Effect of pH,organic matter content and nitrate on the evolution of ethylene from soils

The evolution of C₂H₄ from soils was stimulated by air-drying, and still more by oven-drying at 105°C. The quantities evolved were closely correlated with organic matter content, with no significant difference in this relationship between grassland and arable soils, or between topsoil and subsoil. In arable soils only, the quantities of C₂H₄ also increased significantly with decreasing pH. No significant relationship could be found between NO₃^? concentrations in fresh soils and the quantities of C₂H₄ evolved, but for air-dried soils (arable only) there was a significant decrease with increasing NO₃^?. Artificial addition of NO₃^? only partially inhibited the evolution of C₂H₄, even at concentrations an order of magnitude higher than those found in the field. At normal soil concentrations the only effect of NO₃^? seems likely to be a short delay in the achievement of the maximum C₂H₄ concentrations.