Influence Of Coal Based Humic Acids On Soil Available Zn And Pak-choi

The leaching experiment, germination test, and greenhouse pot experiment were conducted to study the effects of different coal based humic acids and exogenous Zn on the soil Zn leaching, pak-choi seed germination rate, soil nutrient, soil total Zn and form distrbution of Zn, pak-choi growth and Zn content and distribution. The results showed that:(1) The Zn contents in eluents of deionized water and5%KCl solution were decreased as the soil column heights increased in the treatments of11coal humic acids and EDTA.The Zn contents in eluents of first deionized water were higher than that in eluents of second deionized water. The Zn contents in eluents of5%KCl solution were higher than that in eluents of second deionized water. The leaching rate of5%KCl solution was higher than that with deionized water.The No.6and No.9coal based humic acids had the passivation effect on soil Zn and inhibited the mobility of Zn. The No.10and No.11coal based humic acids had the activation effect on soil Zn and promoted the migration of Znin soil, but the activation effect on Zn was less than that of EDTA.(2) Adding Exogenous zinc of both100mg/kg and200mg/kg promoted the germination of pak-choi seeds, and the effect of100mg/kg zinc was greater than that of200mg/kg zinc. The foure tested coal based humic acids and EDTA promoted the germination of pak-choi seeds at different degree, and No.10, No.11coal based humic acids and EDTA had greater promotion effect than No.6and No.9coal humic acids.(3) The addition of exogenous Zn significantly reduced the fresh weight per plant of pak-choi. On the basis of adding exogenous zinc, No.10coal based humic acid had significantly inhibition effect on plant height, plant fresh weight, and root fresh weight of pak-choi, followed by No.6coal based humic acid. No.9and No.11coal based humic acids and EDTA had little effect on plant height, plant fresh weight, and root fresh weight of pak-choi.(4) The addition of exogenous zinc significantly increased the absorption and accumulation of pak-choi to nitrogen. On the basis of adding exogenous zinc, different coal humic acids and EDTA improved the nutrient contents of pak-choi at different degrees.(5) The addition of exogenous zinc significantly improved the soil total nitrogen content and significantly decreased the contents of soil available P and available K. On the basis of adding exogenous zinc, No.6, No.9, and No.11coal humic acids reduced the content of total nitrogen in soil at different degrees, but No.10increased the content of soil total nitrogen. All treatments except No.6coal humic acid all increased the contents of available P available K in soil. No.10, No.11coal humic acids and EDTA increased soil organic matter content at different degrees, but the No.6and No.9coal humic acids decreased the content of soil organic matter.(6) Addition of exogenous zinc significantly increased the absorption and accumulation of zinc in Pakchoi roots, and had not significant influence on the accumulation of zinc in shoot.On the basis of adding exogenous zinc, No.6and No.9coal based humic acids significantly reduced the accumulation of zinc in pak-choi roots, the No.10coal based humic acid significantly promoted the zinc move to the shoot and accumulated in the shoot. No.11coal based humic acid and EDTA promoted more accumulation of the zinc in the roots than that in shoots. The zinc content of pak-choi shoots were lower than that in roots in different treatments.(7) Addition exogenous zinc increased the content of soil total zinc.On the basis of adding exogenous zinc, different coal based humic acids and EDTA significantly increased the content of soil total zinc, and the effect of No.6coal based humic acid was the biggest. From the distribution of zinc in the soil, the residual fraction was highest in all treatments, followed by Fe-Mn oxidation bound fraction, and exchangeable fraction was least. No.6and No.9coal based humic acids increased soil Fe-Mn oxidation zinc and residual zinc at different degree, and reduced the exchangeable zinc. No.10, No.11coal based humic acids and EDTA increased exchangeable zinc and carbonate bound zinc at different degree, and reduced the content of Fe-Mn oxidation zinc and residual zinc. All treatments increased the content of organic zinc at different degrees.