Impact of organic waste amendments on soil hydraulic properties and on water partitioning

Land application of organic wastes can lead to contamination of ground- and surface waters. The pathway taken by particulate contaminants, such as microorganisms, is entirely dependent on the partitioning of the incoming rain or irrigation water. The soil hydraulic properties are critical in determining the infiltration:runoff water-partitioning ratio. Components of the land applied organic waste can modify the soil hydraulic properties and thus alter this ratio. It was shown that liquid manure impacted matrix and macropore flow differently; favouring the later through obstruction of the former. In contrast solid manure favoured matrix flow over macropore flow thereby increasing the water storage in soil, which tended to reduce the likelihood of runoff. The relationships between soil hydraulic conductivity and soil textural and structural properties in repacked soil columns was unrelated to the relationships obtained for the same soils maintained in their natural undisturbed field state. Key words: organic waste, manure, soil type, hydraulic conductivity, water partitioning, transport, contaminants.