Impact of Brewery Waste Sludge on Sorghum (Sorghum bicolor L. Moench) Productivity and Soil Fertility in Harari Regional State, Eastern Ethiopia

Abstract

The study was conducted on farmers field in sofi district of Harari Regional State during 2013/2014 main cropping season, eastern Ethiopia, to investigate the impact of brewery waste sludge on sorghum production, soil fertility and to determine optimum rates of brewery waste sludge applications for sorghum production. The experiment comprised of 8 treatments viz. applications of brewery sludge at (0, 2.5, 5.0, 7.5, 10.0, 12.5 and 15.0 t ha-1) and NP inorganic fertilizer at recommended rate arranged in randomized complete block design with four replications. The experiment has revealed that yields and yield components of Sorghum were the highest for the plots treated with 15 t ha-1 of brewery sludge compared to recommended NP fertilizers and other treatments. Chemical properties of brewery sludge used for this experiment contains 3.5% organic carbon, 1.33% total nitrogen and 39.75 mg kg-1 of available phosphorus. There was no effect of brewery sludge application on heavy metals concentrations in soil after crop harvest, compared to international standard tolerable level. Co and Se levels were high in the control as well as in the soils treated with brewery sludge indicating the already high concentration of these heavy metals in the soils of the area. Plots, which received higher brewery sludge application, resulted in decreased or less percentage of grain nitrogen content showing the independence of grain protein content on lower brewery sludge level. The nitrogen uptake by sorghum grain, straw and the total was maximum (52.68, 44.25 and 79.03 kg ha-1, respectively) with the application of brewery waste sludge at 10 and 15 t ha-1 which were significantly higher than the other brewery sludge and recommended rate of NP mineral fertilizer applications.