Soil depth and tillage effects on glyphosate degradation

Area of Science:

• Soil Science
• Environmental Chemistry
• Agronomy

Background:

• Glyphosate-resistant crops have driven the adoption of no-tillage (NT) cropping systems.
• Understanding glyphosate's fate in soil is crucial for assessing environmental impact.

Purpose of the Study:

• To investigate glyphosate sorption, mineralization, and persistence in soils under conventional tillage (CT) and NT soybean systems.
• To compare glyphosate behavior at different soil depths (0-2 cm and 2-10 cm).

Main Methods:

• Soil samples from CT and NT systems were analyzed for organic carbon (OC) and fluorescein diacetate (FDA) hydrolytic activity.
• Glyphosate sorption (K(d)), mineralization, and residue persistence were quantified.
• Half-lives of extractable glyphosate residues were determined.

Main Results:

• Soils under NT management (NT-A) showed higher OC and FDA activity compared to CT soils.
• Glyphosate sorption (K(d)) was not correlated with OC.
• Glyphosate mineralization was highest in NT-A soil and lowest in NT-B soil, positively correlated with OC and FDA activity.
• Short half-lives were observed for both bioavailable (<1.2 h) and bound (<14.2 days) residues.

Conclusions:

• Glyphosate sorption and persistence are comparable between NT and CT soils at the surface.
• The adoption of NT cropping systems is unlikely to significantly alter the risk of non-target effects or surface runoff of glyphosate.