Assessing Nutrient Sorption and Release in Biochars.

Biochar, the product of the pyrolysis of plant matter, can be used to facilitate the rehabilitation or enhancement of degraded or marginal soils. This study will evaluate the ability of a several distinct biochars to sorb and retain common fertilizers and assess biochar’s potential as a fertilizer carrier. Biochars are ground to <150µm, suspended in double-deionized water by constant stirring, and either allowed to come to their natural pH or stabilized at pH 4.5 or 6. Noncompetitive nutrient isotherms are conducted by adding NH₄⁺, NO₃^-, K⁺, or HPO₄^2- to pH-stabilized biochars. After 24hrs of contact time, solution extracts are filtered through a 0.2µm filter and analyzed for NH₄⁺ and NO₃^- with a flow injection autoanalyzer and Ca, Mg, Fe, Al, S, K and P using ICAP. These elements naturally occur within the biochar, and their presence may affect nutrient sorption and solubility. Additionally, competitive sorption isotherms will be conducted by combining all nutrients in solution in equal quantities. Experimental procedure and analysis will follow the individual isotherms. Certain biochars saturated with the competitive isotherm solution will be rinsed in a vacuum extraction column using simulated rainwater as the leachate in four consecutive leaching events. Leachate from each event will be analyzed with the same methodology as competitive and non-competetive isotherms.