Abstract
AbstractIn 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.
Highlights
With ongoing increases in total dairy cow numbers, herd productivity and concentration over the last half-century, the dairy industry is managing increasing quantities of manure (USDA ERS, 2007; USDA NASS, 2019a, 2019b)
Lander et al (1998), updated as Kellogg et al (2000), calculated N and P balances for each county in the U.S, including Whatcom County, Washington, using data from the Agricultural Census for 1982–1997. In contrast to this approach, we focused solely on nitrogen and combined 1 year’s data collected by the Washington State Department of Agriculture (WSDA) with regional nutrient recommendations to illustrate the impacts given a hypothetical scenario of technological adoption
Based on the calculations described above, annual total N from manure, countywide, ranges from 3810 to 6078 mg (Fig. 2), while manure N required to meet annual cropland N is estimated at 4639.9 mg (Fig. 3)
Summary
With ongoing increases in total dairy cow numbers, herd productivity and concentration over the last half-century, the dairy industry is managing increasing quantities of manure (USDA ERS, 2007; USDA NASS, 2019a, 2019b). Storage and application of these manures and the associated nutrients to soils have, in some areas, contributed to air and water quality impairment (US EPA, 2012; Harter et al, 2017; Ator et al, 2019). The distribution of these nutrients to adjacent crop/horticultural farms, where nitrogen (N) and other nutrients are needed, has been limited due to costs of transport, variable nutrient content and availability, problematic nutrient balance and food safety concerns (Ribaudo et al, 2003; USDA ERS, 2009, 2011; US FDA, 2015). Without accurate accounting for crop nutrient removal and careful attention to soil macro- and micro-nutrient levels, overapplication of manure can result in environmental degradation
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