Fig. 12. Of the solar energy that reaches the earth, about 93% returns to the
atmosphere. With nutrients and water abundant and with a full cover of leaves,
about 7% of that solar energy can be converted in photosynthesis by corn; 2%
goes into respiration, which is required for the growth and maintenance of the
crop, and 5% goes into the dry matter of the crop. In corn, 3 percent goes into
roots, stems, and leaves, which constitute a crop residue that is recycled to the
soil or fed to animals, and 2% emerges as grain that can be eaten by people.
For grass, as much as 4% may be consumed by a cow.
[From R.S. Loomis, Agricultural Systems. Copyright © 1976
by Scientific American, Inc. All rights reserved.]