Public Release: 

Nitrates abundant in arid southwest

US Geological Survey

Deserts soils in the Southwest U.S. may be nutrient poor, but the subsoils below are rich in nitrate according to new research appearing in the Nov. 7 edition of Science.

Dr. Michelle Walvoord, a post-doctoral researcher with the U.S. Geological Survey (USGS) in Denver, Colo., found that desert subsoils in parts of the southwest contain large reservoirs of nitrates that had been previously unrecognized in desert nitrogen budgets.

"This is a finding that raises questions about how desert ecosystems work. The results also have implications for potential groundwater nitrate contamination following major land-use or climate change in natural deserts," said Walvoord, who led a team of USGS and university scientists toward this discovery.

Alteration of the natural desert system to accommodate golf courses, irrigated agriculture, and reservoirs could promote flushing large amounts of nitrate to underlying aquifers.

Nitrogen is thought to be a scarce resource in desert ecosystems that limit plant productivity and is therefore tightly retained in the soil. This new USGS research challenges this concept with the idea that nitrogen, in the form of nitrate, has been episodically leaching through the soil zone since the arid climate shift occurred in the southwest U.S. 10,000 to 16,000 years ago.

The USGS study sites were located in the Mojave, Sonoran, and Chihuahuan Deserts, as well as the High Plains region, and northern New Mexico.


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