Comparative analysis of soil nutrients under different land-use types in the Mun River basin of Northeast Thailand

Abstract

Land-use/cover management is one of the driven forces to induce soil erosion. Meanwhile, the loss of soil nutrients caused by soil erosion severely restricts soil fertility. However, the differences in soil nutrients under different land-use types in an erodible environment are complex and the factors are still unclear in tropical river basin. In the Mun River basin of Northeast Thailand, a total of six soil profiles were selected from the native forest, artificial forest, paddy land, and abandoned paddy lands with 1, 3, and 5-year abandoned history, respectively. The contents of soil nutrients, including soil organic carbon (SOC), soil organic nitrogen (SON), and inorganic minerals (Al2O3, CaO, Fe2O3, K2O, MgO, and MnO), in the soil profiles were analyzed to determine their distribution under different land-use types. Soil erodibility K factor was calculated by the erosion productivity impact calculator (EPIC) model to estimate the potential of soil erosion under different land-use types. Moreover, the relationships between soil nutrients and the K factor were determined by linear regression analysis and Spearman’s rank correlation analysis. The silty soils under artificial forest were significantly larger for the contents of SOC, SON, Al2O3, Fe2O3, and MnO than the sandy soils under native forest, which was mainly attributed to the abundant fine particles in the silty soils. Fine particles played a key role in being the main carriers of inorganic minerals and combining with organic matter. The contents of SOC, SON, and all inorganic minerals in the soils of the abandoned paddy lands were significantly lower than those in the paddy field, resulting from the severe loss of fine particles under intense soil erosion. The soils with abundant fine particles under the native forest land and paddy land had significantly higher K factors compared to the coarse-textured soils under other land-use types. The K factor was mainly controlled by the proportion of fine particles in the Mun River basin. The paddy field easily occurred severe soil erosion at the early stage (1 year) of paddy land abandonment due to the lack of protective management, which caused decreasing SOC, SON, and inorganic minerals with the loss of fine particles. However, the K2O, MgO, and CaO contents significantly increased after 3 ~ 5 years of paddy land abandonment through the supplement from high salinity groundwater. These results suggest that continual paddy cultivation can effectively maintain soil nutrients in the sandy soils of the tropical river basin.