Effects Of Deep Buried Returning Of Straw On Decomposition Characteristics And Wheat Yield

To investigate the pattern of maize straw decomposition and the appropriate straw return method to obtain high crop yield,it was conducted in dry shed ponds at Key Laboratory Test Base of Water Physiology and Drought-Resistant Germplasm Improvement,Ministry of Agriculture and Rural Affairs,South Campus of Shandong Agricultural University from 2021to 2022.This experiment was set up to return maize straw crushed 1 cm to a depth of 5 cm（M1D1）,crushed 1 cm to a depth of 10 cm（M1D2）,crushed 3 cm to a depth of 5 cm（M2D1）,crushed 3 cm to a depth of 10 cm（M2D2）,cuted 5 cm to a depth of 7 cm（M3D3）,cuted 10 cm to a depth of 12 cm（M4D4）,and maize straw not returned to the field（M0）were studied in seven treatments,and their effects on soil organic carbon,soil dissolved organic carbon,soil microbial biomass carbon,and photosynthetic characteristics of winter wheat were investigated.The nylon mesh bag method was also used to study the decomposition pattern of returned maize straw and the nutrient release characteristics of nitrogen,phosphorus and potassium.The experimental results were as follows:1.Decomposition characteristics of maize straw under deep buried returningUnder the joint action of two factors,straw crushed degree and straw returned depth,straw decay shows an opposite trend to shredding length and the same trend to straw burial depth.With the extension of decomposition time,the higher the straw decomposition rate,the lower the straw residual amount.The decay of returned maize straw after the whole wheat season finally showed M1D2（91.72%）>M1D1（83.28%）>M2D2（82.74%）>M2D1（81.69%）>M3D3（80.49%）>M4D4（80.21%）.The decay rate of fiber fractions showed that cellulose>hemicellulose>lignin.At wheat maturity,cellulose decay rate was:69.78～85.64%,hemicellulose decay rate was:60.24～71.45%,and lignin decay rate was:53.15～62.39%.In the wheat maturity period,K release rate was 92.25～96.70%,P release rate was 77.55～86.75%,and N release rate was 59.10～71.15%.2.The effect of returning deep buried on soil organic matterSoil organic carbon,dissolved organic carbon and microbial biomass carbon in the 0-40cm soil layer of wheat at the jointing,anthesis,filling and maturity stages all showed a decreasing trend with the deepening of the soil layer,and the soil organic carbon,dissolved organic carbon and microbial biomass carbon showed a pattern of increasing and then decreasing as wheat fertility progressed,reaching the maximum at the anthesis stage.Soil organic matter content was higher in all ditch-buried return treatments than in the non-returned straw treatment.The soil organic carbon content increased with the increase of the return depth at the same straw shredding level,and decreased with the increase of the straw shredding level at the same return depth.The compost treatment favored the increase of soil organic carbon.Soil dissolved organic carbon and microbial biomass carbon were consistent with the change of organic carbon content.3.The effect of returning deep buried on photosynthetic characteristics of winter wheatUnder the same straw crushing condition,D2 could increase the photosynthetic rate of wheat compared with D1 at each post-anthesis stage,and compared with M1D1,M1D2increased the net photosynthetic rate by 4.88%,stomatal conductance by 9.53%and transpiration rate by 6.79%at each post-anthesis stage.M1 could increase net photosynthetic rate at each post-anthesis stage compared with M2 under the same depth treatment.Compared with M2D2,M1D2 increased net photosynthetic rate by 7.19%,stomatal conductance by 9.53%,transpiration rate by 10.70%,and intercellular CO₂ concentration by 11.48%.Crushed 1 cm to a depth of 10 cm treatment was beneficial to the photosynthetic capacity of flag leaves in the middle and late stages of filling and prolonged the greening period of flag leaves in winter wheat.The maximum photochemical efficiency,photosynthetic performance index and SPAD values of post-anthesis flag leaf of winter wheat showed a decreasing trend with the advancement of post-anthesis fertility stage.D2>D1 under the same straw shredding condition,and M1>M2 under the same depth of returning to the field.PI_ABSin the M1D2 treatments increased by an average of 0.51%at all post-anthesis fertility stage compared to the M2D1treatment.Crushed 1 cm to a depth of 10 cm treatment increased the post-anthesis SPAD value,slowed down the senescence of winter wheat leaves and improved the absorption and utilization of light energy by the post-anthesis leaves.4.The effect of returning deep buried on dry matter accumulation and yield of winter wheatThe accumulation of dry matter in the nutritional organs at anthesis stage is shown as stalk and sheath>spike>leaf,and at maturity stage the accumulation of dry matter in the nutritional organs is shown as spike>stalk and sheath>leaf.As wheat fertility stage progressed,the proportion of dry matter in the spike gradually increased,the proportion of dry matter in the leaf gradually decreased,and the proportion of dry matter in the stalk and stem sheath first increased and then decreased.The number of ears and grains of winter wheat in all treatments increased to different degrees compared to the non-returned straw treatment.The yield of winter wheat with the same straw length at different return depths showed an increase in the number of spikes and thousand grain weight in the M1D2 treatment,resulting in a higher yield than the M1D1 treatment,and an increase in the number of spikes in the M2D2 treatment,resulting in a higher yield than the M2D1 treatment.In summary,Crushed 1 cm to a depth of 10 cm treatment decomposes quickly,increases the release of each nutrient required for plant growth and increases the accumulation of soil organic matter,which can effectively increase crop yields.