What is a primary concern associated with groundwater contamination in agriculture?

Groundwater contamination in agriculture is primarily concerned with the pollution from agricultural nitrates. Nitrates, which often originate from fertilizers and livestock waste, can leach into groundwater systems through rainfall and irrigation practices. Once in the groundwater, nitrates can pose significant health risks to humans and animals, leading to potential issues such as methemoglobinemia, or "blue baby syndrome," which affects infants when they consume contaminated drinking water. Additionally, excessive nitrate levels can lead to eutrophication in surface water systems when groundwater discharges into rivers or lakes.

While the excessive use of water can lead to other environmental issues, and overapplication of pesticides can also contribute to contamination, it is the specific relationship between agricultural practices and nitrate levels that highlights the most pressing concern regarding groundwater quality. Soil erosion, though significant for other reasons, typically affects surface water quality rather than groundwater and thus does not address the primary concern of groundwater contamination in the context of agriculture.