Nitrogen Fertilizer Equivalency of Heat-Dried Biosolids for Winter Wheat.

Most municipal biosolids provide the equivalent of 30 to 40 kg of fertilizer N per 100 kg of total N application.  New technologies for biosolids drying have been introduced, and these technologies may alter plant-available N release characteristics.  We evaluated the N fertilizer replacement value of Soundgro heat-dried biosolids (Pierce County, WA) vs. urea (46-0-0) in  field trials in western Oregon (high winter rainfall, annual cereal cropping).   When applied in fall (preplant), Soundgro was 30 to 40% as effective as spring-applied urea in increasing grain yield. With spring application, Soundgro was 50 to 60% as effective as urea fertilizer.  We conclude that Soundgro, a product of a high-temperature Andritz dryer, has higher N availability than found in conventional biosolids produced via anaerobic digestion and dewatering.