Phosphorus and carbon competitive sorption-desorption and associated non-point loss respond to natural rainfall events

- Application of fertilizer increase P loss due to C and P competitive sorption.
- Application of organic and inorganic fertilizers impact on soil DOC and DTP.
- Measure C and P leaching during natural rainfall events.
- Hanges in the stoichiometric C:P ratios by competitive sorption mechanisms.

SummaryLong-term application of fertilizer or manure can increase the potential for P loss risk to ground and surface waters due to C and P competitive sorption-desorption. The aim of this study was to investigate the effect of long-term agricultural fertilizer application on dissolved organic carbon (DOC) and dissolved total phosphorus (DTP) loss. The study was conducted at the Yanting Agro-Ecological Experimental Station in Sichuan Province, People's Republic of China, during the 2012 rainy season. The results show that the variations in C and P leaching effects in fertilized soils exposed to natural rainfall events. As expected, application of inorganic and organic fertilizers increases DOC and DTP concentrations in soil and decreases the C:P ratio. Similarly, application of inorganic and organic fertilizers results in greater C and P leaching than that seen in unfertilized soils. The DOC flux was higher in subsurface runoff than in overland flow. In contrast, overland flow was the main pathway for P transport; subsurface runoff accounted for a smaller proportion of the total P transport. The increase of DOC and DTP was higher after use of organic manures than after treatment with inorganic fertilizers. DOC derived from surface-applied organic manures was found to leach at higher rates than that seen for DTP derived from the same source. However, organic manure-derived DOC was found to transport from soil prior to P, when they are surface-applied, demonstrating a higher sorption affinity of P over DOC compared to inorganic fertilization. Therefore, we should pay more attention to the P mobilized through long-term fertilization and enhance the P uptake due to C and P competitive sorption-desorption, and avoid potential leaching loss of P during rainfall process.