Alternative sources of potassium for maize cultivation

ABSTRACT Brazil is the largest importer of potassium (K) fertilizers in the world, importing about 95% of all the potassium consumed by its agriculture. Thus, new sources and technologies to increase K availability have been studied. This study aimed to evaluate the agronomic viability of the use of calcined glauconite and phonolite blended and granulated with two organic materials on maize growth in pots, using two soils of contrasting texture in a controlled environment. Were evaluated eight sources of potassium: phonolite; phonolite + poultry manure; phonolite + cattle manure; calcined glauconite; calcined glauconite + poultry manure; calcined glauconite + cattle manure; negative control (no K); and positive control (K - KCl), and two soils of contrasting texture. The experiment was carried out for 38 d. The following parameters were analyzed: plant height, stem diameter, shoot dry mass, leaf number, leaf contents of nitrogen (N), K and phosphorus (P), and the SPAD chlorophyll meter. In the sandy soil, the source consisting of phonolite + chicken manure was similar to KCl application regarding plant height, stem diameter and shoot dry mass. As for the clayey soil, when both rocks were blended with the organic wastes, they were similar to KCl for shoot dry mass. The use of pure granulated rocks, calcined glauconite and phonolite without blending with the organic residues is not efficient to provide available K to maize plants. RESUMO O Brasil importa aproximadamente 95 % dos fertilizantes potássicos usados na agricultura, e, novas fontes e tecnologias para aumentar a disponibilidade do nutriente têm sido estudadas. Objetivou-se avaliar a viabilidade agronômica de uso da glauconita calcinada e do fonolito, granulados com dois materiais orgânicos, sobre o crescimento do milho em vasos, em duas classes de solos, em ambiente controlado. Foi avaliado 8 fontes de potássio (K) (Fonolito; Fonolito + esterco de galinha; Fonolito + esterco de curral; Glauconita calcinada; Glauconita calcinada + esterco de galinha; Glauconita calcinada + esterco de curral; Controle (sem K); Controle (K - KCl) e dois solos distintos em relação à textura. O experimento foi conduzido por um período de 38 dias. Foram realizadas as análises de altura de plantas, diâmetro do colmo, massa seca de parte aérea, número de folhas, teores foliares de N, P, K, e índice SPAD. A fonte fonolito + esterco de galinha equipara-se ao KCl na altura de plantas, diâmetro do colmo e massa seca de parte aé