Siegchrist - Fertilizers for Free

Charles Siegchrist

Readily available plant and animal residues can supply an extremely valuable source of plant foods that over the years will reward you with better soil, better crops, and reduced grocery and fertilizer bills. Some, such as those leaves on your maple trees or the grounds from your morning coffee, come free for the taking. But before you can expect great results, you must put some time and effort into improving the soil. This bulletin is aimed at helping you do just that at as low a cost as possible.

Building a garden soil with organic amendments is an investment in the future. The first year soil-building is undertaken, you probably wont see dramatic results, but as the initial applications of compost, mulch, green manures, and soil amendments break down, youll see changes. The soil will become darker in color, easier to work, and faster to warm in the spring. Youll see more earthworms, and the structure should improve to a crumbly condition. Your gardens will need fewer waterings. Soil tests should start to return with advice to use less fertilizer and less lime, saving you money.

Feed the soil well and it will reward you many times over in the years ahead.

The Makeup of Soil

Most good soils contain consistent percentages of air, water, organic matter, and soil organisms.

Soil is composed of rock particles, soil organisms, water, air, and organic matter in various stages of decomposition. In a fertile agricultural soil, the ratios of these parts might well appear as in the diagram on the previous page.

In terms of both weight and volume, rock particles are the major constituent in soil. The action of glaciers, water, and wind reduces rocks in size by weathering them into tiny fragments. The size of these fragments, also known as soil grains, can vary greatly. The coarsest are known as gravel, followed in order by sand, silt, and clay.

Soils are characterized by the proportions of each of these particle sizes they contain. Sandy soil, with its large, coarse particles, wont retain water very long. For this reason it warms up quickly in spring and can generally be worked earliest. It also quickly shows the effects of water shortage during periods of dry weather. Unfortunately, as water drains out of sandy soil, it often takes essential plant nutrients from applied fertilizers along with it.

Soils containing a large proportion of silt or clay, with their minute rock particles, have more surface area for water to cling to and thus are better able to remain moist. This is advantageous during a dry spell but can mean a later start for the spring gardener, and clay soils may hold on to water too well. Also, clay soils in particular are prone to compaction if worked or walked on when wet; compaction makes soil harder to work and squeezes air out of the soil, so plant roots and soil organisms cant breathe.

The relative sizes of soil particles

Soils that contain a balanced mix of these particle types are called loam. They are easiest to work and have a good balance of other properties, such as retaining a good amount of rainfall while draining quickly enough so they dont stay soggy.

Under ideal conditions, about 25 percent of a soils volume will be air. This circulates through passages between the soil crumbs, aiding in the decomposition of organic matter and sustaining soil life. Earthworms rise to the surface after a rainstorm because the soil channels and pores that supply air for them to breathe have become waterlogged. Roots, too, need air for a good exchange of oxygen and carbon dioxide, so most crops grow poorly on soggy, air-deprived soil. Many beneficial microbes are dependent on an abundant air supply as well; they are killed off when soil remains soggy for long periods.

Another 25 percent of good soil is water. Its value is obvious to anyone whos ever witnessed an extended drought. Though preventing plants from wilting is the most obvious benefit, this soil component plays other essential roles. Water facilitates the liberation of plant food from rock particles and decaying organic matter. Water also transports nutrients to the roots of growing plants and disperses the nutrients through the soil.

Water occupies part of the pore space between the soil crumbs, mostly as a thin film surrounding individual particles. It also becomes absorbed into organic matter, which is capable of holding several times its own weight in water.

The decomposing remains of plant and animal matter within the soil are organic matter. When this material has decomposed to a fine, dark substance in which the source of origin can no longer be determined, its termed humus. All humus is derived from organic matter, but not all organic matter has decomposed to the point that it can be considered humus.

Though organic matter is only a small fraction of most soils, its far more important than you might imagine. It helps hold rock particles loosely together into crumbs, or aggregates, making soil easier to work. It aids in the retention of water and in the passage of air. Further, it provides food for organisms living within the soil.

Numerically, the most common constituent of fertile soil is the population of organisms living within it. But their generally microscopic size makes them the smallest portion of the soil by volume.

One of the largest and most beneficial life-forms in the soil is the common earthworm. Worms consume large quantities of organic matter and soil particles, modifying them through digestion into nutrient forms readily available to growing plants.

Microorganisms also help liberate plant foods from organic matter and soil particles. Many different types and species of microorganisms live in the soil; these include bacteria, fungi, actinomycetes, and algae. The smallest, bacteria, are usually the most numerous; billions live in just a square inch of healthy soil.

Not all soil life wears a white hat, however. Moles ruin lawns, white grubs gnaw off roots, and harmful species of nematodes burrow into roots to strangle the flow of nutrients and water. Other microbes are responsible for wilt diseases and root maladies. Fortunately, soils also contain beneficial nematodes that feed on the harmful species (you can even purchase these if your soil is deficient), plus microorganisms that feed on disease-causing organisms.

The character of a soil can be altered by manipulating any one or all five of its constituents. The most long-lasting way to do this is by adding organic matter.

While you cant change the amounts of sand and clay, you can make a soil with too much of either behave more like ideal loam by working in quantities of organic matter. Well-decomposed organic matter will improve the structure of either light sandy soils or heavy clay soils. In coarse sand, decaying organic matter will act as a sponge for water, reducing this soils tendency to dry quickly. A clay soil will be lightened and made less soggy, as organic matter helps open up air channels and maintain a more porous structure.

Cultivation temporarily increases the amount of air in soil. But cultivating too frequently can destroy the beneficial crumbly structure you work so hard to create and maintain. To get the maximum aeration effects with the minimum amount of cultivation, keep the soil well stocked with humus.