Identification and quantification of main anthropogenic stocks and flows of potassium in Brazil.

Potassium (K), along with nitrogen and phosphorus, is an essential resource to ensure agricultural productivity and, therefore, food security around the world. However, diminishing physical reserves of potash salts and high-price volatility of potassium chloride, the main source of K to agricultural soils, has raised concerns about a K scarcity scenario, mainly in countries that depend on fertilizer imports to sustain its production. In this context, Brazil is one of the main agricultural producers in the world, having a major role in the global K flows, since the country sustains its production by a high consumption of imported K fertilizers. In order to seek opportunities to contribute to a more sustainable management of K resources, tools such as the material flow analysis (MFA) can be used to highlight the main K stocks and flows in a country scale, and identify options for reuse and recycle. This study proposed a MFA of K for Brazil, considering the base-year 2013. A total of forty-four flows and seven stocks were identified and quantified considering nine main processes related to human activity. According to the results, for the year of study, the main inputs of K in Brazil were in the form of fertilizers (4.1 × 103 Gg of K per year), and the main outputs were in the form of grain exports (9.1 × 102 Gg of K per year). Agricultural soils were the main stock for K in the country, and from the total flow of 7.3 × 103 Gg of K per year applied to soils, 67% came out as agricultural products, 13% was lost through erosion and leaching, and 20% remained in the soils. The flow of K actually consumed by the Brazilian population was 3.5 × 102 Gg of K per year, just 8.4% of the total food produced in the country. About 1.9 × 103 Gg of K per year has been lost to the environment in sewage streams and solid landfill waste. Prospects for more sustainable K management in the country are identified and discussed.