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agronomy	the scientific study of the use of soil for producing crops.
amoeba	a tiny living thing made of only one cell. Amoebas move by changing their shape. They eat by wrapping their bodies around their food. Amoebas live in fresh and salt water, soil, and in animals. Most kinds of amoebas can only be seen through a microscope.
bacteria	microscopic organisms that often play a role in the decay of living things, the process of fermentation, and sometimes in causing disease. Bacteria are each made up of only one cell, but different kinds of bacteria can take different shapes. These organisms live in all parts of the earth including oceans, deserts, glaciers, hot springs, and in the bodies of most living things. While some kinds of bacteria are dangerous, most kinds are useful because they help in the digestion of food, in the making of soil, in the creation of medicines, and in many other natural processes.
bacterium	A bacterium is a single bit or type of "bacteria." Bacteria are very, very small living things made up of one cell each. Bacteria live in most living things and in all parts of the earth. Most bacteria are useful to people. They are important in making soil and helping people to digest food, for example. Some bacteria are harmful, though, and cause disease.
bedrock	the solid layer of rock in the earth's surface, found beneath soil, sand, or gravel.
biodegradable	If something is biodegradable, it can be broken down by the action of living things like bacteria and fungi. Paper is something that is biodegradable. It's not good to litter, but if someone drops a piece of paper in the woods, eventually that paper will break down and become part of the soil. It will not be paper anymore.
biodegrade	When something biodegrades, it breaks down because of the action of things like bacteria and fungi. Things like vegetables, meats, and fruits will biodegrade quite quickly. That's why you can't keep them forever, even in the refrigerator. They will eventually break down into tiny substances that are good nutrients for the soil, though.
biome	a major type of global region, such as forest, desert, or grassland, characterized by the community of plants and animals that have adapted to life under the particular soil and climatic conditions that a particular region presents.
blacken	to harm; soil. [1/3 definitions]
bulldozer	a tractor with a large blade attached to the front that pushes or lifts soil or rocks.
clover	a common plant that has leaves in groups of three and small, rounded flowers. Clover is often grown in fields to help enrich the soil.
compost	a mixture of decaying leaves, vegetables, or manure that is used to improve garden soil.
conservation	the protection of natural resources, such as soil, water, or forests, from loss, pollution, or waste. [1/2 definitions]
cultivator	a machine or hand tool that prepares soil for planting by loosening the soil and removing weeds.
degrade	If something degrades soil, it removes the valuable things in the soil and makes it hard to grow crops in it. [1/2 definitions]
delta	a triangle of sand and soil deposited at the mouth of some large rivers. [1/2 definitions]
dirt	loose earth or soil. [1/2 definitions]
dirty	to make dirty; soil. [1/6 definitions]
dust	tiny, dry pieces of soil, dirt, or other material. [1/3 definitions]
earth	soil or dirt. [1/4 definitions]
earthen	made up of earth, soil, or dirt. [1/2 definitions]

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