CORVALLIS - Both the Washington County Unified Sewerage Agency and Sherman County wheat growers are looking closely at an Oregon State University experiment using municipal "biosolids" to fertilize dryland wheat.
The result could be a "win-win" situation, from both environmental and financial standpoints, observers say. Why would hauling wastewater treatment byproducts called biosolids across the state be worth it?
"The Tualatin River basin in Washington County has excessive phosphorus levels, raising concerns about any additional phosphorus inputs," said Dan Sullivan, organic waste recycling specialist in the Department of Crop and Soil Science at OSU.
On the other hand, sparsely populated Sherman County can use supplemental phosphorus and other nutrients. Biosolids can replace organic matter lost through the years of dryland wheat farming, explained Sullivan.
"The biosolids, applied as fertilizer to dryland wheat growing sites, increase organic matter and reduce erosion, as well as provide nutrients for the wheat crop," he said.
Besides keeping excess nutrients out of the Tualatin Basin watershed, the transfer of western Oregon biosolids to eastern Oregon provides financial advantages for eastern Oregon growers.
"Fertilizer costs for winter wheat in the mid-Columbia area run about $10 per acre," Sullivan said. "Biosolids usually come at no cost to the grower, in this case as the Unified Sewerage Agency of Washington County pays for transport in our trials."
There are agronomic advantages for growers too, including possibilities for increased soil quality and higher yields over time in wheat fertilized by biosolids rather than with conventional fertilizers.
"Because biosolids are nutrient rich and high in organic matter, their benefits may last for several cropping cycles after biosolids application," said Sullivan.
The sewerage agency also saves money.
"Transporting biosolids to eastern Oregon is less expensive for Washington County than storing them over the winter or putting them in a landfill," said Sullivan.
Application of biosolids to winter wheat acreage provides the sewerage agency with another option to its current eastern Oregon program, which focuses on dryland grass pasture applications.
"We are looking at several biosolids application rates to find the best rate for dryland winter wheat production," said Sullivan.
Ultimately, any savings recouped by the sewerage agency will trickle down to lower monthly bills for sewage treatment.
Before everyone runs out to try to get biosolids for their fields, Sullivan warned about short supplies.
"A large wastewater treatment facility, like the one in Washington County, only produces about 10,000 dry tons per year of biosolids," said Sullivan. "This is only enough to fertilize less than 1 percent of the suitable dryland cropland with biosolids at the application rate of three dry tons per acre."
Biosolids are quite different from raw sewage, stressed Sullivan. Wastewater treatment facilities remove raw solids from sewage and treat them, according to strict standards set by the U.S. Environmental Protection Agency. The Oregon Department of Environmental Quality oversees application of biosolids to land.
"Biosolids are a beneficial byproduct of domestic wastewater treatment facilities," said Sullivan. "They're made up mostly of nutrient-rich organic materials."
With the consistency of black gelatin, the biosolids that the Washington County United Sewerage Agency haul to land application sites are difficult to store. But they can be very effectively applied with a manure spreader.
"In Oregon, most biosolids are applied to land, for pasture, hay or crop production," said Sullivan. "Oregon is in the top five or 10 states in the amount of biosolids applied to land. More than 95 percent of all municipal biosolids are recycled via land application in Oregon.
"They aren't suitable for all crops, but are good for pastures or crops where the edible part of the crop does not touch the ground, such as wheat."