"Soil primarily had its beginning from rock together with animal and vegetable decay, if you can imagine long stretches or periods of time when great rock ma.s.ses were crumbling and breaking up. Heat, water action, and friction were largely responsible for this. By friction here is meant the rubbing and grinding of rock ma.s.s against rock ma.s.s. Think of the huge rocks, a perfect chaos of them, b.u.mping, sc.r.a.ping, settling against one another. What would be the result? Well, I am sure you all could work that out. This is what happened: bits of rock were worn off, a great deal of heat was produced, pieces of rock were pressed together to form new rock ma.s.ses, some portions becoming dissolved in water. Why, I myself, almost feel the stress and strain of it all. Can you?

"Then, too, there were great changes 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 changes must have caused! You know some of the effects in winter of sudden freezes and thaws. But the little examples of bursting water pipes and broken pitchers are as nothing to what was happening in the world during those days. The water and the gases in the atmosphere helped along this crumbling work.

"From all this action of rubbing, which action we call mechanical, it is easy enough to understand how sand was formed. This represents one of the great divisions of soil--sandy soil. The sea sh.o.r.es are great ma.s.ses of pure sand. If soil were nothing but broken rock ma.s.ses then indeed it would be very poor and unproductive. But the early forms of animal and vegetable life decaying became a part of the rock ma.s.s and a better soil resulted. So the soils we speak of as sandy soils have mixed with the sand other matter, sometimes clay, sometimes vegetable matter or humus, and often animal waste.

[Ill.u.s.tration: Constant Cultivation of the Soil Saved George's Cabbages

Photograph by Karl W. Helmer]

"Clay brings us right to another cla.s.s of soils--clayey soils. It happens that certain portions of rock ma.s.ses became dissolved when water trickled over them and heat was plenty and abundant. This dissolution took place largely because there is in the air a certain gas called carbon dioxide or carbonic acid gas. This gas attacks and changes certain substances in rocks. Sometimes you see great rocks with portions sticking 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 kinds 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 ma.s.s is smaller. You started with a big rock, and ended with little particles of sand. But you had no different kind of rock in the end. Mechanical action might be ill.u.s.trated with a piece of lump sugar. Let the sugar represent a big ma.s.s of rock. Break up the sugar, and even the smallest bit is sugar. It is just so with the rock ma.s.s; but in the case of a chemical change you start with one thing and end with another. You started with a big ma.s.s of rock which had in it a portion that became changed by the acid acting on it. It ended in being an entirely different thing which we call clay. So in the case of chemical change a certain something is started with and in the end we have an entirely different thing. The clay soils are often called mud soils because of the amount of water used in their formation. The slate that Myron brought for road making belongs to the clay family, and so does shale.

"The third sort of soil which we farm people have to deal with is lime soil. Remember we are thinking of soils from the farm point of view.

This soil of course ordinarily was formed from limestone. Just as soon as one thing is mentioned about which we know nothing, another comes up of which we are just as ignorant. And so a whole chain of questions follows. Now you are probably saying within yourselves, how was limestone first formed?

"At one time ages ago the lower animal and plant forms picked from the water particles of lime. With the lime they formed skeletons or houses about themselves as protection from larger animals. Coral is representative of this cla.s.s of skeleton-forming animal.

"As the animal died the skeleton remained. Great ma.s.ses of this living matter pressed all together, after ages, formed limestone. Some limestones are still in such shape that the sh.e.l.ly formation is still visible. Marble, another limestone, is somewhat crystalline in character. Another well-known limestone is chalk. Perhaps you'd like to know a way of always being able to tell limestone. I'll drop a little of this acid on some lime. See how it bubbles and fizzles. Now Albert will drop some on this chalk and on the marble, too. The same bubbling takes place. So lime must be in these three structures. One does not have to buy a special acid for this work, for even the household acids like vinegar will cause the same result. Albert will prove this to you.

"Then these are the three types of soil with which the farmer has to deal, and which we wish to understand. For one may learn to know his garden soil by studying it, just as one learns a lesson by study.

"I believe the boys from their last winter's work feel fairly familiar with soils, I have in these three tumblers the three types of soil. As I pour water on them just see what happens. Observe how little water it takes to saturate sand. The limy soil holds more water and the clayey an amazing quant.i.ty.

"I do not know whether you are much acquainted with the sea sh.o.r.e, I doubt it."

"I am," broke in Katharine, "for each summer, except this last one, I have spent a month at the beach."

"Then possibly you can tell us, Katharine, whether, or not, the sand takes in, or absorbs, much heat during the day."

"Indeed it does absorb heat; why some days we used to go barefooted on the beach right after dinner. I can tell you there were times when we couldn't stand the heat of the sand."

"That is quite true," continued The Chief, "sand absorbs heat to a remarkable degree. This heat is, to be sure, in the upper layers of the sand. Had Katharine burrowed down with her toes below those upper layers she would have found moist, cool sands. But an upper layer of soil, made up of particles which fall apart easily because of the loose make-up, a layer which has absorbed little water and much heat--well, to me that sort of soil doesn't sound quite right for good gardening. Add to such a soil, humus in the shape of stable manure in large quant.i.ties and this same poor soil becomes very good.

"Now here is the lime soil tumbler. This soil has taken up rather more water than the sand took. But it, too, surely needs to develop greater power to take in and hold water. So the same sort of medicine which we gave the sandy soil may be dealt out to the lime soil. Lime is a pretty good substance to have in soil. Lime is a kind of fertilizer in itself; it's a soil sweetener; it helps to put plant food in shape for use, and causes desirable bacteria to grow. This sounds a bit staggering but all of these things I am going to talk over with you. So just at present forget it, Albert, if it is a heavy burden.

"The clay soil, you observe, has taken in quite a quant.i.ty of water.

That seems like a good thing. It is. But clay has a mean little habit of squeezing tightly its particles together with the aid of water so that air is excluded from the ma.s.s. It forms huge lumps; it bakes out and cracks badly; and it is also very damp, cold and soggy in early spring.

"As the problem with sand is to add something so that more water may be held in the soil, so the problem with clay is to overcome that bothersome habit of baking and caking and cracking. To do this we might add sand or ashes. But perhaps it would be better yet to add manure with a lot of straw in it. This is the easiest kind of thing for country boys and girls to get, because the bedding swept out of horses' stalls is just the thing.

"When I speak of clay's horrid habit of tight squeezing, I always have to stop and talk about the two great needs of all soils. One is the need for water; the other, for air. A soil cannot exist without these two things any more than we can. Without these, or poorly supplied with them, a soil is as if it were half-starved.

"That trouble always comes from a lack of one or the other is quite sufficient to prove to us that these are essential. Just see how sand lacks water, as does lime soil too! But there is plenty of air s.p.a.ce, unless these soils are too finely powdered. Now look at clay! plenty of water, but how about the air? When clay begins its packing, then air is excluded.

"So one of the questions to be asked in soil improvement concerns the water and air problem. We must have air s.p.a.ces, and we must have water-holding capacity.

"Before we go home I must just speak of soil and subsoil. When you strike your spade down into the earth and lay bare a section of the soil this is what you see: on top is the plant growth, the soil beneath this, dark in texture and about our locality of a depth of from six to eight inches. This layer is called the topsoil. In sections of the West it is several feet in depth. Now below the topsoil is a lighter coloured, less fertile, more rocky layer, the subsoil. Beneath comes a layer of rock.

"And finally you may be a bit confused by the word loam. It is often given as one of the cla.s.ses of soils. By loam we mean clay, sand and humus. You will often hear people speaking of a sandy loam or a clayey loam according as there is a greater percentage of sand or clay in the soil.

"Next Friday I shall talk about soil fertility. So trot home lively now!"

II

PLANT FOOD

A soil, as I have said before to the boys, may contain all the food necessary for plant growth and still not support any good growth at all.

That means then we ought to be able in some way or other so to understand the soil that it will be possible to unlock these good things for the plants to live on.

"I see a question in Josephine's and Miriam's faces. I guess that this question is concerning what the plant food is in soils. That is right, is it not?

"Well, I'll take that up first, then;--different ways of improving and increasing the goodness of the soil.

"The foods that are necessary and essential to plants and most likely to be lacking in the soil are nitrogen, potash and phosphorus. Now by no means must you think that these are the only chemicals which are foods, for there are something like thirteen, all of which do a share in the food supply. Oxygen and carbon are very necessary indeed. Oxygen is both in the air and in water. Carbon plants take entirely from the air. I might go on and tell you of iron, of sulphur, of silicon and all the others. But you would only get confused, so I am going to make you acquainted with these three entirely necessary ones. They are capricious; often missing, and when not missing hard to make into available food for plants.

"The soil contains many bacteria, small living organisms. These may be divided into two cla.s.ses, the good ones and the bad ones. The good ones acting on nitrogenous matter put it in shape for the plant to absorb or feed upon. You see nitrogen may be in soil in quant.i.ties sufficient for nourishment. But unless it is in a compound available for use, it is of no value to the plant. Then there are the bad bacteria which act upon nitrogen in such a way as to form compounds which escape from the soil as a gas. That is pretty bad, is it not?

"How can the good bacteria be encouraged to grow, and the bad ones prevented from forming? The necessary conditions for the growth of good bacteria are air, water, darkness, humus matter and freedom from acid condition of the soil. If the soil is acid then these other 'chaps' set up their work; so we must see to it that our soils are well cultivated, well aired, have plenty of manure, and, if acid, have a liming, so that these bacteria missionaries can start their good work.

"The manure I spoke of above is the great source of nitrogen upon which most plants depend. There is nitrogen sufficient right in the air, but that again is not available. Certain plants like beans, peas and clovers belonging to the family of legumes are a great deal more fortunate than the rest of the plant families, for, under favourable conditions, they develop bacteria which make it possible to take into themselves free nitrogen. Just look here! See this narrow box; I can drop down one side of it. Here is a sheet of gla.s.s put on so you may look at the roots of the beans which are planted close to this gla.s.s side. Just observe the great extent of root system. Now see on the roots these white lumps, or nodules as they are called. These contain nitrogen-gathering bacteria.

Some farmers in order to get more available nitrogen in the soil plant a crop of some legume. Then these root ma.s.ses with their treasures on them are spaded into the soil.

"But most plants depend for nitrogen on manure. Whenever you see sickly looking foliage know that nitrogen is lacking, and supply manure in order to obtain it.

"The next element is potash. Its most common source of supply is wood ashes, not coal ashes. One may buy potash in the form of the muriate or sulphate. I told the boys before that potash was good for seed and fruit. Pretty necessary to have in the soil, is it not? Stunted fruit and poor seed mean lack of potash. Phosphorus helps in this work too, and also a.s.sists in the forming of fine flowers. Bone ash and phosphates are the sources of this food element.

"So if we just consider the cla.s.ses of soils with which we have to deal, remember the foods that must be had, and the effects on plants where one (or all) of these is lacking, we have in our hands a help to soil troubles.

"Take sandy soil--what is its greatest need? I should say humus. It certainly should have more nitrogen. So add humus in the form of manure.

Spread it on your piece of garden plot anywhere from two to six inches deep. This spaded in will, I think, do the work. You see sand allows water to trickle away too fast. Water must be held properly in the soil.

"The clay soil really needs air. The good bacteria will not work without this. So spade the soil up in the fall, and leave it weathering in huge lumps. Sand or ashes added in the spring helps the air question too. A sprinkling of lime over the surface tends to sweeten the entire soil; for clay soil, so often too wet, is liable to get sour. Lime also adds another plant food called calcium. It would not be bad to add some humus in order to have an even greater supply of nitrogen.

"The lime soil, light and sweet, needs humus too. It should have this to add body and ability to hold water.

"Sometimes it is well to add in the spring a sprinkling of phosphates; that is a chemical fertilizer. Chemical fertilizers are like tonics to the soil.

"All this very briefly puts us in touch with plant foods. I think you all know from your school work that plants take their foods in liquid form. These solutions of foods are very, very weak. That is another reason why we should see that, if possible, there is plenty of nourishment available in the soil, and plenty of water too.

"These bean roots and rootlets show the feeding area or places of plants. Notice the small roots which apparently have a fringe on them.

These fringes we call the root hairs. These absorb, soak up the dilute food which is in the soil.

"It is very wonderful what power they have of penetrating the soil. See the bit of blotter I have put down the path of one bean's root course.

It would seem to shut the rootlets entirely off from the soil.

"Jay will gently press the bit of blotter away from the soil. See here and there how these root hairs have wound their way through the blotter to the soil, their feeding place. It is well that plants have this power of seeking and finding food. Because it greatly increases their food chances.