Performance And Coordination Of Source And Sink System In Winter Wheat Under Water-Saving And High-Yielding Irrigation Patterns

The North China Plain(NCP)is the main wheat production region in China,shortages and uneven distribution of water resources are becoming increasingly serious in NCP;limited irrigation scheme should be applied according to local water resources for achieving the combination of high water use efficiency(WUE)and high yield is very important.Grain yield of wheat is determined by the "sink"and "source" capacity and their interactions,however,water and nitrogen resources have an important effect on "source-sink" relationships.Under the limited water and nitrogen applying condition,we assume the optimum timing and amount of resources to achieve high grain yield and water and nitrogen use efficiency will depend on coordinating"source-sink" relationships.Therefore,single irrigation treatments(irrigation at later tillering,WT;irrigation at jointing,WJ;irrigation at booting,WB;irrigation at anthesis,WA and irrigation at medium milk,WM),two and three irrigations(irrigation at late tillering and booting,TB;at late tillering and anthesis,TA;at late tillering and medium milk,TM;at jointing and anthesis,JA;at jointing and medium milk,JM;at booting and medium milk,BM;irrigation at jointing,anthesis and medium milk,JAM;irrigation at later tillering,booting and medium milk,TBM),and different nitrogen amount(N0,N60,N120,Niso,N240 and N300)treatments were established.The effects of limited water and nitrogen supply on reproductive character,canopy structure,water absorption,"source-sink" capacity,grain yield,water and nitrogen use efficiency were studied.Results showed that:(1)Under single irrigation(75 mm irrigation amount)condition,irrigation before jointing is beneficial to promote sink capacity,but post-anthesis source supply is insufficient,grain yield limited by source supply;irrigation after booting is beneficial to ensure source capacity,but sink capacity is insufficient,grain yield limited by sink capacity;irrigation at jointing or between jointing and booting could improve grain yield(8433 kg ha-1)and WUE(20.1 kg ha-1 mm-1)via coordinating the "source-sink" relationships with the high sink capacity and source supply capacity.Water consumption characteristics:post-anthesis evapotranspiration(ET)shown as:WA>WB>WM>WJ>WT>WO,no significant difference was observed among WA,WB,WM and WJ.The total ET shown as:WT>WJ>WB>WA>WM>W0,no significant difference was observed between WJ and WT,WJ and WB.Source traits:anthesis biomass accumulation shown as:WT>WJ>WB>WA,WM,WO,maturity biomass accumulation shown as:WT>WJ>WB>WA>WM>WO,there was no significant difference in maturity biomass accumulation between WJ and WT;post-anthesis biomass accumulation in WJ and WB were significant higher than that in WT,WA,WM and WO.WJ obtained the highest pre-anthesis biomass remobilization,which was significant higher than WO,WA and WM,and no significant difference was observed among WJ,WT and WA.Sink traits:sipke number in WJ was significant higher than WB,WA,WM and WO,but lower than WT,grain number per spike in WJ was significant higher than WB,WA,WT,WM and WO;sink capacity shown as:WJ>WT>WB>WA>WM>WO,no significant difference was observed between WT and WB,WA and WM,respectively.rain-leaf ratio and harvest index in WJ were significant higher than WT,but lower than WB,WA and WM.Fruiting efficiency(FE)in WJ was significant higher than WO,WB and WM,and no significant difference was observed among WJ,WT and WA.Grain production(GP)and spike partitioning index(SPI)in WJ were significant higher than other treatments,there was no significant difference in SPI between WJ and WB.grain yield and WUE in WJ were significanthigher than those in WO.WT,WA and WM,and there was no significant difference in grain yield and WUE between WJand WB.(2)Under two irrigations conditions,compared with other two irrigation treatments irrigation at jointing and anthesis could improve grain yield(9113 kg ha-1)and WUE(20.0 kg ha-1 mm-1)by increasing biomass post-anthesis(source capacity)and sink capacity,and coordinating source-sink relationship.Water consumption characteristics:post-anthesis ET in JA was significant higher than TB,TA and TM,no significant difference was observed among JA,JM and BM;Total ET shon as:TB>TA>TM>JA>JM>BM.Source traits:post-anthesis biomass accumulation shown as:JA>JM>TB>BM>TA>TM,there was no significant different in pre-anthesis biomass remobilization among all the treatments.Sink traits:spike number in JA and JM were significant higher than BM,but lower than TB,TA and TM;grain number per sipike shown as:JA,JM>BM>TB,TA and TM,sink capacity shown as:JA>JM>TB>TA>TM>BM,no significant different was observed between JA and JM.Grain-leaf ratio in JA and JM was higher than TB,TA and TM,but lower than BM;FE in JA and JM were higher than BM;GP,SPI and harvest index(HI)in JA were higher than TB,TA,TM and BM.Grain yield shown as:JA>TB>JM>TA>BM>TM,WUE shown as:JA>JM>BM>TB>TA>TM.(3)Under adequate soil water content conditions before sowing,no irrigation after sowing,single-limited irrigation(jointing)and two-limited irrigations(jointing and anthesis)schemes could be applied according to different ecological regions of the NCP.Water consumption characteristics:post-anthesis and total ET shown as WO<WJ<JA<JAM and TBM.Source traits:post-anthesis biomass accumulation increased with increasing irrigation amount,the highest post-anthesis biomass accumulation was observed in JA;pre-anthesis biomass remobilization shown as WJ>WO>JM>TBM and JAM.Sink capacity:spike number in WJ,JA and JAM was higher than WO,and lower than TBM,grain number shown as:JAM and JM>WJ>TBM>W0,sink capacity shown as:JAM and JA>WJ and TBM>WO.Grain-leaf ratio in WJ,JA and JAM was higher than TBM,but lower than WO;FE in JA was higher than WO,and no significant difference in FE was observed among Wj,JA,JAM and TBM.GP,SPI and HI in Wj,JA and JAM were significant higher than WO and TBM.JA obtained the higher grain yield and WUE simultaneously,grain yield in JAM and TBM had no differ with JA.compared with JA.WUE in JAM and TBM were lower.Compared with WO and WJ,JA gained the higher post-anthesis biomass accumulation(source supply capacity)and sink capacity,and coordinated "sink-source" relationship;WJ obtained the same level of WUE as JA,but decreased grain yield due to limited post-anthesis biomass;Compared with irrigation treatments,the lower post-anthesis'source supply' and sink capacity at population level limited grain yield of WO,however,WO obtained appropriate grain yield and WUE by improving pre-anthesis biomass remobilization.(4)Under limited irrigation conditions,in the range of nitrogen mount from 0 to 300 kg ha-1,there was a parabolic relationship between grain yield and nitrogen amount,and between WUE and nitrogen amount.Treatments with nitrogen amount of 180-240 kg·ha-1 coordinated"source-sink" relationship,and obtained the optimal grain yield and WUE.Source traits:anthesis,post-anthesi and maturity biomass accumulation shown as:N300,N240 and N180>N120>N60>N0;pre-anthesi biomass remobilization shown as:N60>N0>N120>N180>N240>N300,no signifaicant difference was observed in pre-anthesi biomass remobilization between N180 and N240.Sink capacity:spike number,grain number per spike and sink capacity shown as:N0<N60<N120<N180,N240 and N300;FE and GP in N180 and N240 were significant higher than No,N60 and N120,SPI and HI decreased with increasing nitrogen amount.Total ET and nitrogen accumulation at maturity increased with increasing nitrogen amount;nitrogen utilization efficiency,partial factor productivity and nitrogen harvest index decreased with increasing nitrogen amount.To sum up,treatments with nitrogen amount of 180-240 kg·ha-1 obtained the higher sink and source capacitys,coordinated "source-sink" relationship,and obtained the optimal grain yield and WUE.