Effects of urea fertilization and liming on nitrification in cerrados soils (Brazil)

Abstract

Nitrification is a microbiological process involved in the production of nitrate, which is important from the agricultural and environmental view points due to its mobility in soil. Also, in this form it is easily reduced by the denitrifying bacteria to gases which are released from the soil. Nitrification in soil is controlled by several environmental factors such as pH, mineral nutrition, temperature, and moisture (Haynes 1986). Nitrification has been found to be minimal at a pH value below 5.0 (Dancer et al. 1973; Gilmour 1984). However, nitrification can occur in some acid soils at a pH value below 4.5 (Weber and Gainey 1962; Weier and Gilliam 1986). Although nitrification in acid soils may be associated with the activity of autotrophic nitrifying bacteria (Hankinson and Schmidt 1988; Hayatsu 1993), heterotrophic microorganisms may also be involved in the nitrification process (Schimel et al. 1984; Stroo et al. 1986). In the Cerrados soils that are strongly acidic, information about the microorganisms involved in nitrification is limited.

Key Words:

• autotrophic nitrification
• cerrados
• latosol
• liming
• nitrification
• urea