Regulators of Organic Nitrogen Mineralization

FIGURE 8.24 Relationship between carbon-to-nitrogen ratio of plant litter and mineralization of organic nitrogen (Ponnamperuma, 1981). 

Temperature. The rate of ammonification increases with an increase in soil temperature. In contrast to most microbial processes, optimum temperature for conversion of organic nitrogen to ammonium nitrogen is between 40 and 60°C. These temperatures are seldom encountered under field conditions. In general, several studies reported that the rate of ammonification doubles with a temperature increase of 10°C, especially in the temperature range of 15-40°C (Kadlec and Reddy, 2001). 

Soil pH In most wetlands, pH is buffered around neutrality, whereas under drained soil conditions, pH of the soil decreases as a result of nitrate accumulation during mineralization. The optimum pH range for ammonification is between 6.5 and 8.5. 

Mean Organic N Mineralization Rates (mg N kg day ) for Detritus and Soil from Northern Everglades Wetlands Soils (One Standard Error in Parentheses) n = 8) 

FIGURE 8.25 Schematic showing the fate of ammonia in wetlands. 

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