THE SOIL

OBJECTIVES

Upon completion of this chapter, you should be able to

• state how and why soils differ.

• list the components of soil, major soil separates, and the soil textures they create.

• list the seventeen elements essential to plant growth and their functions and symptoms of their deficiency in plants.

• define good soil structure and list the factors that promote it.

• define soil acidity and alkalinity in terms of pH.

• compare the qualities of fertilizers.

• describe how essential elements in the soil become available for plant use.

KEY TERMS

cation exchange complete fertilizer analysis

low-analysis fertilizer high-analysis fertilizer ammonification nitrification

WHAT IS SOIL?__________________________________

If asked to define soil, most people would probably describe where it is rather than what it is. They might also describe what it does, but not how it does it. Like so much of the natural world, soil is taken for granted— praised when the backyard garden is bountiful and disparaged when it is tracked in on the new carpet. Perhaps the greatest evidence of know­ing little about the soil is to label it dirt.

Soil is the underground environment of plants, and that part of the definition (where it is) is generally understood by all. What it does and how it originates are less widely understood. Most people are aware that the plant life of the continent changes greatly from region to region. It should not be too surprising then to learn that the soil also changes considerably from place to place. Therefore, any attempt to define and describe soil must be approached in general terms, applicable from the red clay regions of Georgia through the loam fields of Iowa to the deserts of Utah.

Soil is the thin outer layer of the earth’s crust, made up of weathered minerals, living and nonliving organisms, water, and air. To understand fully that definition is to understand much of modern soil science.