Nutrient transfer to the atmosphere by burning of debris in eastern Amazonia

After replacement of tropical primary forests, fire becomes an important management tool. During establishment of plantations with fast-growing tree species and within slash-and-burn agriculture, the export of macronutrients and other elements to the atmosphere by burning was estimated. Two plots of clearcut 40-year-old and one plot of 7-year-old secondary forest with dry fuel weight 33.5 t ha−1 (plot A1), 95.2 t ha−1 (plot A2) and 31.2 t ha−1 (plot B1) were burnt. Total element losses including volatilisation, particle and leaching exports ranged from 94 to 98% C, 93–98% N, 30–47% P, 30–48% Na, 42–50% K, 13–35% Ca, 21–43% Mg and 66–76% S related to the initial nutrient. For the small-holder site (plot B1) where the drying period lasted 4 weeks with a total precipitation of 9 mm, this loss was to the atmosphere. Significant preburn losses due to leaching were observed on the moister plots (A1, A2) where the drying period lasted 80 days and 101 days with 250 mm and 296 mm precipitation, respectively. Here, element transfer to the atmosphere due to particle transport and volatilisation were 94–98% C, 95–98% N, 27–33% P, 17–23% Na, 16–31% K, 9–24% Ca, 17–43% Mg, 67–68% S of the initial element stock in the burnt debris.