关键词:  , 粉垄, 坡耕地, 土壤矿化, 土壤团聚体, 蔗田

Abstract:  It is the main way of rain-fed sugarcane in smash ridging production in hilly areas of south China. In order to explore the effects of slope farmland on the mineralization rate, accumulation of mineralization, soil aggregates and compact-degree structure of rain-raised sugarcane soil. In 2018-2019, smash ridging and conventional tillage were adopted in Nanning, Guangxi. Field positioning experiments were carried out on flat land and sloping farmland with no artificial irrigation during the whole growth period. Soil samples were collected in the 0-15cm topsoil and 15-30cm topsoil during the harvest period of sugarcane, and soil compactness meter was used to measure soil compactness at a depth of 0-45cm at multiple points. Soil aggregates were determined by wet sieve method. The content of soil organic carbon mineralization was determined by indoor constant temperature culture-alkali absorption method. The results showed that, (1)the soil organic carbon accumulative mineralization of rain-fed sugarcane soil in flat land is always higher than that in sloping farmland, the soil organic carbon mineralization in the 0-15cm topsoil and 15-30cm topsoil of the flat land under smash ridging was 0.32 and 1.05 times higher than that in the sloping farmland, respectively. The cumulative mineralization of organic carbon in the 0-15cm topsoil and the 15-30cm topsoil of the sugarcane field increased and decreased by 81.7% and 7.5%, respectively, and decreased and increased by 8.4% and 2.6%, respectively, in the flat land. (2)The content of large aggregates in the soil of rain-fed sugarcane was increased by smash ridging. Flat land and sloping land increased by 5.53 and 5.30 percent respectively. The content of large aggregates in flat soil was 1.00-1.03 times of that in sloping farmland. On the contrary, smash ridging reduced the content of small and micro aggregates in rain-fed sugarcane. The average mean weight diameter (MWD) and geometric mean diameter (GMD) of soil water stable aggregates were improved by smash ridging. Compared with conventional cultivated plain land and sloping farmland, MWD increased 15.6% and 58.7%, respectively, and GMD increased 31.4% and 48.1%, respectively. The MWD and GMD values of soil water stability aggregates in the same tillage mode were higher than those of sloping farmland. The MWD values of flat land conventional tillage and smash ridging tillage were 1.19 and 0.60 times higher than that of slope farmland respectively, and the GWD values of flat land conventional tillage and smash ridging tillage were 0.99 and 0.77 times higher than that of slope farmland respectively. (3)The soil compactness of rain-fed sugarcane was affected by smash ridging more than that of plain field. The soil compactness of rain-fed sugarcane was decreased by smash ridging, and the effect was most obvious at 15-30cm. Therefore, rain-fed sugarcane in smash ridging improves the carbon storage in the topsoil of flat land and slope farmland, reduce soil compactivity, increase the formation of large aggregates, and optimize the topsoil structure. This model can be used as a technical measure to control drought and stress in sugarcane fields in southern China.

Key words:  Smash ridging, Slope farmland, Soil mineralization, Soil aggregate, Sugarcane field