Investigation of the Effects of Barberry Stems Biochar on Nitrate Leaching from a Loam Soil Containing Organic Matter

Due to the pollution of water resources by various pollutants such as nitrate, the use of amendments such as biochar can be considered as an approach to solve this environmental problem. To investigate the effect of barberry stem biochar on nitrate leaching, a research was conducted using a factorial and completely randomized design in 2021, in the soil laboratory of the Faculty of Agriculture, University of Birjand, Birjand, Iran. Experimental factors were particle size of biochar at two levels (less than 1 mm, more than 2.8 mm) and biochar volume in three rates (1, 2, and 3 mm on weight basis). Biochar was produced during the thermal decomposition process under limited oxygen conditions (400 0C for 6 h). The pots were subjected to wet cycles (field capacity plus 20%) and drying (permanent wilting moisture) and the nitrate concentration in the drained water from irrigation was measured in two stages with an interval of six weeks. The highest and lowest nitrate leaching rates in the samples were observed in the control treatment without biochar and biochar with particle size less than 1 mm at the rate of 1% by weight, respectively. The results of this study showed that addition of the biochar to the soil significantly reduced nitrate leaching compared to the control without biochar. At the two measuring times, biochar treatments with particle size of less than 1 mm and 1%, 2% and 3%, biochar with natural particle sizes of 1%, 2%, and 3% showed decrease in nitrate leaching by, respectively, 83.6%, 82.4%, 76.8%, 81.7%, 64.2%, and 60.2 % compared to the treatment without biochar. Moreover, the results showed that biochar particles less than 1 mm had more effects on reducing nitrate leaching than biochar particles more than 2.8 mm. According to the results of this study, it seems that application of barberry branch waste biochar left after harvesting can reduce nitrate leaching and the risk of transmitting contamination to other soil.