Turfgrass thatch effects on pesticide leaching: a laboratory and modeling study

Area of Science:

• Environmental Science
• Soil Science
• Hydrology

Background:

• Process-based models are crucial for assessing turfgrass water quality impacts.
• Thatch layers in turfgrass complicate pesticide transport predictions.
• Understanding pesticide movement through thatch and soil is vital for golf course management.

Purpose of the Study:

• Compare linear equilibrium model (LEM) and two-site nonequilibrium (2SNE) models for pesticide transport prediction.
• Evaluate the impact of thatch on pesticide transport using a volume-averaging approach.
• Assess the necessity of explicitly modeling thatch layers in process-based models.

Main Methods:

• Utilized soil and thatch + soil columns to simulate pesticide transport.
• Applied triclopyr and carbaryl pesticides and measured breakthrough curves.
• Employed a constant water flux (1 cm h⁻¹) to mimic steady-state flow conditions.
• Analyzed pesticide and bromide transport parameters to identify nonequilibrium processes.

Main Results:

• Nonequilibrium processes significantly influenced pesticide transport.
• Columns with zoysiagrass thatch exhibited reduced triclopyr and carbaryl leaching compared to soil-only columns (max 15% reduction).
• The 2SNE model, using laboratory-derived retardation factors, explained 70-94% of pesticide variability.
• The 2SNE model successfully predicted peak concentrations and tailing behavior.

Conclusions:

• Explicitly modeling thatch layers may not be essential for accurate pesticide transport predictions under steady-state flow.
• The 2SNE model provides a robust framework for simulating pesticide transport in turfgrass systems.
• Thatch presence offers a slight but measurable reduction in pesticide leaching.