The Effects of Ash Influx on Burned and Unburned Soil Water-Extractable Nutrients Using a Mechanical Vacuum Extractor

A laboratory study was performed to test the effects of burning on soil solutions. Soils from beneath slash piles that had been burned as well as soils from unburned areas were amended with varying amounts of ash to create ratios of ash to soil ranging from pure ash to pure soil. Amended soils were then repeatedly extracted with deionized water. Results showed that a large quantity of nutrients, particularly potassium and NO3−−N, were released from the ash into soil extractant. In most cases, nutrients from ash dominated the observed effects, but in the case of NH4+, burned soil was the main source. Calcium, Mg2+, and PO43−−P showed signs of being more responsive to soil chemical processes (displacement of native soil ions, dissolution, adsorption, and precipitation) than to the ash influx.