Renee Langettel, age 14, of Costa Mesa, California, for his question:
What exactly is alluvial soil?
The Green Revolution has no place for those who regard the soil as plain old dirt. This happens to be the earth's most precious gift and without it neither the plant nor animal worlds could survive. The soil that supports our gardens, forests and farmlands is far more than a mixture of minerals and dirty debris. It is a vital bond between the realm of non living chemicals and the organic realm of all life on earth. The more we know about alluvial soils and soil science in general, the better our chances of survival.
As we strive to halt pollution, more and more ordinary folk are starting to grow better foods in garden plots, window boxes and even pots. Chances are, we soon learn that there is far more to growing things than we suspected. The prime key to success is soil and this vital ingredient happens to come in numerous qualities. Perhaps we learn by sad experience that plants plumb refuse to grow in certain soils. Then we hear tell of rich alluvial soils and marvelous mixtures called compost.
The qualities of these rich soils are mainly their ingredients. All soils are mixtures of numerous organic and non organic chemicals and no two recipes are exactly alike. In most cases, the bulk material is a crumbly mixture of assorted minerals, washed and weathered from the earth's rocky crust. However, this material alone is worthless, at least for growing plants.
It must contain an assortment of plant and animal materials, blended just right ¬like the little bear's porridge. These organic ingredients must be in various stages of decomposition and decay. In nature, these soil blending activities occur patiently wherever the earth provides rocky minerals, water and living things. The term alluvial means washed, and washing on this scale requires abundant supplies of water.
Water is the powerful solvent that dissolves rocky chemicals and also nourishes decay bacteria, earthworms and other creatures that break down organic materials. Hence, alluvial soils tend to be rich blends of ingredients, served in fine particles. It forms on the beds of streams and lakes, where generations of water dwellers sink to the bottom and mingle their organic remains with inorganic clays and sandy silts.
Some of the richest alluvial soils carpet wide valleys, especially where streams tend to flood. Other such soils wash down the slopes of canyons. But some of the richest alluvial layers were deposited through countless ages on the floors of the seas. In many places where ancient seas have receded, these old alluvial deposits became fertile farmlands. However, some of these alluvial soils contain high concentrations of salty alkalines. They must be well washed and irrigated and perhaps treated to adjust their chemical balance before plants can accept them.
As a rule, a farmer's best fields are the bottom land, where the earth washes alluvial deposits down the slopes. We small scale growers, however, can copy nature's super soil recipes for ourselves. The secret lies in recycling so called organic wastes, shredding this plant and animal refuse and mixing it with our impoverished garden dirt. With generous helpings of water, worms and decay bacteria, it will patiently convert this unlikely recipe into the very best plant formula for our garden plots.