Effects Of Modifiers On Zinc-Chromium Accumulation And Nutrient Absorption Of Rice Roots

Farm soil from Sichuan Agricultural University was selected to be cultivated for the zinc and chromium contaminated soil and rice was chosen as the experiment materials; four modifiers (organic modifiers:straw chicken manure, inorganic modifiers: superphosphate and quicklime) were applied in the contaminated soil with the high concentrations(straw,chicken manure and superphosphate:8g/kg;CaO:1.5g/kg respectively), middle concentrations(straw, chicken manure and superphosphate:6g/kg,CaO:1.0g/kg respectively, and low concentrations(straw, chicken manure and superphosphate:4g/kg; quicklime:0.5g/k respectively).Pot experiment of rice was carried out to study the changes of the contents of zinc and chromium and the nutrient(N,P,K) in the soil after the application of the modifiers,and the effects of the zinc and chromium accumulation and the nutrient absorption in the roots(root surface absorption and root accumulation) by the modifiers at different stages(the tillering booting and filling stages), to provide scientific basis for the safety production of rice in the heavy metal contaminated soil and the application of modifiers to restore the zinc and chromium pollution.1.At different growth stages of rice, straw, chicken manure and quicklime reduced the available zinc contents at different concentrations, except that the superphosphate at different concentrations did not reduce the available zinc contents;and compared with the. CK during the same period, the available zinc contents significantly reduced by 77.51%,42.28% and 69.18% respectively when treated by the high quicklime concentration. The minimum of the soil available chromium content, which reduced by 33.69%,27.25% and 39.78% respectively compared with the CK during the same period,appeared in the high straw concentration treatment; while there was no significant change in the chicken manure, superphosphate and quicklime treatment with different concentrations.It showed that high concentration of the quicklime and straw played a significant role in reducing the available zinc and chromium contents and the restoration of the contaminated soil.2. At the different growth stages of rice, the maximum of soil alkaline hydrolyze nitrogen appeared in the high concentration of the chicken manure, and reduced by 148.03%,176.26%andl 19.39%,respectively compared with the CK during the same period; that of the soil available potassium appeared in the high concentration of the straw;while that of the available phosphor appeared in the high concentration of the superphosphate. It indicated that high concentrations of chicken manure,straw and superphosphate played an important role in the improvement of the different nutrient efficiency of rice at different stages.3.At the tillering stage, compared with the CK during the same period, the maximum of reduction of zinc absorption on root surface and that in the roots reduced by 61.62%, 52.11%,respectively,while at the booting and filling stage, the maximum of reduction of zinc contents in the roots appeared in the high concentration of chicken manure;the maximum of reduction of zinc absorption on root surface and that in the roots reduced by 30.84%,38.32% and 60.72%,70.24%,respectively compared with the CK during the same period. The maximum chromium content showed a similar trend with zinc contents in the rice roots.This suggested that the organic modifiers (straw, chicken manure),among the two types of modifiers (organic and inorganic), had significant impact on the zinc and chromium absorption on root surface and accumulation of zinc and chromium in the roots. Obviously, organic modifiers reduced the absorption of the zinc and chromium mainly through the direct effect on rice roots.4.At the tillering and booting stage, the maximum of the total nitrogen in roots appeared in the high concentration of straw, compared with the CK during the same period,the maximum absorption of the total nitrogen on the root surface and that in the roots increased by 203.37%,49.81% and 202.38%,35.25%,respectively;while at the filling stage that appeared in the high concentration of chicken manure, compared with the CK during the same period,the maximum absorption of the total nitrogen on the root surface and that in the roots increased by 68.8%,68.84%,respectively.The maximum total potassium content showed a similar trend with the total nitrogen content in the roots.And the maximum of the total phosphorus content in roots appeared in the high concentration of superphosphate.Obviously, the application of the organic and inorganic modifiers could increase the availability of the soil nutrient of rice roots,improve the active absorption capacity of the nutrient by the roots and promote the root growth.