INFLUENCE OF SOIL-APPLIED COAL COMBUSTION BY-PRODUCTS ON GROWTH AND ELEMENTAL COMPOSITION OF ANNUAL RYEGRASS

The total annual production of coal combustion by-products in the USA is expected to exceed 150 million Mg by the year 2000. Agricultural ut ilisation may offer a partial solution to disposal problems, but the b enefits and risks associated with using these materials must be assess ed. Four coal combustion by-products, bed ash (BA) and fly ash (FA) fr om a fluidised-bed combustion furnace and stabilised scrubber sludge ( SS) and a high gypsum content by-product (G) from flue gas desulphuris ation processes were added to two soils at rates of 0, 20, 40 and 80 g kg(-1). The growth and elemental composition of 'Gulf' annual ryegras s (Lolium multiflorum L.) were evaluated in the treated soils. Adding FA, SS and G to both soils at application rates of up to 80 g kg(-1) w as not detrimental to the growth of ryegrass and resulted in higher yi elds than controls in some instances. Adding BA created a high alkalin ity, high soluble-salt environment that initially inhibited seedling g ermination and significantly reduced (p<0.05) yields of dry matter, so it will probably need to be restricted to rates of lime requirement. Ryegrass concentrations of Cu, Zn, Ni, Pb, Cd and Cr were similar in c ontrol and treated soils, but levels of B, Se, As and Mo were raised i n treatments. Based on low trace-element concentrations in ryegrass sh oots and in soil solution, Se from FA application may be the only pote ntial food-chain risk associated with application of the four coal com bustion by-products used in this investigation.