Trace Element Solubility from Land Application of Fly Ash/Organic Waste Mixtures

Abstract

AbstractUse of fly ash (FA) as a soil amendment is hindered by a lack macronutrients in the ash and concerns about trace element availability. Mixing FA with an organic waste can increase macronutrients while reducing odor and improving material handling, but the trace element solubility requires investigation. This study examined the trace element solubility and availability resulting from land application of such mixed wastes. Two FAs were applied as mixtures with either poultry litter (PL) or sewage sludge (SS) to field plots at rates 100 and 120 Mg ha−1 for FA/PL and FA/SS, respectively. Suction cup lysimeters were used to collect soil solution, and trace element uptake was monitored in maize (Zea mays L.) leaf tissue and grain. Soluble B was initially >25 mg L−1 for one high B FA/PL mixture and led to initial toxicity in seedlings. Soil solution concentrations of dissolved C, P, As, Se, Mo, Cu, and Cr were increased in FA/PL field plots. For P, C, As, and Cu, increased solubility was due to increased load in the FA/PL mixtures, while for Mo, Se, and Cr, mixing fly ash with poultry litter appeared to increase solubilization from the ash when compared with an equivalent mass of FA mixed with sewage. Leaf tissue data confirmed an increase in available As from the FA/PL mixtures, while leaf tissue Se was more dependent on the total Se concentrations of the ash.