Reduced colloidal phosphorus loss potential and enhanced phosphorus availability by manure-derived biochar addition to paddy soils

Abstract

Colloidal phosphorus (Pcoll) and available phosphorus (AP) are of fundamental importance in the nutrient cycle in soil solutions and subsurface drainage of ecosystems. Although many studies have been conducted on soil P loss and P availability, there remains limited focus on the relationship between Pcoll and AP. In this regional-scale study, soils with loam texture were collected from 63 paddy fields in southern China to explore the relationships between Pcoll and AP as well as other soil parameters. Subsequently, three typical paddy soils (sandy loam, silt loam, and clay loam) were incubated to study the effect of cattle manure biochar (CMB) amendment on Pcoll and AP at three application rates (0, 1, and 2%, w/w) for 30 d. The results showed that Pcoll was closely related to AP (R2 = 0.453, P < 0.05) and pH (R2 = 0. 487; P < 0.05) on a regional scale. In addition, clay loam soils contained higher Pcoll than the other soil types. The CMB amendment increased the AP by 129.0–872.0% but reduced the Pcoll by 9.65–22.95%, in which colloidal molybdenum-nonreactive phosphorus (MUPcoll) was reduced by 7.69–34.15% and colloidal molybdenum-reactive phosphorus (MRPcoll) was reduced by 5.13–22.73%. Multiple linear regression revealed that the release potentials of Pcoll (R2 = 0.735), MRPcoll (R2 = 0.543), and MUPcoll (R2 = 0.512) could be predicted by the dissolved organic carbon, total carbon, pH, and AP. Overall, this study confirmed that the application of CMB reduced the loss of Pcoll from paddy soils and enhanced the soil AP content.