Purpose

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.

Methods

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.

Results

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.

Conclusions

These results suggest that continual paddy cultivation can effectively maintain soil nutrients in the sandy soils of the tropical river basin.

中文翻译：

---

泰国东北部门河流域不同土地利用方式下土壤养分的比较分析

目的

土地利用/覆盖管理是引起土壤侵蚀的驱动力之一。同时，土壤侵蚀造成的土壤养分流失严重制约了土壤肥力。然而，在易侵蚀的环境中，不同土地利用类型下土壤养分的差异复杂，在热带流域，其影响因素仍不清楚。

方法

在泰国东北部的芒河流域，分别从原生林，人工林，稻田和废弃稻田中选择了六种土壤剖面，分别有1年，3年和5年的废弃历史。土壤养分含量，包括土壤有机碳（SOC），土壤有机氮（SON）和无机矿物质（Al ₂ O ₃，CaO，Fe ₂ O ₃，K ₂分析土壤剖面中的O，MgO和MnO），以确定它们在不同土地利用类型下的分布。通过侵蚀生产力影响计算器（EPIC）模型计算土壤侵蚀性K因子，以估算不同土地利用类型下土壤侵蚀的潜力。此外，通过线性回归分析和Spearman秩相关分析确定了土壤养分与K因子之间的关系。

结果

SOC，SON，Al ₂ O ₃，Fe ₂ O ₃含量明显高于人工林下的粉质土壤。和MnO比原生林下的沙质土壤更重要，这主要归因于粉质土壤中丰富的细颗粒。细颗粒在作为无机矿物质的主要载体以及与有机物结合方面起着关键作用。废弃稻田土壤中的SOC，SON和所有无机矿物的含量均显着低于稻田，这是由于在严重的土壤侵蚀下细颗粒的严重流失所致。与其他土地利用类型下的粗纹理土壤相比，原生林地和稻田中具有大量细颗粒的土壤具有较高的K因子。钾因子主要受门河流域细颗粒的比例控制。由于缺乏保护性管理，水田在放弃土地的早期（1年）很容易发生严重的水土流失，从而导致SOC，SON和无机矿物质减少，而细颗粒的损失则减少了。但是，K通过高盐度地下水的补充，放弃稻田3〜5年后₂ O，MgO和CaO含量显着增加。

结论

这些结果表明，连续稻田栽培可以有效地维持热带流域沙质土壤中的土壤养分。