| This study was carried out in the wheat-maize crop system in Zhujiabu Village,Laiyang City,Shandong Province,from 2016 to 2018.Four tillage depths were studied: conventional tillage 25 cm(CT25);subsoiling tillage 30 cm(ST30);subsoiling tillage 35 cm(ST35)and subsoiling tillage 40 cm(ST40).In crop production at the same time,the basic physical characteristics of soil in soil tillage layer under different subsoiling depth are analyzed,the influence of soil agglomeration structure stability and the characteristics of soil agglomeration carbon reservoir is improved,the moisture conservation ability of farmland water storage and the improvement of moisture use efficiency are determined,the suitable depth of subsoiling for rational tillage layer in eastern Shandong was determined.The main result were as follows: 1.Yield and component factorsCompared with CT25,subsoiling has a significant effect on improving crop yield.With the increase of subsoiling depth,ST35 and ST40 significantly increased the effective spike number of wheat and the final yield increased.The increase of subsoiling depth increased the number of spike grains in maize and thus increased the yield of maize.2.Soil physical propertiesThe depth of subsoiling has a significant effect on the physical properties of soil tillage layer.Compared with CT25,the results showed that at the 20-40 cm depth ST30,ST35 and ST40 decreased the mean soil bulk by 4.72,7.58 and 8.22%,respectively,the trend of soil porosity is opposite to that of soil bulk density,especially in 30-40 cm soil layer,the effects of ST35 and ST40 treatments on improving soil porosity are remarkable,the soil compactness in 0-40 cm soil layer is reduced,the three-phase ratio of soil in 20-40 cm soil layer is adjusted,the ratio of gas phase to liquid phase is increased,and the solid phase ratio is reduced.Make the soil form a structure with both virtual and real,and ST35 and ST40 have better improvement effect on the physical properties of the soil tillage layer under various subsoiling depth treatments.3.Distribution stability and carbon composition of soil aggregatesThe depth of subsoiling significantly affected the distribution of soil aggregates in different layers,and the number of macroaggregates increased by 0-20 cm(R > 0.25 mm).Compared with CT25 and ST30,ST35 and ST40 decreased the number of macroaggregates by 20-40 cm and increased the stability index(MWD)of aggregates by 0-40 cm,at the same time,under the conditions of dry and wet sieving,the damage degree of large aggregates in 20-40 cm soil layer is aggravated,and the stability index PDA increases with the increase of soil depth.The particulate carbon fraction of aggregates in 0-20 cm soil layer decreases with the decrease of aggregate size.ST35 and ST40 promote the contribution rate of organic carbon to the number of aggregates and help to increase the organic carbon content in 0-40 cm soil layer.4.Spatial and temporal characteristics of soil moistureThe depth of subsoiling has a significant effect on the spatial and temporal distribution of soil moisture,and it significantly improves the soil water content at all levels of soil.Compared with CT25 and ST30 advanced treatment,ST35 and ST40 significantly increased the field water holding capacity of 0-40 cm soil layer,and the saturated water content of 20-40 cm soil layer was increased by loose structure,the deep pine ditch formed by deep pine enhanced the initial infiltration performance of the soil,and the disturbance to the bottom of 30-40 cm plough increased the stabilization rates of ST35 and ST40,and increased the soil water storage capacity of 40-60 cm soil layer.The results of two years showed that the difference of subsoiling depth significantly affected the physical properties of plough soil,the spatial and temporal distribution of soil moisture and the increase of crop yield.Compared with the traditional tillage depth of 25 cm and 30 cm,the treatment of 35 cm and 40 cm reduced the soil bulk density of 20-40 cm in the plough layer and the soil porosity of 30-40 cm,enhanced soil structural stability(MWD)and aggregate carbon storage,reasonably regulated the spatial and temporal distribution of soil moisture,improved soil water storage capacity and water use efficiency,and increased crop yield efficiency.Considering the improvement of soil physical properties and its economic benefits,the subsoiling depth of 35 cm is the reasonable subsoiling tillage depth in this area. |
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