Abstract

Nitrogen fertilization in rice crop are based on crop needs and the capacity of the soil to supply it. In this study six rice soils of central Chile were fertilized with 0, 80 and 160 kg N ha^-1 and incubated in anaerobic conditions for time periods from 0 to 28 days at 20 and 40°C. Field experiments were conducted in the same soils with equal N rates. Nitrogen mineralization showed a quadratic response that was directly proportional to incubation time, N rate used, and increase in incubation temperature. At the same time, mineralized N exhibited patterns of different magnitude, including in soils of the same order; therefore, this N supply capacity indicator is soil-dependent. The yield was maximized with 80 kg N ha^-1 and the N uptake was highly correlated with the N mineralized for both 21 days at 20°C and 7 days at 40ºC. The optimum N rate to apply was represented using a lineal model that associates the yield with the crop N needs, the N soil supply through mineralization and the supplement that must be supplied by the N fertilization.

Key words: Paddy rice soils, anaerobic incubation method, nitrogen, mineralization, nitrogen optimization.