THE VEGETABLE GARDEN 347 



season the result may be an abundant growth of vine and a small 

 yield of stringy potatoes. For some time before harvesting the crop 

 the water should be withheld altogether, in order that the roots may 

 ripen properly. 



Soil. Sweet potatoes thrive on a moderately fertile sandy loam 

 which does not contain an excess of organic matter. They are fre- 

 quently grown upon almost pure sand, especially where the subsoil 

 is a yellow clay. Soils containing considerable calcium or underlain 

 with limestone are well adapted to the growing of the crop. The 

 sweet potato is exceptional in that a fairly good crop can be grown 

 upon soils that are too poor for the production of the majority of 

 farm crops. Sweet potatoes yield a fair crop on the "worn-out" 

 tobacco and cotton lands of the South, especially when used in a 

 rotation including some leguminous crop for increasing the humus 

 in the soil. Like many other crops, the sweet potato thrives on 

 newly cleared land, but the crop should not be planted continuously 

 in the same place. With the sweet potato, as with other crops, rota- 

 tion is the keynote of success. 



Good drainage is essential, the original idea of planting upon 

 high ridges being for the purpose of securing better drainage. The 

 surface soil should extend to a depth of 6 or 8 inches, and the subsoil 

 should be of such a nature that it will carry off excessive moisture 

 without leaching away the fertilizers applied to the land. Too great 

 a depth of loose surface soil or an alluvial soil having no subsoil will 

 produce long, irregular potatoes that are undesirable for marketing. 

 Planting upon land having a loose, sandy surface soil underlain by 

 a well-drained clay subsoil will tend to produce the type of rather 

 thick, spindle-formed potato that commands the highest price. The 

 depth of plowing is a prominent factor in the preparation of land 

 for sweet potatoes, and on soils of too great depth before the subsoil 

 is reached very shallow plowing should be practiced, leaving the soil 

 firm beneath, against which the roots must force their way. If the 

 surface soil is of insufficient depth, it should be gradually increased 

 by plowing a little deeper each year or by subsoiling in the furrow 

 behind the regular turning plow. 



Fertilizers. The root portion of the plant is the part having 

 the greatest value, though the foliage and vines have some value as 

 food for certain kinds of stock. It has been found that an excessive 

 amount of organic matter in the soil will frequently produce an 

 abundant growth of vines at the expense of the roots. It has also 

 been noted that the potatoes will be small and the yield unsatisfactory 

 on soils that do not contain sufficient organic matter to produce a fair 

 growth of vine. The use of stable manure as a fertilizer for sweet 

 potatoes is recommended on lands that are deficient in organic matter. 

 Heavy applications of fresh manure shortly before planting the land 

 to sweet potatoes will stimulate not only the growth of weeds but also 

 of the vines at the expense of the roots. Well-rotted stable manure 

 may be used at the rate of 10 to 15 carloads to the acre, spread broad- 

 cast or beneath the ridges and harrowed into the soil, but it is always 

 well to apply the manure with the crop grown the previous season. 



