Evaluation of Nitrate Leaching from the Soil with the Application of Sugarcane Bagasse Biochar and Slow-release Fertilizer

Nitrate is one of pollutants which is mainly caused by agricultural activities which contaminates groundwater and surface water and threatens human health. Chemical fertilizers which are used in large quantities in agriculture are one of the sources of nitrate in the soil. The purpose of this study was to investigate the effects of the application of different levels of sugarcane bagasse biochar (SBB) and slow-release fertilizer (sulfur-coated urea) on nitrate leaching through a soil profile. A greenhouse experiment with tomato crop grown on a soil mixed with four concentration levels of SBB treatments, including zero percent of soil weight (0B), one percent of soil weight (1B), two percent of soil weight (2B), and three percent of soil weight (3B) and two types of nitrogen fertilizer including conventional urea (CU) and sulfur-coated urea (SCU) fertilizers was performed with three replications. The crop was grown in drained lysimeters and irrigated by surface method. The amount of nitrate was monitored at 5 different times during the tomato growing season. The results showed that nitrate leaching from the lysimeters decreased as the percentage of biochar levels increased. Leaching nitrogen from treatments with biochar levels of 1B, 2B and 3B and with the application of CU fertilizer were 6.2%, 10.1% and 18.3%, respectively and with the application of SCU fertilizer were 8.6%, 22.7% and 24.14%, respectively, less than that of the zero level biochar treatments. The highest and lowest levels of nitrate leaching occurred from lysimeters filled with soil without biochar (0B) and with the application of CU (2307 mg), and from treatment 3B with the application of SCU (1659 mg), respectively. According to the results obtained, application of SBB reduced nitrate leaching from the soil profile and as a result of using SCU fertilizer instead of CU fertilizer, this reduction effect was significant.