Post-anthesis Dry Matter And Nitrogen Dynamics In Winter Wheat As Affected By Nitrogen Supply And Water Deficit

Soil water content and nitrogen are the main factors that affect crop yield formation,moreover, water and fertilizer are obviously relevant to each other during the production ofwheat. Only more reasonable use of nitrogen and water could enhance the yield of wheateffectively. In this experiment, wheat cultivar ChangWu134and ChangHan58were selected,and four nitrogen levels were set for pot experiment:(1) No nitrogen (N0);(2) nitrogenapplication amount0.12gN/kg (N1);(3) nitrogen application amount0.24gN/kg(N2);(4)nitrogen application amount0.36gN/kg (N3). Water contents of pots wereweighing during post-anthesis and three water levels were set:(1) Normal water supplyduring the whole growth period (W1), the soil water contents maintained75%-85%of fieldcapacity;(2) moderate water stress (W2), soil water contents kept the same level to W1beforeanthesis, and then maintained55%-65%of field capacity from anthesis to filling stage;(3)serious water stress (W3), soil water contents kept the same level to W1before anthesis, andthen maintained35%-45%of field capacity from anthesis to filling stage; In the filling stage,two wheat cultivars were exposed to different water stresses, and we assayed and analyzed theeffects of the interaction of nitrogen and water on the grain filling characteristics of superiorand inferior grain, the metabolism of dry matter and nitrogen in post-anthesis. Basing on theseinvestigations, we could systematically study and discuss the transport of dry matter andnitrogen of wheat under the interaction of water and nitrogen in post-anthesis.The main conclusion:1. The nitrogen treatments and post-anthesis water stressessignificantly affected the finalyield formation of wheat, the moderate stress on the one hand enhanced the yield formation ofChangWu134, but on the other hand reduced that of ChangHan58. The wheat yieldformation could be enhanced by the increased application of nitrogen, but it also declinedunder serious water stress in ChangHan58. The kernels per spike and biomass all rose withthe increased nitrogen application and declined with the increased water stresses. Thethousand seed weight was significantly lower under the treatment of N0than the othertreatments including N1, N2and N3, and under these treatments it showed no difference. The harvest indexes of both ChangWu134and ChangHan58all firstly declined and then rosewith the increased application of nitrogen, and another tendency showed that the harvestindexes finally dropped after a temporary increase with the increase of water stress. Theresults indicated that appropriate nitrogen application and moderate water stress couldenhance the wheat harvest index.2. The nitrogen treatments and post-anthesis water stresses significantly affected thefilling characteristics of inferior and superior grain of both two cultivars. The application ofnitrogen increased the maximum theoretic grain weight and the maximum theoretic dryweight (W0) of both inferior and superior grains of the two cultivars, while water stressplayed an opposite role. Under the same treatment, the maximum theoretic dry weight showedsignificantly higher in superior grain than in inferior grain, and significantly higher inChangWu134than in ChangHan58. During the whole growth stage, the filling rate wassignificantly higher in superior grain than in inferior grain. The correlation analysis indicatedthat, the thousand seed weight of superior grain was positively related to the average rate andthe total time of filling stage, while the thousand seed weight of inferior grain was related tothe date that the maximum filling showed up.3. Under the both nitrogen treatments and water treatments, there was a similar dynamicchange in post-anthesis plant dry matter in both ChangWu134and ChangHan58, they allfirstly rose and then dropped during filling. The accumulation of dry matter was enhanced bythe application of nitrogen while reduced by water stresses. The dry matter accumulation inleaf, stem and sheath of ChangWu134all showed higher than ChangHan58in bothpre-anthesis and post-anthesis stages. The contribution made by the post-anthesis dry matterto grain was significantly higher than that of pre-anthesis dry matter.4. Under the both nitrogen treatments and water treatments, the N concentration ofinferior and superior grain were significantly differed from each other, although at the fifthday the N concentration of inferior grain was higher than superior grain, the N concentrationof superior was ultimately dominated. The dynamic change of the N concentration in bothinferior and superior grain all increased after the first decreases. The development of plantorgan, the accumulation of N in the total grain and the transport amount of N in thepost-anthesis nutritive organ of both ChangWu134and ChangHan58were significantlyaffected by the interaction of nitrogen and water during anthesis and mature stages, they allrose with the increase of the amount of supplied N and dropped with the decrease of soilwater content. The accumulated N contents in the nutritive organ and mature seeds ofChangHan58took an advantage of ChangWu134, but the transport amount of N in nutritiveorgan of ChangHan58was lower tha ChangWu134. 5. The effects of nitrogen and water stress that impacted on the amount of accumulatednitrogen(TNA), nitrogen production efficiency(NPE), nitrogen agronomic efficiency(NAE),nitrogen use efficiency(NUE), Nitrogen production efficiency（PFPN） and nitrogen harvestindex (NHI) of ChangWu134and ChangHan58all reached a highly significant level. Underthe same N level, TNA, NAE, NUE and PFPN of ChangWu134all showed a tendency ofW1>W2>W3. While under different N treatments of N0, N1and N2, NPE showed a trend ofW3>W1>W2, and on the contrary increased in the N3treatment. NHI dropped graduallyunder the nitrogen treatment of N0, while declined after an increase under N1, N2and N3. Interms of TNA and NPE, ChangHan58has the similar trend with ChangWu134, however,NAE, NUE and PFPN of it showed a fall after a temporary rise and NHI was overallincreased. Under different water treatments, in both two cultivars of CahngWu134andCahngHan58, TNA, NPE, NAE, NUE and PFPN all dropped with the increase of the amountof the supplied nitrogen. The NHI of ChangWu134firstly rose and then declined with theincrease of the amount of the supplied nitrogen, the maximum showed under N2treatment.