THE EFFECT OF FLY ASH SEWAGE SLUDGE MIXTURES AND APPLICATION RATES ONBIOMASS PRODUCTION/

A greenhouse study was conducted to assess the use of a sewage sludge/ fly ash mixture in soils for increased growth and uptake of nutrients by Sorghum vulgaris var. sudanense Hitchc. (''sorgrass''), a sorghum-s udangrass hybrid plant. This experiment was conducted by using four se wage sludge-to-fly ash ratios (4:1, 4:2, 4:3, and 4:4) and six applica tion rates of sewage sludge/fly ash mixtures to soil (0, 50, 100, 150, 200, and 400 tons/acre). The data in this study indicated that the av ailability of elements to plants varied depending on the mixture ratio s and the application rates. All ratios of sewage sludge amended with fly ash generally improved plant growth and enhanced yield at applicat ion rates of 50-100 tons/acre but showed reduced growth and yield at h igher application rates. The decrease in yield al higher application r ates was probably due to the assimilation of high levels of boron whic h is phytotoxic. These various treatments of sewage sludge/fly ash rat ios and rates of application often resulted in;elevated concentrations of N, P, K, Ca, Mg, Mn, Fe, B, Cu, and Zn in both soil and plants.