Effect of tillage mode on soil structure characteristics of plough layer and sug-arcane yield

In order to establish the mechanical deep-ploughing technology of sugarcane for formation of good plough layer soil structure, the effect of tillage modes on soil plough layer structure and yield components of sugarcane were investigated. An experiment with 3 tillage measures under two planting rows of sugarcane were conducted. The two planting rows were 1.4 m and 1.6 m, respectively, while the subsidiary treatments included three tillage modes as follows-25 cm rotary tillage (as control), 35 cm sub-soiling plus 25 cm rotary tillage (sub-soiling), 50 cm deep plowing plus 25 rotary tillage (deep plowing). Sugarcane yield characteristics, together with soil bulk density, compactness, porosity, three-phase volumetric rate, field water holding capacity, penetration resistance and shear strength were investigated. The results demonstrated that stem yield of 1.6 m rows spacing was significantly lower than that of 1.4 m rows spacing. Also soil compactness of 1.6 m rows spacing was remarkably lower than that of 1.4 m rows spacing. Soil bulk density of 1.6 m rows spacing was strikingly higher than that of 1.4 m rows spacing. The results also indicated that 1.6 m rows spacing significantly improved penetration resistance and shear strength of soil. Also both the sub-soiling and deep plowing significantly increased sugarcane yield. Compared with the control, the sub-soiling and deep plowing treatments increased soil tillage layer depth, and also improved soil com-pactness and bulk density along with the overall porosity of plough layer. It also showed that sub-soiling dramatically increased total porosity of plough layer soil especially capillary porosity of soil. Field water holding capacity of deep soil also greatly improved by sub-soiling, which finally significantly enhanced plant height elongation and stem diameter thickening at the middle and late growth stages of sugarcane. Also both sub-soiling and deep plowing significantly decreased soil penetration resistance, but with insignificant effect on soil shear strength. Among the three tillage measures, there was no significant difference in volume rate of the liquid phase. However, sub-soiling had the smallest solid volume rate and the largest gas phase volume rate. Then the control resulted in the largest solid volume rate, but the smallest gas phase volume rate. In conclusion, sub-soiling and deep plowing had positive effects on soil physical structure and significantly increased yield of sugarcane. We also concluded that in sugarcane planting areas where large horsepower tractors and high quality loosen machines were used, 35 cm sub-soiling + 25 cm rotary tillage method was the most suitable tillage mode. However, in areas without large horsepower tractors and high quality sub-soiling devices, thick plough layer was maintained by the use of 50 cm deep plowing + 25 cm rotary tillage measure.