Dry-Farming

with gravel streaks, crop failures are probable even under a large rainfall; but a deep soil of uniform texture, unbroken by gravel or hardpan, in which

nnot be depended on for good crops; but a fertile soil, though not quite so deep, n

he full dry-farm possibilities of a district. Especially is it necessary to know (a) the depth, (b) the uniformity of structure, and (c) the relative

rid soils needed for the development of dry-farming is small and fragmentary. What is known to-day concerning the nature of arid soils and their relation to cultural processes under a scanty rainfall is due very largely to the extensive researches and voluminous writings of Dr. E. W. Hilga

mation

_weathering, _from the rocks which constitute the earth's crust. Soil is in fact only pulverized and altered rock. The forces that produce soil from rocks are of two distinct classes, _physical and chemical. _The physical agencies o

time, cracks the surfaces of the rocks. Into the tiny crevices thus formed water enters from the falling snow or rain. When winter comes, the water in these cracks freezes to ice, and in so doing expands and widens each of the cracks. As these process

is manner are often washed down into the mountain valleys, there caught by great rivers, ground into finer dust, and at length deposited in the lower valleys. _Moving water _thus

up by the air and hurled against the rocks, which, under this action, are carved into fantastic forms. In still other places, the strong winds carry soil over long distances to be mixed with other soils. Finally, on the seashore the great

re vigorously in arid than in humid sections. Under the cloudless sky and dry atmosphere of regions of limited rainfall, the daily and seasonal temperature changes are much greater than in sections of greater rainfall. Consequently the pulverization of rocks goes on most rapi

emical composition. Chief of these agencies is _water, _which exerts a solvent action on all known substances. Pure water exerts a strong so

is therefore found, normally, in the atmosphere and in soils. Rains or flowing water gather the carbon dioxid from the atmosphere and the soil; few natural

efore more available to plants, many of the important plant-foods. In this way the action of wa

gen of the air. Oxidation is a process of more or less rapid

a strong pressure which helps to pulverize the soil grains; secondly, the acids of the plant roots actually dissolve the soil, and th

However, whether in arid or humid climates, the processes of soil formation, above outlined, are essentially those of the "fallow" or resting-period given to dry-farm lands. The fallow lasts for a few months or a year, while the process of soil formation is always going on and has gone on for ages;

istics of

of soil grains intermingled with clay. The larger soil grains are called sand; the smaller, silt, a

tic and adhesive and is thus easily distinguished from sand. Because of these properties, clay is of great value in holding together the larger soil grains in relatively large aggregates which give soils the desired degree of filth. Moreover, cla

ils 0.5 to 3

soils 3.0 to

10.0 to 15 p

15.0 to 25

25.0 to 35

ils 35.0 per

imatic conditions. In the formation of clay, the extremely fine soil particles are attacked by the soil water and subjected to deep-going chemical changes. In fact, clay represents the most finely pulveriz

ccounts for the statement frequently made that heavy clay soils are not the best for dry-farm purposes. The fact is, that heavy clay soils are very rare in

t that ordinarily a clayey soil is considered "strong" and a sandy soil "weak." Though this distinction is true in humid climates where clay formation is rapid, it is not true in arid climates, where true clay is formed very sl

n of America, in Egypt, India, and other desert-like regions has further proved that the sands of the deserts produce excellent crops whenever water is applied to them. The prospective

er case the decayed remnants of generations of plants form a large percentage of humus in the upper soil; in the latter, the scarcity of plant life makes the humus content low. Further, under an abundant rainf

ndant rainfall. Owing to the prevailing sandiness of dry-farm soils, humus is not needed so much to give the proper filth to the soil as in the humid countries where the content of clay is so much higher. Since

ich are filled with the remnants of decayed vegetable matter and modified by plowing, harrowing, and other cultural operations. The subsoil has been profoundly modifi

ccumulation in the subsoil of the fine clay particles which so compact the subsoil as to make it difficult for roots and even air to penetrate it. The normal process of weathering or soil disintegration will then go on most actively in the topsoil and the subsoil will remain unweathered and raw. This accounts for

carried down to the lower limit of the rain penetration, but the clay and other fine soil particles are not moved downward to any great extent. These conditions leave the soil and subsoil of approximately equal porosity. Plant roots can then penetrate the soil deeply, and the air can move up and down through the soil mass fre

thout further weathering, excellent yields of crops. This granular, permeable structure, characteristic of arid soils, is perhaps the most important single quality resulting from rock disintegration

the farmer must be extremely careful not to turn up with his plow too much of the inert subsoil, no such fear need possess the western farmer. On the contrary, he shoul

ayers of loose gravel. While this is not a very serious obstacle to the downward penetration of roots, it is very serious in dry-farming, since any break in the continuity of the soil mass prevents the upward movement of water stored in the lower s

to which the rainfall has penetrated the soil. Not only is the lime thus carried down, but the finer particles are carried down in like manner. Especially where the soil is poor in lime is the clay worked down to form a somewhat clayey hardpan. A hardpan formed in such a manner is frequently a serious obstacle to the downward movement of the roots, and also prevents the annual precipitation from moving down far enough to be beyond the influence of the sunshine and winds. It is fortunate, however, that in the great majority of instances this hardpan

ar the surface, by layers of rock, marl deposits, and similar impervious or hurtful substances. Such

he rainfall is considerably less, the water drains through the soil into the standing ground water. There is, therefore, in humid countries, a continuous drainage through the soil after every rain, and in general there is a steady

ches out very much more material than pure water could do. A study of the composition of the drainage waters from soils and the waters of the great rivers shows that immense quantities of soluble soil constituents are taken out of the soil in countries of a

It is true that under proper methods of tillage even the light rainfall of arid and semiarid regions may he made to pass to considerable soil depths, yet there is little if any drainage of w

so large a degree in arid soils as to make the lands unfitted for agricultural purposes. Such lands are called alkali lands. Unwise irrigation in arid clim

. It cannot be believed that the water-washed soils of the East retain as much fertility as the dry soils of the West. Hilgard has made a long and elaborate study of this somewhat difficult question

rcentage C

f soil H

amples anal

residue

silica 4

na 3.

0.1

h 0.2

Acid 0

1.22

fully selected and prepared sample with a certain amount of acid of definite strength. The portion which dissol

soluble, it follows that it is safe to assume that arid soils are generally more fertile than humid soils. This is borne out by a study of the constituents of the soil. For instance, potash, one of the essential plant foods ordinarily present in sufficient amount, is found in humid soils to the extent of 0.21 per cent, while in arid soil

ontent. There is nearly eleven times more lime in arid than in humid soils. Conditions of aridity favor strongly the

orated with the soil. (2) When other conditions are favorable, it encourages bacterial life which, as is now a well-known fact, is an important factor in developing and maintaining soil fertility. (3) By somewhat subtle chemical changes it makes th

t growth. There are, however, a great many agricultural soils covering large areas and yielding very abundant crops which contain very much larger quantities of calcium carbonate. For instance, in the

igher the percentage of soluble silica and alumina, the more thoroughly decomposed, in all probability, is the soil as a whole and the more readily can plants secure their nutriment from the soil. It will be observed from the table, as previously stated, that more humus is found in humid than in arid soils,

IX, the greater fertility of arid soils is one of the chief reasons for dry-farming success. Depth of the soil alone does not suffice. There

countries would produce clay; less humus, but that of a kind which contains about 3-1/2 times more nitrogen than the humus of humid soils; more lime, which helps in a variety o

which, however, disappear under the influence of cultivation; their subsoils to a depth of ten feet or more are as fertile as the topsoil, and the availability of the fertility is greate

re was founded. As Hilgard has suggested, the historical datum that the majority of the most populous and powerful historical peoples of the world have been located on soils that thirst for water, may find its explanation in the intrins

div

five great soil districts, each of which includes a great variety of soi

Plains

bia Rive

Basin d

do River

fornia

e Missouri, and includes North and South Dakota, Nebraska, Kansas, Oklahoma, and parts of Montana, Wyoming, Colorado, New Mexico, Texas, and Minnesota. The soils of this district are usually of high fertility. They have good lasting power, though the eff

poken of as the Palouse country. The soils of the western part of this district are of basaltic origin; over the southern part of Idaho the soils have been made from a somewhat recent lava flow which in many places is only a few feet below the surface. The soils o

ho, Oregon, and southern California. This basin has no outlet to the sea. Its rivers empty into great saline inland lakes, the chief of which is the Great Salt Lake.

into the lake and deposited on the lake bottom. When at length, the lake disappeared, the lake bottom was exposed and is now the farming lands of the Great Basin district. The soils of this district are characterized by great depth and uniform

sily disintegrated rocks of comparatively recent geological origin, which themselves are said to have been formed from deposits in a shallow interior sea which covered a large part of the West. The rivers running through this district have cut immense canons with perpendicular walls which make much of this country difficult to traverse. Some of the soils are of

uin rivers. The soils are of the typical arid kind of high fertility and great lasting powers. They represent

f the dry-farming territory of the United States has not progressed far enough to permit a comprehensive and correct mapping of its soils. Our knowledge of this subject is, at the best, fragmentary. We know, however, with certainty that the properties which characterize arid soils, as described in this chapter' are possessed by the soils of the dry-farming territory, including the five great districts

dging

spective dry-farm are: the depth of the soil, the uniformity of the soil to a depth of at least 10 feet, the native vegetation, the climatic conditions as r

e three augers made: one 3 feet, the other 6, and the third 9 or 10 feet in length. The short auger is used first and the others afterwards as the depth of the boring increases. The boring should he made in a large number of average places-preferably one boring or more on each acre if

ered from the local weather bureau an

tain indication that farming without irrigation is feasible. The rabbit brush of the drier regions is also usually a good indication, though it frequently indicates a soil not easily handled. Greasewood, shadscale, and other related plants ordinarily indicate heavy clay soils fre