Regulation Of Tillage Practice And Residues Returning On Soil Quality And Root Growth And Metabolism Of Winter Wheat

Huang-Huai-Hai region is one of the main grain producing areas in China.The low water productivity of crops and the non-sustainable of tillage practices restrict the development of agriculture in this region.This study was based on the long-term experimental field at Shandong Agricultural University(beginning in 2002).Combined with the dynamic changes of soil physical and chemical properties,and yield from 2010 to 2019,the soil structure and stability,soil water retention and availability,dynamics of soil organic carbon,soil quality and sensitive indicators under the wheat-maize two cropping a year were investigated in 2018 and 2019.Through the analysis of the morphology,distribution and differential metabolic pathways of the wheat root and above ground status,the mechanism of the difference in soil quality and yield formation between different tillage practices and residue returning was discussed.It is expected to provide a reference for the improvement of farming management in this area to improve the water retention and effectiveness of farmland,strengthen soil nutrient cycling,make agricultural production sustainable,and regulate the distribution of wheat root to increase productivity.The main results showed that:1.Effects of tillage practices and residue returning on soil water availabilityUnder the condition of normal rainfall(about 550 mm)grown season,the soil water storage among treatments had a significant difference,mainly came from the 0—40 cm soil layer,while no significant differences were found below 40 cm.In the 0—40 cm soil layer,the soil water content is in the below order:rotary tillage>subsoiling tillage>plowing tillage,residue returning treatments>no residue returning treatments.Firstly,the soil evapotranspiration under plowing tillage was significantly higher than that under subsoiling and rotary tillage,and the residue returning hinders and supplements the evapotranspiration of soil water.Secondly,the plowing tillage made the surface layer reduced stability of aggregates,which was not conducive to the infiltration of precipitation and increases runoff.The structure of soil aggregates increased by subsoiling and rotary tillage so that increases the infiltration of precipitation.The residue returning provides a path and time for the infiltration of precipitation.According to the soil water characteristic curve,the soil saturated water content of the rotary tillage and subsoiling tillage in the 0—30 cm soil layer was significantly higher than that of the plowing tillage treatment.The soil saturated water content in the 0—20 cm soil layer of the residue returning treatment slightly higher than the treatment without returning.However,the gravity water of the rotary tillage treatment in the 0—20 cm layer was significantly higher than that of the plowing and subsoiling tillage treatments,and the water infiltrates in the form of gravity water.The low limit of the rotary tillage was significantly higher than that under subsoiling and plowing treatments.The residual water content of subsoiling treatments was significantly higher than that of plowing and rotary tillage treatments.Therefore,subsoiling and rotary tillage have higher soil water storage potential.The soil water content of rotary tillage treatment was high while it was not easy to be used by crops.The soil water content of subsoiling treatment was higher and can be used effectively.2.Effects of tillage practices and residue returning on soil qualityTillage practices and residue returning have led to significant differences between soil organic carbon and total nitrogen storage,which mainly due to the differences in 0—40 cm soil layer.The highest soil organic carbon and total nitrogen storage both were found under subsoiling treatment,followed by plowing and subsoiling treatments.In the treatment of plowing and rotary tillage,the residue returning treatment was significantly higher than that of no residue returning.From 2002 to 2020,the soil organic carbon and total nitrogen both increased firstly and then leveled off.Compared with 2002,the soil organic carbon of subsoiling,plowing and rotary were increased by 41.7%,28.1%and 20.8%,respectively,meanwhile,the total nitrogen of subsoiling,plowing and rotary were increased by 23.6%,13.6%and 10.6%,respectively,in 2010 grown season.Compared with 2010,the soil organic carbon and total nitrogen of all treatments slightly increased in 2018 without significant difference.By exploring the changes in soil organic carbon before and after tillage,after tillage,plowing subsoiling and rotary tillage treatments increased by 4.5%,12.4%and 24.2%on average in two years,and the residue returning and without residue returning increased 15.0%and 10.4%respectively.In addition,compared with 2002,the soil bulk density of the plowing tillage and subsoiling treatments decreased by 14.1%in 2010,while the rotary tillage treatment only decreased by5.5%,there was no significant difference among the treatments in 2010 and 2018.Compared with 2010,the soil TK,AK,TP and AP increased significantly in 2018.The soil quality index showed that the plowing without returning and the rotary tillage without returning were lower,while the subsoiling with residue was higher.In addition,significant linear correlation was found between soil quality index and yield.Therefore,the soil quality of the subsoiling with residue returning treatment is conducive to the sustainable development of agriculture and the improvement of agricultural productivity.The soil positive sensitivity properties of plowing and subsoiling without returning and the negative sensitivity properties of rotary tillage were consistent,which were PR,Porosity,TN,SOC,and TP.The negative sensitivity properties of plowing and subsoiling without returning and the positive sensitivity of rotary tillage were consistent,which were EW,BD,EAW,SWC and AK.SWC,AK,MWD,GMD,R_0.25,AP,TP,SOC,TN and Porosity are positive sensitive properties under subsoiling with returning treatment,while BD,EW,TK and PR are negative sensitive properties.3.Effects of tillage practices and residue returning on morphological distribution and metabolism of wheat rootsThe root distribution of wheat at the seedling stage showed that the angle of root under the rotary tillage and subsoiling treatments was small and the distribution is uneven in the soil layer,while the root angle of the plowing treatment was relatively uniform in the soil layer.The residue returning was benefit for the roots to be rolling down and distributed evenly in the soil layer.The root dry matter weight under plowing and rotary tillage treatments in the 0—10 cm soil layer were significantly higher than the subsoiling treatments,as well as the residue returning treatments.The 10—40 cm soil layer was lower except the rotary tillage treatment.The treatment difference was not significant,the residue returning treatment was slightly lower than the no residue returning treatment.The change trend of root length density was the same as the change of root dry matter weight.The average root diameter in the 0—40 cm soil layer was significantly larger than that of other treatments.The relative root length,relative root dry weight,and relative root surface area have basically the same changing trends with soil depth.The surface layer 0—10 cm specific gravity was lower in the treatment of rotary tillage without returning to the soil and subsoiling without residue returning to the soil.However,in the 10—20 cm soil layer,the relative root length,relative root dry weight and relative root surface area of the rotary tillage treatment were significantly smaller than that under other treatments.The disturbance of plowing makes the surface layer loose and suitable for root growth at the seedling stage.Therefore,the number of root hairs was large and the surface of the long root system was smooth.Rotary tillage makes the soil compact,which was not conducive to the development of roots.The number of root hairs was small and the root system surface was rough.The surface of the root was more organized.The ATP-BC transporter regulatory network of three tillage treatments significant affected the absorption of water and nutrients by wheat roots at the seedling stage,and subsoiling affects xyloglucan:xylo-oligosaccharide glucosyltransferase and histidine kinase affect plant hormones The signal transduction pathway affects salicylic acid through benzoic acid.At the same time,amidase and acyl phosphatase also affect salicylic acid.Salicylic acid was an endogenous hormone that can regulate the development and resistance of plants,and induce cell differentiation.The deep loosening pair of rotary tillage group directly affects ethylene biosynthesis,methionine degradation and cysteine biosynthesis modules by methionine adenosyl transferase,causing differences in the metabolism of cysteine and methionine,and methionine was the plant endogenous hormone ethylene and the precursor of polyamine synthesis,cysteine maintains cell function and antioxidant effect.The biosynthesis process of glycosphingolipids was related to the construction of plasma membrane in the regulation network of subsoiling and rotary tillage.The difference of the purine metabolism network of the subsoiling to the rotary tillage group may be related to the division and differentiation of root elongation cells.In addition,the metabolic pathways of starch,sucrose,and galactose have changed.The aboveground and underground parts of the seedling stage grow in harmony.The dry matter of the aboveground part of the rotary tillage treatment is significantly lower than that of other treatments.The aboveground dry matter of the straw returning treatment is also lower than that of the non-returning treatment,and the root dry matter weight of the tillage treatment is significant higher than other treatments,there was no significant difference in root-to-shoot ratio between treatments.In the range of 0.27—0.29,the difference in root vigor of each treatment was not significant,at 145—154?g g^-1 FW h^-1,which laid the foundation for later growth.4.Effect of tillage practices and residue returning on yieldCompared with plowing and rotary tillage,subsoiling increased stomatal density and net photosynthetic rate of wheat plant height and leaf area,promoted dry matter accumulation,and was beneficial to wheat population health.From the perspective of long-term average output,the yield of wheat in the treatment with rotary tillage without residue returning was significantly lower than that of other treatments,while the yield of maize under plowing tillage without returning and rotary without residue returning was significantly lower than the other treatment.The average yields of wheat and maize were under subsoiling with residue returning was 8.28and 11.83 Mg ha^-1,which was 6.13%for wheat and 7.57%for maize higher than that of plowing tillage,and 13.23%for wheat and 6.70%for maize higher than that of rotary tillage.The yield of wheat and maize under residue returning was increased by 5.96%and 9.46%than that of no residue returning.The long-term grain energy output of subsoiling with residue returning was higher and the coefficient of variation was the smallest,which was greater than the expected value of 3.05×10⁵ MJ ha^-1 in most years.Tillage practices and residue returning affected the soil particle structure and pores,soil water retention and effectiveness,soil organic carbon and nutrient substances.The pores,moisture and nutrients affected the spatial distribution of roots,surface structure,dry matter weight and so on.In turn,it induces changes in root metabolism,roots absorb water and nutrient-related ATP-BC transporters,regulate plant growth and development,stress resistance,and induce cell differentiation phytohormone signal transduction pathways,glycosphingolipid biosynthesis related to plasma membrane construction,starch and sucrose pathway,galactose pathway,purine metabolism and other pathways also changed.Differential metabolites regulate the morphology of the aerial parts,which makes the plant height,leaf area,dry matter accumulation,photosynthetic rate,1000-grain weight and harvest index of each treatment separate differences,and finally constitutes the yield difference.