Colloid-facilitated transport can be important for preferential transfer of phosphorus (P) through the soil profile to groundwater and may in part explain elevated P concentrations in surface water during baseflow and particularly high flow conditions. To investigate the potential for colloidal P (P_coll) mobilisation in soils, this study assessed the role of soil chemical properties and P fertilizer type on medium-sized soil P_coll (200–450 nm) and its association with soil solution soluble bioavailable P (<450 nm). Hillslope soils from three agricultural catchments were sampled and untreated and treated (cattle slurry and synthetic fertilizer) subsamples were incubated. Soil supernatants were analysed for P and soil Water Dispersible Colloids (WDC) were extracted for analysis of P and P-binding materials. Soils physicochemical properties including degree of P saturation (DPS) and P sorption properties were determined. Results indicated that medium-sized P_coll was mostly unreactive P associated to some extent to amorphous forms of Fe. Medium-sized P_coll concentrations correlated negatively with soil maximum P sorption capacity and soluble P concentrations increased with increasing DPS. In soil with low sorption properties, cattle slurry increased soluble P concentrations by 0.008–0.013 mg l⁻¹ and DPS but did not influence medium-sized P_coll. Synthetic fertilizer increased medium-sized reactive P_coll by 0.011 mg l⁻¹ (0.088 mg kg⁻¹ soil) and DPS in a soil with lower DPS whereas it decreased it by 0.005 mg l⁻¹ (0.040 mg kg⁻¹ soil) in a soil with higher DPS. Additional soil parameters (M3-Fe, M3-Al, M3-P, and DPS) should be included in soil testing, especially in Cambisol/Podzol soils, to identify critical areas where risks of P_coll mobilisation are important. Further research should include the roles of finer colloidal and nanoparticulate (<200 nm) soil P fractions and soluble P to inform understanding of plant uptake and assess environmental risk.

胶体促进的运输对于优先通过土壤剖面将磷（P）转移至地下水很重要，并且可以部分解释基流特别是高流量条件下地表水中磷的浓度升高。为了研究胶态P（P _coll）在土壤中的动员潜力，本研究评估了土壤化学性质和P肥料类型对中型土壤P _{coll的作用}（200–450 nm）及其与土壤溶液中可溶性生物有效性P（<450 nm）的关联。对来自三个农业流域的坡地土壤进行采样，然后对其进行未经处理和经过处理的（牛粪和合成肥料）子样本进行培养。分析土壤上清液中的P，提取土壤水分散性胶体（WDC）以分析P和P结合物质。测定了土壤的理化特性，包括磷饱和度（DPS）和磷吸附特性。结果表明，中等大小的P _coll在某种程度上与无定形形式的Fe相关，大部分是不活泼的P。中型P _coll浓度与土壤最大磷吸收能力呈负相关，可溶性磷浓度随DPS的增加而增加。在低吸附性的土壤中，牛粪浆使可溶性P浓度增加0.008–0.013 mg l ^-1和DPS，但不影响中等大小的P _coll。合成肥料在DPS较低的土壤_中使中等水平的反应性P _coll增加0.011 mg l ^-1（0.088 mg kg ^-1土壤）和DPS，而在其中降低了0.005 mg l ^-1（0.040 mg kg ^-1土壤）DPS较高的土壤中）。在土壤测试中，尤其是在Cambisol / Podzol土壤中，应包括其他土壤参数（M3-Fe，M3-Al，M3-P和DPS），以识别出重要的P _Coll动员风险区域。进一步的研究应包括更细的胶体和纳米颗粒（<200 nm）土壤P组分和可溶性P的作用，以帮助人们理解植物吸收并评估环境风险。