Concern about microbial contamination of groundwater from foraging dairy cows has increased as spray-irrigation practices in New Zealand have increased over the years. Bacteria capable of living in both animals and humans are commonly found in cow manure. Addressing the lack of research on the topic, a team of New Zealand researchers studied the transport of microbes from two spray-irrigated dairy pastures into groundwater supplies
The research team, reporting in the May-June 2010 Journal of Environmental Quality and published by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, found little to no transport of microbes due to spray-irrigation application.
When irrigation applications were increased to simulate irrigation, plus heavy rainfall, there was a small increase some forms of bacteria, notably E. coli. But other common bacteria were only detected at very low levels when fresh cow pats where subjected to this treatment.
The results of the study indicate a minimal impact of dairy farm pastures on microbial quality of groundwater as a result of spray-irrigation.