6. In a proper succession of crops the soil is covered with living plants nearly all the time, and thus is prevented from washing or leaching. 7. In addition to these influences upon soil fertility, crop-rotation assists in control of insect and fungous foes and of weeds; it permits such distribution of labor on the farm that the largest total production may be secured by its employment; and it saves the farmer from sole dependence upon a single crop. [Illustration: Penn's Valley, Pennsylvania.] Selection of Crops.--The natural inclination of the farmer is a consideration that cannot be ignored. If a man does not like certain kinds of animals or crops, his farm or market must possess an unusual advantage to counter-balance. Illustration of this truth may be seen in every farming community. As a rule, the crops should be those that are well adapted to the particular soils upon which they are grown. It is up-hill work to compete with producers whose soils have far better adaptation, unless the local markets equalize conditions. The crops should follow each other in such succession that each crop naturally paves the way for the next one in the succession, or at least does not place its successor at a disadvantage. When it is feasible, a rather large proportion of the entire produce of the rotation should be feeding-stuff for livestock, as soil fertility is most easily guarded by livestock farming. This is desirable when consistent with profit, but, as we have seen, it is not an absolute essential. An Old Succession of Crops.--In the corn belt of the northern states some time-honored crop-rotations have been formed by corn, oats, wheat, clover, and timothy. The number of years devoted to the grain and to the sod has varied with the soil and the desire of its owner. A common succession is corn one year, oats one year, wheat one year, clover and timothy one year, timothy one year--a five years' rotation that has much substantial success behind it. Such a rotation is wholly reasonable and in accord with the nature of things. Every year furnishes some organic matter for the soil in roots and stubble, and all the produce of four years out of the five may be fed on the farm. There is one cash crop, or two if the price of the clear timothy hay justifies sale. The manure may be hauled upon the sod when other work does not press, and it goes where the crop is one that prefers fresh manure, be that the grass or the corn. There is plenty of time after the corn to prepare for oats, and after the oats to prepare for wheat. The preparation for the wheat is sufficient for the clover and timothy. The seedings come only in the spring and the fall, when rainfall is more abundant and effective than in mid-summer. The danger of failure in case of this rotation is relatively small.