Degradation Kinetics of Oxadiargyl and Thiobencarb in Calcareous Paddy Soils of Mazandaran Province
2013
Mahmoudi, Mojtaba | Eshaghi, Ali
The time that herbicide remains persistence and active is important from sustainable agriculture and the environmental point of view. Herbicides persistence is suitable to some extent to control unwanted plants. Herbicide residues, however, may have environmental risk for and/or affect next crop. It is, therefore, necessary to investigate their degradation trend in paddy water and soil, bioactivity, movement in soil and groundwater contamination. Most of the paddy soils are calcareous in Mazandaran province and no complete information is available about herbicide integrations and their half-life. In this research project, degradation kinetics of thiobencarb and oxadiargyl, which are widely used in paddy fields, was studied. Residual effect of the herbicides on rotational crop (spinach) was also investigated. To meet this purpose, field experiments were conducted with treatments, which applied in three replications in a randomized complete block design, including control, thiobencarb at 3.16 and 6.33 kg a.i./ha, and oxadiargyl at 0.15 and 0.30 kg a.i./ha at Dashtnaz and Gharakhil agricultural research stations. Thiobencarb and oxadiargyl concentrations were monitored in soil solid phase and soil solution via sampling during 315 and 60 days periods, respectively. Results showed that half-lives of two herbicides were ranged from 2 to 4 days. In soil solid phase, however, half-lives were calculated 50 and 20 days for thiobencarb and oxadiargyl respectively. Oxadiargyl affected rice and spinach fresh yield greater than thiobencarb. Spinach fresh yield was significantly influenced by oxadiargyl soil residues. Key words: Water and soil contamination, Rice, Half-life, Thiobencarb, Oxadiargyl, Residual effects.
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