Abstract: The accumulation and adsorption characteristics of phosphorus (P) in tropical vegetable soils were studied to assess the risk of soil P loss from different long-term vagetable cultivation systems in Lingshui County, Hainan Province. The results indicate that vegetable/cereal crop rotation system had significant higher P concentration than other systems, and its available P concentration was normally higher than 30 mg·kg^-1. Deficient level of P was identified for the single-cereal cropped soil, whose available P level was commonly lower than 22 mg·kg^-1. It has also been observed that 25.39% of the sampled soils revealed available P levels lower than 3 mg·kg^-1. The overall capacity of P absorption was low for most of the soils, mainly due to their low clay and amorphous iron oxide concentrations. More than 80% of the samples' P absorption index (PSI) were lower than 30, indicating high P loss risks. The latosol had the highest PSI value, followed by paddy soil and coastal sandy soil. PSI was significantly and positively correlated with the contents of organic matter and amorphous iron. The southeastern vegetable area was identified as the key area of P loss because of its high available P concentration but low PSI level (PSI<15). In addition, implementating fertilizer reduction technology, reinforcing the control of P loss in the key areas and shortening the interval of vegetable rotation cycle were effective approaches to the control of non-point source P pollution in tropical vegetable area.

Key words: vegetable cultivation area, soil P accumulation, P-sorption capacity, risk of loss