Have you ever wondered what dirt is made of? The simple
answer is that dirt is mixture of a whole lot of “stuff” such as rocks, sand,
clay, and organic matter. The characteristics of the dirt in your area depend
on the weather, the combinations of rocks, sands and clays, your geographic
location, and what kind of organic matters are in the soil.
You might ask how in the world does this happen. Well, the
climate has a major effect on the breakdown of solid materials. Alternate
freezing and thawing cycles as well as wet and dry phases will accelerate the
breakup of rocks and over time smaller and smaller particles are formed. Rocks
are responsible for soil texture and, sometimes, alkalinity. Soils produced from
limestone are often finely textured, neutral to alkaline and fertile. Soft
shale rock can develop into a heavy clay soil; sandstone becomes a coarse sandy
soil. Granite usually turns into a sandy loam, slightly acidic soil.
The topography, or shape of the land surface, also plays a
role in soil development. Soils are often deeper in low areas and flat
geographic surfaces and shallower on slopes and rims. Dirt in drier regions can
often turn salty where as low areas in wet climates can become peat bogs.
is another important component of diet; as a matter of fact
it is the source of most nutrients found in the soil. The nutrients are
released during the decaying process of organic matter. Living creatures play another
essential role in the development of soil. Animals like moles and earthworms
help aerate the dirt, while humans rearrange the landscape by moving large
amounts of dirt or turning over the soil in their gardens and yards. Over the
span of thousands of years, all these factors work together to create the soil
we see today.
Did you know that only about half of the dirt or soil on
Earth is made up of solid material like rock, organic matter and living soil
creatures (worms, ants, fungi and bacteria)? The other half consists of air and
water. If you’re lucky these will be present in approximate equal amounts in
your yard. Air is essential because it supplies oxygen to soil creatures and
plant roots, without it both would suffocate. Aerated soil also makes good
Soil with a good percentage of water is crucial because nutrients
and other chemicals vital for healthy plants are dissolved in it. This nutrient
filled water is held on the surface of the soil particles. Clay soils hold more
water because the soil particles are smaller and there is more surface area.
Sand particles are larger, yet more porous so they have less surface area and
therefore do not hold water very well. This is why clay soils stay wet longer
and sandy soils dry out quickly, requiring more irrigation and fertilization. A
good soil mix should include 50% solid material, 25% air and 25% water and it
would possess soil particles of various sizes.