Fig. 78.—Schematic profile of the Mississippi
Coast Belt, through Jackson County.
The annexed schematic profile ([fig. 78]) illustrates these changes of soil and vegetation, which furnish a striking example of the effective modification of vegetative features by physical and chemical soil-conditions.
It would be difficult to find a more striking exemplification of the effect of lime carbonate, not only upon the vegetation but also upon the physical and chemical characters of the hopelessly unproductive soil of the sand hammocks and pine meadows; no longer brown and sour, but jet black and neutral, modifying favorably every physical quality. Humus likewise nowhere shows its benefits more strikingly.
Table of Lime-Percentages.—The table below shows the average lime percentages observed in most of the several vegetative areas mentioned above. To meet the objection sometimes made that the vegetative changes noted may be due to the larger amounts of phosphoric acid and potash frequently found in calcareous lands, the percentages of the latter are also given. Considering the origin of limestones, such a connection is not unexpected, but it is far from constant. On the contrary, the frequent co-occurrence of much lime and high production with small percentages of phosphoric acid and potash leads to the conclusion, already discussed ([see chapter 19, p. 365]), that in presence of abundance of calcic carbonate, smaller percentages of phosphoric acid may be considered adequate than when lime is deficient, on account of greater availability. Almost the same may be said of potash; and it is quite possible that the presence of large amounts of lime tends to prevent the leaching-out of this base, in consequence of greater facility for the formation of zeolites. Illustrations of this kind have already been given (chapters 3, 22).
Definition of “Calcareous Soils.”—It will be noted that the very obvious and important changes of vegetation are brought about by comparatively slight differences in lime-content. In fact, only two of the soils enumerated above would, according to the estimates usually given in books on soil composition, be considered as properly calcareous. But the decisive feature in this matter must evidently be the native vegetation, which expresses the nature of the land much more clearly and authoritatively than any arbitrary definition or nomenclature can possibly claim to do. A soil must be considered as being calcareous whenever it naturally supports the vegetation characteristic of calcareous soils.
TABLE SHOWING NATIVE FOREST GROWTH, POPULAR ESTIMATE
OF DURABILITY AND INITIAL PRODUCTION, AND PERCENTAGES
OF LIME, PHOSPHORIC ACID AND POTASH, IN MISSISSIPPI LANDS.
| No. | Name. | Natural Vegetation. | Production Per Acre. |
|---|---|---|---|
| 172 | Black Prairie Soil. | Mainly sturdy black-jack and post oak, red cedar, crab apple and honey locust. | 400 lbs. cotton lint, decreasing to 200 lbs. in 30 years. |
| 164 | Pale Yellow Ridge Loam. | Scarlet, post and Spanish oak, small. | 200 lbs. cotton first year, tailing off to 75 to 100 lbs. by 5th year. |
| 226 | Pontotoc Ridge Soil. | Oak, hickory, walnut, sweet and black gum, honey locust. | 350-400 lbs. cotton lint. 300 lbs. after 20 years. |
| 230 | Heavy Flatwood Soil. | Post and black-jack oak, and some short-leaved pine. | 20 bushels of corn first year—then nubbins only. |
| 345 | Black-Jack Ridge Soil. | Black-jack oak, pine, huckleberry. | Unproductive. |
| 142 | Oak and Pine Upland Loam. | Red and post oak, pig-nut hickory, short-leaved pine. | 200 lbs. cotton lint at first; 100 lbs. 6-8 years. |
| 219 | Brown Table-land soil. | Black, post, Spanish and black-jack oak, hickory, sweet and black gum. | 400 lbs. cotton—250 lbs. after 20 years. |
| 237 | Bluff or Loess Soil. | Cane, black and white oak, tulip tree, linden, sassafras. | 400 lbs. cotton, decreasing to 250 lbs. after 30 years. |
| 390 | “Buckshot” Soil. | Hickory, ash, sweet gum, pecan, cow oak, honey locust, cane, crab-apple, plum. | 800 lbs. cotton lint, reduced to 500 lbs. in 30 years cultivation. |
| 206 | Pine Hill Soil. | Long-leaved pine, with scarlet and post oak, scattered small and occasional pig-nut hickory. | 20-30 bushels corn for one year—then nubbins. Usually good sweet potatoes for 2-3 years. |
| 215 | Pine Meadow Soil. | Dwarf long-leaved pine, cypress, sedges, orchids, Hæmodoracæ, etc. | Unproductive. Bears small-seeded “sour” vegetation. |
| 88 | Shell Hammock Soil. | Live and water oak, cedar, magnolia, holly, dogwood, sweet gum, hickory, sassafras, grape, Hercules club, etc. | 300 lbs. sea-island cotton for 15 years. |
| No. | Name. | Physical Character. | K₂O. | CaO. | MgO. | P₂O₅. | Humus. |
|---|---|---|---|---|---|---|---|
| 172 | Black Prairie Soil. | Heavy adhesive dark-colored clay. | .333 | 1.367 | .363 | .104 | 1.25 |
| 164 | Pale Yellow Ridge Loam. | Pale yellow sandy loam. | .093 | .069 | .126 | .033 | ★ .50 |
| 226 | Pontotoc Ridge Soil. | “Mulatto” medium loam. | .374 | .281 | .234 | .082 | 1.00 |
| 230 | Heavy Flatwood Soil. | Heavy gray clay. | .753 | .178 | 831 | .052 | .305 |
| 345 | Black-Jack Ridge Soil. | Very sandy loam. | .073 | .142 | .100 | Trace. | ★ .20 |
| 142 | Oak and Pine Upland Loam. | Medium loam. | .236 | .092 | .196 | .091 | ★ .50 |
| 219 | Brown Table-land soil. | Clay loam. | .630 | .270 | .450 | .210 | .79 |
| 237 | Bluff or Loess Soil. | Sandy loam. | .511 | 5.921 | 3.278 | .143 | .72 |
| 390 | “Buckshot” Soil. | Heavy calcareous clay soil. | 1.104 | 1.349 | 1.665 | .304 | ★ 1.0 |
| 206 | Pine Hill Soil. | Light sandy loam; mere sand at 3 feet. | .259 | .129 | .180 | .030 | .35 |
| 215 | Pine Meadow Soil. | Very sandy loam, gray clay subsoil. | .061 | .023 | .069 | .021 | |
| 88 | Shell Hammock Soil. | Very sandy loam, deep. | .080 | .115 | .065 | .107 | .75 |
| Starred values (★) are approximate. | |||||||