Effects of rainfall and fertilizer types on nitrogen and phosphorus concentrations in surface runoff from subtropical tea fields in Zhejiang, China

The increasing input of fertilizers in tea (Camellia sinensis L.) fields may contribute to the deterioration of surface water quality. A plot study was conducted over a 2-year period (2010-2011) to evaluate the effects of rainfall and fertilizer types on nitrogen (N) and phosphorus (P) concentrations in surface runoff from tea fields. Studies were arranged on slope of 18 % of red clay at a subtropical tea fields in Tiaoxi watershed of Zhejiang province, southeast China. Organic (OF), slow-release (SRF), and conventional chemical fertilizers were applied to different plots at rates of 248 kg N ha(-1) and 125.2 kg P ha(-1) in 2010 and 300 kg N ha(-1) and 100 kg P ha(-1) in 2011. Rainfall amounts showed statistically significant correlations with concentrations of TN and TP in runoff water from all fertilized treatments. Although equivalent N and P were applied in each fertilized treatment, the OF treatment had the lowest annual arithmetic mean concentration of total N in runoff in 2010 (6.1 mg L-1) and was amongst the lowest in 2011 (9.2 mg L-1) with concentration statistically similar to SRF (9.0 mg L-1). The SRF treatment had the lowest annual arithmetic mean concentration of total P in runoff in 2010 (1.50 mg L-1), while few differences were observed in concentration of total P between fertilized treatments in 2011. The research results suggested that replacement of conventional chemical fertilizers with organic or slow-release fertilizers in tea fields could reduce N and P losses while maintaining tea yields.