Impact of application of coal combustion products to soil on soil characteristics, concentration of elements in plant material and crop product safety

Field and glasshouse experiments using coal combustion products (CCP) from Tarong and Millmerran power stations have been conducted since 2005 to assess effects of their use in land management on soil properties, uptake of nutrient and non-nutrient elements, crop safety and crop yield – this paper concentrates on the first three, drought having limited crop yield responses. CCP from the flue (‘fly ash') and furnace (bottom ash') have been applied at up to 80 t/ha to ferrosols and vertosols. In glasshouse studies, soils have been cropped repeatedly using chick pea, cowpea and peanut, while maize, sorghum and peanut have been grown in field trials. The impact of CCP application on soil physical and chemical properties was assessed. Elemental concentrations in vegetative and reproductive plant parts were determined by plant analysis. There has been very little or no evidence of increased uptake of elements that may cause adverse impacts on plants (eg B, Se) or plant products (eg. Cd), concentrations being well within prescribed limits. Decreases have also occurred. No evidence of increase in uptake of either nutrient or non-nutrient elements from year to year was found, and reduced availability of manganese in ferrosols, probably due to liming effects of the CCPs has occurred. Fly ash increased soil pH in vertosols (from 6.1 to 6.6) and ferrosols (5.2 to 5.4). The application of CCPs from the two power stations is discussed from environmental and product safety viewpoints.