Herbicide loading to shallow ground water beneath Nebraska's Management Systems Evaluation Area

Area of Science:

• Agricultural Science
• Environmental Science
• Hydrology

Background:

• Groundwater quality is deteriorating due to agricultural practices.
• Pesticide contamination is a significant concern in groundwater resources.
• Effective management practices are crucial for mitigating groundwater pollution.

Purpose of the Study:

• To assess the impact of improved irrigation practices on groundwater pesticide contamination.
• To evaluate the effectiveness of different irrigation methods in reducing herbicide leaching.
• To understand the relationship between irrigation, microbial degradation, and groundwater quality.

Main Methods:

• Field study comparing conventional furrow, surge, and center pivot irrigation systems over six years (1991-1996).
• Application of a banded herbicide (atrazine + metolachlor) to corn fields; alfalfa field remained untreated.
• Collection and analysis of groundwater samples from 31 multilevel samplers at 16 depths.

Main Results:

• A >50% reduction in irrigation water lowered average atrazine concentrations from 5.5 to <0.5 µg L⁻¹ in the upper aquifer.
• Increased deethylatrazine (DEA) to atrazine ratios indicated enhanced microbial degradation with reduced water application.
• Sprinkler irrigation limited focused recharge and promoted greater atrazine degradation compared to furrow irrigation.

Conclusions:

• Improved irrigation management, particularly reduced water application and sprinkler systems, significantly enhances groundwater quality.
• Reduced irrigation water promotes microbial degradation of herbicides in soil zones.
• Optimized irrigation strategies are vital for preventing pesticide contamination of groundwater resources.