Fluidized Bed Combustion Bottom-Ash Effects on Infiltration and Erosion of Variable-Charge Soils
- José Miguel Reichert and
- L. Darrell Norton
Highly weathered soils generally maintain low electrolyte levels (EC) in soil solution, which, along with raindrop impact, causes aggregate dispersion and enhanced erosion. This study was conducted to determine if application of fluidized bed combustion bottom ash (FBCBA) could control erosion of variable-charge soils. Seven highly weathered soils (six Oxisols and one Ultisol) were prewetted and then subjected to high-intensity rainfall (110 mm h-1) for 2 h. The FBCBA was surface applied at a rate of 5 Mg ha-1. Infiltration, runoff, and erosion were measured throughout the rains. The FBCBA increased EC and pH of the soil solution, because it contained CaO (23%), Ca(OH)2 (3%), and CaSO4 (73%). Steady-state infiltration rates (Is) ranged from 7.2 to 54.8 mm h-1 for the control and from 9.5 to 44.4 mm h-1 for the FBCBA. The FBCBA had either a favorable, an unfavorable, or no effect on the parameters tested, depending on the soil. On soils with a favorable response to FBCBA, Is was increased by 1.7 to two times, total runoff reduced by two times, and total erosion reduced by 2.2 to 2.4 times. On soils with an unfavorable response, Is was decreased by 1.2 to 1.6 times, total runoff increased by 1.2 to 1.6 times, and erosion increased by 1.6 times. The increased infiltration and reduced erosion and runoff occurred only for soils that had low pH (ΔpH ≤ 0.6) and negative charge (≤ 2.0 cmolc kg-1). Unfavorable responses were found when ΔpH was >2.1, charge increase was at least 6.8 cmolc kg-1, and final pH was >9.
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