| The effects of water-nitrogen management on the dry matter accumulation,nutrient uptake and root formation of hybrid indica rice(F you 498)and the physicochemical properties of soil were evaluated in wheat-stubble-rice system.A two-factor split-plot design field experiment was conducted from 2017-2018.The main plot was two irrigation managements:submerged irrigation(W0)and alternating dry-wetting irrigation(W1),while the subplot was three nitrogen(N)application methods based on a total amount of150 kg/hm~2N in 2017.The ratio of basal fertilizer:tillering fertilizer:panicle fertilizer was4:4:2(N1),3:3:4(N2)and 2:2:6(N3),respectively.And no N application(N0)was set as the control.In 2018,two N managements as the follows was designed based on the experiment in 2017:the total N application rate was 176.22 kg/hm~2with the ratio of basal fertilizer:tillering fertilizer:panicle fertilizer were 3:3:4(N4),which carried out on the basis of the three-year local average rice yield to increased by 10%as targeted;the total N application rate was 120 kg/hm~2(N5),which based on the following principle,from 7 days after transplanting to the heading stage,SPAD value was measured by the latest fully unfolded leaves.If SPAD<37.5,15 kg/hm~2N fertilizer would be applied(30 kg/hm~2at elongation stage),if SPAD>37.5,no N fertilizer would be applied.The effects of water-nitrogen management on the dry matter accumulation,nitrogen uptake and translocation,and root formation of hybrid rice and the physicochemical properties of soil in the wheat-stubble-rice were systematically researched.The main results are as the follows:1 Effects of water and nitrogen application on yield and its components in wheat stubble indica hybrid riceThe grain yield,1000-grain weight and spikelet number per panicle were increased in alternative dry-wetting irrigation but had not reached the remarkably level as compared with submerged irrigation.The grain yield of rice in wheat-stubble-rice system increased first and then decreased with the increasing panicle fertilizer in the total 150 kg/hm~2N).The grain yield of rice in N2 treatment could be increased by 9.09%and 6.48%(submerged irrigation),9.09 and 6.48%(alternating dry-wet irrigation)than N1 and N3 by the suitable postponing N application,while the grain yield of rice in N4 treatment could be increased by 0.82%~8.25%(submerged irrigation)and 4.73%~13.81%(alternating dry-wet irrigation)as compared with others N management.Although the spikelet number per panicle and seed-setting rate could be effectively improved in SPAD-diagnosis N management,and the grain yield of rice was increased by 36.32%(submerged irrigation)and 34.97%(alternating dry-wet irrigation)than that of the control,the lower effective panicle limited the further increasing of grain yield.2 Effects of water and nitrogen application matter accumulation and it translocations in wheat stubble indica hybrid riceThe alternative dry-wetting irrigation could improve the dry matter accumulation of stem-sheath,leaves and plant,and significantly promoted the dry matter translocation as compared with submerged irrigation,and also significantly increased the dry matter transportation from the stem-sheath and leaves in 0-20 days and 21-35 days after the full heading stage,while the transportation of dry matter in 0-10 days and 11-20 days was6.16%,21.98%and 22.72%higher than that in the same period of submerged irrigation,respectively.The submerged irrigation mainly promoted the dry matter transportation of leaves accounting for 47.08%of the total transportation in 0-10 days after the full heading stage,which was 36.04%higher than that of the alternative dry-wetting irrigation in the same period.In the same N application conditions,the dry matter accumulation of leaves and stem-sheath in submerged irrigation increased with the nitrogen fertilizer proportion increasing in different growing phases from transplanting to maturity,while the dry matter accumulation of stem-sheath always kept higher of 40%panicle N application from 30days of transplanting to maturity in alternative dry-wetting irrigation.From the perspective of matter translocation of stem-sheath and leaf.Under the same N application conditions,the 20%panicle fertilizer application could significantly increase the dry matter transportation from the stem-sheath,which accounting for 12.17%(submerged irrigation)and 12.03%(alternative dry-wetting irrigation)of the total transportation at 21-35 days after heading,respectively.However,the 40%panicle fertilizer application could increase dry matter transportation of leaves,especially in alternative dry-wetting irrigation,which significantly increased the dry matter transportation of leaves at 21~35 days after heading,accelerated the dry matter accumulation in panicle,properly prolonged the time of rapid accumulation of matter to the maximum accumulation time,promoted grain filling,and further increased the harvest index.3 Effects of different water and nitrogen management on nitrogen accumulation and transport characteristics in wheat stubble indica hybrid riceThe alternative dry-wetting irrigation significantly increased the N accumulation in the stem-sheath at the early stage and 50 days after transplanting,promoted the N accumulation in the leaves from 30-50 days and 70-90 days after transplanting,and also significantly increased the N transportation of stem-sheath during 0-10 days and of leaves during 11-20 days after full heading stage,while the transportation were 19.42%and50.42%higher than that in the same period of submerged,respectively.In the submerged irrigation,the N transportation from leaves during 0-10 days and 11-20 days after heading accounted for 39.68%and 39.12%of the total N transportation,respectively,while the N transportation during 0-10 days after heading was 59.68%higher than that in the same period of the alternative dry-wetting irrigation.In the same N application conditions,increasing the basal fertilizer application could significantly increase the N accumulation in stem-sheath and leaves within 50 days after transplanting.The N accumulation of leaf and stem-sheath in submerged irrigation increased with the nitrogen fertilizer proportion increasing in different growing phases,while the N accumulation of stem-sheath from 60days after transplanting to the mature stage was the highest when 40%panicle fertilizer was applied in the alternative dry-wetting irrigation.In the view of the N transportation of stem-sheath and leaves,increasing the basal and tillering fertilizer application could advance the N transportation,improve the N use efficiency for grain output and N partial factor productively,but reduce N transportation in the middle and late stage.Furthermore,the excessive panicle fertilizer would slow down the N transportation,increase the N transportation proportion during 21-35 days after full heading,which had the higher apparent N use efficiency,but lower N transportation from stem-sheath and leaf to grains,and lower agronomy N use efficiency.Increasing the panicle fertilizer application properly could improve the nitrogen transportation during 0-20 days after the full heading stage,promote the further nitrogen output during 21-35 days after the full heading stage,and improve the nitrogen transportation contribution rate,N agronomic efficiency and recovery efficiency.4 Effects of different water and nitrogen management on root traits of wheat stubble hybrid riceCompared with the submerged irrigation,the alternative dry-wetting irrigation could significantly increase the root dry weight,surface area,volume and diameter of rice in the wheat-stubble-rice system at the different growth stages.The root traits indexes reached the maximum value at the 70 days after transplanting and then decreased from 80 days after transplanting to maturity.In the different nitrogen application rate,the combination of regular optimize fertilization(N4)with the alternative dry-wetting irrigation could significantly promote the later growth of root in the early stage of transplanting(30 days after transplanting),while the combination of N4 and the submerged irrigation could promote the elongation and growth of rice root system in the early stage of transplanting(30 days after transplanting),and improve the root activity from the full heading stage to the mature stage.The root dry weight of rice during transplanting to 40 days after transplanting in wheat-stubble-rice was the highest in the 60%tillering fertilizer application treatment under the same N application level(150 kg/hm~2).However,the shortage of N nutrient supply in the later stage,which accelerate the root system senescence,decrease the root surface area significantly,and weaken the root activity at the filling stage.However,the root growth was not coordinated with the aboveground growth during the whole growth period,which affected the construction of populations.Combined appropriately increasing the N application in the later stage(basal fertilizer:tillering fertilizer:panicle fertilizer=3:3:4)with water management could significantly increase the root diameter and volume before heading stage,promote the elongation and growth of the root system in the middle and later stages,expand the total root absorption area in the whole growth period,and improve the root activity in the middle and later stages.Correlation analysis showed that the correlation coefficient between root surface area and yield was relatively high at 70,80 and 105 days after transplanting(r=0.92**-0.94**),and the ridge regression coefficient was also above 0.16.The correlation between root average diameter and yield was the highest at 70 d and 80 d after transplanting(r=0.60**-0.67**),and the ridge regression coefficients were 0.25 and 0.33,respectively.The root dry weight,root length and root volume during 70-105 days after transplanting were significantly positively correlated with grain yield.5 Effects of different water and nitrogen management on physicochemical properties of soil in wheat stubble indica hybrid riceThe total N and available N contents of soil at different growth stages in wheat-stubble-rice were increased first and then decreased under different water and nitrogen management.Compared with the submerged irrigation,the alternative dry-wetting irrigation could improve the sucrase and peroxidase activities of soil from transplanting to maturity,significantly increase the soil microbial biomass carbon and N contents at 60~70days after transplanting.In the same N application conditions,the sucrase and catalase activities and available N of soil increased with the increasing of basal fertilizer proportion at the early stage of transplanting;however,the available N and total N content and activities showed an increase in the alternative dry-wetting irrigation but decrease in the conventional flooding irrigation with the postponed nitrogen fertilizer application after full heading stage.However,appropriately increasing the N application in the later stage could conducive to the accumulation of microbial carbon and N. |
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