Gerarde's Herball, published in 1597, describes the potato, and the edition published in 1636 con tains a woodcut of it. Many of the other works of like nature contain descriptions of it. In 1663, the Royal Society of England tried to popularize the plant, especially in Ireland. So late as 1699 Evelyn barely mentioned the potato, and in 1719 London and Wise did not consider the plant worthy of listing in their Complete Gardener. Only two varieties were listed in 1771, yet by the end of the eighteenth century they were numerous.
Potato-culture spread slowly in Europe but more rapidly in the south of Ireland, because the peas ants realized that it was a useful food and planted it everywhere ; and with this as their commis sary they were able to maintain the opposition to English rule. Two and a half centuries of reliance on this crop led to the neglect of other crops, and, when the blight occurred in Ireland in 1846, it was attended by one of the worst famines known in Europe. The potato has been more highly devel oped in Europe than in America, and much higher average yields are secured in the United Kingdom and northern Europe than in this country.
Geographical distribution and extent.
Next to rice, the potato is probably the most extensively grown and most valuable crop in the world. The annual yield of the world is nearly five billion bushels. The potato crop of Europe in value and volume exceeds the tabulated wheat crop of the world. One acre of potatoes fre quently furnishes as much human food as ten acres of wheat, and wherever wheat is a preca rious crop, as in northern Europe, potato-grow ing has been extensively developed. Yields of 1,000 to 1,200 bushels of potatoes per acre con taining 10,000 pounds of starch are on record. About 30,000,000 acres of potatoes are grown an nually in Europe, and of this area one-third is in Russia, the average yield per acre being about 95 bushels ; Germany is sec ond in total area with 8,000,000 acres and a yield of nearly 1,600,000, 000 bushels, an average of 200 bushels per acre. France grows between 3,500,000 and 4,000,000 acres, Austria nearly 3,000,000, Hungary 1,500,000 and the United Kingdom 1,250,000. The average yield of England is about 230 bushels per acre, that of Ireland about 150 bushels. The United States grows about 3,000,000 acres, and the average yield for the past ten years is 84.5 bushels. Since the potato thrives best in a cool climate, potato-growing has been developed to the greatest extent in the Northern states. (Fig.
745.) According to the report of the Twelfth Census, the five states reporting the greatest number of bushels in 1899 were New York, 38,060,471 bushels ; Wisconsin, 24,641,498 bush els; Michigan, 23,476,444 bushels ; Pennsylvania, 21,769,472 bushels ; and Iowa, 17,305,919 bushels. Fig. 746 shows the average yield per acre in bushels for the period 1900-190-1.
In Canada, the potato crop has always been important, although the output has not shown so great an increase as some other crops, notably oats and wheat. In 1871, the potato crop was 47,330, 187 bushels. In 1901, it reached 55,362,635 bushels, raised on 448,743 acres. The production in bushels by provinces in 1901 was as follows : Ontario, 20,042,258; Quebec, 17,135,739; Prince Edward Island, 4,986,633 ; New Brunswick, Nova Scotia, 4,394,413; Manitoba, 1,920,794 ; The Territories, 1,277,793; British Columbia, 955,946.
Soil.—The soil usually considered best is a deep, mellow, free-working loam, although crops are raised on lighter or heavier soils, provided the latter are well drained. Fall-plowing is generally advisable, since it facilitates the spring work. It should be as deep , as possible, to a depth of twelve inches if the soil will permit. The land is generally left rough-plowed during winter and is fitted as early as possible in spring. The seed bed should be well prepared by using the disk or acme harrows.
Fertilizers.—An application of ten tons or more per acre of barnyard manure may be made in the fall before plowing,or, if the manure is well rotted,it may be applied in spring and disked in. It is important for potatoes that three be plenty of homes, hence the crop is fro ineptly grown after a crop of clover or on a two 0..r-01,1 sod. It would do well after a much older sod,but there is likely to be trouble from wire worms and white grubs; for this rea son, when po tatoes are to be planted on such land, it is considered advisable to follow another crop, such as oats or corn, by potatoes, which may then lie grown for two or three successive years if desired. If com mercial fertilizers are applied, generally a complete fertilizer —containing nitrogen, phosphoric acid and potash— gives best results. Nitrate of soda is a good source of nitrogen for potatoes.