Influence the amount of erosion that will take place.

Among these are the quantity and season of rainfall, the

slope of the land, the texture of the soil, the organic

matter in the soil, and the crops raised.

Where the precipitation is light, erosion does not take

place to any great extent unless the water falls in a

few heavy storms and then only local damage is done.

Erosion is more serious where the land has considerable

slope and damaging streams are formed. A loose,

coarse-textured soil is in more danger of erosion than a

fine one that is compact. Organic matter in the soil

reduces erosion by increasing its water-holding capacity

.and its absorptive power.

169. Methods of preventing erosion. ВЂ” Erosion cannot

be avoided by the same methods under all conditions. One

way of preventing it in hilly regions where the precipi-

tation is excessive is to keep the land continually in crops.

As soon as one crop is harvested something else is planted.

This may later be plowed under as a green manure before

Special Soil Problems 159

the regular crop is seeded. Parts of the land most likely

to wash are kept constantly planted to grass.

Erosion usually begins by the formation of small

furrows across the field. These rapidly increase until in

time they become great washes. This condition may be

avoided in the beginning by making regular channels with

less slope to take care of all the run-off. The construction

of terraces and plowing at right angles to the slope are

useful devices for counteracting this tendency to wash.

Large quantities of stable manure are also beneficial in

reducing erosion. On some soils one or two of the

methods given will successfully prevent washing, but in

some sections every practice in soil management has to

be directed toward reducing erosion.

BLOWING

In many sections, considerable difficulty is experienced

with soils being blown away, leaving fields bare to the

bottom of the plowed zone. After the land is plowed

and a crop planted a wind-storm may carry the plowed

soil and seed to a neighboring field. This condition,

particularly serious in certain parts of the Great Plains,

is also found to a lesser degree in many other regions

having an arid or a semi-arid climate. In places where

the soil drifts readilv, farms have been abandoned over

large areas. Houses, bams, and trees have been almost

completely covered with soil and the entire surface of the

land transformed by dust storms.

In regions where the soil blows in this way, every opera-

tion has to be directed toward holding the soil in place.

The greatest care must be taken in plowing and harrow-

ing. If the soil is left loose and fine, it is sure to be carried

away. A fine, dry mulch such as is most effectual in

160 The Principles of Agronomy

preventing evaporation of moisture cannot be used at

all, but it is necessary to leave a surface of small clods

which cannot be readily moved by wind. Plowing is

usually done at right angles to the direction of wind. In

this way the ridges break the force of the wind next to

the ground, and the soil does not easily get into motion.

170. Prevention of blowing. — It is on the long

stretches of barren soil that the greatest injury is done.

Where a large tract is left summer fallowed in dry-farming

districts, blowing may begin and the whole district be

affected. When the soil begins to move, it rapidly cuts

the ground over which it passes. The great problem,

therefore. Is to prevent the first blowing. One effective

means is the alternate cropping and fallowing of long

strips of land. A crop, say corn, is planted in a long strip

a few rods wide at right angles to the wind. Next to

this comes a strip of fallow land, and then another of

crop. In this way there is no large area of fallow land in

one body and the soil does not start to blow. Seeding

to grass or to some other permanent crop is sometimes

necessary in places where drifting is worst. The methods

to be used vary with conditions ; sometimes one measure

will be sufficient, while at other times every known means

must be used to prevent the soil's being carried away by

the wind.

METHODS OF JUDGING SOILS

Since there are so many factors entering into the value

of land, it is very difficult to tell just what it is worth.

The amount of money involved in land transactions is so

great that considerable care should be exercised to deter-

mine as nearly as -possible its true value. Often in one

transaction there is sufficient money wasted to pay a

man's expenses through an entire course at an agricul-

Special Soil Problems 161

tural college. The value of old land that has been farmed

for a generation can be determined rather accurately;

but new land in a district where agriculture has not been

practiced is more difficult to appraise. It is necessary

on such lands to use every available means to aid in making

a proper judgment. Among the things that must be

taken into consideration are: (1) the native vegetation

supported by the land ; (2) the topography ; (3) depth

and structure of the soil; (4) chemical analysis; (5)

crop yields obtained in the neighborhood; and (6)

external factors such as rainfall and nearness to market.

The importance of rainfall is discussed in Chapter X,

while Chapter XXXII considers market problems.

171. Indicator value of native vegetation. — The veg-

etation that grows naturally on a soil in its virgin state

is one of the best indicators of its value. Certain plants

show a condition of drouth; others show an excess of

moisture ; a number of species indicate an acid condition ;

while others are a sure indication of the presence of large

quantities of soluble salts. Since the entire flora of

various sections is different, it is necessary to become

acquainted with the plants of each region and determine

what their growth indicates. When this is done the

judging of virgin soils is greatly simplified.

172. Topography of the land. — In many sections of

the country, the topography of the land must be given

considerable attention in judging its value. Where irri-

gation water is to be used, the land must be so situated

that it can be reached by ditches. In regions where

erosion does damage, the slope of the land is very impor-

tant ; and in sections likely to be affected by frosts, the

land should be so located that it has a good air drainage.

The expense of tillage may be greatly increased if the

surface of the land is rough, but the need of drainage is

M

162 The Principles of Agronomy

probably less on land of this kind than where the surface

is flat. Under some conditions a rolling surface may be

desirable, while under others smoother land may be pre-

ferred. Under practically all conditions, however, the

topography of the land must be given consideration in

judging of its value.

173. Depth and structure of the soil. — The depth of

the soil and its general make-up are very important ele-

ments entering into its value. A soil may be nearly

perfect at the surface, but if it is only a few inches deep,

it is of little value for some classes of farming. A shallow

soil has a low water-holding capacity and its root-zone is

not sufficient to give the best results for certain crops.

The presence of a hardpan or of a streak of coarse gravel

near the surface greatly reduces the value of any piece

of land. Too often land is purchased on a surface ex-

amination merely. This is a dangerous practice, since

it is impossible by looking at the surface to tell what lies

below. The condition of the sub-soil can best be studied

by examining washes, railroad cuts, and wells, or by

using a soil auger. It is impossible to make a sound

judgment regarding land without knowing its nature to

a depth of at least eight or ten feet.

174. A chemical analysis of the soil tells the amount

of plant-food contained, and gives some index to the best

methods of handling the land. It shows which elements

are likely to be deficient and which are abundant. It may

also tell the reaction of the soil as well as the presence of

excessive quantities of soluble salts. Special skUl and

considerable time are required to make a chemical anal-

ysis; hence, this item is often overlooked by practical

farmers in judging land. If the chemical composition

of a soil is not known, however, any judgment made of

it must be somewhat superficial.

Special SoU Problems 163

176. The mechanical analysis of a soil shows its tex-

ture, or the size of particles composing it. After a little

experience the texture can be judged with fair accuracy

without an analysis simply by feeling it. There is no

difficulty, for example, in distinguishing between a

coarse sand and a fine clay ; but in determining the tex-

ture of an intermediate soil, a mechanical analysis is

useful. Since the texture of a soil helps to determine

what crops to grow, it should be known.

176. Productivity. — The real value of land is deter-

mined by what it will produce. Its chemical composi-

tion and texture may seem favorable, but they count for

little if crops do not thrive. For this reason it is not wise

to judge hastily the value of land in a new project before

crops are tried, even though chemical analyses and other

indicators are available. So many factors enter into crop

production that it is easy to overlook some of them,

but all must be right if yields are to be satisfactory.

Natural vegetation, topography, depth of soil, and

chemical and mechanical composition are all good indica-

tors of the value of land; but the real "proof of the

pudding is in the eating," and the best indicator of the

value of land is its productivity.

SUPPLEMENTARY READING

How to Choose a Farm, T. F. Hunt.

Soils, E. W. Hilgard, pp. 313-370, 422-526.

Soils, Lyon, Fippin, and Buckman, pp. 375-403, 718-740.

The Soil, A. D. Hall, pp. 233-370, 289-297.

Cyclopedia of American Agriculture, Vol. I, pp. 480-483, 513-531.

Physics of Agriculture, F. H. King, pp. 92-107.

Fertility of the Land, I. P. Roberts, pp. 303-341.

Reports of Soil Surveys of U. S. D. A. Bureau of Soils and of State

Experiment Stations.

PART III

FIELD CROPS

CHAPTER XVI

WHEAT (Triticum sativum)

The word " wheat *' comes to us, Dondlinger ^ says,

from the Middle English " whete/' which in turn came

from old English " hwaete." To this day the Germans

call it " weizen.** Strange though it may seem, both

these words are related to others which mean white.

Dondlinger further suggests that perhaps wheat was

called white on account of rye and other grains being

darker in color.

Wheat is one of the oldest cultivated plants. Far

back beyond the time when the first histories were written,

this plant was nurtured. It seems to have been

cultivated about thirty centuries before Christ, in

China. It has also been found in the Lake dwellings of

the Swiss, which discovery throws its history back into

the prehistoric Stone Age. The Bible speaks of wheat

harvest in very eariy times (Genesis xx. 14). With-

out intermission this plant has served men down to the

present day.

Geographically, its origin is equally uncertain. The

supposition that the Tigris-Euphrates valley is its birth-

place is favored by de Candolle, Dondlinger, and Hunt.

At any rate, when recorded history began, it was

cultivated widely over the earth from China to Egypt.

Perhaps the search for a center of spread suggested the

Euphrates region.

^ Book of Wheaty p. 1.

167

168 The Principles of Agronomy

177. Relationships. — The Graminese is the botanical

family to which wheat belongs. Many species of this

family have become valuable for the production of seed

which supplies food to both man and animal. These

plants are designated as cereals, or grains. Into this

category fall wheat, oats, barley, rye, rice, com, the

sorghums, and the millets. The Graminese include not

only all of the cereals but also the common tame and wild

grasses. The general field conditions for good wheat are

well indicated in Figs. 48-53.

178. Roots. — When wheat kernels germinate, they

send out three roots which gather food from the soil to

supplement that stored in the kernel. From these two

sources, comes sufficient nourishment to keep the young

plant growing until it can establish itself.

Once the green leaflets push into the sunlight, food

manufacture begins. In the meantime roots grow out

in all directions from a node, or joint, about an inch be-

neath the surface, leaving the first ones to die because

they are of no further use. These new roots grow out-

ward from eight to twenty inches and then turn down-

ward, rapidly reaching into deeper soil which is both a

reservoir for water and a storehouse for plant-food. The

depth to which they penetrate and the number of branches

they send out depend on the looseness, the dampness,

and the warmth of the soil; on the time of the year;

and on the kind of wheat. The limits of variation are

wide, yet under the most unfavorable conditions, the ex-

tent of the root-system far exceeds what the ordinary

person thinks it to be.

One plant, showing roots seven feet two inches long

profusely branched, was dug up at the Utah Experiment

Farm at Nephi. The Minnesota Station reports finding

a branch root every eighth of an inch for eighteen or

Wheat 169

twenty inches. Naturally many of these rebranch,

thus forming a complete network in the soil. More-

over, many broken-off roots remained undisturbed. A

total length of 2000 feet would probably be obtained

Fia. 48. — A good stand ol wheat.

170 The Principles of Agronomy

if all of these thread-like branches were placed end

to end.

179. The plant above ground. — Like all other members

of the grass family, the wheat stem, known as a culm, has

four or five distinct joints, or nodes, from two to ten inches

apart in the mature plant. These nodes are solid, while

the straw between, in most cases, is hollow and sometimes

partly filled with pith. In the young plant, nodes are close

together. Growth consists in a lengthening and thicken-

ing of the internodes at a point just above the nodes. If

the plants are so few that they do not fill the ground in

which they are planted, underground nodes send out

more cidms, that is, the plant stools.

Leaves grow upward from the nodes along the stem,

clasping it closely half or two thirds of the way to the next

joint. This part of the leaf is called the sheath; that

which springs away from the stem is called the blade.

The leaves have parallel veins, a prominent one in the

middle forming a midrib. Leaf blades may be large or

small, smooth or rough; some have edges so sharp as

to cut the skin when brought in contact by a sliding

movement.

The head, or spike, consists of smaller sections borne

alternately upon the rachis, a zig-zag stem, which may be

studied in a picture or by carefully pulling off the spike-

lets, as the sections are called. On each side of the

spikelet is a coarse chaff, or glume. Between are two to

five flowers so completely inclosed by other chaff, that

pollen seldom escapes. This causes the flowers to be

self -fertilized. Generally two of these flowers, but some-

times only one or even three, bear a kernel, or berry.