IF YOU SQUEEZE a handful of material and water drips or trickles out, it is the right moisture content for composting.” This bit of hands-on wisdom comes from the proverbial squeeze-test for evaluating moisture in composting piles. It has been uttered by Master Gardeners and other composting educators for many years as a tool for determining, and teaching about, the balance of moisture in the composting process. Balance is the key word because, while moisture is necessary, too much can be detrimental. The squeeze-test mantra goes on to say that if you cannot squeeze any water out of the handful, the material is too dry and if water trickles out without squeezing, it is too wet.
Although the squeeze-test is useful, and often sufficient, for monitoring moisture in the composting process, it loses utility as the scale of composting grows larger and management becomes more scientific. Simply squeezing material is subjective and inexact, and it does not provide a quantitative measure of the moisture content. Therefore, composters have come to rely on other techniques to gauge moisture in the materials being composted and the compost produced. Such techniques range from the standard of drying and weighing samples to more recent electronic sensors that furnish an immediate reading or output signal.
Moisture Is Number One,But Heed The Sponge
Assuming organic matter is already on hand, water is more important than any other composting requirement. Water is essential to biological decomposition. It allows organisms to live, acquire nutrients from their surroundings, and move about. It also provides a medium for chemical and biochemical reactions. Most composting organisms would be happy in a saturated environment except for the fact that they also need a continuous supply of oxygen. Too much moisture interferes with oxygen transfer and leads to anaerobic conditions. Decomposition continues anaerobically, but it is incomplete, creating odorous and phytotoxic compounds.