The second year the hay is nearly clear timothy. The sod should not be left until it becomes thin, but should be turned under while heavy, no matter if this must be after one season's harvest, or two. A sod stands three or four years for harvest on some farms, and without heavy fertilization there is decrease in fertility. Two Legumes in the Rotation.--If all the crops of this five years' rotation, excepting wheat, were fed on the farm, and if all the manure were saved and rightly applied, there would be little or no difficulty in maintaining fertility, provided the soil were friendly to clover. The fact is that much such land has grown poorer, and it is known that another legume is needed in the rotation. The substitution of the soybean or cowpea for the oat crop gives excellent results. It makes a large supply of rich hay, and it fits the soil nicely for winter grain. The use of the breaking-plow is escaped. The surface of the land is in good tilth, especially if the legume was planted in rows so that cultivation could be given. A cutaway harrow, run shallow, and a roller make the seed-bed. Near the southern edge of the oat belt this substitution gives more value in the crop following corn, and at the same time conserves soil fertility. Where land is thin, a four years' rotation of corn, soybeans or cowpeas, wheat, and clover is one of the best, because it contains two leguminous crops, and because one of them favors the wheat which follows and the clover seeded in the wheat. Potatoes after Corn.--When potatoes are grown in the corn belt, a five years' rotation of corn, potatoes, oats, wheat, and clover, or corn, potatoes, wheat, clover, and timothy, is one of the best. When a late potato crop is grown, there is not time for seeding to wheat in cool latitudes, and the oat crop, or the soybean, fits in best. Farther south, where the oat crop is less profitable, there usually is time to go directly to wheat. The advantage in this rotation is that the fresh manure can be used on the sod for the corn, and the potato thrives in the rotted remains of the sod and manure. Corn leaves the soil in good physical condition for the potato. Commercial fertilizer is used freely for the potato, which repays fertilization in higher degree than most other staple crops. The land can be prepared for seeding to wheat and grass with a minimum amount of labor. The rotation is excellent where there is enough fertility for the potato, which usually can be by far the most profitable crop in the entire rotation.