Studies On Physiological Mechanism And Technical Approach Of Reducing Yield Gap And Increasing Efficiency In The South Of Huang-Huai Wheat-producing Area

In order to solve the problems of continuous increased yield and low resource utilization efficiency in current winter wheat production,we combined different appropriate agronomic strategies such as farming practices,planting techniques,and fertilizer management into different cultivation and management models experiments(Local farmers' traditional cultivation,FP;optimized cultivation in comparison with FP,JH);super high-yielding cultivation,SH;high-yield and high-efficiency cultivation,HH)on the basis of optimizing the management technique of single factor cultivation,and design nitrogen application rate experiments and water-nitrogen mode experiments.The three experiments were carried out at three sites in the Huang-Huai Plain of China from 2012 to 2016: Shangshui(SS),Kaifeng(KF)and Wenxian(WX),in southern,central and northern Henan Province,respectively.In this paper,we studied the characteristics of winter wheat population structure,material production and transportation,nutrient absorption and transportation,light use efficiency,and water use efficiency under different cultivation and management techniques,and investigated the approach to closing the yield gap and improving the efficiency of resource utilization simultaneously in winter wheat production.The main experimental results are shown as follows:1.Effects of different cultivation management techniques on population growth and dry matter production of winter wheatThe effects of different nitrogen application rates on dry matter accumulation and yield of winter wheat showed differences,and N240 treatment had the highest total dry matter accumulation and yield at maturity.With the increases of irrigation and nitrogen application,both the total dry matter,grain number per unit area,spike number,grain number per spike and yield at maturity showed increased trends.However,excessive nitrogen application would lead to a decrease in grain number per spike,dry matter productivity and yield.Both the W1N240 treatment in SS and W2N240 treatment in WX had better population growth,dry matter accumulation and yield.The population dynamics of winter wheat accorded with the characteristics of two prosperous growth phases,one peak,continuous growth at wintering and mass mortality after booting under different cultivation management modes,and had highest value at jointing stage.Specifically,FP treatment had the highest population before booting stage,but decreased rapidly after booting;SH and HH treatments could effectively reduce stem tillers death and achieve more spike number.Leaf area index increased from wintering to booting and reached top peak at booting,and reduced slowly during booting to early filling,but reduced fast from early filling to later filling stage under four cultivation management models treatments.Before booting stage,leaf area index was the highest in FP treatment,but lowest in JH treatment;after booting stage,FP treatment decreased early and had the maximum amplitude,but HH treatment could slow down the rate of leaf area index decrease and delay senescence.Under different cultivation management techniques,the accumulation dynamics of dry matter were consistent with the Logistic growth curve,i.e.,the growth rate was low during wintering to jointing,fast during jointing to anthesis,and slow during anthesis to maturity.For different cultivation management models,before booting stage,dry matter accumulation of FP treatment was higher than SH,HH and JH treatments,but was lower than SH,HH and JH after booting stage.The dry matter contribution rate of pre-anthesis vegetative organs to grains in FP treatment were higher than SH,HH and JH treatments,however,the post-anthesis dry matter accumulation was more important for increasing yield in SH,HH and JH treatment.2.Effects of different cultivation management models on light and water use efficiency of winter wheatThe total light radiation,photosynthetic production potential and light temperature production potential are different in different regions,and shows a trend: SS > KF > WX.Both the production equivalent of photosynthetic production potential and light temperature production potential were less than 30%,however,WX site was higher than SS and KF.Compared to FP treatment,SH,HH and JH could effectively improve the light utilization rate of winter wheat,and showed the trend of SH > HH > JH > FP.The total water consumption in wheat season in different regions showed a trend of WX > SS > KF,and that of the different treatment was SH > FP > HH > HH,and increased with the year changing during 2012-2016.Compared to FP treatment,SH,HH and JH treatments could significantly improve the yield-water use efficiency,i.e.,SH > HH > JH> FP;the soil-water use efficiency of FP treatment was higher than other three treatments,but the rainwater use efficiency and irrigation-water use efficiency of SH and HH treatments were higher than FP and JH treatments.3.Effects of different cultivation management models on nutrient absorption and utilization of winter wheatUnder different cultivation management model treatments,both the N,P and K content showed a decreasing trend of slow-fast-slow;compared to FP treatment,both SH,HH and JH treatments could improve the N,P and K content.The accumulation dynamics of plant N,P and K in SS,KF and WX showed a similarity,both plant N and P accumulation showed an S-shaped curve,but plant K accumulation showed a sickle-shaped curve.The plant N,P and K accumulation rates showed slow increase during wintering to turning green,fast increase during turning green to jointing,rapid increase during jointing to anthesis;during anthesis to maturity,N and P accumulation slowly increased and reached top peak,but K accumulation reached top peak at anthesis,and then rapidly decreased.Before jointing stage,the plant N,P and K accumulation rates of SH,HH and JH treatments were lower than FP treatment,but higher than FP treatment after jointing stage,and the difference of SH and HH with FP treatment reached significant level.The ratios of plant N,P and K accumulation during turning green to anthesis in whole growth stage were the highest,but jointing to anthesis was the fastest;after anthesis,N and P accumulation slowly increased,but plant K accumulation rapidly decreased because of the outward leakage of K from root to soil.Compared to FP treatment,SH and HH treatments significantly improved the transportation rate of preanthesis plant N,P and K to grains,but the contribution rate of pre-anthesis plant N and P to grains were lower than FP treatment.The N absorption efficiency of SH,HH and JH treatments was higher than PF treatment,the P and K absorption efficiency of HH and JH treatments was higher than FP and SH treatments.The N use efficiency of HH and JH treatments was higher than FP treatment,but the P use efficiency of SH,HH and JH treatments was lower than FP treatment,the K use efficiency of SH and HH was higher than FP and JH treatments.For the N harvest index,SH,HH and JH were higher than FP treatment.However,the P and K harvest index of HH,JH and FP treatments were higher than SH treatment.4.Approaches and techniques of increasing yield in Huang-Huai wheat-producing areaIn Huang-huai Plain of China,improvement of yield under below 7500 kg ha-1 is attributed to increases in both grain number per spike and spike number,by contrast,spike number is primarily factor.Under higher yield over 7500 kg ha-1,increasing yield mainly depends on marked increasing grain number per spike.GN showed significant positive relationships with above-ground biomass and dry matter(DM)accumulation rate from jointing to anthesis whether it's at a high or low yield levels,and correlation coefficient were higher under yield level over 7500 kg ha-1,this indicated the importance of plant rapid growth in spring for achieving higher GN and yield.Spike and non-spike organs DM both demonstrated strong relationships with GN.Moreover,spike DM distribution also showed a significant positive correlation with GN,this revealed that stronger spike DM growth was more helpful for GN formation.Similar to DM,spike and non-spike organs nitrogen also both showed strong positive relationships with GN from booting to anthesis.But spike organ nitrogen distribution revealed a negative correlation with GN,and this means higher nitrogen metabolic activity in non-spike organs was more beneficial to improve GN.Overall,in the progress of spike organ growth before anthesis(March~April),rapid plant DM growth,improving N absorption in non-spike organs and DM production in spike organ are beneficial to improve GN for achieving higher wheat yield in Huang-Huai Plain of China.In Huang-huai plain,increased yield under low yield rate of < 7500 kg ha-1 was attributed to increases in both total DM and HI.Increased yield under higher yield rate>7500 kg ha-1 mainly depends on further increasing in HI.Under higher yield levels,HI shows significantly negative correlation(R2=0.203-0.297)with total DM and parabolic relationship(R2=0.360)with net accumulation of DM during filling.Higher net accumulation capacity of DM during filling is helpful to slow down HI reduction and maintain high HI value.What's more,net DM accumulation during filling shows a positive correlation(R2=0.154)with grain yield.The post-anthesis net DM accumulation shows significant linear relationship with leaf area potential(LAP,R2=0.408-0.517)and radiation interception potential(RIP,R2=0.459-0.576)during grain filling.This indicates that greater LAP and RIP can produce more post-anthesis net DM.For different spatial canopy layers under anthesis DM of >13000 kg ha-1,maintaining higher LAI and RI of lower layers during grain formation is conducive to achieving higher yield.The ratios of upper layers RI to lower layers show curves of second-order equation relationship with yield during grain filling stages,and the suitable ratios range values increase continuously with grain development.The three preanthesis assimilates translocation parameters(translocation amount,translocation ratio and contribution ratio)show the curves of second-order equation with yield over 7500 kg ha-1,and their suitable ranges were 3000-4500 kg ha-1,25-35% and 30-50%,respectively.These results verify the importance of HI and provide some feasible approaches to improving HI under higher yield levels,and which also provide theoretical basis for further improving higher grain yield in the Huang-huai plain of China.5.Approaches and techniques of achieving high yield and high nitrogen efficiency in Huang-Huai wheatproducing areaHigh plant N accumulation(PNA)was the base of high yield,beneficial to yield but not for NUE.High PNA during jointing to anthesis contributed to total PNA at maturity,and generated the best correlation coefficient with yield and NUE,which was good for achieving high yield and NUE simultaneously.The dry matter produced by unit N was defined as the N productivity,such as plant nitrogen partial factor productivity(PNPP),plant nitrogen net phase productivity(PNPn)and leaf N productivity(LNP).PNPP showed poor relationship with yield and NUE at different stages,but high PNPn during jointing to anthesis was significantly related to both yield and NUE.LNP indicator,photosynthetic nitrogen use efficiency(PNUE)in flag after booting stage showed significant correlation with both yield and NUE at middle and high PNA level.These indicated that N productivity indicators PNPn and PNUE could cooperate high yield and high NUE under higher PNA condition.PNA showed close quadratic curve relationships with soil nitrate N accumulation and alkali-hydrolyzable N(AHN)content.To match soil N supply to plant N demand,optimum nitrate N accumulation and AHN content ranges were determined in the Huang-Huai Plain.This study provided theoretical basis and practical guidance to achieve high yield and high NUE for N management in wheat field production.