THE GENESIS OF SOIL
Soil is not only a support for vegetation, but it is also the zone (the pedosphere) of numerous interactions between climate (water, air, temperature), soil life (micro-organisms, plants, animals) and its residues, the mineral material of the original and added rock, and its position in the landscape
Soil mainly had its origin from rock collectively with animal and vegetable decay, if you are able to guess long stretches or time period when great rock masses were crumbling and breaking. Heat energy, water action, and friction were mostly causative for this. By friction here is meant the rubbing and grinding of rock mass against rock mass. Think of the large rocks, a perfect chaos of them, breaking, scraping, settling against each other. What would be the outcome? Well, I am sure you all could work that out. This is what happened: pieces of rock were worn off, a good deal of heat energy was raised, pieces of rock were pushed together to build new rock masses, some parts becoming dissolved in water. Why, I myself, almost feel the stress and strain of it all. Can you?
Then, also, there were great alterations in temperature. First everything was heated to a high temperature, then gradually became cool. Just think of the cracking, the crumbling, the upheavals, that such alterations must have caused! You know some of the effects in wintertime of sudden freezes and thaws. But the small instances of bursting water pipes and broken pitchers are as nothing to what was going on in the world during those days. The water and the gases in the air helped along this crumbling work.
From all this action of rubbing, which action we call mechanical, it is easily understandable how sand was formed. This corresponds one of the great divisions of soil sandy soil. The coasts are great masses of pure sand. If soil were nothing but broken rock volumes then indeed it would be very poor and fruitless. But the early types of animal and vegetable life decomposing became a part of the rock mass and a better soil resulted. So the soils we talk of as sandy soils have merged with the sand other matter, sometimes clay, sometimes vegetable matter or humus, and often animal waste.
Clay takes us to different category of soils clayey soils. It happens that certain parts of rock masses got dissolved when water trickled over them and heat was enough and ample. This dissolution occurred largely because there is in the air a gas called carbon dioxide or carbonic acid gas. This gas attacks and changes contents in rocks. Sometimes you see great rocks with parts holding up looking as if they had been eaten away. Carbonic acid did this. It changed this eaten part into something else which we call clay. A change like this is not mechanical but chemical. The difference in the two forms of change is just this: in the one case of sand, where a mechanical change went on, you still have just what you started with, save that the size of the mass is smaller. You started with a large rock, and ended with little particles of sand. But you had no dissimilar kind of rock in the end. Mechanical action might be exemplified with a piece of lump sugar. Let the sugar act a big mass of rock. Break the sugar, and even the smallest bit is sugar. It is just so with the rock mass; but in the case of a chemical action you begin with one matter and end with another. You started with a big mass of rock which had in it a part that became altered by the acid working on it. It finished in being an totally different thing which we call clay. So in the case of chemical process a certain something is started with and in the end we have an totally different thing. The clay soils are frequently called mud soils because of the quantity of water used in their formation.
The third sort of soil which we farm people have to deal with is lime soil. Remember we are looking on soils from the farm’s viewpoint. This soil of course ordinarily was formed from limestone. Even as shortly as one thing is referred about which we know nothing, another comes up of which we are just as uninformed. And so a whole string of queries follows. Now you are probably saying within yourselves, how was limestone first formed?
Ages ago the lower animal and plant forms picked from the water particles of lime. With the lime they formed frames or houses about themselves as protection from larger animals. Coral is representative of this class of skeleton-forming animal.
As the animal perished the skeleton persisted. Great volumes of this living matter pressed all together, after ages, formed limestone. Some limestones are still in such condition that the shelly formation is still viewable. Marble, a different limestone, is somewhat crystalline in quality. Another familiar limestone is chalk. Maybe you’d like to know a way of always being able to tell limestone. Drop a bit of this acid on some lime. See how it bubbles and fizzles. Then drop some on this chalk and on the marble, too. The same bubbling takes place. So lime must be in these three structures. One doesn’t have to purchase a particular acid for this work, for even the home acids like vinegar will cause the same result.
Then these are the three types of soil with which the farmer has to handle, and which we wish to understand. For one may learn to know his garden soil by analyzing it, just as one learns a lesson by study.