Effects Of Tillage And Residue On Topsoil Environment And Yield Formation Of Maize

In recent years,yield instability of spring maize becomes increasingly pronounced under the traditional cropping system.However,years of plow-till increased the compactness and thickness of the plow layer,which might inhibit the growth of crop and the increase of yield.Reduced tillage and residue incorporation are important measures of conservation tillage.In 2014 and 2015,short-term effects of tillage(no-till,rotary-till and plow-till)and residue(removal and incorporation)on soil properties,maize growth and yield were investigated in a brown soil region.Our results indicated that:1.Short-term reduced tillage(rotary-till and no-till)and residue incorporation promoted soil properties.Both of the tillage and residue treatments had significant individual effects on percentage of soil water stability aggregates and soil water content(SWC)in 0-40 cm and soil temperature(Temp)in 0-10 cm in 2014 and 2015.The interaction effects of tillage and residue on percentage of water stable aggregates at each grade were highly significant.Compared with plow-till,no-till decreased soil compaction below the plough layer(30-40 cm)and clay particle in 0-20 cm.No-till increased the percentage of macroaggregate(Macroaggregat R0.25)and aggregate stability indexes in 0-10 cm,furthermore,no-till had obvious effect on improving soil water content in 0-40 cm.Compared with plow-till,rotary-till significantly decreased soil bulk density and soil compaction and increased soil porosity and the percentage of macroaggregate(0.25~2 mm)in 0-10 cm.Compared with residue removal,residue incorporation decreased soil compaction and soil temperature and increased soil porosity,percentage of macroaggregate and soil water content in 0-40 cm.2.Residue treatment had significant effects on soil total nitrogen content(TN),soil total potassium content(TK),soil organic carbon content(SOC)and soil C:N ratio(C:N)in 0-30 cm in 2014 and 2015.The interaction of tillage and residue had no significant influence on soil chemical properties in 2014 and 2015.There was a phenomenon of nutrient enrichment in surface soil under no-till and rotary-till.Compared with plow-till,no-till increased soil total nitrogen content,soil total potassium content,soil organic carbon content and soil C:N ratio in 0-10 cm significantly.Compared with plow-till,rotary-till increased soil total nitrogen content,soil total potassium content and soil organic carbon content in 0-20 cm.The differences were significant between residue removal and residue incorporation in soil total potassium content and soil organic carbon content.Compared with residue removal,residue incorporation increased soil total nitrogen content in the residue-incorporated soil layers and soil total potassium content in 0-30 cm significantly.Furthermore,residue incorporation increased soil organic carbon content and C:N ratio in 0-30 cm.3.Soil respiration was measured by closed static chamber technique.The results showed that tillage and residue treatments could increase soil respiration obviously.The soil respiration rate was the highest under rotary-till treatment and the lowest under no-till treatment.The diurnal respiration rate of soil was increased by 40.2% compared with residue removal treatment.4.Both of the tillage and residue treatments had significant individual effects on root diameter(RAD)and leaf area index(LAI)of maize in 2014 and 2015.Besides,tillage residue treatment had significant effects on root length density(RLD),root surface area density(RSD)and stem diameter(SD).The interaction of tillage and residue had no significant effects on maize growth indexes in 2014 and 2015.Compared with plow-till,no-till significantly increased root diameter and root surface area density,significantly decreased root length density of maize,however.Compared with plow-till,rotary-till significantly increased root surface area density.Root diameter was higher under rotary-till than plow-till.Compared with residue removal,residue incorporation significantly increased root diameter,root surface area density and root length density of maize in 2014 and 2015.Plant high(PH),stem diameter and leaf area index were lower in the early growth period of maize under no-till,rotary-till and residue incorporation treatments.However,plant high,stem diameter and leaf area index of maize under reduced tillage and residue incorporation were higher than plow-till and residue removal treatments.5.Both of the tillage and residue treatments had significant individual effects on root biomass(RB)and root-shoot ratio(R:S)of maize in 2014 and 2015.However,tillage residue treatment had no significant effects on growth indexes of maize.The interaction of tillage and residue had no significant effects on maize growth indexes in 2014 and 2015.Compared with plow-till,no-till and rotary-till increased root biomass in the growth season and shoot biomass(SB)in maturity stage,and the difference was significantly between no-till and plow-till.Compared with plow-till,no-till and rotary-till increased total biomass(TB)and root-shoot ratio(R:S)in the growth season and the differences were significantly in maturity stage.Root biomass and root-shoot ratio were significantly higher under residue incorporation than residue removal in the growth season.Shoot biomass and total biomass were significantly higher under residue incorporation than residue removal in maturity stage.6.Both of the tillage and residue treatments had significant individual effects on ear number,kernel number and yield of maize,their interaction effect on ear number was significantly.Compared with plow-till,no-till significantly increased ear number,kernel number and yield of maize.Rotary-till significantly increased kernel number of maize.Yield was higher under no-till(30.7%)and rotary-till(16.0%)treatments,the difference between plow-till and no-till was significant.Compared to residue removal,residue removal also significantly increased the yield of spring maize(7.2%).7.Although there were positive relationships between soil water content,soil organic carbon content,C:N ratio,root diameter,root surface area density,root biomass,shoot biomass,R:S ratio and yield,structural equation modeling showed maize yield was directly controlled by R:S.These findings will have important implications for improving the current cropping system(i.e.,plow-till with residue removed)in this area.