Towards a method for optimized extraction of soluble nutrients from fresh and composted chicken manures

A preliminary method for extraction of soluble nutrients from organic materials is presented that investigates important characteristics of design for efficient extraction. The study was conducted in Polyvinyl Chloride (PVC) columns (length: 50 and 100 mm, diameter: 87.5 mm) filled with fresh and composted chicken manures, packed to densities in the range of 0.2-0.6 g cm(-3). The columns were leached with distilled water. A total of 5 cm(3) of water per cm(3) of material was applied. Leachate collection was sequentially partitioned to enable determination of soluble nutrients throughout time, including: total dissolved nitrogen (TDN), water soluble phosphorus (P) and potassium (K). Waste material state, density of packing and lengths of column all significantly (P<0.05) affected the concentration of ions in the leachate. In general, longer contact time between the percolating water and the material resulted in higher (P<0.05) concentration of ions in the leachate. Cumulative TDN and water soluble-P were greater (P<0.05) in fresh manure leachates, compared with compost leachates. Although, compost leachates provided relatively greater (P<0.05) concentration of K. Salinity ionic concentration of leachates, determined as Na and Cl, was consistently greater from fresh manure as compared to that from mature compost. Fresh manure and mature compost were determined to provide different responses to nutrient leaching because of differences in physico-chemical characteristics. Saturated hydraulic conductivity in fresh manure columns reduced rapidly with application of water to the columns. The mechanisms involved in this process are discussed with the implication for nutrient extraction and use of leachate from chicken manure waste sources.