Water Quality Will Suffer Long After Farmers Stop Using Nitrates

A new study demonstrates that nitrates in fertilizers pose a strong and enduring threat to drinking water.

“Even if farmers stopped using nitrogen fertilizers today, levels of dangerous nitrates in rivers and lakes would remain high for decades,” HealthDay reported, citing the study.

“Canadian scientists analyzed more than 2,000 soil samples from the Mississippi River Basin and found an accumulation of nitrogen. This buildup was not evident in the upper ‘plow’ layer, but instead was found 2 inches to 8 inches beneath the soil surface,” the report said.

The research from scientists at the University of Waterloo was published this month in an issue of the scholarly journal Environmental Research Letters. “Our study, for the first time, provides direct, large-scale evidence of N accumulation in the root zones of agricultural soils,” the study said.

The study drew conclusions about the effectiveness of water quality practices for reducing nitrates in the environment, arguing that nitrate sticks around for years:

[Nitrate concentrations] will persist for decades after fertilizer inputs have ceased. Indeed, the time lag would in most cases be significantly greater than that estimated based on the hydrologic legacy alone. Our study for the first time links multiple lines of evidence to show convincingly that N, like P, has a biogeochemical legacy, a legacy that complicates our previous understanding of the fate of this nutrient in anthropogenic landscapes and that must be accounted for in intervention efforts to improve water quality.

Nandita Basu, a researcher on the study, weighed in per a statement.

"The presence of this legacy nitrogen means it will take even longer for best management practices to have a measurable benefit," said Basu, a member of the Water Institute. "If we're going to set policy goals, it's critical we quantify nitrogen legacies and time lags in human impacted landscapes."

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