Abstract
Abstract. Riparian buffers can trap sediment and nutrients sourced from upper cropland, minimizing the eutrophication risk of water quality. This study aimed to investigate the distributions of soil inorganic phosphorus (Pi) forms among profile and particle-size fractions in an established riparian buffer and adjacent cropped area at the Dian lake, southwestern China. The Ca-bound fraction (62 %) was the major proportion of the Pi in the riparian soils. After 3 years' restoration, buffer rehabilitation from cropped area had a limited impact on total phosphorus (TP) concentrations, but has contributed to a change in Pi forms. In the 0–20 cm soil layer, levels of the Olsen-P, non-occluded, Ca-bound, and total Pi were lower in the buffer than the cropped area; however, the Pi distribution between the cropped area and the buffer did not differ significantly as depth increased. The clay fraction corresponded to 57 % of TP and seemed to be both a sink for highly recalcitrant Pi and a source for labile Pi. The lower concentration of Pi forms in the silt and sand particle fraction in the surface soil was observed in the buffer area, which indicated that the Pi distribution in coarse particle fraction had sensitively responded to land use changes.
Highlights
Eutrophication of surface water has been linked to the runoff of excess nutrients from agricultural soils in many parts of the world
Because of the filtering function of soil, the effectiveness of riparian buffers in reducing sediment and nutrient loading in surface and subsurface flows from cropland has been shown across many geographic regions (Dosskey et al, 2010; Keesstra et al, 2012)
Soil organic carbon (SOC) and nitrogen (N) concentrations at the NL sites were significantly higher than the HG and XL sites (Fig. 3)
Summary
Eutrophication of surface water has been linked to the runoff of excess nutrients from agricultural soils in many parts of the world. Minimizing the risk of P enrichment of surface water bodies with P transported from soils will require specific attention to the forms of P in soils. Phosphorus distribution in chemical fractions can vary among land uses, which can be a useful indicator for assessing the potential stability of P in soils (Sheklabadi et al, 2014). Soil inorganic P (Pi) has been considered as a greater risk for eutrophication of surface water than the organic forms of P (Mooer and Reddy, 1994; Kang et al, 2011). The conversion of cropped soils to buffer strip can alter P stability. The conversion of cropped soils to buffer strip can alter P stability. Roberts et al (2012) found that the buffer strip soils are enriched in soluble P compared with adjacent agricultural land. Schroeder and Kovar (2006) reported that levels of the iron (Fe)-P fractions were higher in the buffer area than crop field over a 20-year period
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