Determination of Physical and Hydraulic Properties of Cattle Manure Using Soil Analysis Techniques.

Livestock manure is widely applied as fertilizer in agricultural production. Surface runoff from manure amended areas and from pastures with grazing livestock commonly result in transport of nutrients, pathogens, and organic material to aqueous systems, both ground and surface water. Similar to soils, the transport and fate of dissolved nutrients in manure depends on the magnitude and direction of the water flux, primarily affected by the hydraulic gradient, which is the driving force of water flow, and by the physical and hydraulic manure properties. From a physical perspective, manure is a heterogeneous, polyphasic, disperse porous medium and can generally be considered as a three-phase system, composed of solid (organic matter), liquid, and gas. Our study focuses on the fundamental physical and hydraulic characteristics of cattle manure that primarily affect the transport of liquid water and gas within the manure. We used techniques commonly applied in soil analysis to measure physical properties of fresh cattle manure, including the determination of the manure dielectric permittivity - volumetric water content relationship with TDR and a commercially available dielectric sensor, and the development of a water retention curve for cattle manure using the chilled-mirror dew point technique. In our presentation, we will discuss experimental techniques, associated challenges, and the application of gathered results to characterize gas and liquid transport processes in cattle manure and their implications on the release of dissolved nutrients and gas emissions.