Effects Of Integrated Agronomic Practices Management On Field Soil Characteristics And Yield Formation Of Winter Wheat-Summer Maize Double Cropping System

Long-term irrational management practices with high input,high intensity,and high demand lead to reduced crop productivity,poor soil structure,and increased environmental effects.Integrated agronomic practices management can effectively improve yield and nitrogen use efficiency,but the physiological mechanisms that promote yield and their environmental effects are not clear.Therefore,long-term field experiments were conducted with integrated agronomic practices management（IAPM）and nitrogen rate texts（NAT）at Xiaohou Village,Dawenkou Town,Tai’an city,China.This study was in 2017-2022.The Zhengdan 958（summer maize hybrid）and Tainong 18（winter wheat hybrid）were used as experimental materials.The IAPM was established with three systems:an increasing yield system（T2）,a super high-yield production system（T3）,and an integrated soil-crop management system（T4）,using the conventional cropping system（T1）as control.The NAT was established with four rates based on T4:no nitrogen rate（N0）,low nitrogen rate（N1）,suitable nitrogen rate（N2）,and excessive nitrogen rate（N3）(summer maize:0,129,184.5,and 300 kg N ha^-1;winter wheat:0,168,240,and 312 kg N ha^-1).This experiment investigated soil structure and function,winter wheat-summer maize yield formation and greenhouse gas emissions to clarify the microbial mechanisms of IAPM regulating soil nutrient transformation and uptake and the effects on annual production yield and environment effects of winter wheat-summer maize;investigated the spike differentiation,grain filling characteristics,and canopy structure of summer maize,to clarify the effect of IAPM on crop yield formation,the relationship between leaf nitrogen accumulation and spike differentiation,and the key metabolic pathways affecting spike differentiation.That will help to fully understand the interaction of soil physical and chemical,microbial community composition,and environmental factors and its impact on yield formation and carbon footprint,realizing high yield,high efficient,and sustainable production of summer maize and winter wheat.The results are as follows:1 Optimized IAPM improved soil structure and function of winter wheat-summer maize to promote soil carbon and nitrogen cycleOptimized IAPM significantly improves soil structure and nutrient content,which significantly changes soil bacterial structure and function to increase yield and reduce GHG emissions.Heavy fertilizer application in T3 treatment caused a decrease in soil p H and significant enrichment of Rhodococcus,resulting in high N₂O emissions.During wheat jointing stage and maize harvesting stage,T4 significantly increased the abundance of dominant bacteria related to carbon metabolisms,such as aromatic hydrocarbon degradation and hydrocarbon degradation,which promoted soil carbon cycling.At tassel stage of summer maize,T4significantly increased the abundance of dominant bacteria related to nitrogen metabolism,such as nitrification,and promoted soil nitrogen cycling.Optimized IAPM significantly affected rhizosphere microbial community composition and function in summer maize.Excessive N rate,high soil nutrient content,and low p H in T3treatment inhibited rhizosphere microbial activity and significantly reduced the function of some N cycle-related microorganisms.However,the function of microorganisms associated with gaseous N loss of T3 increased,resulting in higher N₂O emissions.The T4 had a more diverse rhizosphere uptake of bacterial OTU species by optimizing agronomic management and fertilizer application,including a wide range of nitrogen metabolism-related microorganisms,which promoted soil nitrogen cycling,thereby increasing plant available N supply,maintaining higher aboveground productivity.2 The IAPM increased material accumulation and promoted ear and grain formation of summer maize to increase yieldThe dry matter accumulation and yield of summer maize showed a trend of increasing and then leveling off with increasing nitrogen rate;there was no significant difference between N3and N2 treatments,which indicated that the effect of nitrogen rate alone to increase yield was limited.Therefore,further yield improvement requires the optimal synergy of multiple cultivation management practices.The IAPM significantly increased dry matter accumulation and yield of summer maize,with the highest yield in T3 treatment followed by T4 treatment.The yield in T2,T3,and T4 treatments increased by 18.9-31.8%,14.9-62.3%,and 33.1-47.6%compared with T1 treatment,respectively.（1）Optimized IAPM coordinated nitrogen metabolism to promote spike differentiation and increase the grains number per ear pre-anthesisOptimized IAPM and appropriate nitrogen rate could increase leaf nitrogen content to promote spike differentiation,but insufficient nitrogen rate reduced the leaf nitrogen content to slowe the process of spike differentiation,which was not conducive to spikelet development.During tassel floret differentiation-ear spikelet differentiation stage,the leaf nitrogen content was significantly related to spike differentiation characteristics of summer maize.No nitrogen rate（N0）or low nitrogen rate（N1）decreased the nitrogen metabolizing enzyme activity of leaves,decreased the nitrogen accumulation of leaves,which delayed the spike differentiation of summer maize,and increased anthesis silking interval by 1-4 days,resulting in the serious degradation of florets and a significant reduction in silk and grain set rate;finally,grain number per ear and yield were significantly reduced.Excessive nitrogen application（N3）could not further promote spike differentiation and there was no significant difference in tassel and ear characteristics between N2 and N3.Therefore,a suitable nitrogen rate could significantly improve the nitrogen metabolizing enzyme activity of leaves,promote nitrogen accumulation and transformation,which was beneficial to the synchronous spike differentiation,increase the number of silk and grain set rate,and significantly increased grain per ear.（2）Optimizing IAPM coordinated light and nitrogen distribution in canopy and promote grain filling accumulation pro-anthesisAn appropriate nitrogen rate increased the light and nitrogen partition coefficient of the canopy,but an excessive nitrogen rate led to a significant decrease in the light and nitrogen partition coefficient.Optimized IAPM could coordinate the canopy light and nitrogen distribution,improve photosynthetic rate,increase photosynthetic nitrogen use efficiency,promote material accumulation and increase yield.Compared to T1,the chloroplast structure in the up and middle canopy of T4 was significantly improved,the number of chloroplasts was significantly increased by 21.7-30.4%,and the photosynthetic capacity was significantly improved.Furthermore,the high nitrogen content of the middle canopy leaves and more light radiation intercepted by adjusting the leaf area in T4 resulted in a better match between light and nitrogen distribution and a significant increase in photosynthetic nitrogen use efficiency.The photosynthetic N use efficiency of the upper and middle canopy in the T4 increased significantly by 41.4%and 9.4%compared to T1,respectively;the middle canopy at the milking stage could still maintain a high photosynthetic N use efficiency,which increased by18.2%compared to T1.However,the photosynthetic N use efficiency of T3 was lower than that of T4.Optimized IAPM and appropriate nitrogen rate promoted endogenous hormone balance and improved grain filling characteristics.The content of indole-3-acetic acid（IAA）,zeatin Riboside（ZR）,and gibberellin（GA₃）of T2 and T4 treatments was higher,and the content of abscisic acid（ABA）were lower compared to T1.The content of ZR and GA₃ of T3 was higher than that in T1.So,the weight at maximum grain filling rate（Wmax）and active grain filling period（P）of T2,T3,and T4 treatments were significantly higher than those of T1 treatment,which promoted the accumulation of dry matter and grain weight.3 Optimized IAPM reduced carbon footprint of winter wheat-summer maize production,increased net proceedsOptimized IAPM increased soil carbon sequestration（SOCS）,and reduce carbon footprint.The T3 treatment had the largest SOCS(39.8 Mg ha^-1),followed by the T4 treatment(35.2 Mg ha^-1),which increased by 11.5 and 6.9 Mg ha^-1 compared to the pre-test,and by 9.9 and 5.3 Mg ha^-1 compared to the T1,respectively.The T3 treatment had the highest yield,but the excessive agricultural inputs and greenhouse gas（GHG）emissions resulted in the highest carbon footprint.In contrast,the T4 treatment reduced fertilizer application and reduced agricultural inputs to maintain higher yields and SOCS,with the lowest final yield-carbon footprint.The yield-carbon footprint of T4 was 60.4%lower than the T1 treatment and 38.7%lower than the T3.And the net proceeds was increased in T4.In conclusion,the appropriate nitrogen rate could promote yield formation in summer maize,but an excessive nitrogen rate did not continue to increase yield.Therefore,it was necessary to optimize and coordinate multiple agronomic management measures to further improve the yield.In IAPM,the highest yield was achieved in T3,followed by T4.However,T3 had lower photosynthetic nitrogen use efficiency and higher GHG emissions and carbon footprint than T4 treatment.Therefore,the T4 treatment was the most suitable management system to increase crop yield and reduce environmental effects,which could achieve high yield and high efficient crop production and provide a direction for developing sustainable production-oriented agricultural production.