The subsoil plow does not turn the soil; it simply loosens the soil so that the air and plant roots can penetrate to greater depths.
In the choice of plows and their proper use the dryfarmer must be guided wholly by the conditions under which he is working. It is impossible at the present time to lay down definite laws stating what plows are best for certain soils. The soils of the arid region are not well enough known, nor has the relationship between the plow and the soil been sufficiently well established. As above remarked, here is one of the great fields for investigation for both scientific and practical men for years to come.
Making and maintaining a soil-mulch
After the land has been so well plowed that the rains can enter easily, the next operation of importance in dry-farming is the making and maintaining of a soil-mulch over the ground to prevent the evaporation of water from the soil. For this purpose some form of harrow is most commonly used. The oldest and best-known harrow is the ordinary smoothing harrow, which is composed of iron or steel teeth of various shapes set in a suitable frame. (See Fig. 79.) For dry-farm purposes the implement must be so made as to enable the farmer to set the harrow teeth to slant backward or forward. It frequently happens that in the spring the grain is too thick for the moisture in the soil, and it then becomes necessary to tear out some of the young plants. For this purpose the harrow teeth are set straight or forward and the crop can then be thinned effectively. At other times it may be observed in the spring that the rains and winds have led to the formation of a crust over the soil, which must be broken to let the plants have full freedom of growth and development. This is accomplished by slanting the harrow teeth backward, and the crust may then be broken without serious injury to the plants. The smoothing harrow is a very useful implement on the dry-farm. For following the plow, however, a more useful implement is the disk harrow, which is a comparatively recent invention. It consists of a series of disks which may be set at various angles with the line of traction and thus be made to turn over the soil while at the same time pulverizing it. The best dry-farm practice is to plow in the fall and let the soil lie in the rough during the winter months. In the spring the land is thoroughly disked and reduced to a fine condition. Following this the smoothing harrow is occasionally used to form a more perfect mulch. When seeding is to be done immediately after plowing, the plow is followed by the disk harrow, and that in turn is followed by the smoothing harrow. The ground is then ready for seeding. The disk harrow is also used extensively throughout the summer in maintaining a proper mulch. It does its work more effectively than the ordinary smoothing harrow and is, therefore, rapidly displacing all other forms of harrows for the purpose of maintaining a layer of loose soil over the dry-farm. There are several kinds of disk harrows used by dry-farmers. The full disk is, everything considered, the most useful. The cutaway harrow is often used in cultivating old alfalfa land; the spade disk harrow has a very limited application in dry-farming; and the orchard disk harrow is simply a modlfication of the full disk harrow whereby the farmer is able to travel between the rows of trees and so to cultivate the soil under the branches of the trees without injuring the leaves or fruit.
One of the great difficulties in dry-farming concerns itself with the prevention of the growth of weeds or volunteer crops. As has been explained in previous chapters, weeds require as much water for their growth as wheat or other useful crops. During the fallow season, the farmer is likely to be overtaken by the weeds and lose much of the value of the fallow by losing soil-moisture through the growth of weeds. Under the most favorable conditions weeds are difficult to handle. The disk harrow itself is not effective. The smoothing harrow is of less value. There is at the present time great need for some implement that will effectively destroy young weeds and prevent their further growth. Attempts are being made to invent such implements, but up to the present without great success. Hogenson reports the finding of an implement on a western dry-farm constructed by the farmer himself which for a number of years has shown itself of high efficiency in keeping the dry-farm free from weeds. Several improved modifications of this implement have been made and tried out on the famous dry-farm district at Nephi, Utah, and with the greatest success. Hunter reports a similar implement in common use on the dry-farms of the Columbia Basin. Spring tooth harrows are also used in a small way on the dry-farms.
They have no special advantage over the smoothing harrow or the disk harrow, except in places where the attempt is made to cultivate the soil between the rows of wheat. The curved knife tooth harrow is scareely ever used on dry-farms. It has some value as a pulverizer, but does not seem to have any real advantage over the ordinary disk harrow.
Cultivators for stirring the land on which crops are growing are not used extensively on dry-farms. Usually the spring tooth harrow is employed for this work. In dry-farm sections, where corn is grown, the cultivator is frequently used throughout the season. Potatoes grown on dry-farms should be cultivated throughout the season, and as the potato industry grows in the dry-farm territory there will be a greater demand for suitable cultivators. The cultivators to be used on dry-farms are all of the riding kind. They should be so arranged that the horse walking between two rows carries a cultivator that straddles several rows of plants and cultivates the soil between. Disks, shovels, or spring teeth may be used on cultivators. There is a great variety on the market, and each farmer will have to choose such as meet most definitely his needs.
The various forms of harrows and cultivators are of the greatest importance in the development of dry-farming. Unless a proper mulch can be kept over the soil during the fallow season, and as far as possible during the growing season, first-class crops cannot be fully respected.
The roller is occasionally used in dry-farming, especially in the uplands of the Columbia Basin. It is a somewhat dangerous implement to use where water conservation is important, since the packing resulting from the roller tends to draw water upward from the lower soil layers to be evaporated into the air. Wherever the roller is used, therefore, it should be followed immediately by a harrow. It is valuable chiefly in the localities where the soil is very loose and light and needs packing around the seeds to permit perfect germination.
Subsurface packing