During the first weeks following the introduction of chemical soil conditioners, I often made a statement to the effect that "Five
dollars spent on organic matter will do your soil far more good than $50.00 spent on chemical conditioners." At that time, these chemicals were being touted as "permanent amendments and conditioners." Today, we know that they have a life of about three years in soils that are worked annually. If I were making that statement today, I would change the latter figure to $100.
In contrast to the three-year life for chemicals, barnyard manures have shown both soil conditioning and fertilizing effects for as long as 50 to 60 years following application.
Organic matter is a soil conditioner which can be matched by no other material. When it can be had practically free, as it can from the home compost pile, it is sheer folly to let it go to waste. Humus is a storehouse for plant "foods" and (along with absorption by bacteria and fungi) prevents the loss of nutrients if they are not used by plants immediately. The extent of these nutrient reserves can be enormous, as in the case of rich prairie soils of the Middle West, many of which continued to produce crops for half a century after they were broken by the plow, often without the addition of any outside source of fertility. While such soil depletion is to be condemned, the case mentioned does show the extent to which soil rich in humus can build up stores of plant nutrients.
In addition to this function, humus also makes a soil more porous so that air and water move freely. Humus-rich soil turns easily under the plow or spade and does not pack readily. There is a special "feel" to such gardener's loam which the true gardener learns to know.
One of the most valuable functions served by organic matter is in providing favorable living conditions for bacteria, fungi and other microorganisms. When soil is examined under the microscope, the bacteria will be found clustered around nodes of decaying vegetation or clinging to crumbs of humus. Here they find the food, moisture and air they must have to maintain life and carry on their soil-improving functions.