Effects Of Water And Nitrogen Interaction On Yield And Quality Of Direct-seeded Rice And Its Physiological And Ecological Basis

In order to explore the effects of water and nitrogen（N）interaction on yield and rice quality of direct seeding rice and its physiological and ecological basis,this study used F you 498 as material from 2018 to 2019.This experiment used a two-factor split zone design.The main zone is irrigation mode.Based on the preliminary test to determine the stable yield and high efficiency of N application(150 kg·hm^-2),this experiment set three N fertilizer ratio:base fertilizer:tillering fertilizer:panicle fertilizer at 5:3:2,3:3:4,3:1:6,and the control is no N treatment.The effects of water-nitrogen interaction on yield,N utilization characteristics,population quality,grain filling dynamics,canopy microclimate and rice quality of direct seeding rice were studied systematically.The relationships between direct-seeded rice yield and population quality,rice quality and canopy microclimate under the interaction of water and N were discussed.This experiment provides theoretical and practical basis for the development of water-saving,high-yield and high-quality direct seeding rice production.The findings are as follows:1.Effect of water and N interaction on yield and its component factors of direct seeding riceWater and N interaction had significant or extremely significant effects on yield components other than spikelets and yield.Under the conditions of N application rate of150 kg·hm^-2 for each irrigation method,suitable panicle N-fertilizer should account for20%～40%,panicle N-fertilize reached 60%and drying irrigation will lead to a decline in direct seeding rice production.Dry-wet alternation irrigation can increase the yield by increasing the effective panicle and spikelets,combined with N fertilizer,the base fertilizer:tillering fertilizer:panicle fertilizer 5:3:2 is the optimal treatment for this experiment.2.Effects of water-N interaction on population quality,N absorption and transport of direct seeding riceThe interaction of water and N had significant or extremely significant effects on N absorption,transport,utilization of features and population quality indexes of direct seeding rice.W₂ treatment could increase the rate of production tillers,dry matter accumulation,rice harvest index,N uptake,transport volume/rate,NAE and yield of direct seeding rice.According to population quality,N fertilize absorption,transport and utilization characteristics of direct seeding rice,suitable panicle N-fertilizer should account for 20%～40%under each irrigation mode.panicle N-fertilize reached 60%and W₃ will significantly reduce the population quality,N fertilizer stem and sheath transport capacity,transport rate,N increase in panicle,NAE,NPFP of direct seeding rice.The correlation analysis shows that under the condition of water-N interaction,yield and N utilization characteristics of direct seeding rice were significantly or extremely significantly correlated with effective panicle,dry matter accumulation at fruiting stage,other leaf dry weight reduction,total leaf dry weight reduction and light exposure rate between middle（50cm from the ground）and base（15cm from the ground）of population at seed setting stage（r=0.532*～0.972**）.3.Effects of interaction of water and nitrogen on grain filling dynamics of direct seeding rice at fruiting stageThe interaction of water and nitrogen has a significant regulation effect on inferior grain filling of direct seeding rice.W₃ treatment could shorten the T_maxof inferior grains under the application of N fertilizer（time to reach the maximum grain filling rate）.Under different irrigation methods,with panicle fertilizer increase,the B,K,GR_max（weight of a kernel at the time of max grain filling rate）and GR_mean（mean grain filling rate）of superior grain and inferior grain of direct seeding rice increased at first and then decrease while D（active filling stage）and T₉₉（effective filling period）decreased at first and then increased.Grain filling of direct seeding rice under different irrigation method,suitable panicle N-fertilizer should account for 20%～40%,which is good for promoting production.panicle fertilizer reached 60%could led to the decrease of grain filling rate and the prolongation of grain filling time of direct seeding rice.Under different irrigation methods,the effect of N application on the A value of superior grains was different,while the A value of inferior grains decreased at first and then increased with the increase of panicle fertilizer increase.Under the interaction of water and nitrogen,A,K,R₀,GR_max and GR_mean of direct seeding rice were higher than those of inferior grains,while B,T_max,D and T₉₉ were lower than those of inferior grains.4.Effects of water and nitrogen interactions on quality and canopy microclimate of direct seeding riceWater and N interactions had significant or extremely significant effects on rice milling quality,appearance quality,and cooking and palatability rice quality of direct seeding rice.Under the conditions of N application ratio of 150 kg.hm^-2 for each irrigation method,most suitable panicle N-fertilizer should account for 20%of direct-seeding rice,and coupled with W₂can further improve rice quality.When panicle N-fertilize increased to 60%,it will lead to the decrease of temperature difference,total temperature difference,accumulated temperature,effective accumulated temperature,daily average light intensity and rice quality of direct seeding rice under various irrigation methods.Under the interaction of water and N,the canopy microclimate in the field has the greatest impact on milling quality,and cooking and palatability rice of direct seeding rice.The effect of temperature on the head rice rate is greater than the light intensity,and the effective accumulated temperature has the highest correlation with head rice rate.Light intensity is most closely related to the appearance,taste and comprehensive score of rice cooking and palatability quality.