Herbicide transport in surface runoff from conventional and zero-tillage fields

Area of Science:

• Agricultural Science
• Environmental Science
• Ecotoxicology

Background:

• Canadian prairie crop production has shifted from conventional management (CM) to conservation tillage management (CTM), replacing tillage with herbicides.
• This shift may impact snowmelt runoff quality, necessitating an investigation into herbicide transport.

Purpose of the Study:

• To assess the impact of conservation tillage on herbicide concentrations and fluxes in snowmelt runoff.
• To compare herbicide runoff from zero-till management (ZTM) and conventional management (CM) systems against an organic control.

Main Methods:

• A 6-year field study using side-by-side runoff watersheds.
• Comparison of herbicide concentrations and mass loss in snowmelt runoff from CM and ZTM systems.
• Analysis of fall- and spring-applied herbicides, including trifluralin, triallate, and 2,4-D.

Main Results:

• Zero-till management (ZTM) resulted in higher snowmelt runoff volumes compared to conventional management (CM) in 5 out of 6 years.
• Fall-applied herbicides showed higher detection frequencies, concentrations, and mass loss than spring-applied herbicides.
• Edge-of-field herbicide concentrations frequently exceeded Canadian aquatic life water quality guidelines.

Conclusions:

• Conservation tillage adoption increased herbicide use by ~20% and herbicide transport in snowmelt runoff by ~25%.
• Incorporation of trifluralin and triallate significantly reduced their losses in runoff.
• The study highlights potential risks to aquatic ecosystems from herbicide runoff under conservation tillage practices.