Estimating and comparing cropland nitrogen need with dairy farm nutrient recovery: a case study in Whatcom County, WA

In agricultural regions, like Whatcom County, Washington, crop and dairy production co-exist, but increased agricultural specialization and intensification have divorced what was, historically, an integrated approach to production. This agricultural segregation contributes to farm, regional and watershed-scale nutrient imbalances, and several different management approaches have been devised to improve, correct and close these nutrient cycling disparities. In high-density production regions, utilizing locally produced bio-based fertilizers may provide one avenue toward closing regional nutrient loops. Technologies such as dairy-operated nutrient recovery systems may help improve the flow of nutrients between dairy and cropping systems by extracting nutrients from raw manure and producing materials that are more easily used on farms than raw manure. To evaluate the potential impact of a nutrient recovery system and its related product, we estimated nitrogen balances between cropland use and manure production within Whatcom County, Washington and examined a theoretical scenario in which a specific nutrient recovery product was utilized across the region. We considered one economic barrier, transportation cost, and calculated a hypothetical comparison for transporting nitrogen in two forms, a downstream nutrient recovery product and raw manure. The scenarios presented here demonstrate a potential gap between regional nutrient supply and demand, illustrate the tradeoffs with a technological approach, and make clear that both technological tools and practical management strategies are needed to address the challenges of redistributing nutrients in high-density production areas.