The primer of irrigation

Front matter

COPYRIGHT DEPOSIT.

THE

Primer of Irrigation

Preface

THE author of this work has had in mind for many years the outlines of a book which would lend aid to those who are beginners in irrigation farming.

After work was commenced on this book it was realized that much more than fifty or even one hundred pages would be necessary to even half-way cover the subject, and before it was completed nearly three hundred pages of type were used.

While much of value could be added, and no doubt a lot could be taken away without serious loss, the author offers it as it is, hoping that its readers may find some profit in its perusal. ^ , . .

D. H. Anderson.

Chicago. July 1. 1905.

THE PRIMER OF IRRIGATION.

Chapter I

Soil in General — Its Formation, Charaoteeistics AND Uses — Fertility and Sterility.

The mere planting of a seed in the ground is not sufficient to insure its growth, or development into a useful or profitable plant. This fact is well known to everybody, but what is not so well known is, the reason or cause why a seed grows up into a; vigorous plant capable of reproducing seed similar to the one from which it sprang, and how it does it.

There are certain elements which are essential to the growth of every plant, the development of every germ, for without them it cannot live; these are heat, light, air and moisture. A few grains of wheat discovered in the coffin of an Egyptian mummy after three or four thousands years' deprivation of the four essential elements, were found inert, that is, they were not alive, neither were they dead, for upon giving them the essentials above referred to, the wheat sprang into life and produced a plentiful supply of grain.

plants are like animals.

Still, notwithstanding the necessity of heat, light, air and moisture, plants cannot flourish without proper food. In this respect plants are similar to animals. Among animals there is no universal specified diet, some eating one kind of food, others another. We see many that eat flesh exclusively, others whose sole diet is insects. Certain animals eat herbs and grass, others orain, and when we reach man we find an animal that will eat anything and everything, hence we call man "omnivorous."

It is the same with plants, some devouring in their fashion a certain kind of food, some another, and so on all along the list. Plants are substantially like animals that possess a stomach, they eat and digest, absorb and assimilate the food they obtain. If the plant is not furnished with its proper food, or if it is prevented from obtaining it, it shrivels, droops, withers and dies just like an animal that starves to death.

There is another striking resemblance between plants and animals, which is the instinct and power to seek food. The plant being a fixture in the soil, cannot of course, "prowl" about in search of food, but it throws out roots, fibres and filaments in every direction, its instincts reaching in the direction of food as surely and with as much certainty as the nose of an animal scents its prey, or the eye of an eagle sees its quarry. Not only does the plant seek food beneath the surface of the earth, but it thrusts shoots, branches and leaves up into the atmosphere for the purpose of extracting nourishment there also.

It is, however, from the soil that plants receive the principal supply of food necessary for their development, hence an acquaintance with its chemical and physical properties is important in helping us to understand the nutritive processes of plants, and the operations of agriculture.

Volumes of books have been written on the general subject of agriculture, but they are more adapted to soils upon which falls sufficient rain to dissolve the salts necessary to produce a crop. In a book devoted to irrigation, the principles of agriculture and the adaptation of the various elements of plant food in the soil, are all the more important as the water employed in irrigation — ^which is nothing but artificial rain — is absolutely within the control of man, and not dependent upon meteorological uncertainties. One fact should.

Soil in General. t

however, be constantly borne in mind by the practical irrigator, thart pure water is absolutely sterile so far as plant food is concerned, and if poured upon a pure soil, which is also sterile, there can be no crop of any sort raised. A remedy for supplying a defect of plant food in irrigating water will be given in detail in another chapter, the scope of this chapter being limited to soils that contain plant food, or are arable, in which case the quality of the water is of secondary importance.

ORIGIN OF ARABLE SOIL.

Arable soil owes its formation to the disintegration of minerals and rocks, brought about by mechanical and chemical agencies. The rock may be said to stand in about the same relation to the arable soil resulting 'from its disintegration as the wood or vegetable fibre stands to what is called the humus resulting from its decay. To be fertile, however, the soil must contain disintegrated vegetable matter. There is no fertility in a heap of sawdust, nor is there in a heap of powdered rock; indeed, the two might be combined and still remain sterile, it is only after both have been disintegrated by chemical or mechanical action that they become plant foods capable of nourishing and maintaining plant life.

From this it results that soil consists of two grand divisions of elements : inorganic and organic. The inorganic are wholly mineral, they are the products of the chemical action of the metallic, or unmetallic elements of rocks. They existed before plants or animals. Life has not called them into existence, nor created them out of simple elements. Yet these inorganic mineral elements of soil become part of plants, and under the influence of the principle of life they no longer obey chemical laws, but are parts of a living structure. Through the operation of the laws of the life of the plant, these mineral elements become organic and so continue until death comes and decay begins, when they return to their mineral form.

Organic elements are the products of substances once endowed with life. This power influences the elements, recombines them in forms so essentially connected with life that they are, with few exceptions, produced only by a living process. They are the products of living organs, hence termed organic, and when formed, are subject to chemical laws. The number of elements in the inorganic parts of soil is twelve: Oxygen, sulphur, phosphorus, carbon, silicon and the metals : potassium, sodium, calcium, aluminium, magnesium, iron and manganese.

The number of elements in the organic parts of soil does not exceed four: Oxygen, hydrogen, carbon and nitrogen.

The great difference between these two divisions is, that while the inorganic elements are combina'tions of two elementary substances, the organic are combinations of three or four elements, but never less than two. These three elements, however, are variously combined with the other elements to form salts which enter into the great body of vegetable products, in fact they are continually changing, the mere change of one element, or its abstraction forming a new product. It is this susceptibility to change, and the constant assumption of new forms by vegetable products which is the foundation of tillage, and the essence of the knowledge of irrigation.

HOW PLANTS FEED.

We do not know and we may not understand what life is, nor how plants grow, but it is a knowledge which comes to the most superficial observer, that all plants feed upon various substances their roots find in the soil, which substances are called "salts," and they are prepared for the uses of the plant by the action of organic matter on the inorganic or vice versa. That is to

Soil in Gtfural. 11

say, vegetable matter combines with decomposed rocks or minerals and forms a plant food without which the plant cannot live. We know as a fact that the silicates or rock elements and minerals or metallic salts compose all the earthy ingredients of soil, and are always found in plants, the ashes of any burned vegetable or plant showing this. But these silicates and salts do not make fertility in soil. Fertility depends on the presence in the soil of matter which has already formed a part of a living structure, organic substances in fact. It is this matter which causes constant chemical changes in which lies the very essence of fertility. To make this quite clear, it will be sufficient to refer to the fertility in the valley of the Nile in Egypt caused by the overflow of the river and the deposits, upon the silicates and minerals or metallic salts, which in plain language means the sands of the desert, of a layer of mud containing decomposed vegetable or organic matter. The consequence is, chemical action takes plaxje and a rich harvest follows. The result would be the same in our arid plains where the soil contains all the ingredients necessary to plant life, but the element of moisture to dissolve and unite them is absent. Here, irrigation creates fertility. The oxygen and the hydrogen in the water supplies the soil with the elements it lacks to manufacture plant food.

There is a curious, not to say mysterious, fact connected with the transformation of the organic and inorganic elements in the soil into plant food, and that is, the chemical change does not take place except through the intervention or agency of the living plant itself. It is life that is necessary to the process and this life of the plant gives life to the inert elements around it. The mere presence of a living plant gives to the elements power to enter into new combinations, and then these combinations occur in obedience only to the well-known, established, eternal laws of chemical affinity.

If, on a dry day, a wheat or barley plant is carefully pulled up from a loose soil, a cylinder of earthy particles will be seen to adhere like a sheath around every root fibre. This will be also noticed in the case of every plant. It is from these earthy particles that the plant derives the phosphoric acid, potash, silicic acid, and all the other metallic salts, as well as ammonia. The little cylinders are the laboratories in which nature prepares the food absorbed by the plant, and this food is prepared or drawn from the earth immediately contiguous to the plant and its roots. This demonstrates the importance of the mechanical tillage of the ground. Cultivated plants receive their food principally from the earthy particles with which the roots are in direct contact, out of a solution forming around the roots themselves. All nutritive substances lying beyond the immediate reach of the roots, though effective as food, are not available for the use of the plants, hence the necessity of constant tillage, cultivation of the soil, to bring the nutrition in contact with the roots.

FORMATION AND USE OF EARTH SALTS.

A plant is not, like an animal, endowed with special organs to dissolve the food and make it ready for absorption; this preparation of the nutriment is assigned to the fruitful earth itself, which in this respect discharges the functions performed by the stomach and intestines of animals. The arable soil decomposes all salts of potash, of ammonia, and the soluble phosphates, and the potash, ammonia, and phosphoric acid always take the same form in the soil, no matter from what salt they are derived.

It is essential that these "salts," as they are called, should be understood, for without them there can be no fertility- Unless these "salts" exist in a soil in certain quantities the organic elements, or what are known as "humic acids," are insoluble and cannot be absorbed into the plant through its roots, and so there can be no fruit

Soil in Central. 18

or vegetable. Yet there is such a thing as an excess of these same salts, and then there is barrenness. A common illustration of which may be seen in what axe termed "alkali lands," which will be treated in detail in another chapter.

To simplify an acquaintance with these various salts, we shall divide them into three general classes depending upon the acids formed from them, all of them nutritious to plants.

First — Carbonates.

Second — Nitrates.

Third — Phosphates.

The carbonates compose a very large portion of the salts used in agriculture, and include limestone, marble, shells. These salts are set loose from the rock, that is the decomposed rock already alluded to, by the action of the living plant, and their business is to dissolve, or render soluble, the organic matter in the soil, so that the plant may absorb it through its roots. When there is an excess of these salts, or of lime or alkali, the organic matter is rendered insoluble, that is, the plant cannot absorb it, and then the soil is barren. There are, however, certain plants known as "gross feeders," which flourish in such soils, but of them more will be said in another chapter.

The second class of nourishing salts is the nitrates, and includes saltpeter, nitrate of potash, nitrate of soda, and all composts of lime, alkali and animal matter. This class of salts produces ammonia which hastens the decay or decomposition of the organic matter, and prepares it for absorption by the plant. All the nitrates act under the influence of the growing plant and yield nitrogen which is essential to its life, indeed, if there are any salts which can be called vegetable foods, they are the nitrates, and they hold the very first place among salts in agriculture.

The third class of plant nourishing salts is the phosphates. They are found in bones, liquid manure, and in certain rocky formations which are abundant in the United States, and ground up, are largely used upon land to add to its fertility and increase the supply of plant food.

The phosphates act much like the nitrates, their acid forming a constituent of the plant.

The proper, proportionate quantity of all these salts in the soil, is generally in the order already given ; the carbonates in the greater quantity, the nitrates in less quantity, and the phosphates least. The quantity of any salt which may be used to advantage, however, will depend upon the demands or necessity of the plant which will show for itself the salt proper for its well being and perfection.

To still further simplify the idea of the use and operation of these salts and their necessity, it will be well for the reader to again imagine a similarity between the plant and an animal. The stomach of the animal secretes, or produces, gastric juice and other acids which come from practically similar salts, by the action of which the organic matter — the meat and vegetables — put into the stomach, are digested and distributed to nourish every part of the body. If there were no gastric juice, or other acids formed from the salts of the body, the organic matter put into the stomach could never become food, and the body, left without nourishment, would starve and die.

So it is substantially with plants. The main difference being that the plant has no stomach within itself, but it requires food just the same as the animal, and if it does not receive it, it starves and dies. By the active principle of life in the plant as in the animal, the salts of the soil are brought into the presence of each other to form acids which act upon the organic matter in the soil, or the humus, in very much the same manner as the gastric juice and other acids of the

Soil in General. 16

animal stomach, convert it into prepared food, so to speak, and the plant absorbs it, is nourished by it and grows to maturity.

SILICATES AS ESSENTIAL TO FERTILITY.

There is one important prevailing element in all soil which can neither be overlooked nor ignored, in fact, its power of fertility is unlimited; we refer to the silicates. Salts are spoken of as the inorganic substances acting upon humus or organic matter to produce nourishing foods that can be absorbed by the plant, but behind these salts, there is another substance which really constitutes the framework of the plant structure, the bony framework of the plant, the sinew of the soil.

Silex, or silica, which is the earth of flints, is, in its pure state, a perfectly white, insipid, tasteless powder. Glass pulverized is an illustration, so also is a sand heap. But earth of flints, sand heaps, are barren and worthless, as much so as a peat bog, but put the two together, and there is astonishing fertility. This silica unites readily with the mineral substances or bases, forming what are called "neutral salts," to which is given the name "silicates." Thus we have the silicate of soda, of potash, of lime, of magnesia, of alumina, of iron and of manganese, a class which forms the great bulk of all rock and soil.

The action of the silicates is simple and easily understood. When humus, or decomposed organic matter — manure for instance — is mixed with silica, that is added to a common sand heap, there is an immediate decomposition of the silicate of potash, which we have said is a neutral salt, and it becomes an active salt of potash which dissolves the humus, or organic matter and fits it for plant food. So the same process goes on with the other silicates as the various plants growing in the soil may demand for their nourishment. They are converted into active salts, which are capable of dis-

16 The Primer of IrrigatUn.

solving organic matter, whereas, as neutral, inactive salts or silicates, they are powerless to act.

Were it not for these silicates, the various active salts and acids would lose their virtue, but as it happens, the silicates hold them in a firm grip, intact, until the action of plant life demanding food, sets them free to aid in preparing plant food.

The base, or fixed element of the earth called silex, or silica — keep in mind a sand heap and it will be easy to remember — is "siliconi,^' It is pure rock crystal, common quartz, agate, calcedony and cornelian. All these are silicon acidified by oxygen, and hence called silicic acid. It is this which forms, with potash, the hard coat of the polishing rush, the outer covering of the stalks of grasses. It is the stiff backbone of cornstalks which stand sturdily against the blast. Wheat, rye, oats, barley, owe their support to this silica, and where grain is said to "lodge" during a heavy storm, the trouble may be traced to a deficiency of silica in the soil. It cases the bamboo and the rattan with an armor of flint so hard that from it sparks may be struck. Entering into the composition of all soil, and hard and unyielding as it appears, forming not only the solid rock, but the delicate flower, combining with the metals of soil whose gradual decomposition is the birth of fertility, silica, or the sand heap, may well be likened to the bony structure or framework of the animal.

The next chapter on particular soils will give more in detail, the component elements which enter into their composition, and present a series of tabulated analyses showing proportions favorable to the growth of various products.

Chapter II

Particular Soils, and Their Adaptation to Varietieb of Plants.

Although this book is intended to apply exclusively to irrigation, that is, the artificial application of water to lands deprived of a sufficient rain fall to raise a crop, such as the arid and semi-arid lands, which constitute so vast a portion of our western country, yet, as all arable or fertile soils in whatever part of the world they may be, must contain certain elements necessary to plant life, an inquiry into the specific nature of soils will supply whatever information may be needed to till irrigable lands, as successfully as those where a rain fall may be depended upon to raise a crop. It is even possible that such information may be of greater practical value, because the elements in the soil and the crop itself, are under better control and management when the ncessary water is in an irrigating ditch, than when it is in a cloud beyond control.

As a matter of fact, there is very little difference in soils as such, wherever they may exist. All of them are capable of producing some variety of plant life, omless absolutely barren on account of the absence of plant food, as the Desert of Sahara, for instance, or by reason of an excess of the elements essential to plant life, as our so-called "alkali lands." But, when it comes to the comparative quantities of organic and inorganic elements to be found in all soils, there is a vast difference, particularly when crops of a certain kind are to be successfully raised.

It was stated in the last chapter that soil consists of inorganic and organic elements. The inorganic material being decomposed rocks and minerals ; to be more precise, such as were never endowed with life, and the organic material consisting of decomposed vegetable matter, which once possessed some form of life, both of

18 The Primtr of Irrigation.

which elements are absolutely necessary to grow any kind of plant.

A little experiment, which any one can perform, will make this clear to the reader. When any vegetable substance is heated to redness in the open air, no matter whether it be a peach or a potato, a strawberry or a squash, a handful of straw or a beautiful rose, the whole of the so-called organic elements, which are carbon, hydrogen, oxygen, and nitrogen, are burned away and disappear, but there remains behind an "ash" composed of potash, soda, lime, magnesia, iron, etc., which does not burn, and which, in most cases, does not undergo any diminution when exposed to a much greater heat. It is this "ash" which constitutes the inorganic portion of plants.

The predominance of certain of these substances, which, it was stated in the last chapter, are absorbed from the soil by the operation of plant life, is what enables agriculturists to give certain names to various kinds of soils, which names, however, are of very little practical importance, except to enable a farmer to specify which of them are best adapted to the varieties of plants he desires to raise.

So far as these inorganic substances are concerned, they must exist in the soil in such quantities as easily to yield to the plant, so much of each one as the kind of plant specifically requires. If they be rare, the plant sickens and dies just the same as does an animal when deprived of its necessary food. The same thing will happen if the organic food supplied the plant by the vegetable matter in the soil be wholly withdrawn. It should be noted, however, that a plant will sometimes substitute one inorganic element for another, if it does not find exactly what it requires, as soda for potash, the tendency of every plant being to grow to perfection if it possibly can do so. This matter will be treated at length in the chapter on "Plant Foods."

P»rticmlar Soils,

The following table of the essential inorganic elements found in soils will prove useful and well worth study. The first column gives the scientific, technical name of the elementary bodies; the second column the elements or substances they combine with, and the third column contains the result of the combinations, that is, the various substances ready to form salts which enter into the life of the plant.

Elementaky Body

Combines with Fosming

Chlorine.

Metals

Chlorides.

Iodine

Metals

Iodides.

Sulphur

Metals

Sulphurets.

Sulphur

Hydrogen

Sulphuretted Hydrogen.

Sulphur

Sulphuric Acid.

Phosphorus

Phosphoric Acid.

Potassium

Potash.

Potassium

Chlorine

Chloride of Potassium.

Sodium

Soda.

Sodium

Chlorine

Chloride of Sodium, or Common salt.

Calcium

Chlorine

Chloride of Calcium.

Calcium

Lime.

Magnesium

Magnesia.

Aluminum

Alumina.

Silicon

Silica.

Iron and Manganese

Oxides.

Sulph'ir'"ts.

Sulphur

All the above elementary suh-.tances, except sulphur, exist only in a state of combination with other substances, principally oxygen, and are found only in the soil, in no combination are they generally diffused through the atmosphere, so as to be capable of entering into the life of the plant through the leaves, or those portions above the ground. Hence, they must be taken up by the roots of plants, for which reason they are said to be the necessary constituents of a soil in which plants are expected to grow.

The enormous quantity of inorganic matter in soil may be estimated by a simple calculation. Out of five hundred samples of soil gathered from different parts of the world, the average weight of a cubic foot, wet, has been found to be 126.6 pounds. Now, let us ascertain how many pounds of mineral, or metallic salts exist in an acre of soil, say eight inches deep, the usual tilled depth, or surface soil; of the subsoil, we shall speak later on. We shall give the chemical analysis of an ordinary alluvial, or river bottom soil, such as is common in the western lands. The first column gives the name of the mineral, and the figures in the second column the parts of the mineral in an agreed one hundred parts, and the third column the weight of each substance in the surface soil eight inches deep:

Elementary bodie* and their combinations Percentage Weight in pounds

Silica and fine sand 87.143 3,203,781-f

Oxides of Iron 2.220 8i,6i74-

Oxide of Magnesia 0.360 13,235+

Potash combined with Silica 0.120 4,4H-|-

Soda combined with Silica 0.025 919+

Phosphoric Acid combined with Lime

and Oxide of Iron 0.060 2,205+

Sulphuric Acid in Gypsum 0.027 992+

Chlorine in common Salt 0.036 1,323+

Carbonic Acid united to the Lime 0.080 2,941-}-

Insoluble Humus 1.07a 39,4ii+

Organic substances containing Nitrogen i.oii 37,169+

Total Inorganic and Organic substances 100. 3,676,464

It should be remembered that these immense quantities are contained in only eight inches of top soil, and that twelve inches, or one foot of soil, which is about the depth before reaching the subsoil, would contain a total of inorganic and organic matter equal to 5,514,- 696 pounds, or 2,757 and one-third tons.

Particular Soiis. 21

The calculation is made by multiplying 43,560, the number of square feet in an acre, by 126.6. poimds, the estimated average weight of one cubic foot of wet soil, which gives the weight of one acre twelve inches deep. Then dividing by twelve, we get the weight of an acre one inch deep. To ascertain the weight of eight inches, we have only to multiply by eight inches, and again multiply by the number of parts of any organic or inorganic matter to ascertain the exact weight of that particular matter in the acre, thus :

43,560x126.6=5,514,696 pounds per acre one foot deep.

5,5i4,696-=-i2=:459,558 pounds per acre one inch deep.

459,558x0.120=551.46960 pounds of Potash in one inch acre.

551.46960x8=4,411 pounds of Potash in acre eight inches deep.

Five right hand figures must be cut off, three for the decimal places and two more because the calculation is based on a percentage of one hundred parts.

The average weight of a cubic foot of dry soil, according to the foregoing estimate, based upon the tests taken in the cases of five hundred soils collected from various places on the globe, is 94.58 pounds, which will make the dry soil acre eight inches deep weigh 2,715,792 pounds, a difference in weight between wet and dry soils of 960,672 pounds per acre eight inches deep, which, of course, represents the weight of water.

This information will prove of value in considering the question of applying water to the soil. As a rule, the proportions of inorganic and organic matter remain about the same, except that the application of water by irrigation adds to the quantity in soluble matter carried to the soil, which is greater in the case of irrigation than when rain is depended upon^ humus and salts in solution being carried in the ditch water.

ORGANIC MATTER IN THE SOIL.

By referring back to the test table of a specimen soil, it will be noticed that the first twelve substances are "inorganic," and the three last "organic." It will also be noticed that the proportion of inorganic matter is vastly greater than that of the organic. It is necessary that this should be so, for the organic matter is the "active" principle, the dynamic force, and the inorganic matter the "passive" principle. If the proportions were reversed, the inorganic matter would react upon and destroy itself, and as it could not be replaced very well, there would soon be an end to the growth of plants. Hence, nature provides a store-house of raw material, so to speak, to be utilized in the manufacture of plant food, and it is practically inexhaustible, the subsoil, for an unlimited depth, containing all the ingredients necessary to restore the top soil should it become jaded and unresponsive to the demands of cultivation and fertility, if the farmer will take the trouble to dig down after them and bring them to the surface.

Moreover, the inorganic elements in the soil are permanent. They are insoluble except when acted upon by the acids formed through the chemical action of the organic matter, and the vital force exercised by the growing plant.

In the table of specimen soil, given on another page, the percentage of inorganic matter passes 95 per centum, while the organic matter is about three and one-half per cent. Yet that particular soil is a fertile one, in which it is possible to produce a good crop of any kind of plant. It is only an analysis, it is true, and a chemical analysis is not always to be depended upon, because there are so many unknown and mysterious applications of the laws of nature, but there are many things to be said in favor of ascertaining what ingredients the soil does contain, approximately, if not with rigorous exactitude. It gives the practical farmer valu-