Autotrophic nitrification in acid tea soils

Abstract

Investigations to analyze the nature of nitrification in acid soils were carried out in the laboratory using 2 soil types from a tea field. The optimum temperature for the nitrification activity in these soils was 25°C and the activity was inhibited above 35°C, suggesting that the nitrifying bacteria became adapted to the soil conditions. The optimum NH₄ ⁺-N concentrations for nitrification ranged between 20 and 200 mg N/100 g of soil and the activity decreased at a concentration above 300 mg N. The effect of acidity on nitrification was studied by using soil samples amended with various amounts of CaCO₃. Although the pattern of NO₂¯ production changed, the rate of ammonia oxidation was not influenced by the addition of CaCO₃. The nitrification activity was completely inhibited by the addition of nitrapyrin or acetylene. These results suggest that acid-tolerant or acidophilic autotrophic nitrification occurs in acid tea soils in Japan.

Key Words:

• acid tolerant
• nitrification
• tea soil