Formation Mechanism Of Yield Gap And Regulation Ways Of Reducing Yield Difference And Increasing Efficiency Of Summer Maize In Jiangsu Province

At present,maize yield gap and efficiency gap are a research hotspot.Maize production has been in short supply in Jiangsu Province.How to improve the situation to meet people’s needs better plays a vital role in ensuring food security in Jiangsu.Therefore,it is of great significance to clarify yield gap and efficiency gap of maize in Jiangsu Province and the technical ways to reduce the difference and increase the efficiency.This experiment was conducted in Xuzhou,Suqian and Yangzhou of Jiangsu Province from 2017 to 2019,using Jiangyu877 variety from Jiangsu Province as the material.Through investigation and construction of four yield levels of summer maize in Jiangsu,the formation mechanism and main controlling factors of yield gap and efficiency gap were clarified,and the main technical ways of reducing difference and increasing efficiency wer clarified.Meanwhile,in order to explore the physiological mechanism of combined application of slow-release nitrogen fertilizer and common nitrogen fertilizer to regulate the yield and efficiency of summer maize in Jiangsu,an experiment of applying nitrogen at a reasonable density was carried out in Xuzhou,Suqian and Zhenjiang,Zhenjiang in 2019、2021 and 2022.The main results are as follows.1 Yield gap and efficiency gap of summer maize in Jiangsu ProvinceThe results showed that the yield gap between the yield of summer maize farmers and basic soil capacity was 1688.4～2781.0 kg/ha(mean 2090.6 kg/ha),and the yield gap between high yield and high efficiency was 741.5～1763.8 kg/ha(mean 1178.4 kg/ha).The difference of nitrogen partial productivity was 19.9～32.3 kg/kg(mean 25.5 kg/kg),the difference of nitrogen agronomic efficiency was 3.1～13.7 kg/kg(mean 9.3 kg/kg),and the difference of nitrogen use efficiency was 12.8%～19.7%(mean 17.7%).The yield gap between high yield and high yield and high efficiency was 758.3～2064.8 kg/ha(mean 1212.8 kg/ha),and the difference of nitrogen partial productivity was12.3～-20.1 kg/kg(mean-15.3 kg/kg).Nitrogen agronomic efficiency difference was 0.4～6.5 kg/kg(mean 2.4 kg/kg),nitrogen use efficiency difference was 2.0%～9.6%(mean 6.4%).Compared with the high yield and high efficiency,the yield of super high yield level was higher,but the fertilizer use efficiency was lower.The comprehensive analysis showed that high yield and high efficiency was the best,which indicated that the corn shrinkage difference and efficiency improvement of maize in Jiangsu Province was mainly to reduce the yield gap and efficiency gap between the farmers’ yield and high yield and high efficiency.2 Formation mechanism of yield gap and efficiency gap among maize populations and ways of reducing difference and increasing efficiencyCompared with the basic fertility,the panicle number,grain number per spike,1000-grain weight,biomass accumulation rate and population light energy utilization rate were increased by increasing the nitrogen application rate at the farmer’s level,which promoted the accumulation of biomass.The results showed that farmers could increase maize yield by increasing density and fertilizer.The yield gap and efficiency gap between farmer level and high yield and high efficiency were due to the fact that high yield and high efficiency increased panicle number and biomass accumulation rate,prolonged nutrient absorption cycle,improved population light energy utilization rate,promoted biomass accumulation,and significantly increased fertilizer utilization rate.This study found that the yield gap can be reduced and the efficiency gap can be increased by increasing the density,optimizing fertilization and precise quantitative fertilization.The reason for the yield gap and efficiency gap between high yield and high efficiency and super high yield level was that super high yield level increased nitrogen application amount,increased panicle number,biomass accumulation rate and population light energy utilization rate,and promoted the population biomass accumulation.Our research found that the fertilizer efficiency could be improved by reasonable densification,extended application of slow release fertilizer,deep application and topdressing of chemical fertilizer,and combined with cultivation measures such as chemical control to reduce yield gap and increase efficiency gap.3 Mechanism of optimal fertilization on maize yield under reasonable densityThe results showed that the combined application of slow-release nitrogen fertilizer and common nitrogen fertilizer had significant effect on the yield increase and efficiency of Jiangsu maize under the density of 75,000 plants/ha and the same nitrogen application rate(225 kg/ha).The optimal ratio of slow-release nitrogen fertilizer to common nitrogen fertilizer was 2:1(slow-release nitrogen fertilizer 150 kg/ha:common nitrogen fertilizer 75 kg/ha).Compared with single application of common N or slow release N,combined application could increase the yield by 2.2%to 25.4%(mean 9.3%)and increase the N use efficiency by 2.5%to 12.5%(mean 9.6%).Combined application significantly increased the pre-anthesis vegetative organ transport rate and the contribution rate of post-anthesis transport to grain,and improved nitrogen partial productivity and agronomic efficiency.Through the analysis of physiological and biochemical indexes of leaves under different nitrogen fertilizer combinations,we found that the relative chlorophyll content,net photosynthetic rate,intercellular carbon dioxide concentration,transpiration rate and stomatal conductance of maize leaves under different nitrogen fertilizer combinations were higher than those under single fertilizer treatment.Compared with single fertilization treatment,soluble sugar content,soluble protein content,photosynthetic enzymes,nitrogen metabolism-related enzymes,antioxidant enzyme activities and IAA content of corn leaves were significantly increased under combined fertilization,while ABA content was significantly decreased.Transcriptomic and metabolomic analysis showed that leaf biosynthesis of flavonoids and flavonoids and plant signal transduction pathways responded positively to nitrogen fertilizer.Physiological indicators showed that the photosynthetic index,enzyme activity and endogenous hormone content of maize were higher under combined application.These results indicated that combined application enhanced photosynthesis and respiration,delayed leaf senescence and increased the accumulation of photosynthates by affecting photosynthetic capacity,hormone balance,signal transduction and antioxidant capacity of leaves,thus increasing the yield.