Decomposition will occur whenever the pile is above freezing, but will occur more slowly the lower the temperature. Appropriate temperatures encourage the activity of thermophyllic, or heat-loving, microorganisms. Turning the pile with a shovel, spade fork or manure fork, increases the oxygen level. Water is added to a pile until it is as moist as a wrung-out sponge. A cover or tarpaulin over the pile will prevent it from getting too wet during heavy rain or drying too fast during drought or hot weather.
Decomposition stops when a pile is too dry and becomes anaerobic if too wet.
Nitrogen is necessary for decomposition to occur. Rotted oak leaves and pine needles are only slightly more acidic when fully decomposed. There are usually enough microorganisms on leaf surfaces, in the soil on roots of weeds, etc. for decomposition to occur. This means 25 parts carbon to 1 part nitrogen. Small pieces break down more rapidly and give a more even result.