Arnold, 1980 (2) | 224 ft^{3} of soil total for tree 21 to 40 ft. in height (8’ × 8’ × 3½’ depth pit). |

Bakker, 1983 (3) | 2½ ft^{3} of soil for every î ft^{2} of CP^{A}. |

Vrecenak and Herrington, 1984 (46) | 5543 ft^{3} for a 64 ft. diameter tree. |

Perry, 1985 (35, 36) | 27 ft^{3} of soil for every 1 “ of caliper, later refining this to come up with 600 ft^{3} total for a 10” caliper tree (20’× 20’× 18” depth pit). |

Kopinga, 1985 (20) | 2500 ft^{3} of soil total as the optimum volume tor a large tree. |

Cervelli, 1986 (7) | 570 ft^{3} 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 ft^{3} of soil. |

Moll and Urban, 1989 (30) | 1200 ft^{3} 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.