SWEET POTATO, or BATATAS (Iponicea Batatas). A perennial plant of the natural order Coivol•ulace:r. with long creeping stems, heart shaped leaves on long stalks, and variously lobed, large purple flowers much resembling those of the best known species of Convolvulus, and large oblong or elongated roots. Authorities differ as to whether it owes its origin to East India or America, hut it is now cultivated in all tropical and sub-tropical countries for its sweet, wholesome roots, which are highly esteemed as an article of food.
The sweet potato is propagated by sets ob tained from the tubers sprouted in a specially prepared bed and when about inches tall planted IS inches asunder in rows feet apart in the field; the later vine cuttings, which are commonly used in the Gulf states and as far north as Virginia, require from 90 to 105 days to mature their roots. The crop grows best in a warm, sandy, well-drained soil. It requires clean cultivation. Early digging yields only one-half to two-thirds as much as may be obtained from the matured crop, which averages from 250 to 275 bushels per acre. The roots should be har vested before frost and when the ground is dry. The roots must be stored in a rather warm, dry place, as otherwise heavy losses are almost sure to occur from rotting. The so-called 'yams' grown in the United States are all sweet potatoes.
The most serious diseases of the sweet potato destroy the fleshy roots. The black rot I Cera toeystis limbriata), which appears as greenish black, irregular spots which increase in size and eventually destroy the whole root, may be spread through planting diseased tubers in the seed bed or through the presence of the fungus in the soil. At the New Jersey Experiment Station sulphur in the soil has been used with success as a pre ventive. Dry rot (Pkoina batatca) dries,
wrinkles, and fills the roots with powder. It at tacks the whole root in the field. Rotation of crops and destruction of diseased material are recommended as preventives. A soft rot (Rhi:opus nigricans) attacks stored roots, usu ally commencing at places where the skin has been broken. Since moisture favors its spread, sweet potatoes should be stored in well-ventilated, dry rooms. A leaf spot (Phyllosticta batati cola) often attacks and turns the foliage white, and a leaf mold (Cystopus ipoincrm-pandurance) turns the leaves, especially the older ones, brown. Spraying with Bordeaux mixture or other fungi chic (q.v.) is recommended for these last two and the first disease.
As ordinarily prepared for the table the skin constitutes on an average 20 per cent. and the edible portion SO per cent. of the root. The edible portion has the following percentage composition: water, 69.0; protein, 1.8; fat, 0.7; nitrogen-free extract. 27.4; and ash, 1.1 per cent., the fuel value being 570 calories per pound. Like ordi nary potatoes, sweet potatoes are a succulent food, the chief nutrient being carbohydrates, the principal of which is starch. Sugars are also found, 2.5 per cent. cane sugar and 3.4 per cent. invert sugar being the average amount found in a large number of analyses. In addition to the quantities consumed in the fresh state, sweet potatoes are also canned and evaporated. They are sometimes fed to farm animals, especially pigs. To secure the greatest profit the pigs should harvest the crop and some nitrogenous feed like cowpeas should also he fed. See Plate of YAM, SWEET POTATO, ETC.