Stone Mulching in the Garden Part 2



RODALE PRESS                 1949


Chapter 2: Rocks – Parents of the Soil


“And this our life exempt from public haunt

finds tongues in trees, books in brooks,

sermons in stones, and good in everything.”

Shakespeare, As You Like It

In Biblical times stones were employed contemptuously as a means of warfare against goliaths, or of punishment, as in the case of pious but unfortunate Stephen. Today we have turned them to a better end, directing our knowledge of their value and ingredients to treatment and use of them in our gardens. Since this book is to deal exclusively with rocks it should be helpful to the reader to acquire a rudimentary knowledge of the relationship between rocks and the soil, a little bit of elementary geology, so to speak. Then he will see that there really are “sermons in stones.”

As you learn more and more about the origin and makeup of rocks the subject under discussion will take on more significance and interest.

  • Beneath the earth’s surface lies a hard covering, a layer of rock known as bed rock.
  • This is covered by loose and unintegrated materials called mantle rock, that sustains the growth of plants. It is, of course, the soil.
  • This mantle rock is classifiable into three divisions: igneous, sedimentary, and metamorphic.
  • We classify rocks as either acidic (those with a high percentage of silica) or basic (those containing large amounts of iron, calcium, magnesium or sodium).
  • Basic rocks condition soil better than siliceous, acidic ones.

Igneous rocks constitute the principle source of phosphorus, potash, lime and soda. The best-known rock of this type is granite, which sometimes contains excessive quantities of potash.

Sedimentary rocks are produced by the debris of other rocks and so are called fragmentary, or clastic. From the viewpoint of soils they compromise the great soil-creating formations, and contain a very high percentage of silica, 58.38%.

The process of metamorphism which transforms rocks originally of other types to that which we have called metamorphic sometimes strengthens rather than weakens them; for example, marble is much harder than the more friable limestone from which it was derived. Gneiss, schists, slates, quartzite and marble are the common types of metamorphic rocks.

For millions of years the earth’s crust has been “weathering” – its rock structure decomposing through the action of heat and cold, winds, rains, fogs, glacier movement, climatic change, and the life and death cycles of plants and animals. From the activity of the lowly lichen – a peculiar association of microscopic plant, the alga, and a fungus, acting in a partnership – the “weathering” of rock begins. From the digging of tiny roots into the rock and their existence on air-borne particles of dust a process of evolution in plant life gradually takes place, until we have the teeming life of a tropical jungle, with its dense growths, quick decay, and vast census of animal and plant life and organisms. Soil is constantly being created by the factors of climate, rock and soil structure, and plant and animal life.

  • The well-being of cattle and human beings is closely related to the kind of soil which grows their food, and this, in turn, is influenced by the kind of rock out of which the soil is formed.
  • The better soils are on limestone, basalt, dolerite, diorite, and gabbro formations.
  • In 1931 in Florida a “salt sick” disease, an anemic condition of cattle, was found to occur in practically all parts of that state, but only on light, sandy soils. No such sickness occurred on clay soils.
  • In New Zealand in 1932 it was found that bush sickness was found mostly over granitic formations.
  • A bone disease of livestock was discovered in Australia in 1895 in cattle fed largely from granite soils, where there was a deficiency of lime.
  • In 1920 there was a deficiency disease called “creeping sickness” in southern Alabama along the Coastal Plains; it was found only among people who lived on sandy soils low in lime content.
  • In 1924 in South Texas there was noticed a fatal disease in cattle called “loin disease” or “down-in-the-back,” in a section where the soil was notably lime-deficient.
  • A nutritional anemia in Florida was discovered in 1934 in the flatwoods country, affecting 96% of the children in that section. The soil is known as Leon, and it is thin, sandy, and low in lime content.
  • Six miles away where the soil overlays hard rock phosphate, only 3% of the children have this amemic condition.
  • Deaf Smith County, Texas, became known as “the county without a toothache.” The soil derives from rocks that are rich in lime and phosphorus and contain some fluorine which is important in the making of bone and teeth.
  • Even when strangers come to Deaf Smith County, the cavities in their teeth glaze over and progress no further.
  • The farmers bring in spindly cattle from Mexico and in a short time make fine, big-boned animals out of them.
  • What kind of rock structure you have under your soil is important. It is a large factor in determining the nature of good soil.
  • In northwest India there is a race called the Hunzas, who are about the healthiest people in the world. Across the river from them live the Nagyrs, who are of the same race, but whose health is entirely different.
  • The main reason for the differences between them seems to lie in the organic matter in which the Hunzas produce their food. The Hunzas have a much more desirable geologic formation under the soils on their side of the river.
  • Rakaposhi, the glacier-topped mountain that is more than 20,000 feet high and which dominates the Hunza, is of limestone formation.
  • Sir Robert McCarrison who spent eight years as physician and medical investigator among the Hunzas (1904 to 1911) continually mentions the fertile Hunza soils in his published works.
  • Roger Babson, in his column for the New York Times of February 4, 1944, said: ‘Europe will always have trouble with those Prussians. There is something in the soil of Prussia which grows people with that fighting instinct. European peace is unalterably linked up with the minerals of the soil.’
  • Germany is noted for its tremendous potash deposits. Germany, according to the 1928 figures, uses seventeen times the amount of chemical fertilizers we use here in the United States, a practice which may, and very likely does, aggravate the difficulty.
  • The Germans may behave the way they do because of the mineral content of their soil, overrich in some elements and doubtless deficient in many others.
  • In Japan you have a somewhat analogous situation. The Japanese islands consist mainly of a volcanic ash soil, destitute of lime and considered very low in the scale of soil values.
  • It may be that Japanese soils need tremendously heavy dressings of limestone, of phosphatic rocks, dolomites, etc., the materials for which would have to be imported.
  • Perhaps the new world organization to maintain peace ought to study this subject as it may have a great deal to offer in explaining national behavior.
  • Dr. Greene in The Cancer Problem says that cancer is least frequent in districts that lie on a limestone geologic formation.
  • A group of French physicians and chemists in1932 suggested a direct relationship between the incidence of cancer and the rock formation from which the soil derives.
  • Certain rocks of a dolomitic character (a form of limestone rich in magnesium) produce a soil which seems to be low in cancer incidence, whereas rock formations such as granites which are rich in potash have the reverse effect.
  • Potash is slightly radio-active and seems to be suspect as a cause of cancer. If magnesium goes down then potash goes up. In many orchards because of increasing potassium – magnesium deficiency diseases occur.

These French scientists carefully plotted maps which indicated the extent of magnesium in the geologic formations of various parts of the world, and then they placed on top of it the cancer mortality figures for those regions. The agreement is startling. Egypt, a country rich in magnesium, shows an extremely low cancer rate. Certain parts of France also show a similar situation. There are doubtless other factors known and unknown, in the cancer equation, the sulphur theory of Dr. Greene, for instance, but in this connection one must point out that sulphur is found more often in granites and the other rock formations listed as producers of inferior soils than in limestone.

  • If a farm is located on one of the unfavorable soil formations, use liberal amounts of the lime, phosphate rock and dolomite and none of the strong chemical fertilizers. Try to get oyster-shell lime and other organic amendments. Make and apply as much compost as possible. I believe you can gradually build up a perfectly safe soil, the organic way.


Chapter 3: The Reasons

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