Quirks & Quarks

Nitrogen fertilizer leaves legacy in deep soils

Nitrogen fertilizer has been accumulating below the plow level in agricultural soils and will take decades to clear.

Large amounts of fertilizer have accumulated under agricultural lands

Runoff from a farm field in Iowa during a rain storm (U.S. Department of Agriculture, Natural Resources Conservation Service)
Nitrogen fertilizers are used in vast amounts in modern agriculture to ensure productive harvests. But authorities have been trying to limit the problem of excess nitrogen running off farmer's fields, which can cause a range of problems, including algal blooms, ocean "dead zones" and drinking water contamination that can be a threat to human health.

Now, Dr Nandita Basu, an assistant professor in the Departments of Earth and Environmental Sciences and Civil and Environmental Engineering at the University of Waterloo, and her colleagues, have found that this task is likely to be much more difficult because of decades of accumulated nitrogen in deep soils of agricultural land.

Her group found that as much as one-third of fertilizer applied every year ends up deep in the soil, and it will take decades for it to leach out or be broken down.

Related Links

Paper in Environmental Research Letters
- University of Waterloo release
- Newsweek article