Stem rot (Nakataea oryzae) limits rice (Oryza sativa) production in Uruguay when there are high inoculum levels in the soil. This disease is particularly damaging in potassium (K)-deficient soils that receive excessive nitrogen (N) fertilization. Nevertheless, no data exist for the response to stem rot in modern rice cultivars with respect to the interaction between balanced N and K fertilization. The aim of this work was to evaluate the combined effect of K and N fertilization and a foliar phosphite (Phi) in reducing stem rot severity in rice to prevent significant yield losses. A 3-year field study was conducted in a rice-producing region of Uruguay to investigate the effects of:(1) K fertilization rate, 0 or based on the Mg:K ratio; (2) N fertilization rate, 0 or 140 kg ha?1 N; and (3) Phi treatment, with or without foliar Phi (1.775 kg ha?1 of K Phi, 71%), at growth stage R2-R3. While the experiment was conducted in a soil with sufficient potassium, K fertilization reduced the severity and percentage of rice tillers that were severely affected by stem rot, resulting in a mean yield increment of 2% to 18% depending on the year (mean 7.5%). Nitrogen fertilization increased stem rot severity in only 1 year, but resulted in a mean yield increment of 10% over the 3 years of the experiment. Foliar Phi applied at the late boot to panicle exertion stage did not reduce disease incidence or severity and failed to increase the total rice grain and milling yield.