Nutrient Recovery: Products from Dairy Manure to Improve Soil Fertility

Dairies are in the business of producing milk. Dairy herds also produce manure, and managing this byproduct—and the nutrients it carries—can be a significant challenge for some dairies. Meanwhile, crop farmers, sometimes in areas close to dairies, generally use commercial, inorganic fertilizers to provide nutrients to their crops. Due in part to intensive cultivation with little input of organic matter, many of these same crop farmers face soil health challenges related to decreases in organic matter content and loss of soil through erosion. Previous research has found that manure application can reduce soil erosion at multiple sites across the United States (including Moscow, Idaho), and that manure-derived organic amendments reduced soil-borne pathogens in red raspberry fields in British Columbia. Manure and its nutrients can be a valuable source of organic matter as well as nitrogen, phosphorus, and other nutrients for soils and crops. Such uses could help solve manure management challenges for dairies while helping to address soil health issues and meeting—partially or fully—the nutrient demand of crops. Recovering and using nutrients from manure also recycles those nutrients, and can therefore address some of the longer-term societal challenges to inorganic fertilizer use: the limited supply of mined nutrients such as phosphorus and the high-energy consumption of producing synthetic nitrogen.