Compost has been used for a very long time. In fact, it was first discovered as a beneficial planting process by ancient Romans. They found that that by adding manures to the soil it would enrich and improve crop productivity. This is a concept that is still used today.
Let’s learn about soil and the soil horizons. The composition of garden soil may be surprising to some. Soil consists of not only solid mineral particles, but also of decaying organisms, living organisms, air and water.
Specifically, soil is composed of the following:
• - mineral matter - sand, silt and clay or nonliving material from rock
• - microbes - bacteria, fungi and algae
• - animals - worms, insects, snakes, mammals
• - organic matter - decaying matter that was once alive (plants, animals and microbes)
• - pore space - open spaces occupied by air or water
SOIL HORIZONS are individual horizontal layers seen by exposing a vertical cross section of soil. Driving through the countryside where roads cut through hills, the traveler sees distinct layers of soil.
Every soil profile includes the following horizons:
· A HORIZON - the "living layer," often called "topsoil." It is dark due to organic matter. This is the coarsest, most fertile layer where most roots grow.
· B HORIZON - the second layer often called "subsoil" made of more COMPACTED material. It contains finer particles. Brighter in color, it is often nutrient rich but low in organic content. It stores water.
· C and R HORIZON - the parent soil material and rock native to the locale. This layer determines natural fertility, pH, and soil depth.
With planting there are 2 schools of thought on whether to add or not to add compost to the soil planting area. The idea of not adding compost is especially recommended by people who plant native plants. The idea is that the plant will perform better if the soil is similar to what it would grow in in nature. They suggest that nothing be done to change the root zone environment. The addition of organic composts would create an inversion layer of create more soil moisture around the plant which would inhibit the native plant’s growth. This can be true.
The drawback with this argument is that most popular native plants are not native to the San Joaquin Valley. Example would be the Coast Redwood found on the central to northern California coast near the Pacific Ocean. This tree when planted in the valley is being placed into alkaline pH soil, it likes acidic soil. The top soil is deep and rich with organic matter from the forest. How many redwood forests are found in the San Joaquin Valley? None. Many of our soils were originally grass lands. Unless you live in a flood plain odds are your soil isn’t rich in organic matter. In fact, many times it is lacking organic matter.
Soil is a living environment for the plant. Soils that have a rich organic top soil will have microbes and insects and animals that enrich the soil. Microbes help to break down and convert organic matter into usable nutrients for the plant. Insects add to the soil by consuming organics and burrowing through the soil to improve soil aeration. Soils will also have Mycorrhizae which is a beneficial fungus that helps plants absorb nutrients and water.
The trick to planting success is to create the living soil environment that your new plant will enjoy. This is why we add soil amendments or compost mixed into the planting hole. An ideal soil environment would be to amend the entire yard with compost 2 feet deep. This is not realistic, so we do the next best thing and amend the planting hole.
Make sure that you mix the compost into the soil to prevent an inversion layer and make the planting area as wide as possible to allow for adequate root development of your plants.