The nutrient credits from applied manure vary by animal species and the manure management system in place on the farm. Traditionally, the most common approaches have been liquid handling systems (minimal bedding) and solid manure systems, which is a more highly bedded management strategy. In more recent years, practices such as running the manure through a digester or composting process as well as liquid-solid separation have become more common. These actions can have a significant impact on total nutrient content and potential availability of the nutrients when field applied. The use of sand bedding has replaced wood products as a bedding source on many farms as well.
With any change in management there is the potential for a significant shift in the manure characteristics and nutrient content. The best way to track these changes is though a comprehensive manure sampling and testing program. In cases where this is not practical, book values exist to give an estimate of the typical nutrient content for a specific manure type. This can be an effective strategy but only if the manure on the farm is relatively normal or typical.