Effects of Pulverized Fuel Ash on the Moisture Characteristics of Soils

Abstract

THE available water capacity (AWC) of a soil has been shown to be positively correlated with the percentage of fine sand (0.2–0.02 mm) and organic carbon present, and negatively correlated with the percentage of coarse sand (2.0–0.2 mm)¹. Pulverized fuel ash, produced from the combustion of finely ground coal, is a dust containing between 50 and 70 per cent of “fine sand” size particles². It occurred to us that pulverized fuel ash could be applied to increase the AWC of coarse textured soils. To test this hypothesis a field experiment was carried out on a coarse sandy loam of the Newport Series. Rates of ash, equivalent to 0, 50, 100 and 200 tons/acre, and containing 65 per cent of particles of size 0.2–0.02 mm, were incorporated into the top 12 in. of soil in small plots by putting soil and ash through a concrete mixer. There were five replications of each treatment. A satisfactory crop of red beet was grown on all plots, but there was a reduction of 9 per cent in the yield of roots with the highest rate of ash applied, which was probably caused by the presence of toxic quantities of boron. After harvest the various moisture characteristics of the soil were determined³: the upper limit of available water by the gravimetric method on samples taken 48 h after rewetting and the lower limit by the 15 atm. percentage method.