Abstract
PurposePersistence 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 effects of municipal waste compost (MC) and sheep manure (SM) on metribuzin degradation and phytotoxicity of this herbicide.MethodsIn 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 fortification of selected samples. A liquid extraction method was chosen and final extracts were analyzed by HPLC. In bioassay study, the phytotoxic effects of different 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.ResultsThe 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 non-amended soil as compared to 87.72 and 103.43 days in MC and SM application, respectively. MC was the most efficient treatment to accelerate metribuzin dissipation from the soil. Bioassay results showed that metribuzin residues had a negative effect on root and shoot biomass of oilseed rape. However, the root parameter was more sensitive than the shoot.ConclusionsIt 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.
Highlights
Triazine herbicides are one of the most widely used herbicide classes and play a major role in managing the weed populations in the agricultural production systems
The present study revealed that metribuzin residues at concentrations higher than 0.2 mg kg−1 soil had an irretrievable effect on oilseed rape; the application of municipal waste compost (MC) and sheep manure (SM) has led to a decrease in the susceptibility of this plant to metribuzin residues in the soil
By knowing the level of metribuzin residues in the soil and the effect on sensitive crops, agricultural managers can apply the necessary considerations about crop rotations if sensitive crop such as oilseed rape is supposed to be planted in the field that was previously treated
Summary
Triazine herbicides are one of the most widely used herbicide classes and play a major role in managing the weed populations in the agricultural production systems. These herbicides are valued because of their low costs, moderate persistence, and long season weed control in. Some researchers reported that the application of organic-based fertilizers under different situations increases the herbicide degradation and movement in soil and under other conditions may decrease them (Singh 2008; Fernandez-Bayo et al 2009; Kravvariti et al 2010). Different studies showed that the addition of organic matter including manures, composts, and plant residues to soils is a widely accepted non-chemical approach for improving the soil characteristics as well as the different crop production (Garcia-Gomez et al 2002; Perez-Murcia et al 2006; Bastida et al 2008; Mehdizadeh et al 2013; Pampuro et al 2017a). Cox et al (2000) concluded that the infertile soils had a minimum effect on herbicide movement; the presence of organic matter can be considered as an important adsorbent for herbicides
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