Rotation

in agriculture, a short series of crops following each other in regular succession. In politics, rotation in office is taken to mean that an officeholder shall hold the position for a short time and then step down and out for good.

A system of rotation of crops is a changing of crops from field to field according to a fixed plan whereby the same crop comes back to the same field every few years. To carry out such a system requires as many fields as there are kinds of crops in the system adopted. If a farmer decides on the old time rotation of wheat, oats, and corn, he requires to divide his farm land into three fields or groups of fields as nearly equal as may be. For instance, if a farm consists of six fields, one of eighteen acres, one of twenty acres, and four smaller fields whose combined acreage is twenty-one acres, the four small fields may be grouped together and considered one in a plan of rotation. If we start with wheat in the first field and oats in the second, the rotation for the three fields will run, wheat, oats, corn; oats, corn, wheat; corn, wheat, oats. Thrown into a table we have:

The fourth year each field is planted or sown to the kind of crop it had the first year of the rotation.

There are several reasons for a change of crops. Each kind of crop draws on the soil for a particular kind of plant food. When the supply of this kind of food runs short, the crop yield falls off. It is well to grow some other crop for a while. In the meantime the soil water may soak up a fresh supply of this plant food. The soil may in some cases get it from the air; or the farmer may supply the deficiency. No matter what the crop, it will run out if planted continuously in the same field.

The roots of a plant are likely to give off certain poisons that work against its own growth. In this way repeated croppings make some soils "wheat-sick," "flax-sick," etc. Then, too, a field devoted to one crop is likely to attract or breed plant and animal enemies. A field planted to potatoes year after year is likely to become infected with the germs that produce potato scab, and is sure to be the wintering place of potato beetles. A number of plant diseases, known as wilts, die out when the particular crops on which they feed are not planted continuously. Cotton, watermelons, tomatoes, flax, and a long list of other useful plants are, for this reason, the better for a change of soil. There is an old adage that it is not well to carry all of one's eggs in one basket. It is equally true that a farmer should not depend on one crop. Rotation gives variety. If one crop does not do well, another may. A variety of crops distributes farm work through the seasons to better advantage. The principles that underlie a plan of rotation are:

1. The series should include a money-making crop. This may be any one of the staple crops. The choice is dependent on soil and climate. In the Mississippi Valley, wheat, corn, cotton, and cane are the leading money-making crops, but each of the cereals leads in certain localities.

2. The plan of rotation should include a cultivated crop. This gives opportunity to kill weeds and get the soil into fine tilth.

3. A crop should be included that feeds the land, or else that gives a chance to enrich it. All plants of the pea family feed the soil. The best for the purpose are the clovers and the cowpea. The article on CLOVER will tell why. Meadow crops feed the land by increasing the supply of humus or decaying vegetable matter. Timothy is an excellent crop for the purpose. Timothy and blue grass sods will do wonders for a worn out field. Under ordinary circumstances, proper rotation requires the keeping of stock, not only to consume certain crops to advantage, but also to provide a supply of barnyard manure for the benefit of the soil. Put in another way, proper rotation includes forage crops. The rotation of corn, wheat, and oats mentioned above presumes a supply of wild hay and a liberal supply of barnyard manure to be applied to cornland before plowing. In some sections having a long growing season, two crops, as corn and potatoes, give a good chance to dress fields with fertilizers.

The following plans of rotation are typical of various parts of the United States and Canada. They vary in time from a three-crop rotation, requiring three years, to an eight-crop rotation.

See Clover; Cowpea; Soiling