Effects of EDTA, Sheep Manure Extract, and Their Application Time on Cd Uptake by Helianthus annuus from a Calcareous Mine Soil

Abstract

Sunflower (Helianthus annuus L.), a potential phytoextraction plant, can accumulate high concentrations of Cd from metal-contaminated soils. Helianthus annuus was grown in a mine calcareous soil treated with increasing concentrations of EDTA (0, 0.5 and 2 g EDTA kg⁻¹ soil) or sheep manure extract (0, 0.5 and 2 g SME kg⁻¹ soil) 30 or 10 days before sowing (T1, T2) and 10 or 30 days after sowing (T3, T4). The EDTA application before seed germination reduced sunflower seedling emergence and dry weight. Cadmium concentrations in harvested shoots increased with EDTA concentration but the actual amount of phytoextracted Cd decreased at high EDTA concentrations, due to severe growth depression. Although application time of SME had no significant effect on shoot dry weight, it had significant effect on Cd uptake by Helianthus annuus. Applying 0.5 or 2 g SME kg⁻¹ at T3 or T4 increased the DTPA-extractable Cd in soil and the metal concentrations accumulated in shoots and roots of sunflower. The results showed that the most efficient treatment for Cd phytoextraction by sunflower is application of 0.5 g SME per kg soil at 30 days after sowing. However, the removal efficiency of Cd from soil was very low (0.15%).

Keywords:

• cadmium
• phytoextraction
• Helianthus annuus
• EDTA
• sheep manure extract
• application time

Notes

*Values with different character for each parameter are significantly different.

**Sheep manure extract.

*Values with different character for each parameter are significantly different.

**Sheep manure extract.

*Values with different character for each parameter are significantly different.

**Sheep manure extract.

*Values with different character for each parameter are significantly different.

**Sheep manure extract.