| Phosphorus（P）is an important soil factor that limits plant growth and affects the environmental behavior of heavy metals in calcareous soils.However,it is not clear how to apply P to improve the biomass of hyperaccumulator without affecting the shoot absorption of heavy metals.Therefore,the present study focused on the slightly contaminated calcareous soil under sewage irrigation with cadmium（Cd）in the upper reaches of the Yellow River.Using the Cd hyperaccumulator Solanum alatum（S.alatum）as the test plant.To investigate the enhancement effect of P application on Cd phytoremediation efficiency,we used different growth stages,different forms,and phosphorus solubilization bacteria enhanced P application modes.The results are as follows:（1）Compared with the control,the biomass of stems and leaves of S.alatum treated with different topdressing patterns at seedling stage,full flowering stage,and fruit setting stage changed significantly,with an increase of 0～30%and 5～38%,respectively.The biological enrichment factor（BCF）and transfer factor（TF）of Cd in the shoot increased to 1.15～1.19 times and 1.04～1.38 times,respectively.Cd extraction by plant shoots was increased by 22 to 53%.The addition of 1/2,1/8,1/4and 1/8 P in basal fertilizer,seedling stage,full flowering stage and fruit setting stage was the best way to improve the efficiency of Cd extraction and restoration,and the amount of Cd extraction from shoot reached 16.39 mg plant-1.In addition,through correlation analysis,the application of P induces the decomposition of organic matter,promotes the release of organically bound Cd,and increases the content of available Cd in soil.（2）After the application of different forms of P,such as calcium superphosphate,hydroxyapatite,adenosine triphosphate,inositol hexaphosphate and iron phosphate,the biomass of stem and leaf of S.alatum significantly changed,with an increase of8～16%and 7.5～55%,respectively.The BCF and TF values of the shoot were increased by 0.94～1.26 and 0.84～1.19 times,respectively.The amount of Cd extracted by the shoot increased by 6.6～57%.Among them,the application of 150 mg P kg-1of adenosine triphosphate and 300 mg P kg-1of iron phosphate had the best effect on the improvement of Cd extraction and repair efficiency,and the Cd extraction amount of shoot reached 16.78 mg plant-1and 16.38 mg plant-1,respectively.The increases were 57%and 53%,respectively.In addition,soil p H was reduced by 0.01～0.23 units(except 150 mg P kg-1superphosphate treatment),and soil dissolved organic carbon（DOC）content was increased by 1.00～1.72 times.Together,the content of bioavailable Cd in soil increased by 0.64～2.30 times.（3）Compared with the control,the biomass of stems and leaves of S.alatum changed significantly after the application of phosphate-soluble inoculant at different growth stages,with an increase of 0～40.6%and 6.6～47.3%,respectively.The shoot BCF and TF values were increased by 0.94～1.24 and 0.84～1.11 times,respectively.The amount of Cd extracted by the shoot increased by 20 to 72%.Among them,the treatment of applying phosphorus solubilization bacteria at seedling,full flowering and fruit setting stages had the best effect on improving the extraction and restoration efficiency of Cd plant.The amount of Cd extracted from the shoot of reached 18.40mg plant-1,with an increase of 72%.In addition,the soil p H decreased by 0.08-0.14units,the content of DOC increased by 1.10-1.30 times,and the content of bioavailable Cd increased by 1.29-1.36 times.In conclusion,reasonable application of exogenous P on calcareous soils could not only promote the shoot growth of hyperaccumulator,but also induce the activation and absorption of fixed Cd in soil,and ultimately significantly improve the extraction and remediation efficiency of Cd. |
PDF Full Text Request