NUTRIENT CONCENTRATION OF RICE HUSK BIOCHAR

Biochar is a porous, solid material that is produced by the thermochemical conversion of organic materials under a limited or oxygen-free environment; it has physical and chemical properties suitable for the long-term storage of carbon, and potentially, improves the fertility of soils. The objective of this study was to evaluate the nutrient concentration of biochar prepared with rice (Oryza sativa L.) husk and added with citric, maleic and propionic acids at 5 and 10% as catalysts. The biochar was prepared through the hydrothermal carbonization technique at 200 degrees C for 19 h. The yield of biochar and concentration of organic matter, N, P K, Ca, Mg, Cu, Fe, Mn, Zn, Si and Na were determined. The highest yields of biochar (66%) were obtained when 10 % maleic and citric acids were added. The highest content of organic matter (71%) was obtained with 5 % maleic acid. In general, the three macronutrients with the highest concentration (mg kg(-1)) were Ca (4386-10,988), N (3067-4467) and K (327-3530), while the micronutrients with the highest concentration (mg kg(-1)) were Fe (77.1-238.3) and Mn (75.4-281.4), as well as the beneficial element Na (92.8-160.0). Due to its yield, organic matter and nutrient concentrations, the rice husk biochar could be used, potentially, as an improver of agricultural soils.