a1 Bothamsted Experimental Station, Harpenden, Herts
1. The factors affecting denitrification in soil have been studied by determining loss of nitrogen from soil under various conditions by total-N analysis.
2. It was found that the rate of denitrification of nitrate in soil was dependent upon various factors such as the pH, temperature and water content of the soil and that, under conditions conducive to denitrification, 80–86% of nitrate-N added to Rothamsted soils was lost by denitrification in 5 days.
3. The rate of denitrification was greatly affected by the pH of the soil. It was very slow at low pH (below 4·8), increased with rise in soil pH and was very rapid at pH 8·0–8·6.
4. The rate of denitrification increased rapidly with rise in temperature from 2° to 25° C. The optimum temperature for denitrification was about 60° C.
5. The degree of water saturation of the soil had a profound influence on the rate of denitrification. Below a certain moisture level practically no denitrification occurred; above this level denitrification increased rapidly with increase in moisture content. The critical moisture level was about 60% of the water-holding capacity of the soil.
(Received July 24 1957)