~ 2236 ~ International Journal of Chemical Studies 2019; 7(1): 2236-2239 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2019; 7(1): 2236-2239 © 2019 IJCS Received: 11-11-2018 Accepted: 14-12-2018 Shivarajkumar M Kamble Ph.D. Scholar, Department of Soil Science and Agril. Chemistry, UAS, Dharwad, Karnataka, India Manjunatha Hebbara Professors of Soil Science and Agril. Chemistry, University of Agriculture Sciences, Dharwad, Karnataka, India SS Gundlur Professors of Soil Science and Agril. Chemistry, University of Agriculture Sciences, Dharwad, Karnataka, India GV Dasar Professors of Soil Science and Agril. Chemistry, University of Agriculture Sciences, Dharwad, Karnataka, India Correspondence Shivarajkumar M Kamble Ph.D. Scholar, Department of Soil Science and Agril. chemistry, UAS, Dharwad, Karnataka, India Effect of long-term irrigation of treated distillery waste water on microbial activity and heavy metals content in a Vertosol under sugarcane cropping system Shivaraj Kumar M Kamble, Manjunatha Hebbara, SS Gundlur and GV Dasar Abstract A field experiment was conducted to evaluate the effect of long-term application of spentwash on heavy metals content in soil and sugarcane crop in Northern Dry Zone of Karnataka. The distillery effluent was characterized by neutral pH (7.37), high EC (17.32 dS m -1 ), high biological oxygen demand (7200 mg L - 1 ), and chemical oxygen demand (18032 mg L -1 ). The application of spentwash significantly increased the microbial activity in the soil; among different periods of spentwash irrigation dehydrogenase activity ranged between 51.77 to 43.77 μg TPF g -1 of soil day -1 , phosphates activity 105.22 to 88.24 μg PNP g -1 of soil hr -1 and urease activity 141.7 to 107.5 μg NH4- N g -1 soil hr -1 . Distillery effluent application for 5- 10 years recorded the higher dehydrogenase (51.77 μg TPF g -1 of soil day -1 ) and urease activity (141.7 μg NH4- N g -1 soil hr -1 ) while higher phosphates activity (105.22 μg PNP g -1 of soil hr -1 ) in 10-15 years spentwash irrigated treatment. The distillery effluent application appeared to have promoted the enzymatic activities in soil as lower microbial activity was observed in the control treatment. The present study has shown that sugarcane distillery effluent had slightly elevated levels of toxic heavy metals like cadmium (Cd), arsenic (Ar), and chromium (Cr) therefore seemed not fit for long-term irrigation or disposal without applying proper remedial measures. Keywords: Treated distillery wastewater, heavy metals, micro-organisms and sugarcane Introduction The distillery wastewater (spentwash) is a dark brown coloured liquid with an unpleasant odour of burnt sugar. The raw spentwash is acidic in nature with the pH ranging from 3.8- 4.2, while the primary treated spentwash otherwise known as post methanated distillery spentwash (PMDSW) is near neutral in reaction (pH of 7.2). The dark brown colour of raw spentwash is due to the presence of melanoidin of cane molasses which is not decomposed effectively by yeast and methane bacteria in its activated sludge process. In comparison to raw spentwash, the PMDSW contains lower BOD and COD values. The annual treated distillery spentwash obtained in India can supply 16,800 tonnes of N, 6,300 tonnes of P and 1.26 lakh tonnes of K and by this it is estimated that Indian distilleries could save about 10,000 million rupees annually as cost of fertilizers is increasing (Chandraju, 2005) [4] . Wastewater characteristics and levels of pollutants vary significantly from industry to industry. The use of industrial waste as soil amendment has generated interest in recent time (Devarajan and Oblisamy 1995). The wastewater produced continuously could cater the needs of irrigated crops. In the initial years, use of wastewater to the crop may benefit the crop due to its nutritive and growth promoting effect. However, continuous use of spentwash not only pollutes the environment but also results in accumulation of salts in the root zone adversely affecting the crop. In recent years, expansion of distilleries in the sugarcane growing areas and indiscriminate disposal of spentwash in sugarcane cultivating lands adjacent to industries has affected soil health through salinity and heavy metal toxicity. Materials and Methods The soil type of the experimental site was medium calcareous Vertisol. The soil was alkaline in nature with pH ranging from 7.84 to 8.11. The electrical conductivity was higher in spentwash irrigated plots (4.46 dS m -1 ) compared to control treatment (0.45 dS m -1 ).