Abstract: Tillage has important impacts on soil quality and crop yield. The purpose of this study was to clarify the impacts of deep vertically rotary tillage on soil physicochemical properties, particle size distribution, and stability of latosolic red soil aggregates. We analyzed various indices of soil aggregates stability in sugarcane field under four tillage treatments, including rotary tillage (XG), subsoiling (SF), deep vertically rotary tillage to 20 cm (FL20), and deep vertically rotary tillage to 40 cm (FL40). The results showed that soil fertility decreased in the four tillage treatments after planting sugarcane for one year. Soil pH increased significantly by 0.27-0.31  in the FL40 treatment compared with the XG treatment. There were no significant differences in soil organic matter (SOM) among the various tillage treatments. In 0-40 cm soil layer, content of water-stable aggregates at 0.25-0.5 mm particle size under FL20 treatment was 22.38%-27.33% and 23.78%-31.59% higher than those under XG and SF treatments, respectively. FL40 treatment increased water-stable aggregates at 0.25-0.5 mm particle size in 20-40 cm soil layer. In addition, geometric mean diameter (GMD) and mean weight diameter (MWD) of mechanical-stable and water-stable aggregates under FL20 and FL40 treatments were higher than those under XG and SF treatments. FL20 and FL40 treatments increased aggregate stability rate (WSAR) of water-stable aggregates. The destruction rate (PAD) of water-stable aggregates under FL20 and FL40 treatments was lower than that under XG and SF treatments. The PAD was ertremely significantly negatively correlated with WSAR, bias coefficient (C_S), wet sieve means weight diameter (WMWD), wet sieve geometric mean diameter (WGMD), and >0.25 mm particle size of water-stable aggregates (P<0.01), and was ertremely significantly positively correlated with peak convex coefficient (C_E) and <0.25 mm particle size of water-stable aggregates (P<0.01). Overall, deep vertically rotary tillage significantly enhanced aggregates content and the stability of medium and small particle sizes, as well as soil permeability, and improved soil structure, which in turn could promote soil nutrient mineralization and improve nutrient use efficiency of crops. Therefore, this tillage practice can be used as an efficient and popularized method in latosolic red soil areas.

Key words: deep vertically rotary tillage, latosolic red soil, soil aggregate, water-stable aggregate.