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produce its maximum content of sugar in areas where the mean temperature for the three months of June, July, and August rises above 70 degrees F. The southern limit of this area is an irregular, waving line, as indicated in the accompanying map (Fig. 69). There are, of course, localities where high-grade beets can be produced south of this line, but in point of fact nearly every successful beet sugar enterprise has been located within the field indicated. There is really no limit to the northern edge of this belt except that of short seasons, incident to late frosts of spring and early frosts of autumn. To successfully compete in the sugar markets of the world the sugar beet should enter the factory with an average percentage of sugar of not less than 12. Very much richer beets are often produced and in some of the irrigated areas of the west, where the climate is remarkably dry, an average percentage of 16 and 18 even has been obtained. In the whole beet sugar crop of the United States the average percentage of sugar in the beet is probably not far from 13 or 14. In this respect it is seen that the beet is richer in sugar than the average sugar cane of Louisiana, which does not contain over 11 or 12 percent of sugar.

Fig. 70.—A Field of Beets Ready for Harvesting.—(Bureau of Plant Industry.)

Yield per Acre.—The average yield per acre of sugar beets in the United States is unfortunately very low, due chiefly to ignorance of the proper method of culture. The sugar beet is more of a garden than a field crop and requires special cultivation and fertilization. The average yield in the United States