Effects Of Different Tillage Methods On Soil Environment And Maize Yield Of Semi-humid Region In Jilin Province

Northeast Plain of China with precious black soil resources,covers a total area of 1.03million km~2 and is famous for being one of the three black soil belts in the world.However,the pattern of"long-term land utilization without protection"accelerates the degradation of black soil,and poses serious threat to national food security,sustainable agri cultural development and the role of"Cornerstone"of Northeast China.The degradation of black soil has attracted extensive attention from scholars and the Chinese government.Therefore,it is of great significance for the protection of black soil and sus tainable agricultural development of China to solve the problems of traditional tillage methods and promote reform and innovation of the farming system.Generally,conservation tillage and straw returning are considered as a direct way to protect black soil and agricultural sustainable development.The semi-humid region of Jilin is the primary grain production and the typical black soil area in northeast China.Therefore,it is of great significance for protecting black soil and the sustainable agriculture development in northeast China to study the effects of tillage methods with straw returning as the core on the soil environment and maize yield in this region.This experiment was conducted in Xiangshan Country,Fanjiatun,the Gongzhuling City of Jilin(43°45'N,125°01'E)from 2017 to 2020.Eight tillage methods was designed in the field,such as conventional tillage(CT),plow tillage with straw returning(PT),rotary tillage with straw returning(RT),no-tillage with complete straw mulching(NT1),no-tillage with 30%straw removed(NT2),no-tillage with 30%straw removed+subsoiling(NT3),no-tillage with high stubble and complete straw returning(NT4),no-tillage with compelete straw strip mulching(NT5).All treatments of tillage methods kept the same location during the test.In this study,some growth indicators of maize(emergence rate,phenological period,plant height uniformity,dry matter accumulation of different periods and yield),soil physical properties(soil bulk density,total porosity,and three-phase ratio),soil chemical properties(total nitrogen,phosphorus,and potassium,organic matter content and available nitrogen,phosphorus and potassium,p H),soil temperature and soil water content were measured.A structural equation model(SEM)was used to analyze the primary factors and potential mechanisms of tillage methods on maize yield.The main research results are as follows:(1)Tillage methods will affect emergence,growth and yield of maize.Compared with CT,the treatments of PT and RT reduced dry matter accumulation,and improve the plant height uniformity(31.7%and 12.3%,respectively)at the V6 stage,but had the similar emergence time and growth period of maize.Meanwhile,maize yield of PT and RT showed an increasing trend,with an average increase of 2.0%for PT and 0.5%for RT in three years.However,all conservation tillage treatments contributed to the delayed emergence time and phenological period,and reduced plant height uniformity,dry matter accumulation per plant and y ield:the delay time of emergence and maturity was 2-7 days and 1-4 days,respectively.And the treatments of NT1 and NT4 had the longest delayed time.The uniformity of plant height was decreased by 11.7%-30.2%.And the yield was decreased by 0.7%-11.0%,in which NT1 and NT4 were 11.0%and 10.1%respectively,and NT2,NT3,and NT5 were 2.4%,2.9%,and 0.7%,respectively.The emergence rate,100-grain weight and the ear number were positively correlated with yield,but the difference of phenological period was negatively correlated.(2)Tillage methods affected soil bulk density,total porosity and three-phase ratio of 0-40 cm,and soil organic matter and nutrient contents of 0-30 cm.However,in all tested indexes,soil physical properties of 10-20 cm and soil chemical properties of 0-5 cm were more easily affected by tillage methods.Compared with CT,the treatments of PT,RT and NT1 reduced soil bulk density of 10-20 cm by 4.6%-10.7%,4.1%-5.9%and 0.7%-4.1%respectively,decreased the R value of three-phase ratio by 6.7-48.3%,14.5%-24.3%and 15.8%-20.6%respectively,and increased the soil total porosity by 6.0%-14.6%,3.6%-8.0%and 1.0%-5.6%respectively.The similarity is that,all conservation tillage treatments reduced soil bulk density and the R value of three-phase ratio by 0.7%-10.0%and 8.9%-56.3%,and increased soil total porosity by 1.0%-13.7%.The treatments of PT and RT decreased soil organic matter and nutrient contents in 0-5 cm soil,while all conservation tillage treatments increased in all indicators.The soil organic matter content in 0-5 cm soil at treatments of PT and RT decreased by 8.7%and 7.9%,respectively,and increased by 22.6%in treatment of NT1.All conservation tillage treatments increased soil organic matter content in 0-5 cm by 1.4%-22.6%.(3)The tillage methods affected the soil water content during the all growth period and soil temperature in the early growth of maize.Compared with CT,all treatments increased soil water content,and the maximum values was found in the treatments of NT1 and NT4.The soil water content of PT,RT,NT1,NT2,NT3,NT4 and NT5 increased by 0.13%-2.45%,0.91%-3.35%,2.79%-6.82%,2.3%-5.0%,1.95%-3.27%,1.14%-5.35%and 1.33%-5.16%,respectively.Tillage methods mainly affected soil temperature from sowing to V12 stage,and had a greater impact on soil temperature from sowing to emergence.The soil temperature in the treatments of PT,RT,NT1,NT2,NT3,and NT5 decreased by 0.51?,0.96?,2.73?,1.90?,1.70?,2.17?,and 1.49?,respectively,compared with CT.At the same time,tillage methods significantly affected soil accumulated temperature.The mean of?10?accumulated soil temperature at 5 cm in PT,RT,NT1,NT2,NT3,NT4,and NT5 decreased by 22.6?,86.1?,216.2?,158.3?,111.8?,210.0?,and 112.7?,respectively.(4)Ears Number and 100-grain weight are direct factors of influencing maize yield.The soil water content and temperature is the most important indirect factors.The soil water content and temperature influenced the emergence time,thus influencing the ears number and 100-grain weight,which ultimately influenced the maize yield.However,soil temperature gave more contribution to maize yield than soil water content in conservation tillage methods.(5)Plow tillage with straw returning(PT)and rotary tillage with straw returning(RT)were more suitable tillage methods in the semi-humid region of Jilin Province at the aim of only improving maize yield.If the methods of protecting black soil was needed,the effect of no-tillage with complete straw mulching(NT1)and no-tillage with high stubble and complete straw returning(NT4)was suitable.If pursuing agricultural sustainability,no-tillage with 30%straw removed(NT2),no-tillage with 30%straw removed+sub soiling(NT3),and no-tillage with complete straw strip mulching(NT5)should be priory to consider.