It must be recognized that all life forms on Earth are carbon-based. When we live we eat carbon-based life forms, and they sustain our bodies in a great cycle of life, death, renewal and decay. Each time a plant is grown in the soil it takes from the soil a certain amount of carbon and other elements and nutrients it needs to survive. When the plant is eaten, some of those nutrients are taken into our bodies to sustain our own life processes. This means that those certain amount of elements that are in our system are no longer in the soil. Most soils of course have a great reserve of these elements in it. Many of them are locked up in the soil particles and are only released when the particles are attacked by soil microbes that live in the soil. Some of the elements are released when water passing through picks up certain acidic elements that work together on the particles releasing a small amount to the water in a chemical exchange. This can all get rather complex, but is actually a fascinating study for those with an eye towards chemistry.

Slash and Burn Neolithic farmers and the soil Each time you take the bit of plant you eat you have additional nutrients and elements bound up in the main body of the plant that you do not eat. This is often thrown away by the tidy gardener who wishes to keep the beauty of the landscape. How long can one continue taking from the soil without replenishing it? Well that of course depends on the native fertility of the soil, and the amount of cropping that is done on it, and this in turn is influenced by season and long term climatic and rainfall patterns, as well as the types of crops grown. In some areas without supplemental additions low input gardens are worked for only a few years before fertility declines to the point that the garden is unprofitable to maintain. At this time it is often abandoned to re-grow in the natural processes we are familiar with when formerly used tracts of land are left 'fallow'. The natural vegetation will re-grow. The grasses and forbs first, then small bushes and finally small trees will take over the plot. This process might take just a few years to return fertility to the soil, or it might take a generation or more. At this time the native gardeners would slash-and-burn the area, the ashes would fall to the ground, and the elements in them would return to the earth to let it yield acceptable crops for a few years again.

This type of primitive agriculture might have been acceptable in the Neolithic past when humans numbered in only the few millions. But now with a large population, little arable land which we wish to take out of cultivation for years, and a hard-edged economy which demands high production and low labor input per food value extracted this type of agriculture system must be replaced by a more regenerative form of food production/land stewardship system.

Enter regenerative agriculture, with it's emphasis on putting back into the soil all that is taken from it. With regenerative agriculture one can conceivably maintain the fertility of the soil in a given spot for generations, even millennia, all the while improving the depth of the soil, it's fertility and ability to be easily worked. Compost figures highly in this regard due to the ability of compost to re-use the spent plant material from the harvest, and decompose and make acceptable to plants the brought in material from off-site.

Compost is a necessary plan for nearly every garden. Whether it be the first year on virgin soil, or the three hundredth year on established fields. In poorer soils I go with the surmise that more is better, I like to add a minimum of a couple of inches of compost to soils to make sure that they get off to a good start. Once soil has been worked for several years, with compost added before each planting, one can then reduce compost applications, and move to a semi permanent or permanent mulch system using wood chips, hay, straw or some other natural plant material that will decompose into the soil naturally. This will in effect have much the same effect as compost in that it will add carbon to the cycle of renewal in the garden. It will add humus as it decomposes and enable the soil to have the tilth you wish for good airflow and water retention combined. Even after a soil is made healthy by large additions of compost for several years, and then is moving onto the mulch stage it still behooves one to add a bit of compost every year or so. Compost made properly has a team of micro-organisms that work their magic on the soil particles in a way that humus alone may not be able to do. And they will likely remain in the soil in good numbers as long as the soil is maintained in a good fashion.

Making soil healthy is something that cannot be rushed, one must work slowly and steadily for many years to enable the soil to accept the compost in a wholesome way. The compost even though it may be completely composted will not all be available to plants in the first year, much of it may take some time to break down into humus which is that sponge-like dark substance that is such an essential portion of a good soil even if it is just a small percentage. As the humus is absorbed into the soil through the years and finally disappears, it will provide a home and haven to the micro-organisms which will use it as a base of operations to attack soil particles around them. It may take years for a piece of compost to become the home you wish it to be and then to decompose entirely. At this time you need more. So it is a good idea to start big with compost, four inches in the first season, then two to three inches each season after that, then finally after four to five years the soil may have the good buffer built into it (the fat bank account), that one reaches the 'mass proportion' that one can at that time get by with just seasonal mulching and a decent application of compost each year.