t hm-2,12.87 t hm-2,respectively,and increased by 4.94%,11.06%,14.33%,18.86%,23.55%,7.88%respectively,compared with that under the LFP(control).The grain yield of Wuyunjing 24 under IDRN,PI,ACF,DP,ASZF and AEM was 10.19t hm-2,10.88 t hm-2,11.70 t hm-2,11.98 t hm-2,12.57 t hm-2,10.46 t hm-2,respectively,and increased by 6.14%,13.33%,21.88%,24.79%,30.94%,8.94%,respectively,compared with that under the control.Compared with the control(LFP),IDRN,PI,ACF,DP,ASZF and AEM significantly increased the percentage of the productive tillers by 1.83%-10.34%,NSC remobilization by 10.63%-71.20%,dry matter by 5.19%-24.99%,leaf area index(LAI)by 5.35%-22.18%,the efficient LAI by 3.60%-9.31%,the high efficient LAI by 2.87%-8.99%after heading,for Yongyou 2640.These cultivation patterns also significantly increased photosynthetic rate of canopy and the grain-leaf ratio.In addition,the accumulation of nitrogen increased by 4.07%-32.07%before heading,except for the slight decrease in AEM.For Wuyunjing 24,IDRN,PI,ACF,DP,ASZF and AEM significantly increased the percentage of the productive tillers by 2.08%-7.71%,NSC remobilization by 19.76%-70.36%,dry matter weight by 2.81%-26.54%after heading,LAI by 7.19%-28.44%,efficient LAI by 3.52%-6.58%,high efficient LAI by 3.79%-9.25%after heading,and significantly increased photosynthetic rate of canopy and the grain-leaf ratio.In addition,the accumulation of nitrogen was increased by 2.03%-34.74%before heading,except for the slight decrease in AEM.The results indicate that population quality can be improved,source-sink relationship can be optimized,and consequently,grain yield can be increased through the improvement in cultivation practices.2.Nitrogen use efficiencyThe combination of cultivation techniques,such as reducing N rate during early vegetative stage,alternate wetting and moderate soil drying,and organic fertilizer application can significantly increase the nitrogen uptake and nitrogen use efficiency of plants,but excessive increase fertilizer application will reduce the nitrogen yield increase efficiency of plants.Taking nitrogen paddy productivity(IE)as an example,the IE values of Yongyou 2640 under IDRN,PI,ACF,DP,ASZF and AEM were 55.61 kg kg-1,56.99 kg kg-1,58.41 kg kg-1,56.53 kg kg-1,50.56 kg kg-1 and 60.54 kg-1 respectively,which were increased by 3.06%,5.62%,5.67%,8.25%,4.76%,-6.30%,12.19%compared with the LFP(control).Under the same cultivation patterns,the IE values of Wuyunjing 24 were 50.79 kg kg-1,52.03 kg kg-1,54.18 kg kg-1,51.35 kg kg-1,48.34 kg kg-1 and 54.87 kg kg-1,respectively,which were 2.19%,4.69%,9.01%,3.32%,-2.74%,10.40%higher than those of the control.ACF is an improved cultivation pattern based on IDRN and PI,its main cultivation techniques are reducing N rate during the early vegetative stage,alternate wetting and moderate soil drying(AWMD),and its IE value is the highest.On the basis of ACF,the pattern of ASZF added 30%of inorganic nitrogen fertilizer,its IE value is the lowest,and significantly lower than the control.3.Physiological mechanisms of cytokinin in regulating plant growth and development and nitrogen use efficiencyBefore heading,the fertilizer-water management mode of combining reducing N rate during the early vegetative stage and AWMD can increase the content of cytokinins in plant,enhance root activity and nutrient uptake capacity of root system,increase nitrogen accumulation of plant in early growth stage,and provide sufficient nitrogen source for shoot photosynthetic organ construction.It's also can optimize the composition of leaf system,improve the panicle formation rate of tillers,and promote spikelets formation at the same time.The development of spikelets lays a solid foundation for the improvement of total spikelets after anthesis.After heading,the above-mentioned fertilizer and water management patterns can significantly increase the level of cytokinin in plant canopy,regulate the opening of canopy stomata,promote the transport of nitrogen from middle canopy to upper canopy,increase the activity of nitrogen metabolic enzymes in canopy,enhance the photosynthetic assimilation ability of canopy,promote the filling of disadvantaged grains,increase the accumulation of dry matter in panicle and increase the seed setting rate.At grain filling stage,the synergistic effect of water and nitrogen can increase the level of cytokinin content,maintain strong source,ensure adequate supply of photosynthetic assimilates,enhance the ability of translocation of stem and sheath substances,promote the development of endosperm cells in panicle,increase sink capacity,and promote the further increase of rice grain yield.