The Story of the Soil Part 4

"Of course the chemical element is the simplest form of matter. An element is a primary substance which cannot be divided into two or more substances All known matter consists of about eighty of these primary elements; and, as a matter of fact, most of these are of rare occurence--many of them much more rare than the element gold.

"About ninety-eight per cent. of the soil consists of eight elements united in various compounds or combinations; and only ten elements are essential for the growth and full development of corn or other plants. If any one of these ten elements is lacking, it is impossible to produce a kernel of corn, a grain of wheat, or a leaf of clover; and in the main the supply is under the farmer's own control. But we can discuss this matter more fully later. Let us see what we have here."

Percy poured a few drops of the hydrochloric acid into the hollow of the cake of soil.

"What should it do?" asked Mr. West.

"If the soil contains any limestone, the acid should produce foaming, or effervescence," replied Percy; "but it is very evident that this soil contains no limestone. You see the hydrochloric acid has power to decompose calcium carbonate with the formation of carbonic acid and calcium chlorid, a kind of salt that is used to make a brine that won't freeze in the artificial ice plants. The carbonic acid, if produced at once decomposes into water and carbon dioxid. Now, the liberated carbon dioxid is a gas and the rapid generation or evolution of this gas const.i.tutes the bubbling or foaming we are looking for; but since there is no appearance of foaming we know that this soil contains no limestone."

"Then you have already found that those three elements,--calcium, carbon, and oxygen, you called them, I think--you find that those elements are all lacking in this soil."

"No, this test does not prove that," said Percy. "It only proves that they are not present as limestone. Calcium may be present in other compounds, especially in silicates, which are the most abundant compounds in the soil and in the earth's crust; and, as indicated by the ending _-ate, _oxygen is contained in calcium silicate as well as in calcium carbonate."

"I see; the subject is much more complicated than I thought."

"Somewhat, perhaps," Percy replied; "but yet it is quite simple and very easily understood, if we only keep in mind a few well established facts. Certainly the essential science of soil fertility is much less complicated than many of the political questions of the day, such as the gold standard or free-silver basis, the tariff issues, and reciprocity advantages, regarding which most farmers are fairly well informed,--at least to such an extent that they can argue these questions for hours."

"I think you are quite right in that," said Mr. West. "Of course, it is important that every citizen ent.i.tled to the privilege of voting in a democracy like ours should be able to exercise his franchise intelligently; but the citizen who is responsible for the management of farm lands ought surely to be at least as well informed concerning the principles which underlie the maintenance of soil fertility; provided, of course, that such knowledge is within his reach; and from what you say I am beginning to believe that such is the case. At any rate this simple test seems to show conclusively that this soil contains no limestone, and it is common knowledge that limestone soils are good soils."

Percy took up the ball of soil containing the slip of blue paper, broke it in two again, and it was seen that the paper had changed in color from blue to red

"There's a change, for certain," said Mr. West, "that has some meaning to you I suppose."

"This is litmus paper," said Percy. "It is prepared by moistening specially prepared paper with a solution of a coloring matter called litmus, and the paper is then dried. This coloring matter has the property of turning blue in the presence of alkali and red in the presence of acid. The blue paper is prepared with a trace of alkali, and the red paper with a trace of acid. If more than a trace were present the litmus paper would not be sufficiently sensitive for the test.

"This little bottle containing two dozen slips of paper cost me five cents, and it can be obtained at most drug stores.

"Alkali and acid are exactly opposite terms, like hot and cold. The one neutralizes the other. This test with litmus paper is a test for soil acidity, and the fact that the moisture of the soil has turned the litmus from blue to red shows that this soil is acid, or sour.

The soil moisture contained enough acid to neutralize the trace of alkali contained in the blue paper and to change the paper to a distinctly light red color; and the fact that the paper remains red even after drying, shows that the soil contains fixed acids or acid salts, and not merely carbonic acid, which if present would completely volatilize as the paper dries.

"Now, these two tests are in harmony. The one shows the absence of limestone, and the other shows the presence of acidity, and consequently the need of limestone to correct or neutralize the acidity, for limestone itself is an alkali."

"But limestone soils are not alkali soils, are they?" asked Mr.

West.

"Not in the sense of containing injurious alkali, like sodium carbonate, the compound which is found in the 'black alkali' lands of the arid regions of the far West; but chemically considered limestone is truly an alkali; and, as such, it has power to neutralze this soil acidity."

"Is the acidity harmful to the crops?"

"It is not particularly harmful to the common crops of the gra.s.s family, such as wheat, corn, oats, and timothy; but some of the most valuable crops for soil improvement will not thrive on acid soils.

This is especially true of clover and alfalfa."

"That is certainly correct for clover so far as this kind of soil is concerned," said Mr. West. "Clover never amounts to much on this kind of land, except where heavily fertilized. When fertilized it usually grows well. Does the farm fertilizer neutralize the acid?"

"Only to a small extent. It is true that farm manures contain very appreciable amounts of lime and some other alkaline, or basic, substances, but in addition to this, and perhaps of greater importance, is the fact that such fertilizer has power to feed the clover crop as well as other crops. In other words it furnishes the essential materials of which these crops are made. In addition to this the decaying organic matter has power to liberate some plant food from the soil which would not otherwise be made available although to that extent the farm manure serves as a soil stimulant, this action tending not toward soil enrichment but toward the further depletion of the store of fertility still remaining in the soil."

"This seems a complicated problem," said Mr. West, "but may I now show you some of our more productive land?"

"As soon as I collect a sample of this," replied Percy, and to Mr.

West's surprise he proceeded to bore about twenty holes in the s.p.a.ce of two or three acres. The borings were taken to a depth of about seven inches, and after being thoroughly mixed together an average sample of the lot was placed in a small bag bearing a number which Percy recorded in his note book together with a description of the land.

"I wish to have an a.n.a.lysis made of this sample," remarked Percy, as they resumed their walk.

"But I thought you had a.n.a.lyzed this soil," was the reply.

"Oh, I only tested for limestone and acidity," explained Percy. "I wish to have exact determinations made of the nitrogen and phosphorus, and perhaps of the pota.s.sium, magnesium, and calcium.

All of these are absolutely essential for the growth of every agricultural plant; and any one of them may be deficient in the soil, although" the last three are not so likely to be as the other two."

"How long will it take to make this a.n.a.lysis?" was asked.

"About a week or ten days. Perhaps I shall collect two or three other samples and send them all together to an a.n.a.lytical chemist.

It is the only way to secure positive knowledge in advance as to what these soils contain. In other words, by this means we can take an absolute invoice of the stock of fertility in the soil, just as truly as the merchant can take an invoice of the stock of goods carried on his shelves."

"So far as we are concerned, this would not be an invoice in advance," remarked Mr. West, with a shade of sadness in his voice.

"If we knew the contents of the crops that have been sold from this farm during the two centuries past, we would have a fairly good invoice, I fear, of what the virgin soil contained; but can you compare the invoice of the soil with that of the merchant's goods?"

"Quite fairly so," Percy replied. "The plant food content of the plowed soil of an acre of normal land means nearly, if not quite, as much in the making of definite plans for a system of permanent agriculture, as the merchant's invoice means in the future plans of his business.

"It should not be a.s.sumed that the a.n.a.lysis of the soil will give information the application of which will always a.s.sure an abundant crop the following season. In comparison, it may also be said, however, that the merchant's invoice of January the first may have no relation to the sales from his store on January the second. Now, the year with the farmer is as a day with the merchant. The farmer harvests his crop but once a year; while the merchant plants and harvests every day, or at least every week. But I would say that the invoice of the soil is worth as much to the farmer for the next year as the merchant's invoice is to him for the next month.

"It should be remembered, however, that both must look forward, and plans must be made by the merchant for several months, and by the farmer for several years. Your twelve-year rotation is a very good example of the kind of future planning the successful farmer must do. On the other hand, some of your neighbors, who have not practiced some such system of rotation now have 'old-field' pine on land long since abandoned, and soil too poor to cultivate on land long cropped continuously."

"This is a kind soil," remarked Mr. West, as he paused on a gently undulating part of the field.

"That is a new use of the word to me," said Percy. "Just what do you mean by a 'kind' soil?"

"Well, if we apply manure here it will show in the crop for many years. It is easy to build this soil up with manure; but, of course, we have too little to treat it right."

"The soil is almost neutral," said Percy, testing with litmus and acid. "Does clover grow on this soil?"

"Very little, except where we put manure."

Another composite sample of the soil was collected, and they walked on.

"Now, here," said Mr. West, "is about the most productive upland on the farm."

"Is that possible?" asked Percy, the question being directed more to himself than to his host.

"That is according to my observation for about fifty years," he replied. "Where we spread the farm fertilizer over this old pasture land and plow it under for corn, we often harvest a crop of eight barrels to the acre, while the average of the field will not be more than five barrels.--A barrel of corn with us is five bushels."

They had stopped on one of the steepest slopes in the field.

"These hillsides would be considered the poorest land on the farm if we were in the corn belt," said Percy, "but I think I understand the difference. Your level uplands when once depleted remain depleted, because the soil that was plowed two hundred years ago is the same soil that is plowed to-day; but these slopes lose surface soil by erosion at least as rapidly as the mineral plant food is removed by cropping; and to that extent they afford the conditions for a permanent system of agriculture of low grade, unless, of course, the erosion is more rapid than the disintegration of the underlying bed rock, which I note is showing in some outcrops in the gullies.

"I want some samples here," he continued, and at once proceeded to collect a composite sample of the surface soil and another of the sub-soil.

"In the main this soil is slightly acid," said Percy, after several tests, with the hydrochloric acid and the litmus paper; "although occasionally there are traces of limestone present. The ma.s.s of soil seems to be faintly acid, but here and there are little pieces of limestone which still produce some localized benefit, and probably prevent the development of more marked acidity throughout the soil ma.s.s.