Use of organic matter to mitigate multicontaminated soil and sunflower plants as phytoextractor [Uso da matéria orgânica como mitigadora de solo multicontaminado e do girassol como fitoextratora]

The objective of this study was to evaluate the filter cake and peat as sources of organic matter (OM) in order to mitigate contaminated soil with boron, under the sunflower cultivation. The experimental design adopted was completely randomized in a factorial scheme distributed in 2 (organic matter types) × 4 (organic matter dose of each type), with three replications. The doses of each organic material added were based on the content of C, being equivalent to 0, 20, 40 and 80 t ha-1. In each experimental plot, pots containing 5.0 kg of contaminated soil was cultivated with three plants of sunflower during 65 days. The plants showed no symptoms of toxicity of B, Cu and Zn, although high levels were observed in the aerial part. The type of organic matter significantly influenced the dry mass of stem, flower and root, though the addition of filter cake promoted higher production. The time required to remove 50% of the total content of B in soil was 11.1 years without the use of OM, 15 years with the use of filter cake and 25 years with the use of peat. The sunflower has the potential to be grown in the contaminated area and the application of filter cake or peat was not as efficient in mitigation of heavy metals and B