Effects Of NP Fertilizers On Activity Of Copper And Lead In Meadow Cinnamon Soil And Their Phytoavailability

The effects of several kinds of nitrogen, phosphorus fertilizers on soil water-solublesalt, Cu/Pb activity in soil and their phytoavailability of wheat were conducted by potexperiments. The changing trendances of soil water-soluble salt with different rates offertilizers application was emphasized, as well as the relationship between soilwater-soluble salt ions and soil available Cu/Pb and accumulation of Cu/Pb in wheatrespectively. For the issue of Cu/Pb transportation and transformation in the soil—plantsystem, the relationship between the change of Cu/Pb activity in soil caused by fertilizerapplications and the growth of wheat, the absorption and accumulation of Cu/Pb by roots,stems and leaves of wheat was further discussed. The results were shown as follows:1. In the Cu-contaminated soil, the soil-pH was decreased and the soil-conductivitywas increased significantly with the increment of N fertilizers; however, they were notobviously changed with the increment of P fertilizers. Under the condition of N fertilizersapplied, the content of the water-soluble cations, Cl^-, SO₄^2- were distinctly enhanced, thecontent of water-soluble P and the HCO₃^- were remarkably reduced. The water-soluble Pcontent, however, was remarkably elevated with the increment of P fertilizers, while otherions content depended on Cu/Pb-polluted soil and varieties of P fertilizers.2. In the Cu-contaminated soil, at lower N fertilizer rate(＜0.3g/kg), the activation ofCu was promoted in soil, and that activation of urea to soil-Cu was weak than NH₄HCO₃.But at higher N fertilizer rate(0.5～0.7g/kg), there weren't remarkable variations of contentof soil available Cu among N-fertilizer treatments and check experiment. The P fertilizersapplied restrained the activation of soil Cu, which caused the content of soil available Cureduced, and the decreasing degree of available Cu caused by (NH₄) ₂HPO₄ was greaterthan that of Ca(H₂PO₄)₂.In the lead-contaminated soil, the influencing rule and the effect of N fertilizers on thesoil available Pb were generally consistent to that of P fertilizers, that is the lower Nfertilizer rate (＜0.3g/kg) remarkably enhanceed the content of soil available Pb, and athigher N fertilizer rate(0.5～0.7g/kg), the content of soil available Pb was not obviouslyincreased. With the increment of P fertilizer, the content of the activation of Pb wasdecreased, especially at the higher P fertilizer rate (0.5～0.7g/kg), the availability of leadwas remarkably reduced in soil. 3. There was a certain correlation between the N, P fertilizers and the Cu/Pbaccumulation in wheat. In the Cu-contaminated soil, the Cu-accumulation amounts inwheat were fluctulated with the increment of the N, P fertilizer—initially increased andfollowing decreased. But the increasing or decreasing degrees of the Cu accumulation inwheat varied with types of fertilizer and the amounts applied. Of them, the highestenhancing degrees for Cu in roots by Ca(H₂PO₄)₂ application occurred, similarly, for Cu instems and leavie by urea. Besides corresponding amounts of fertilizers application for thehighest Cu-accumulation varied with types of fertilizers, ranging from 0.1 to 0.5g/kg. Inthe Pb-contaminated soil, at the lower fertilizers rate of＜0.5g/kg, the changing rule of thePb content in wheat roots showed similar to that of the Cu in the wheat roots with theincrement of N, P fertilizers. While the Pb accumulation in wheat stems and leaivs didn'tchanged obviously with the increment of fertilizers (0.1～0.7g/kg).4. The result of stepwise regression analysis for soil available Cu and soilwater-soluble salt indicated that the effect of the anions on the activation of soil Cu/Pbperformed greater than cations. Water-soluble P, CI, HCO₃^- and Ca²⁺ were the mainfactors caused the change of soil available Cu/Pb, and their relative importances weakenedin following order: water-soluble P＞Cl^-＞HCO₃^-＞Ca²⁺. Whether the activation of soilCu/Pb was promoted or limited by these anions was related to the varieties of fertilizersand Cu/Pb-polluted soils. In few treatments, soil available Cu/Pb to a certain extent wasaffected by only Na⁺, Mg²⁺.5. The correlation analysis of the content of Cu/Pb in wheat roots and soil base ionsindicated that HCO₃^-, SO₄^2- in soil promoted the Cu/Pb accumulation in wheat roots; Theeffect of water-soluble P and cations on Cu/Pb accumulation roots was depended on thevarieties of fertilizers and the type of soil-polluted.6. In the copper-contaminated soil, at the lower N fertilizer rate (＜0.3g/kg), theenzyme activity of POD and CAT were restrained. With the increment of P fertilizersapplied, the POD activity was slightly enhanced, while CAT activity was reduced. In thelead-contaminated soil, with the increment of N fertilizer applied, there was the tendencyof the POD and CAT enzyme activities reduced; While with the increment of P fertilizersapplied, the POD and the CAT enzyme activity were promoted.