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Soil Colloidal P Release Potentials under Various Polyacrylamide Addition Levels

Anionic polyacrylamide (PAM) can prevent soil erosion, but its effect on fine particulate phosphorus (P), such as colloidal P, has not been thoroughly examined. The effects of PAM on the release potentials of water‐dispersible colloids (WDC) and total P, molybdenum‐reactive P (MRP), and molybdenum‐unreactive P (MUP) in the colloidal and truly dissolved phases (i.e., TPcoll, MRPcoll, MUPcoll, TPtruly, MRPtruly, and MUPtruly) from six soils across South China were tested in this study. The results showed that the release potentials of TPcoll in the control treatments were 6·9–46·1 mg kg−1 and generally highest in sandy loam soil. Following low (12·5 kg ha−1), middle (25 kg ha−1), and high (50 kg ha−1) levels of PAM application, the release potential of TPcoll decreased by 41·7, 63·2, and 77·4% compared to the control group, respectively. Additionally, PAM may trigger MRPcoll and TPtruly releases in sandy loam and/or silt soils, and for most soils, MRPtruly and MUPtruly showed the highest release potentials at middle or high PAM levels. A significant PAM application level by soil site interaction for the release potentials of WDC and colloidal P was observed. Multiple linear regression showed that the PAM rate combined with soil sand content can successfully predict the release potentials of WDC (R2 = 0·552, p < 0·001) and TPcoll (R2 = 0·738, p < 0·001). Our results suggest that PAM can effectively reduce the loss of soil colloids and colloidal P, while its effects are related to both application level and soil texture. Copyright © 2017 John Wiley & Sons, Ltd.