The effects of phosphorus addition on phytoavailability of zinc by diffusive gradients in thin films (DGT)

Diffusive gradients in thin films (DGT) have been used for the assessment of Zn phytoavailability. Phosphorus is of particular interest in soils having Zn toxicity because of the Zn–P interaction. A greenhouse study was carried out to assess the influence of different P rates on the Zn phytoavailability to sorghum-Sudan grass (Sorghum vulgare var. sudanese) in soil systems by DGT. Soil was amended with ZnSO4 at 0, 150, 300, 600, and 1200 mg Zn kg^–1 in order to create various levels of Zn phytoavailability. Phosphorus was applied to soil at 0, 100, and 200 mg P kg^–1 as KH2PO4. Plant nutrients were added as Hoagland’s solution. In general, plant tissue Zn concentrations were elevated by increasing Zn concentration in soils, and they decreased by increasing P concentrations. However, this reduction was not found in C-DGT results. In other words, DGT did not predict the effects of P additions compared to Zn. P application decreased plant Zn concentrations and increased plant biomass yields. The highest relative yield in shoot tissue was with P200 × Zn150 treatment, while the lowest one was with P0 × Zn1200 treatment. In general, increasing P concentrations in the soil increased shoot yields relative to control, while increasing Zn concentrations decreased the relative shoot yields where no P was added. P addition might be an alternative strategy for remediation of Zn contaminated soil, since addition of P decreased Zn phytoavailability and enhanced plant growth.