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Hexazinone and simazine dissipation in forestry field nurseries
M J Calderón1, M Ortega, M C Hermosín
1Cons. Sup. de Invest. Cientif. (CSIC), Instituto de Recursos Naturales y Agrobiologi;a de Sevilla, Apartado de Correos, P.O. Box 1052, 41080, Sevilla, Spain
Chemosphere
|October 16, 2003
Summary
Hexazinone and simazine dissipation varied by soil type. Hexazinone degraded faster in Toledo soil, while simazine persisted longer overall due to higher adsorption and lower mobility, impacting forest nursery applications.
Area of Science:
- Environmental Chemistry
- Soil Science
- Agrochemistry
Background:
- Forest nurseries for Pinus nigra in Spain utilize herbicides like hexazinone and simazine.
- Understanding herbicide dissipation is crucial for environmental risk assessment and sustainable land management.
Purpose of the Study:
- To investigate the field dissipation of hexazinone and simazine in two distinct Spanish soils (Toledo and Burgos).
- To elucidate the mechanisms governing herbicide dissipation, including adsorption, desorption, leaching, and degradation.
Main Methods:
- Laboratory experiments: adsorption-desorption isotherms, leaching studies using soil columns, and degradation assays.
- Field residue analysis to assess herbicide persistence under actual conditions.
Main Results:
- Hexazinone adsorption was higher in Toledo soil (higher organic matter) than in Burgos soil. Simazine adsorption was similar in both soils and higher than hexazinone.
- Hexazinone leaching was greater in Burgos soil, while simazine leaching was similar but lower overall.
- Hexazinone degradation was faster in Toledo soil (t1/2 = 47 d) compared to Burgos soil (t1/2 = 91 d). Simazine degraded slowly, with a t1/2 of 50 days in Burgos soil and negligible degradation in Toledo soil.
- Field studies confirmed higher persistence for simazine than hexazinone, attributed to its greater adsorption and lower mobility.
Conclusions:
- Soil properties, particularly organic matter content, significantly influence hexazinone and simazine dissipation.
- Simazine exhibits greater persistence in these Spanish soils due to strong adsorption and low mobility, posing a longer-term residue risk.
- Environmental factors like rainfall and temperature also play a role in herbicide persistence, with lower temperatures in Burgos contributing to longer dissipation times for both herbicides.