COUNTERACTING THE PHYTOTOXICITY OF SOIL CONTAMINATED WITH EXCESS ZINC AND PENDIMETHALIN RESIDUE

摘要

This research has been carried out in order to assess the phytotoxic effect of a light soil (loamy sand) polluted with excess zinc and pendimethalin residue. Another aim has been to evaluate the effectiveness of detoxifying the analyzed soil by amending it with peat (3% of soil mass) or calcium carbonate (according to 1.5 hydrolytic acidity). The experiment consisted of pot trials, kept in a greenhouse, in which the simulated soil contamination with zinc reached the levels of 240 and 480 mg Zn kg~(-1) of soil and pendimethalin was introduced in the amounts determined in soil after the herbicide Stomp 400 SC had been applied while cultivating the preceding crop. When no soil remediation had been performed, adverse interaction of the analyzed pollutants on the yield of sunflower plants was observed, with the availability of zinc being elevated. Soil remediation (peat and CaCO_3 introduced to soil) reduced the unfavourable interaction of both pollutants more strongly than the toxic effect produced by zinc added to soil separately. This effect can be associated with the reduced availability of zinc and accelerated degradation of pendimethalin in the zinc contaminated soil once the soil pH had been improved and the soil enriched with organic matter. This was demonstrated through determinations of the so-called bioavailable forms of zinc (soluble in 1 mol HC1 dm~(-3_) and residual amounts of pendimethalin in soil after harvesting sunflower plants. Pendimethalin was not found in aerial parts of the sunflower.