镉污染土壤上偏施氮磷钾肥对蕹菜产量及镉积累的影响

Effects of Partial NPK Fertilizer Application on the Yield and Cd Accumulation of Water Spinach in Cd Contaminated Soil

为了研究偏施化肥对Cd污染区蔬菜产量和Cd含量的影响,取韶关矿区典型Cd污染菜地土壤和蔬菜品种蕹菜(Ipomoea aquatic),通过盆栽试验,在Cd1(4.0 mg·kg-1)和Cd2(8.0 mg·kg-1)2种土壤Cd污染水平下,设置CK、单倍(NPK)、双倍N(2NKP)、双倍P(N2PK)和双倍K(NP2K)共5种处理,研究偏施氮磷钾肥对土壤p H值、土壤有效态Cd含量、蔬菜产量、Cd含量及其积累量的影响。结果表明:与不施肥相比,在2种土壤Cd水平下,上述4种施肥处理均极显著(P<0.01)降低土壤p H值、提高蔬菜Cd含量及其积累量和富集系数;在Cd1水平下,施双倍N和双倍P处理蔬菜产量极显著(P<0.01)低于不施肥、单倍NPK和双倍K处理,幅度分别达到32.0%、25.6%、22.1%和30.8%、24.4%、20.8%。在Cd2水平下,施双倍N的蔬菜产量极显著(P<0.01)低于不施肥处理22.0%,显著(P<0.05)低于单倍NPK、双倍P和双倍K 16.1%、12.2%和14.5%;在5种处理下,Cd2水平的蔬菜产量均显著(P<0.05)或极显著(P<0.01)低于Cd1水平的。在Cd1水平下,4个施肥处理分别较不施肥处理极显著(P<0.01)增加了蔬菜体内Cd含量66.7%、74.5%、56.8%和72.5%,其中以双倍N处理蔬菜Cd含量最高,但4个施肥处理间差异不显著。在Cd2水平下,4个施肥处理分别较不施肥处理极显著(P<0.01)增加了蔬菜体内Cd含量72.8%、104.9%、88.9%和66.7%。4个施肥处理中以双倍N蔬菜Cd含量最高,极显著高于单倍NPK和双倍K处理18.6%和23.0%。Cd2水平中5种处理的蔬菜Cd含量均极显著(P<0.01)高于Cd1水平的。由此说明,土壤Cd污染水平和施肥水平均会显著影响蔬菜产量及其Cd含量,在Cd污染的土壤应慎重施用NPK肥,特别在高Cd污染土壤上,不能偏施N肥,否则不仅会降低蔬菜产量,还会加大蔬菜Cd污染风险。

In order to study the effects of applying partial nitrogen, phosphate and potash fertilizers on the yield and cadmium （Cd） cumulative properties of water spinach, a pot experiment was conducted by examining the typical Cd contaminated soils in the vegetable fields around Shaoguan mining areas. Two Cd contaminated levels （Cd1, Cd2） and five fertilization treatments （CK, haploid NPK fertilizer, double N fertilizer, double P fertilizer and double K fertilizer treatment） were used in this experiment. The results showed that all types of fertilization treatments, other than the one without fertilizer, significantly lowered the pH values of soil and increased the Cd absorptive and accumulative capacities of vegetables under the two Cd levels. Unlike the sample without fertilizer, haploid NPK fertilizer treatment, the double K fertilizer treatments and the double N and P fertilizer treatments significantly reduced the vegetable yields under the Cd1 level （4.0 mg·kg^-1）. The relative decrease rates for the double N and P fertilizer were 32.0%, 25.6%, 22.1% and 30.8%, 24.4%, 20.8%, respectively. Under the Cd2 level （8.0 mg·kg^-1）, the vegetable yield with the double N fertilizer treatment decreased markedly compared to that of the no fertilizer by 22.0%, and was significantly lower than those of the other three treatments by 16.1%, 12.2% and 14.5%, respectively. In addition, all of the samples with the five fertilizer treatments under the Cd2 level showed lower vegetable yields than those under the Cd1 level. Under the Cd1 level, the Cd contents in vegetables with the four fertilizer treatments were significantly more than those without fertilizer-66.7%, 74.5%, 56.8% and 72.5%. The Cd content with the double N fertilizer treatment was the largest, but there was no significant difference between the four fertilizer treatments. Under the Cd2 level, the Cd contents in vegetables with the four fertilizer treatments were also significantly more than those without fertilizer by 72.8%, 104.9%, 88.9% and 66.7%. In particular for the double N fertilizer treatment, the Cd content was significantly more than those with the haploid NPK and double K fertilizer treatments by 18.6% and 23.0% respectively. Additionally, with the same fertilizer treatment, the Cd contents of vegetables under the Cd2 level were significantly higher than those under the Cd1 level. In summary, the results suggested that both the soil Cd pollution levels and fertilization levels clearly affect the vegetable yield and the Cd accumulative content. Therefore, one should be cautious when using the nitrogen, phosphate and potash fertilizers for the Cd contaminated soil. Especially in the highly Cd-contaminated soil, overuse of N fertilizer would not only reduce the vegetable yield, but also create more hidden problems relating to the Cd pollution risk of vegetables.