Soil Organic Matter Dynamics in a Sloped Sandy Cropland of Northeast Thailand with Special Reference to the Spatial Distribution of Soil Properties

摘要

Sandy soils are widely distributed in Northeast Thailand. We analyzed the spatial distribution of soil properties and the dynamics of organic matter on a sloped cropland near Khon Kaen city in Northeast Thailand. Our research site included a sugarcanefield on the main slope, a mango plantation on the lower slope, a wetland rice field in the lowland, and a teak plantation on the opposite slope. 116 soil samples were collected from this 510 X 270 m field at 30-m intervals, and the spatial distributions of various soil properties were evaluated using geostatistical analysis. A clear spatial variation was observed for organic C and N soil content, particle size distribution, and other related properties. In the teak and mango plantations, the soil texture was finer and the C and N levels were higher than in the sugarcane field. Soil organic matter (SOM) dynamics and soil erosion were postulated to be driving forces behind the observed heterogeneity in soil properties. The dynamics of the SOM were analyzed in five plots, which were representative of the site's topography and land use. Both the SOM stock and annual soil respiration were higher under tree vegetation than in the sugarcane plots, as measured in the upper 15 cm of the soil layer. Annual soil respiration was high, often exceeding 40% of the total SOM stock. The SOM was observed to rapidly increase under tree vegetation through litter input. The redistribution of soil properties through SOM dynamics could be easily implemented in this sandy, sloped land.