Caustic lime is found to have two distinct effects on the soil:
1. A partial sterilisation effect,
2. A chemical action, decomposing some of the soil organic matter.
The amount of caustic lime necessary to induce specific changes in the flora and fauna of the soil depends very largely on the character of the soil. The light sandy Millbrook soil, poor in organic matter and in carbonate, reacted sharply with 0·2 to 0·3 per cent. caustic lime; the Rothamsted clay soil, poor in organic matter but rich in carbonate, was found to react to 0·3 to 0·4 per cent.; the acid Woburn soil required an amount between 0·5 and 1·0 per cent., as did also the rich Chelsea garden soil, which already contained carbonate; the Craibstone soil, with a high organic and a low carbonate content, failed to react even to applications of 1·0 per cent, caustic lime.