Earthworms, vital to the health of soil, prefer soil that is approximately neutral on the acid-to-alkaline scale
Since decomposition of dead plants makes the top layer of soil highly acidic, application of crushed limestone, which is highly alkaline, to the soil' s surface should make the soil more attractive to earthworms
After its application to the soil's surface, crushed limestone stays in the soil's top layer long enough to neutralize some of the top layer's acidity.