EFFECT OF POTASSIUM SOURCES AND RATES ON ARABICA COFFEE YIELD, NUTRITION, AND MACRONUTRIENT EXPORT

The use of potassium (K) rock powder can be an alternative for K supply of crops. Thus, to reduce K fertilizer imports from abroad, possibilities of extracting this nutrient from Brazilian rocks are being studied. The objective was to evaluate the effect of phonolite rock powder (F2) as K source (Ekosil (R)) on the air-dried fruit yield, nutrition and macronutrient export of Arabica coffee. The experiment was carried out on a dystroferric Red Latosol (Typic Haplorthox), in Piraju, Sao Paulo State, Brazil, in the 2008/09 and 2009/10 growing seasons. The experimental design was a randomized complete block, in a factorial 2 x 3 + 1 arrangement, with four replications. The treatments consisted of two K sources (KCl -58% of K2O and F2 - 8.42% K2O) and three rates 1/2-, 1-, and 2-fold the K2O rate recommended for coffee, i.e., 75, 150, and 300 kg ha(-1) of K2O), plus a control (without K application). Potassium supply increased coffee yield, regardless of the source. Application of source F2 increased coffee yield similarly to KCl at the recommended K rate for coffee (150 kg ha(-1) K2O), proving efficient as K supply for coffee. Potassium application increased macronutrient export in coffee, especially in the growing season with higher yield.