Manure subsurface injection reduces antibiotic-resistant bacteria runoff

Compared with surface application, subsurface injection of manure generates less surface runoff of nutrients, sediment, and antibiotics. However, it is unclear how subsurface injection affects the fate of antibiotic-resistant microorganisms in manure.

The Journal of Environmental Quality reports new research where dairy manure was surface-applied and subsurface-injected and followed by simulated rainfalls on the first and seventh day. Culturable antibiotic-resistant fecal coliform bacteria (ARFCB) were tested for the surface runoff generated from each simulated rainfall and for the soils up to the 45th day.

Subsurface injection, compared with surface application, resulted in less ARFCB in surface runoff after each simulated rainfall with higher reduction during the first day of simulated rainfall compared with the seventh day. The ARFCB were undetectable in surface soil (0–5 cm) beyond the 14th day after manure surface application, but they were still detectable in the manure injection slits on the 45th day.

This study suggests the co-benefits of manure subsurface injection in reducing the surface runoff of antibiotic-resistant microorganisms along with other manure-associated contaminants. However, longer-term monitoring should be conducted to understand the fate and impact of ARFCB in the manure injection slits.