海南省陵水县蔬菜种植区土壤磷素的积累、固定特性及流失风险评估

The Accumulation and Adsorption of Phosphorus in Vegetable Soils and the Risk of Soil Phosphorus Loss in Lingshui County of Hainan,China

为探究海南陵水黎族自治县蔬菜种植区农田土壤磷素的积累、固定特性及流失风险,对比该县不同种植制度下土壤有效磷含量差异及主要类型土壤对磷的吸附特征,评估蔬菜种植区土壤磷的流失风险。结果表明:蔬菜/粮食作物轮作区土壤磷素积累明显,有效磷平均含量多在30 mg·kg^-1以上;而单一粮食作物轮作区土壤磷素缺乏,有效磷平均含量通常在22 mg·kg^-1以下,25.39%的土壤样品有效磷含量低于3 mg·kg^-1。区内土壤黏粒含量和无定形氧化铁含量较低,对磷的吸持能力整体较弱,超过80%的样品磷吸持指数(PSI)低于30这一敏感值。研究区不同土壤类型PSI由大到小依次为砖红壤、水稻土和滨海砂土。PSI分别与有机质含量和无定形铁含量之间呈极显著正相关(P<0.01)。土壤有效磷积累明显的东南部蔬菜密集种植区与低固磷能力(PSI<15)土壤在空间上重合,是磷流失的关键源区。除大力实行肥料减量化技术外,针对性加强关键源区磷素流失的控制和缩短种植轮转周期是控制蔬菜种植区非点源磷污染的有效途径。

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.