设施栽培地土壤富营养化及其潜在的环境影响

Nutrients Accumulation in Soil Profile under Greenhouse Cultivation and Their Potential Environmental Effects

采用野外采样与室内分析相结合的方法,探讨了武汉市郊设施蔬菜地土壤有机质和氮、磷、钾养分的累积状况及剖面分布特征,同时分析了土壤pH值的变化。研究结果表明：（1）与露天菜地和植棉地相比,设施蔬菜栽培地耕层土壤有机质含量比露天菜地和植棉地分别增加了14.7%和36.7%,全氮与碱解氮含量在不同栽培类型间的变化趋势及程度与有机质的变化态势趋近;（2）硝态氮在设施栽培地的耕层土壤中有明显累积,其含量分别是露天菜地和植棉地的1.6倍和5.3倍,其均值达到151.35 mg/kg,硝态氮构成了设施菜地土壤中速效氮的主要成分。在0~100cm剖面的各个土层中,设施菜地硝态氮的含量也显著地高于露天菜地,尤其在0~20cm土层中,硝态氮的最高值达到291.5 mg/kg,表聚的硝态氮既会影响食物链安全、亦可能威胁地下水环境;（3）设施土壤表层全磷增加显著,表层土壤速效磷、速效钾水平虽仅略高于露天菜地,但却显著地高于植棉地;（4）设施菜地pH值比露天菜地和植棉地分别下降0.29和0.84个单位,有酸化趋势,可能会增加镉（Cd）等有毒重金属的活性及其生态风险。

A method of field sampling coupled with lab analysis was used to investigate the cumulative state of soil organic matter,nitrogen,phosphorus and potassium in top soil layer as well as their pattern in soil profile under greenhouse cultivation in the suburbs of Wuhan,Hubei Province.Meanwhile the pH changes were analyzed.Results showed that the soil organic matter content in top layer of greenhouse soils increased by 14.7% and 36.7% respectively as compared with that of the uncovered vegetable soils and cotton growing soils.Differences of total nitrogen and alkali hydrolysable nitrogen among 3 kinds of cultivation were like that of organic matters.There was an obvious accumulation of nitrate nitrogen in top layer of greenhouse vegetable soils with average value up to 151.35 mg/kg,which was 1.6 and 5.3 times of uncovered vegetable soils and cotton growing soils respectively,leading in nitrate nitrogen as primary component of available nitrogen.In each of 0～100 cm soil profile,the content of nitrate nitrogen in greenhouse soils was significantly higher than that in uncovered vegetable soils,especially in 0～20 cm soil layer,with the highest value of 291.5 mg/kg.Nitrate nitrogen accumulated in the surface was probably to increase the risk of food chains and groundwater.Total phosphorus in greenhouse soils increased significantly,and available phosphorus as well as available potassium in the surface was significantly higher than that in cotton growing field,even though slightly higher than that in uncovered vegetable soils.pH value in greenhouse soils decreased respectively by 0.29 and 0.84 units as compared with that of the uncovered vegetable soils and cotton growing soils.Soil acidification under greenhouse cultivation may contribute to the activity of heavy metals such as cadmium.