Increased risk of phosphorus and metal leaching from paddy soils after excessive manure application: Insights from a mesocosm study

Livestock manure has gradually become an alternative fertilizer for maintaining soil fertility, whereas excessive application of manure leads to the release of phosphorus (P) and toxic metals that may cause complex environmental risks. To investigate the accumulation and migration of P within soil profiles, a mesocosm experiment was conducted to analyze the content and leaching of soil P, metals, and dissolved organic carbon after different fertilization treatments, including control (no fertilizer, CK), chemical fertilizer (CF), chemical fertilizer combined low (CF + LPM) and high (CF + HPM) rate of manure application. Results showed that a high rate of manure application significantly enhanced the accumulation of total soil P (by similar to 14%) and P availability (easily-available P, by similar to 24%; Olsen-P, by similar to 20%) in topsoil, and also increased the content of easily-available organic P (EA-Po) in both topsoil and subsoil compared to the CK treatment. The migration of dissolved inorganic and organic P (DIP and DOP) in leachate within soil profiles was strengthened by manure application. Moreover, significant positive correlations between P, metals, and dissolved organic carbon (DOC) in leachate indicated that downward co-migration occurred within the soil profiles, and also suggested that excessive manure application can intensify the risk of P loss by increasing the migration of manure-derived DOC. Overall, our findings provide insights into P accumulation and migration within soil profiles after excessive manure application, which is useful for predicting the potential risk of P and metal leaching from paddy soils. (C) 2019 Elsevier B.V. All rights reserved.