The goal-directed study sought to determine the effects of mineral fertilizers on the productivity of two rice cultivars in the Kyzylorda region, Kazakhstan. In 2015, with the constant flooding of rice crops, the growing of two rice cultivars (Anait – a Russian breed, and Tugusken – a national breed of Kazakhstan) sustained mineral fertilizers with rates of N₁₂₀Р₉₀K₆₀. In 2016, the field experiments continued on the norms of mineral fertilizer application. The highest density of rice herbage, tillering, and grain yield were visible on the fields with the rice cultivar Tugusken. In 2015, the low rice yield of 31.34–34.5 t/ha was evident, caused by severe soil salinization and insufficient mineral fertilizers. Therefore, in 2016, the following varied doses of mineral fertilizers gained scrutiny for rice on the degraded site: N₁₂₀Р₉₀K₆₀, N₁₅₀Р₉₀K₆₀, and N₁₈₀Р₉₀K₆₀. Based on the 2016 study results, for rice, the optimal dose of fertilizers N₁₅₀Р₉₀K₆₀ performed better, and the increased dose of nitrogen (180 kg) did not considerably enhance the rice grain yield (49.2-47.5 = 1.7 t/ha). With enhanced nitrogen dose, the rice growing season also lengthened, causing the appearance of empty grains in panicles.

Keywords: Rice, degraded soils, soil salinization, mineral fertilizer doses, growth traits, rice productivity

Key findings: Based on the study results in 2016, the identified optimal dose of fertilizers was N₁₅₀Р₉₀K₆₀ for better rice productivity. Increasing the nitrogen dose (180 kg) does not significantly increase the rice grain yield. Even with enhanced nitrogen dose, the rice growing season extended and led to the appearance of empty grains in panicles.