NPK养分对Pb在土壤-玉米系统中转化行为的影响

NPK Effects on the Transformation of Pb in Soil-Maize System

采用根袋技术,研究了NPK养分对土壤-玉米系统中Pb转化行为的影响。试验设5个处理:NPK、NP、NK、PK和CK(不施肥)。结果表明,P对土壤中Pb有显著的固定作用,与不施P处理相比,根际与非根际土壤中交换态Pb降低了4%～9%,根际土壤残渣态Pb增加了5%～8%,非根际土壤增加了5%～12%。加入N后,土壤pH显著下降,P固Pb作用显著增强,交换态Pb降幅增加了1%～4%,残渣态增幅提高了3%～6%。根际土壤残渣态Pb含量较非根际显著降低,根际过程对土壤中残渣态Pb的形成有显著的抑制作用。这可能与根际土壤较高的可溶性有机物含量、微生物活性以及酸性环境等有关。CK处理玉米地上部Pb含量最高,施P大大降低了玉米地上部Pb含量,其约为CK处理的1/2。与NK相比,CK地上部Pb含量也显著增加。因此,Pb在低肥力污染土壤中,生物有效性更大。

The rhizobag method was employed to investigate the effect of NPK on the transformation of Pb in soil-maize system.Five treatments were arranged：NPK,NP,NK,PK,CK （deionized water only）.Results showed that the transformation of Pb varied greatly in different treatments.Compared with P-unfertilized treatments,the exchangeable fraction of Pb decreased by 4%～9% in rhizosphere and bulk soils,while the residual fraction of Pb increased by 5%～12% in rhizosphere soils and 5%～8% in bulk soils in P-fertilized treatments.With addition of N,Pb immobilization by P was enhanced.The decrement of the exchangeable fraction increased by 1%～4%,and the increment of the residual fraction improved by 3%～6% in comparison to the PK treatment.The residual fractions of Pb in rhizosphere were significantly lower than those in bulk soils in all treatments.Hence,rhizospheric processes had the negative effect on the formation of the residual fraction.This may be due to the low pH,high dissolved organic carbon content and microbial activity in rhizosphere.The greatest shoot Pb content was observed in the CK treatment,which was significant grater than that in the NK treatment,and was about 1 time higher than that in P-fertilized treatments.Therefore,application of P can significantly decrease shoot Pb concentration,and the bioavailability of Pb enhanced in soil with poor nutrition condition.