Modeling Alachlor Transport in Saturated Soils from No-till and Conventional Tillage Systems
- S. K. Xue *,
- Shulin Chen and
- H. M. Selim
Batch and transport experiments with alachlor were conducted in soils from no-till and conventional tillage systems. Alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide] adsorption was described with equilibrium and multireaction models (MRM), and alachlor transport was evaluated with a multireaction transport model (MRTM) in undisturbed soils. In batch experiments, alachlor retention was greater in no-till soil, based on the parameters of equilibrium adsorption models, than in soil with conventional tillage. This is due to the increase in organic matter. The MRM improved fitting of adsorption data compared with the equilibrium model. Preferential flow in no-till led to earlier tritium and alachlor breakthrough and higher hydrodynamic dispersion coefficients, compared with conventional tillage. The breakthrough concentrations in no-till soils are spread more widely over time than in conventional tillage soils, which showed a steady high peak concentration. The MRTM adequately described alachlor transport in soils of both systems. There was no significant difference in alachlor retention capacity between undisturbed soils of no-till and conventional tillages, and among different cover crops, based on overall parameters fitted from alachlor breakthrough curves (BTCs) in undisturbed soil columns. The higher recovery and lack of irreversible reaction indicated that no-till soils may have reduced bound alachlor residue during transport.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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