The object in not connecting the flues from the furnace with the chimney is to economize heat. The air chamber under the entire bed becomes evenly heated, and the smoke escapes finally by the chimney. This chimney may be made of wood, and a height of 8 or 10 feet will afford ample draft. Either wood or coal may be burned, but preferably wood.
The planting distance in the field is about 3 feet by 2, the young plants being set upon ridges. It requires about 9,000 plants to the acre. The work must not be done until the ground is warm. The crop is ready in from sixty to ninety days.
Cultivation.—Shallow cultivation is all that is required. The vines at the North are not permitted to take root along their length, but in the South they are sometimes allowed to do so, and additional tubers thus secured. At the North the vines are lifted and turned, to clear the way for the cultivator and to prevent rooting.
Enemies.—Black rot is one of the worst of sweet potato diseases. Stem rot is another serious enemy. The best treatment for these and other fungous troubles is prevention, and the best prevention is a healthy soil. It is, therefore, best to go to new land occasionally.
Harvesting.—The common practice is to plow the sweet potatoes out of the ground just after the first frost has touched the vines. The tubers must be exposed to the air for a time, and partially dried. They are prepared for market, if wanted immediately, by rubbing off the soil and sorting into two sizes.
Storage.—At the South one of the several methods of winter storage is to build a light wooden flue of lattice work, and pack about it a conical-shaped heap containing about forty or fifty bushels of sweet potatoes. Straw is used as a covering, with earth upon the straw, the earth to be increased as the weather becomes colder. Over the entire heap a rough shed is erected to turn the rain. The top of the flue or ventilator is closed with straw in really cold weather. The spot must be a dry one.
The New Jersey sweet potato house is a stone building, say 16 × 18 feet on the inside, with walls 10 feet high, and a good roof. The building is half under ground, and the earth is banked up around it. There is a passage way through the centre, and the bins for the sweet potatoes are 6 to 8 feet square and 8 to 10 feet deep. There is a door on the south side, with window above, and a stove is placed inside the building, for use when required. The walls are plastered, and the under side of the roof is also covered with lath and plaster, and the place is thoroughly weather-proof. A house of this kind will afford storage room for 3,000 or more bushels of sweet potatoes, and will keep them in excellent condition, if all details receive proper attention. The requirements for successful storage are that the tubers shall not be too hot, nor too cold, nor too wet, and that sudden changes of temperature shall be avoided. The sweet potato crop may be said to vary from 100 to 150 bushels per acre, under ordinary management, with higher results under good conditions.