Effects Of Rotational Tillage Pattern On Spring Maize Yield,soil Physico-chemical Properties,and Carbon Emission In West Region Of Northeastern China

Northeastern is an important grain production area in China.Under the condition of long-term continuous cropping of maize,single tillage method,large amount of straw returning to the field,slow decomposition and high amount of chemical fertilizer input in Northeast China have led to a series of problems such as soil quality degradation,unstable crop yield,decreased resource utilization efficiency and increased farmland carbon emissions.Reasonable combination of tillage measures is conducive to solving the adverse effects of single tillage methods on soil quality and crop production.While ensuring the stability of crop productivity,it can achieve the synergy of soil quality improvement,resource utilization efficiency improvement and carbon sequestration and emission reduction in farmland system.To this end,this study takes the corn field in the semi-arid area of western Jilin Province as the research object.During 2017-2021,seven tillage methods were set up,a rotation cycle is 3 years,including continuous rotary tillage with straw removal（CK,conventional tillage）,continuous rotary tillage with straw retention（CR）,continuous no-tillage with straw retention（CN）,continuous subsoiling with straw retention（CS）,no-tillage-no-tillage-rotary tillage with straw retention（NNR）,no-tillage-no-tillage-subsoiling with straw retention（NNS）,rotary tillage-subsoiling-no-tillage with straw retention（RSN）.The purpose of this study was to investigate the effects of inter-annual tillage combinations on spring maize grain yield,soil physical and chemical properties,energy input and output,and farmland carbon emissions in the semi-arid region of Northeast China,in order to provide technical support for the optimization of rotational tillage methods in Northeast China.The main results are as follows:1.The 5-year average maize grain yield of each treatment showed a trend of CR(11939.1 kg ha^-1)>CK(11656.1 kg ha^-1)>CS(11150.0 kg ha^-1)>RSN(11019.4 kg ha^-1)>NNR(9776.8 kg ha^-1)>NNS(9507.4 kg ha^-1)>CN(8524.3 kg ha^-1),among which CN treatment was significantly different from CR and CK treatments.The trend of maize yield in a complete rotation cycle from 2017 to 2019 was the same as that of 5-year average yield,but there was no significant difference among treatments.2.The trend of average net income of each treatment in 5-years was CR>CK>RSN>CS>NNR>NNS>CN,and the trend of CK>CR>CS>RSN>NNR>NNS>CN in the complete rotation cycle of 2017～2019.The trend of output-input ratio in the first rotation period and 5-years was consistent,which was CK>CR>RSN>CS>NNR>NNS>CN.3.Compared with CK,the soil compactness of 0-20 cm layer under CN treatment was significantly increased by 32.8%,while CR,RSN and NNS treatments were significantly reduced by 29.6%、56.8%and 58.3%,respectively.In the 20-40 cm soil layer,CR treatment was significantly increased by 19.7%,while RSN,NNS,CS and NNR treatments were reduced by 27.7%、24.2%、10.7%and 8.0%,respectively.Compared with CK,CN、NNR、CS、NNS、RSN treatments increased the water-stable aggregates in the>2 mm particle size range of 0-20 cm soil layer by 106.1%、100.1%、88.2%、39.1%、24.5%,respectively;CS and CR treatments significantly reduced>2mm soil macroaggregates by 69.8%and65.5%in the 20-40 cm layer.4.The soil total nitrogen content in 0-20 cm layer of each treatment showed a trend of CN>NNR>CR>CS>RSN>NNS>CK,and each treatment showed an increasing trend compared with the control,especially the CN treatment significantly increased by15.7%.Compared with CK,the soil organic carbon content of CN、CR and NNR treatments in 0-20 cm soil layer increased significantly by 15.0%、14.5%and 14.2%,respectively.5.The cumulative emission of N₂O showed a trend of CS>RSN>CK>CR>NNS>CN>NNR,and the difference between CS treatment and NNR and CN treatment was significant,which was 50.1%and 38.9%lower than that of the control treatment.The cumulative absorption of CH₄ showed a trend of NNS>CS>RSN>CK>CR>CN>NNR,and there was no significant difference among the treatments.6.Comparing the carbon footprint of different treatments,the carbon footprint per unit area was the highest in CK treatment,and the carbon footprint per unit yield and net income was the highest in NNS treatment,while the carbon footprint per unit area,per unit yield and net income of other treatments showed the trend of CS>CR>NNR>CN.Among them,the carbon footprint per unit area of CN treatment was-699.6 kg CO₂-eq ha^-1 yr^-1,which was the’sink’of carbon absorption,and the other treatments were positive,which was the’source’of farmland soil carbon emissions.In summary,the rotation tillage mode of two years of continuous no-tillage followed by one year of rotary tillage can maintain relatively stable crop yield,improve soil quality,reduce energy input and have low farmland carbon emissions.It is a feasible practice to achieve the comprehensive goals of regional stable yield,high resource efficiency,and low environmental footprint in the region.