120 THE HANDBOOK FOR PRACTICAL FARMERS 



of the highest quality may be expected from the sandy or sandy 

 loam soils. Fairly heavy clay soils may give a satisfactory yield, 

 but in appearance, flavor, and keeping qualities, the potatoes 

 are inferior to those produced on lighter soils. Light soils, as a 

 rule, are better drained, more easily tilled, and lessen the cost 

 of harvesting the crop. Potatoes grown on light soils have less 

 dirt clinging to them than those grown on clay soils. 



Stucky states that when a friable sandy loam soil is properly 

 fertilized and cultivated it gives a larger yield and a better grade 

 of tubers than clay soils. 



Fig. 38. — Map of the United States, showing the areas adapted to the growing 

 of sweet potatoes. The heavy line represents the northern limits of sweet- 

 potato production for home use. The shaded portion indicates the sections 

 adapted to the commercial growing of sweet potatoes. — U. 8. Dept. of 

 Agriculture. 



Johnson and Rosa found that stiff, clay soils produced 

 excessive growth of vine, while the tubers were long, irregular, 

 rough and inclined to be somewhat watery. 



Garcia writes that sweet potatoes do better in a sandy loam 

 than in an adobe soil, and adds that w^hile the best results may 

 be had from a loam which is rich and conserves moisture well, 

 very sandy soils produce low yields. 



Rotation. — Sweet potatoes should not be grown on the same 

 piece of ground year after year. Even if the fertility of the soil 

 is maintained by leaving the vines and adding other plant food, 

 the danger of diseases, which may live over in the soil, becomes 

 too great. The sweet potato responds as readily to intelligent 

 crop rotation as any of our staple crops. The following is sug- 



