Abstract
Soil erosion on slope farmland causes the degradation of soil quality and eutrophication of water bodies due to the loss of phosphorus. In order to explore the influence of soil mechanical composition and mineral composition on phosphorus fixation, we selected calcareous soil on slope farmland in the Three Gorges Reservoir area as the research object and separated the samples on the basis of particle size. Next, we determined the content of different forms of phosphorus for each particle size, and then characterized and analyzed the mineral composition. The adsorption performance of each particle size was also studied. The results show that the calcareous soil on slope farmland has a high proportion of coarse fractions, and the carbonate minerals enriched in coarse fractions will fix a large amount of phosphorus and degrade soil quality. As slope farmland is prone to soil erosion, when the soil undergoes selective migration, the loss of fine fractions will increase the proportion of coarse fractions and aggravate soil quality degradation. Meanwhile, because of the large amount of phosphorus adsorbed by fine fractions, the available phosphorus is easily lost with fine fractions, leading to eutrophication of water bodies.
Highlights
Slope farmland refers to the cultivated dry land distributed on a hillside
The slope farmland in the Three Gorges Reservoir area (TGRA) accounts for a high proportion (42%) [3], and it overlaps with the heavy rain area in the Yangtze River Basin [4], resulting in serious soil erosion in the area
The soil samples were separated on the basis of particle size (Table 3)
Summary
When the landform slope type is between 6 and 25◦ and it is cultivated, it can be called slope farmland. Due to the instability of slopes and uneven rainfall [2], slope farmland is prone to soil erosion, which carries soil, nitrogen, phosphorus, and other nutrients into water bodies, leading to siltation of rivers and lakes and eutrophication of water bodies. Calcareous soil, accounting for 34.1% of the total area of the reservoir area [6], is one of the main soil types in the TGRA, and one of the soils with a high risk of loss. Calcareous soil on slope farmland is a main source of soil erosion in the reservoir area
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