Previous soil volume estimations
| Arnold, 1980 (2) | 224 ft3 of soil total for tree 21 to 40 ft. in height (8’ × 8’ × 3½’ depth pit). |
| Bakker, 1983 (3) | 2½ ft3 of soil for every î ft2 of CPA. |
| Vrecenak and Herrington, 1984 (46) | 5543 ft3 for a 64 ft. diameter tree. |
| Perry, 1985 (35, 36) | 27 ft3 of soil for every 1 “ of caliper, later refining this to come up with 600 ft3 total for a 10” caliper tree (20’× 20’× 18” depth pit). |
| Kopinga, 1985 (20) | 2500 ft3 of soil total as the optimum volume tor a large tree. |
| Cervelli, 1986 (7) | 570 ft3 of soil total (10’× 19’ x 3’ depth). |
| Helliwell, 1986 (17) | A rooting volume 1/1 Oth of the canopy volume; a 65’ tree with a 40’ spread will need over 7000 ft3 of soil. |
| Moll and Urban, 1989 (30) | 1200 ft3 of soil total (20’ × 20’ × 3’ depth pit) for a tree expected to reach a caliper of over 25 inches. |
↵A Crown projection (CP) is defined as the total ground area under the dripline of a canopy. It is easy to measure and frequently used as a way to quantitatively describe the canopy relative to some other measurement of plant growth or development.