弃耕行为对亚热带农田土壤有机质 时空变化作用机理研究.

With the acceleration of non-agricultural processes in China, the marginal cost of agricultural production is increasing, leading to the increasingly serious phenomenon of disordered abandonment and its adverse impact on national food security. Therefore, it is necessary to analyze the mechanism of abandoned behavior on the quality of cultivated land, especially the key index of farmland soil organic matter. In this study, the farmland of Haifeng, Lufeng, and Luhe, the main grain-producing areas in east Guangdong, was used as target areas. From 2015 to 2018, 205 typical subtropical farmland samples were tracked and monitored. Field survey and sampling, household surveys, and indoor laboratory analysis were used in combination with statistical analysis and a geodetector method to construct the typical abandonment behavior pattern in the study area and analyze the mechanism of the effects of abandonment on soil organic matter content in farmland under different geographical conditions. Results showed that there were four patterns of farmland abandonment in the study area：seasonal abandonment, adjustment abandonment, annual ring abandonment, and long-term abandonment. Among the total monitoring sites, 173 farmland samples were abandoned, accounting for 84.39% of the total, of which annual ring abandonment and long-term abandonment accounted for 59.03% of the total. Soil organic matter increased under all kinds of abandoned tillage patterns but decreased under long-term tillage. Results showed that the average increase during the four years was as follows：season abandonment （1.55 g kg-1 ）> adjustments abandonment（1.43 g·kg-1 ）> annual ring abandonment（0.27 g·kg-1 ）> long-term abandonment（0.24 g·kg-1 ）> long-term cultivation（-0.42 g kg-1 ). For different geographical situations, as the altitude increased, the of abandoned farmland in the soil organic matter decreased. If the water content in the field was too high or too low, the abandonment behavior would significantly affect soil organic matter. Compared with coastal sandy soil, the response of soil organic matter in lateritic red soil and red soil with higher bulk density was stronger than that in coastal sandy soil. Therefore, it is necessary to focus on the prevention of farmland quality degradation caused by abandoned tillage in the mesa area, in irrigated land, and in areas containing soil type with high bulk density. The behavior of farmland abandonment is very serious in some areas of China. Moreover, the effects of different types of abandoned land on soil organic matter content are different under different geographical situations. Therefore, it is necessary to formulate relevant policies and regulations to convert disordered abandonment into orderly abandonment. [ABSTRACT FROM AUTHOR]