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Capturing excess nutrients from waterways


Fertilizers applied to farm fields, golf courses, and residential landscaping to benefit plants do not always stay in place. These added nutrients, including nitrogen (N) and phosphorus (P), can be washed away by rainfall into nearby waterways. An abundance of nutrients in aquatic ecosystems can result in algal blooms, which deplete oxygen as they decompose.

Low levels of dissolved oxygen, or hypoxic conditions, create what are known as “dead zones” because few organisms can survive under such conditions. One of the largest dead zones occurs where the Mississippi River meets the Gulf of Mexico. The Mississippi River drains roughly 40% of the lower 48 U.S. states, picking up nutrients from farms, lawns, and animal waste along the way. Given the negative impacts on the fishing industry, tourism, and marine ecology in the Gulf of Mexico and other dead zones worldwide, it is important to reduce nutrient runoff upstream.

During a symposium at last year’s ASA, CSSA, and SSSA International Annual Meeting in Phoenix, AZ, researchers gathered to explore new and creative solutions to not only remove N and P from agricultural waters, but to recover those nutrients for reuse.

 “We've got an “abundance” of nitrogen and phosphorus in our waters at times,” says Gary Feyereisen, an agricultural engineer with the USDA-ARS and organizer of the symposium. “Wouldn't it be great if we could capture that abundance and then make those nutrients ‘scarce’ in the waterways that are leaving agricultural land?” 

From adapting existing water treatment techniques to emerging technology, four speakers shared ideas and initial results. Feyereisen, who chairs ASA’s Managing  Denitrification in Agronomic Systems Community, which sponsored the symposium says, “Right now, those solutions may not look economical,”  but all have potential to help solve the problem of nutrients polluting surface waters. Here, we share these thought-provoking ideas with those unable to attend this session in Phoenix. 

Algae production tanks

Continue reading in the March issue of CSA News online.