Economic return of potassium fertilization of alfalfa pasture in a tropical soil.

The objective of this study was to evaluate the effect of doses and frequency of application of potassium fertilizer on the alfalfa dry matter yield and economic return to dairy cattle production. The experiment was carried out on a Typic Hapludox and was designed in randomized blocks in 4 X 4 factorial with 3 replications. The treatments were 4 levels of potassium in topdressing fertilization (0, 600, 1200 and 1800 kg/ha/year of K2O) and 4 frequency of application (12 = after each cutting, 6 = after two cuttings, 4 = after three cuttings; and 2 = two applications per year). The use of 1420 kg/ha/year of K2O applied after two cuttings (6 applications per year) increased alfalfa dry matter yield until 30,500 kg/ha. Profit functions were adjusted considering four scenarios for milk and potassium fertilizer prices. Estimated profit functions were a useful aid in economic decisions for alfalfa fertilization than just the dry matter yield curves. Since the maximum profit for K2O doses was 1,212 kg/ha for the lower price of fertilizers and 1,045 kg/ha for the higher price of fetilizer