The immediate effect of burning and ash-fertilization

Summary Changes in the vegetation and soil store of major nutrients were followed under the local practice of shifting cultivation. Changes in the soil store of N, P, K, Ca, Mg and Na were recorded under recently cleared forest before, 24 hours, and 40 days after the burning of vegetation of known biomass and chemical composition.The immediate increase of K and the delayed increase of P in the upper 50 cm—although equal to the content of the above-ground vegetation before burning—is not to be explained by the ash-fertilization alone. The immediate increase of K after burning was not observed after 40 days at any depth, and less Ca and Mg were found in the topsoil immediately after the burning and after 40 days, than before. Apparently mobilization and/or diffusion due to heat are important factors, even in the deeper horizons.