14 THE POTATO 



a depth of two and a half feet. The deep-growing 

 roots are very tender and brittle and easily broken, 

 differing in this respect from corn roots. The hori- 

 zontal roots send out vertical branches, which often 

 descend to a depth of two feet or more. 



Shallow tillage, such as hand-hoeing without hill- 

 ing, retains all the roots. Moderately deep tillage 

 with a five-tooth single horse-cultivator and slight 

 hilling destroys practically all the surface roots, and 

 undoubtedly interferes seriously with the plant's de- 

 velopment ; while with deep tillage nearly all the long 

 horizontal roots are destroyed, and with them all their 

 numerous vertical branch-roots with their intricate 

 system of fibres and root hairs, by which the potato 

 receives its food. In very heavy soils it may be wise to 

 plant potatoes shallow and then hill them, but in most 

 soils it is better policy to plow deep, plant fairly deep, 

 and give shallow flat cultivation. With deep tillage 

 the roots nearest the surface were at a depth of seven 

 inches, while in the case of those receiving shallow 

 tillage the bulk of the horizontal roots were in the sur- 

 face seven inches. The hilling covers the potatoes and 

 prevents them from sunburning, and this seems to be 

 all the benefit received. The loss of roots is very 

 hurtful, and takes place at a time when the plant can 

 least afford to suffer injury. Experiments conducted 

 at Vermont Experiment Station 1 show that during 

 the last weeks of growth the weekly increase in weight 

 of tubers is at its maximum, and that checks when the 

 tubers are approaching maturity depress the yield coi- 

 respondingly. 



i Ver. Bui. 72, p. 5. 



