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Improved soil phosphorus (P) management can be achieved through an understanding of regional soil–P interactions and their relation to soil properties. To this end, soil samples from different use types (paddy soils, dry farmland soils, forest soils, and urban green land soils) were collected from 10 sites across the west to the east of Sichuan Basin, China. These samples were analyzed to determine their P sorption properties and physical and chemical compositions. P sorption was described using a modified Freundlich equation. The results demonstrated a gradient in P sorption within the basin, characterized by higher values in urban areas and a west-to-east decrease trend, along with the null-point values of soil sorption–desorption equilibrium. This variation was linked to the extensive use of P fertilizer, which altered soil particle surface conditions and significantly reduced both the quantity and rate of subsequent fertilizer sorption. Furthermore, P sorption was found to be correlated with the soil clay fraction, amorphous aluminum oxides, and soil organic matter contents. Urban expansion and accelerated erosion of productive agricultural land increase mean soil particle size and may decrease soil P holding and retention capacity. As preliminary deterioration in soil properties was found, conservative soil management is needed to address the potential threats of soil degradation in the central Sichuan Basin. [ABSTRACT FROM AUTHOR]

Background: Purple soil has a fragile structure and is highly vulnerable to soil erosion and phosphorus (P) loss risks. Despite this, the region is endowed with abundant crop residue resources. To ensure sustainable agricultural development in this area, we conducted a study to investigate the impact of crop residue removal on soil aggregate structure, soil erosion, and the risk of P loss. Methods: We conducted a three-year on-farm experiment and analyzed various soil parameters. These parameters include mean weight diameter ( M W D ), geometric mean diameter ( G M D ), soil aggregates with a diameter greater than 0.25 mm ( R > 0.25 m m ), saturated hydraulic conductivity, soil erosion estimated by RUSLE 2, total soil phosphorus (TP) concentration, geometric mean concentration of TP ( G M C ), and geometric mean concentration of TP adjusted for aggregate size ( G M C d ). Results: Retaining all crop residue can significantly improve soil saturated hydraulic conductivity, which was 2.56 times higher than the complete removal treatment. After three years of experimentation, compared to four months, the 50% residue removal treatment increased the G M C d by 32.7%, while the 0% removal treatment increased the G M C d by 16.6%. Both improvements were higher than the complete removal treatment. Partial or complete removal of the crop residue can reduce the soil aggregate stability and increase the risk of soil erosion and P loss. Conclusions: The G M C and G M C d have the potential to serve as indicators for evaluating soil P loss risk. Removing crop residues can cause the degradation of the structure of purple soil aggregates, thus resulting in increased soil erosion and P loss. It is not recommended to remove crop residues in the purple soil region to ensure sustainable agricultural development. [ABSTRACT FROM AUTHOR]

Soil erosion is a global environmental problem related to anthropogenic activities which are influenced by natural factors. The sloping cultivated lands, with serious soil erosion, constitute a significant proportion of the landscape in the remote mountain regions of southwestern China. The traditional soil conservation strategy, involving a certain height of lynchets on the edge of the terracing hedgerows of the sloping lands, plays an effective part in soil and water conservation. A typical sloping landscape with a lynchet of terracing hedgerows was chosen in this study. The objective of this study was to explore soil particle size fraction and spatial redistribution of 137Cs in sloping landscapes with different lynchet heights of terracing hedgerows. The results showed that fine-grained sediments were deposited in front of the lynchet of terracing hedgerows, especially particle sizes grouped at <0.002 mm clay and 0.002–0.02 mm silt. The 137Cs concentration profiles of the lynchet from the upper to the lower sloping landscape showed first increasing and then decreasing trends when the soil depth increased. 137Cs inventory generally increased along with the whole sloping landscapes. Moreover, the results suggested that the mean 137Cs inventory and erosion rate could be represented by the average value of the middle slope position. The highest value of annual erosion modulus reached 4917.06 t km−2 a−1 on the upper site of the sloping lands. Moreover, the annual erosion modulus was synchronously reduced from the upper to the lower sloping landscape and the erosion rate had a similar trend. Meanwhile, the K values of soil erodibility changed from 0.0338 t hm2 h (hm−2 MJ−1 mm−1) to 0.0375 t hm2 h (hm−2 MJ−1 mm−1) along the slope length. There was a logarithmic relationship between the K value and the 137Cs inventory. Therefore, it is useful to study spatial patterns of soil erosion in different slope positions with different heights of lynchet of terracing hedgerows of the whole sloping landscape. Moreover, it is important to implement a soil conservation strategy in the remote mountain regions of China. [ABSTRACT FROM AUTHOR]