Agriculture, even in its most primitive state, includes activities related to the collection and storage of solar energy in a form that can be used to sustain life. Energy must be expended in terms of human labor, animal labor, and fossil energy used for products and machinery utilized by agriculture. Because fossil energy is in short supply, many people are concerned, and rightfully so, about the effect that restricted energy availability will have upon agriculture production.
Walker, John N., "Energy in the Home: Energy Usage in Agricultural Production" (1978). Agricultural Engineering Energy Series. 30.