Abstract
The persistence and degradation of two common herbicides, atrazine and bromacil in two organic media, wood pulp and sawdust were compared with two soils. The hypothesis tested was that herbicide degradation will be faster in high organic matter media compared to soil. Degradation of two herbicides was carried out in four different temperature regimes and in sterilised media. The degradation half-life (t½) was determined under above-mentioned conditions then compared to degradation in soil. The degradation as quantified by t½ of the herbicides was generally longer in both organic media. Although microbial degradation was an important factor in the mineralisation of these herbicides, overall, the pH of the media had a more profound effect on the desorption and subsequent degradation rate than the organic carbon content. The results of this study revealed that the hypothesis was only partially correct as organic matter content per se did not strongly relate to degradation rates which were mainly governed by pH and microbial activity.
Highlights
The persistence and degradation of two common herbicides, atrazine and bromacil in two organic media, wood pulp and sawdust were compared with two soils
The reasoning behind this was that herbicides tend to degrade more rapidly in high organic matter soils due to this supporting greater microbial biomass, and high organic matter waste material would be an extension of this
Microbial degradation proved to be an important factor in the mineralisation of these herbicides and was the cause of enhanced degradation in the Horotiu soil which had a long history of application of atrazine
Summary
The persistence and degradation of two common herbicides, atrazine and bromacil in two organic media, wood pulp and sawdust were compared with two soils. Microbial degradation was an important factor in the mineralisation of these herbicides, overall, the pH of the media had a more profound effect on the desorption and subsequent degradation rate than the organic carbon content. In soils with a high organic matter content (generally > 10%), the primary factor controlling herbicide degradation in soil is microbial t ransformation[13]. This degradation often follows a simple exponential decay model and is assumed to follow first-order kinetics[14,15]. It is difficult to quantify and parameterise the various environmental conditions that influence degradation in such field situations as they are constantly changing
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