Fig. 608. Diagrams of Cole's New System" of handling soil water. AA, surface soil; B, trenches; C, subsoil; D, overflow trenches; E, outlet or drainage trench. From Cole's "New Agriculture," published by the late Wm. C. Harris.

it until drawn on by the growing crops. Cobblestones to the depth of a foot or two are put loosely in the bottom of the trench, covered with flat stones, over which is placed a quantity of smaller stones. This is covered with weeds, brush, cornstalks, or any other available material, to prevent the fine earth filling the open spaces. Manure might be put above this, and then the surface soil replaced. The trenches are all connected by overflow drains. The system never became popular, but shows what may be done on hilly land. The results secured by Mr. Cole were marked.

Cost of irrigation.

Equipment varies so widely that general statements as to cost are of little value. Below are given the costs of a few typical irrigation plants, as published in reports of the United States Department of Agriculture:

In Northampton county, Pa., 3 acres are irrigated with a No. 6 ram. The ram is fed through 160 feet of 2-inch pipe, with a head of 20 feet, and discharges through 2,000 feet of 11-inch pipe, into a boiler-iron tank 44 by 8 by 7 feet, 185 feet above the ram. The water is distributed by hand sprinkling and by a 4-arm revolving sprinkler, which is moved about once an hour. The distribution requires 1,500 feet of 14-inch pipe, and several lengths of 2-inch and 1-inch hose. The total cost of the plant was $850, or $252.90 per acre. Assuming interest, taxes and depreciation to equal 20 per cent, the annual fixed charges on the plant are $48.60. The average cost of applying water with hand sprinklers is reported to be $1.80 per acre.

With rams there is no fuel cost, and the total annual cost is therefore $50.40 per acre.

In the same county another tract of 4 acres is irrigated with a No. 8 ram. The ram is fed by 75 feet of 3-inch pipe, with a head of 11 feet, and raises the water 80 feet through 575 feet of 11inch pipe, discharging into a cistern 8 by 8 by 8 feet. Water is distributed through 1,000 feet of 11-inch and 1-inch pipe, with T's for outlets every 40 feet. The water is applied by sprinkling partly by hand and partly by a waterwitch. One hundred feet of 1-inch hose is used, half of which is replaced each year. The cost of the plant was $180, or $45 per acre. Estimating fixed charges as before gives an annual cost of $9 per acre, and adding $1.80 for applying the water gives a total annual cost of $10.80 per acre.

In Middlesex county, N. J., 2 acres of truck are irrigated with city water from New Brunswick, at $1 per 1,000 cubic feet. The water is applied in furrows, to which it is carried by hose. The total cost of hose and pipe was $25, or $12.50 per acre, making annual fixed charges $2.50 per acre. The average cost of applying water in this way is 75 cents per acre, and the charges for water vary with the seasons, in 1905 being $12.50 per acre. This makes the total annual cost $15.75 per acre.

Seven acres of truck in Queens county, N. Y., are irrigated with a plant costing $1,200, or $171 per acre. There are five 2-inch driven wells 20 feet deep, costing $28 each. The water stands at 10 feet below the surface. A vertical boiler supplies steam to a duplex pump delivering 80 gallons per minute against a vertical lift of 67 feet, through 1,200 feet of 2-inch pipe, into a wooden reservoir holding 10,000 gallons. A 12-foot windmill furnishes an additional supply. The water is distributed through a 2-inch main with 1-inch branches 150 feet apart. These branches have 1-inch outlets 75 feet apart, to which waterwitch lines are connected by hose. The waterwitch lines consist of 1-inch pipe with -inch risers every 12 feet, on which there are sprinklers. About 50 feet of hose is used in connecting these to the standpipes. Three thousand feet of 2-inch pipe is used. Fixed charges at 20 per cent amount to $34.20 per acre, applying water costs about $2 per acre, and fuel costs about $1 per 10-hour day, and the area watered in this time is one acre. The number of irrigations varies with the seasons. Assuming it to be five, it gives a fuel cost of $5 per acre. This gives a total annual cost of $41.20 per acre. Literature.

The literature on the subject of irrigation in humid parts of the United States consists chiefly of reports issued by the United States Department of Agriculture, that department having issued a number of bulletins describing plants now in use and giving the results of experiments at the State experiment stations. Among other works treating this subject may be mentioned: New Agriculture, or The Waters Led Captive, by Asahel N. Cole, New York, 1885; and Irrigation and Drainage, by F. H. King, New York, 1889.

therefore not to be found in appreciable quantity in desert soils. In moist soils they are always found, and their abundance is proportional to the amount and kind of organic matter in the soil. When the amount of vegetable matter in and on the soil, such as wood, leaves, cellulose and the like, is abundant, the higher fungi, the molds and mushrooms are abundant. Thus, in the forests, the soil, for some inches in depth, is filled with an interlacing mass of the threads, or mycelium, of many varieties of these plants, which permeate it in all directions. Whenever the soil contains considerable quantities of sugar, the yeast fungi will be scattered in great abundance through the superficial layers.

When the quantity of proteid material is large the bacteria abound. Proteid matter is found wherever any animal or vegetable substance accumulates. Animal remains and animal secretions are particularly rich in proteid and, hence, wherever such substances are found, bacteria accumulate in great numbers. Around barnyards and in manure heaps, at any place where sewage leaches into the soil, around the decaying carcasses of animals, bacteria may be found in inconceivable numbers. In such places they have been found in numbers as high as 100,000,000 per gram of soil. Even in ordinary loam the bacteria are very abundant, 5,000,000 per gram having been found in common garden soil.

These microscopic organisms are found chiefly in the superficial layers of the soil and never at any great depths. The bulk of them are in the first six inches. Below this they decrease rapidly, and at depths of six feet they are very few or absolutely wanting. In some places, however, they may be found at greater depths, being carried downward by the percolating streams of water. At great depths they are never found. The reason for this superficial distribution is readily understood when we remember that their food is derived from the surface of the ground, and also that, as a rule, they require oxygen, which gas is abundant near the surface, but does not readily penetrate to any considerable depth.

The cycle of life.

Primarily these organisms are, of course, simply filling the ordinary functions of life, growth and reproduction, but incidentally their activities form one of the links in nature's grand adjustments. To comprehend this we must understand how it is that the life of the world continues indefinitely without exhaustion. Both plants and animals require food, and much of this food is limited in quantity. Of plant-foods the soil contains only a moderate amount at any time, and yet for unknown millions of years both plants and animals have been consuming food; nor is there any reason for thinking this food is less abundant today than in ages past. The explanation of this phenomenon is that nature's laws are such that the same material is used over and over again. One group of organisms consuming the material fits it for food for the second group, and the second group, likewise consuming it

for its own purposes, fits it for a third group, and the third group brings it back again into a condition to be used once more by the first group. Thus the food ingredients are passing around in endless cycles, and as long as the circulation can be kept up there need be no exhaustion of the supply.

One of the essential links in this cycle is supplied by the germ life in the soil. Agriculture is, of course, dependent on the continued growth of green plants, for all agricultural products can be traced to the vegetation on the soil. All soil manipulation has as its aim the stimulation of the growth of green plants. Such plants are at work constantly, building compounds of greater or less complexity out of soil ingredients. The compounds thus made are commonly called organic compounds, and when once built up into such materials the elements of which they are composed are no longer in condition to be used by plants as food. They are too complex. Such complex compounds, however, do constitute the food of animals. Used now by animals these bodies are, in part, built up into even more complex bodies and are, in part, more or less broken down into simpler bodies again. But even though thus broken down, most of the fragments are not reduced to a condition in which the green vegetation can use them, for such vegetation requires its food in the form of simple chemical compounds of less complexity than most of the secreted products of animals or plants.

It is the function of the soil organisms to complete this reduction of compounds so as to bring them once more within the reach of the green plants, thus completing the cycle. Each of the above-mentioned groups of soil organisms has its own functions in this work. The higher fungi are chiefly concerned in breaking down the woody tissues of vegetable growth. The yeasts act on the sugars and also on the starches after they have been changed into sugar by enzymes (or ferments). The bacteria act on almost all kinds of organic materials, but primarily on proteids. By the combined action of the three, all kinds of organic products are broken down into simple ingredients and thus pushed around one step in nature's food cycle. Without their aid the soil would soon become clogged with the dead bodies of plants and animals as well as with their excretions, and would rapidly become unfit to support vegetation; and all life on the globe would cease.

The function of the soil organisms does not stop here. While green plants cannot feed on complex organic compounds, neither can they feed on simple elements nor on some of the simplest compounds. In this general destruction of organic bodies which is taking place in the soil, a considerable part of the material is reduced to forms too simple to be used by plants as food. Some parts are reduced to the simple chemical elements (as nitrogen, sulfur. hydrogen), while others reach such a simple condition of chemical combination (H2S, CH4, etc.) as to be still outside the reach of green vegetation. Here come into play certain of the soil organisms that are able to utilize these simple substances as part of their food. In doing so they

cause the simple bodies to combine into more complex ones and, in the end, to assume a form in which they can once more be utilized by green vegetation, and thus start again in their journey around the cycle. Some of the soil bacteria even seize the free chemical elements.

Our knowledge of the functions of germ life in the soil is still very incomplete. The subject is new, scarcely thirty years having elapsed since the first bits of information were obtained. We already know enough to demonstrate that the continuation of life is dependent on them. They are aids in the breaking up of rocks into grains which constitute the soil; they are concerned in the production of available phosphorus and potassium salts from the rocks; they are intimately concerned in the production of the proper compounds of sulfur and iron for plant-life; they are constantly acting as scavengers, consuming, and thus destroying, the accumulation of offensive products which would otherwise clog the soil, and thus they are the agents which bring about the so-called “self-purification of the soil." They are also ever building up simple substances into more complex ones, thus making them into plant-foods. In all these as well as other respects they are indispensable allies to agriculture. Although invisible, and to most farmers unknown, they are ever at work.

Bacteria in relation to soil fertility.

The most important of the various soil organisms are bacteria, and these are most closely related to fertility. Apart from the question of moisture, the fertility of any soil depends on the presence of an abundance of easily assimilable plant-food, and this is chiefly dependent on the amount of organic material. Soil with plenty of organic matter will yield good crops, but without organic matter, even though minerals are 'supplied in quantity, the soil will yield little. The organic matter is largely in that part of the soil called the humus, and it has been long recognized that the richness of a soil is usually proportional to its quantity of humus.

Humus is a complex substance, especially abundant in rich loam, whose nature and origin is as yet only partly understood. In large degree, at all events, it comes from the decomposed bodies of animals and plants, and is produced chiefly, if not wholly, through the agency of soil organisms. It contains many different substances, including compounds of phosphorus, potassium, sulfur, iron and others, all of which are usually classed with minerals. But, in addition, it contains as its most important ingredient, from the fertility standpoint, nitrates or other bodies capable of easy conversion into nitrates. While bacteria do not, of course, supply the food ingredients to the soil, they are intimately concerned in the conversion of these ingredients into plant-food. We may best consider this relation under the heads of (1) nitrogen compounds and (2) other soil ingredients.

Nitrogen compounds and bacteria.

All green vegetation uses nitrogen, and there is good reason for believing that the nitrogen plant

food is largely assimilated in the form of nitrates. Thus nitrates are necessary to the production of soil fertility. For the production of nitrates in the soil, bacteria are absolutely necessary, and their action is therefore indispensable to vegetation.

The origin of these nitrates is twofold: (1) The decomposition of organic materials in the soil, (2) atmospheric nitrogen.

(1) Decomposition of organic matter.-The soil in all fertile regions is full of organic substances, a considerable part of which contain nitrogen. These are chiefly from three sources. (a) Vegetable remains, such as roots, fallen branches and leaves, and the fruits, nuts, and the like, of all kinds of plants. (b) The secretions of animals, the most prominent of which is urea and its allies. This material (contained in urine) is the condition in which practically all of the nitrogen leaves the bodies of animals, and, since all animals, great and small, secrete it and most of it enters the soil, the total amount of soil nitrogen from this source is very great. (c) The dead bodies of animals. With the exception of the few animals whose bodies fall into the streams, practically all others lie within or on the soil, and the total amount of such material is very large.

Such organic substances, although the foundation of soil fertility, are in no condition to be utilized until after they have undergone a series of chemical transformations. They must first be pulled to pieces. This process of pulling to pieces we commonly call decomposition, rotting, putrefaction or decay. The agents that produce the ordinary decomposition are wholly living, no purely chemical forces being able to accomplish it. Molds, yeasts and bacteria are all concerned, but in the decomposition of the nitrogenous material, bacteria are the chief agents. There are many species of soil bacteria engaged in the production of decay and putrefaction, and they bring about a variety of chemical changes, but there is a considerable similarity in the final results in all cases. The organic compounds are pulled to pieces and the fragments largely dissipated in the air. A variety of gases is produced containing the hydrogen, sulfur, carbon and oxygen. The carbon and part of the oxygen join the store of CO2 (carbon dioxid) in the air. The sulfur, as explained later, is in part seized by sulfur bacteria and converted into sulfates. The nitrogen assumes different forms. A large part of it is reduced to ammonia gas (NH3), which also tends to fly off into the air, as is indicated by the smell of ammonia commonly noticeable in the vicinity of a manure heap. Ammonia gas, however, is an active agent and readily combines with any acids that may be present, forming carbonates, sulfates or some other ammonium salts, and these, being solids instead of gases, remain fixed in the soil. Another part of the nitrogen is freed wholly from its combinations and becomes free nitrogen. This, being an inert gas, does not combine with anything, but flies off into the atmosphere and thus out of the reach of plants. So, by the agency of decomposition bacteria, the nitrogen is wholly freed from its complex compounds and reduced to far simpler forms.