Soil failure characteristics and loosening effectivity of compacted grassland by subsoilers with different plough points

Mechanical disturbance of compacted grassland soil can reduce the compaction level. This paper aimed to provide recommendations for optimising plough point design and the formulation of grassland loosening operation standards by analysing the disturbance degree and loosening effectivity of compacted grassland soil. A grassland disturbance test was conducted by using different types of plough points (straight, chisel, diamond, and arrow), tillage depths (50, 100, and 150 mm), and shank spacings (250, 300, and 350 mm). A soil disturbance model was established to determine the disturbance threshold of the compacted soil. The results showed that the straight point cut through the grassland soil along the edge of the shank, the chisel point sheared it into strips and blocks, the diamond and arrow point produced furrows in the grassland. The disturbance degree of the grassland soil increased as the tillage depth increased for all four points and as the shank spacing decreased for the chisel, diamond, and arrow point. The average values of the soil disturbance index (SDI) were 1.19, 1.34, 1.30, and 1.22 for the straight, chisel, diamond, and arrow point, respectively. The significance analysis showed that the loosening effectivity of the chisel and diamond point was significantly better than that of the straight and arrow point. The chisel point plot had the highest mean SDI, indicating it was more effective than the other three points in loosening the compacted grassland soil. The optimum loosening effectivity was achieved at a soil disturbance rate of 26%.