bedrock
	Unbroken, solid rock overlain by sand, gravel, or soil.
contour plowing
	Plowing along hill contours; reduces erosion.
cover crops
	Plants, such as rye, alfalfa, or clover, that can be planted immediately after harvest to hold and protect the soil.
gully erosion
	Removal of layers of soil, creating channels or ravines too large to be removed by normal tillage operations.
humus
	Sticky, brown, insoluble residue from the bodies of dead plants and animals; gives soil its structure, coating mineral particles and holding them together; serves as a major source of plant nutrients.
mulch
	Protective ground cover, including manure, wood chips, straw, seaweed, leaves, and other natural products, or synthetic materials, such as heavy paper or plastic, that protect the soil, save water, and prevent weed growth.
parent material
	Undecomposed mineral particles and unweathered rock fragments beneath the subsoil; weathering of this layer produces new soil particles for the layers above.
perennial species
	Plants that grow for more than two years.
reduced tillage systems
	Systems, such as minimum till, conserve-till, and no-till, that preserve soil, save energy and water, and increase crop yields.
regenerative farming
	Farming techniques and land stewardship that restore the health and productivity of the soil by rotating crops, planting ground cover, protecting the surface with crop residue, and reducing synthetic chemical inputs and mechanical compaction.
rill erosion
	The removing of thin layers of soil as little rivulets of running water gather and cut small channels in the soil.
salinization
	A process in which mineral salts accumulate in the soil, killing plants; occurs when soils in dry climates are irrigated profusely.

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