FERTILIZERS FOR POTATOES 427 



are produced on very heavy clay. The greater portion of 

 the crop is produced on the lighter types of soil. Sandy and 

 sandy loam soils are especially desirable for producing 

 smooth, clean potatoes of high quality. Such soils, how- 

 ever, are quickly exhausted, unless kept up by the rotation 

 of crops and by the application of manure. Any soil, to 

 produce a good crop of potatoes, should be well supplied 

 with vegetable matter, and be rich and mellow to a consider- 

 able depth. 



559. Manures and Fertilizers. Stable manure is one of 

 the most desirable fertilizers for potatoes. It not only fur- 

 nishes the necessary plant food, but helps to loosen the soil 

 and to hold moisture, providing conditions very favorable for 

 potatoes. On ordinary soils, a dressing of from 8 to 15 loads 

 of stable manure to the acre, well mixed with the soil, is a 

 suitable application for the crop. Potatoes use much potash, 

 but most soils are well supplied with this element. When 

 commercial fertilizers are used, a complete fertilizer con- 

 taining from 2 to 4 per cent of nitrogen, 6 per cent of phos- 

 phoric acid, and 8 per cent of potash, is usually applied. 

 Five hundred pounds or more of this fertilizer are applied 

 to the acre, the rate depending upon the condition of the soil. 

 In the South, where soils are subject to considerable washing 

 and loss of fertility during all or nearly all of the year, larger 

 applications are usually made, often from 1000 to 2000 

 pounds to the acre. On some of the lighter types of soils, 

 or where leaching is at all likely to take place, the fertilizers 

 are often added during the growing season. 



560. Preparing the Land. Soil for potatoes should, as 

 a rule, be plowed deep, from 8 to 10 or 12 inches on the better 

 soils. It is not desirable, however, to plow an extremely light 

 soil so deep, unless it has been heavily fertilized with stable 

 manure, and the manure thoroughly mixed with the soil. 



