Impacts of diferent organic amendments on soil degradation and phytotoxicity of metribuzin

Persistence of herbicides in soil is a major concerning world issue due to their negative impacts on environment and human health. Laboratory and bioassay experiments were conducted to evaluate the efects of municipal waste compost (MC) and sheep manure (SM) on metribuzin degradation and phytotoxicity of this herbicide.

In degradation studies, soil samples were mixed separately with amendments at a rate of 2.5% (w/w) and metribuzin at a concentration of 5 mg kg−1 soil was used for fortifcation of selected samples. A liquid extraction method was chosen and fnal extracts were analyzed by HPLC. In bioassay study, the phytotoxic efects of diferent concentrations of metribuzin (0, 0.01, 0.05, 0.1, 0.2, 0.4, 0.8 and 1 mg kg−1 soil) on oilseed rape (Brassica napus L.) were evaluated.

The results indicated 88.8% degradation of metribuzin in MC during 120-day period followed by SM recording 72.2%, compared to non-amended soil where 59.8% of metribuzin were removed. The half-life was 119.48 days in nonamended soil as compared to 87.72 and 103.43 days in MC and SM application, respectively. MC was the most efcient treatment to accelerate metribuzin dissipation from the soil. Bioassay results showed that metribuzin residues had a negative efect on root and shoot biomass of oilseed rape. However, the root parameter was more sensitive than the shoot.

It could be concluded that application of organic amendments to agricultural soils is an eco-friendly strategy to improve soil conditions and non-target crop protection as well as the removal of herbicide residues from soil environment.