Implications of Fly Ash Application to Soil for Plant Growth and Feed Quality

Abstract

Fly ash has shown potential as a soil amendment and a source of trace elements beneficial to plants. However, agricultural utilization of fly ash has been restricted due to variability in chemical composition, elemental toxicity, induced nutrient imbalances in plants, and inconsistent response of vegetation to fly ash amendment. Fly ash was applied to reclaimed mine soil near Edmonton, Alberta, at rates of 0, 25, 50, 100, 200, and 400 t ha⁻¹. Total and water soluble concentrations of selected elements were determined from soil samples collected at 0 to 15 cm. Growth, development, and elemental uptake of barley (Hordeum vulgare, L., Jackson cv.), brome (Bromus inermis, Leyss), and alfalfa (Medicago sativa, L., Beaver cv.) were measured at select stages of development. Water soluble concentrations of B, Mo, Ca, Cr, K, Mg, Mo, Na, P, Se, and Sr variably increased with increasing fly ash rate. Boron concentration in plant tissue increased significantly to toxic levels with symptoms evident at early stages of barley development and increasingly severe at later stages. Toxicity symptoms were less severe for brome and alfalfa. The Cu:Mo ratio of vegetation decreased with increased fly ash rate to levels which could cause Cu deficiency in livestock. Yield of barley silage was significantly increased at intermediate rates of fly ash application, but significantly reduced at 400 t ha⁻¹.

Keywords:

• Fly ash
• trace elements
• boron
• vegetation
• soil