Regionalizing potential for microbial bypass flow through New Zealand soils

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Understanding microbial transport in soils is crucial for assessing environmental risks.
• Dairy shed effluent application can introduce microorganisms into soil ecosystems.
• Soil properties significantly influence the movement and retention of microbes.

Purpose of the Study:

• To rank soils based on their potential for microbial bypass flow.
• To correlate microbial bypass flow potential with soil properties and classification.
• To spatially map microbial transport risk across different soil types.

Main Methods:

• Generated microbial breakthrough curves using undisturbed soil cores.
• Applied dairy shed effluent followed by artificial rainfall.
• Ranked bypass flow potential based on breakthrough curve peak position.
• Linked soil properties to the New Zealand Soil Classification system.

Main Results:

• Soils were categorized into high, medium, and low potential for microbial bypass flow.
• Soils with drainage impediments or well-developed structure showed high bypass potential.
• Soils from tephra and Recent Soils with less developed structure exhibited low bypass potential.
• Spatial mapping of risk was achieved using a 1:50,000 scale soil map.

Conclusions:

• Soil structure and drainage characteristics are key indicators of microbial bypass flow potential.
• The New Zealand Soil Classification system provides a framework for predicting microbial transport.
• Management practices can potentially alter the assessed risk of microbial bypass flow.