Organic phosphorus leaching risk from agricultural soils across China

Abstract

Background Leaching from agricultural land is one of the major pathways of phosphorus (P) loss from soils to waterbody and may induce adverse effect on territorial environment. Past studies usually focused on the loss of inorganic P (PI) while ignored the role of organic P (PO) in leaching process. A total of 63 agricultural soil samples were collected from across China with various soil types including 21 paddy soils, 13 chernozems, 11 red soils and other type soils (n = 18) to identify the potential risk of PO and PI leaching from agricultural lands and to explore their relationships with soil basic properties, Fe/Al oxides, and P status. Results CaCl2-extractable organic P (CaCl2-PO) accounted for 8–89% (35% on average) of CaCl2-extractable total P (CaCl2-PT) and available organic P (APO) accounted to over half of available total P (APT) (57 ± 25%). CaCl2-PT was positively correlated with APT under all soil types except paddy soils. CaCl2-extractable inorganic P (CaCl2-PI) and available inorganic P (API) were strongly correlated for chernozem (r = 0.968), while CaCl2-PO the was strongly correlated with APO for red soils (r = 0.901). Conclusions PO greatly contributed to the potential P leaching risk and should be included in the risk assessment of total P leaching. The control of soil APT excess accumulation in both PO and PI fractions in agricultural land is the key point to cut down P leaching. Mitigation measures to limit PO leaching should be established based on the soil types. Graphical abstract