8 
S. DEPARTMENT OF AGRICULTURE. 
branching and distortion. It is, therefore, quite evident in studying 
transplanted plants — whether from pots to field or from field to 
field — that due consideration must be given to the effect of such 
treatment upon root development. 
Cultivation modifies the normal root system by injuring or de- 
stroying a large number of the surface roots. The use of the disk 
harrow on alfalfa fields has been recommended frequently on the 
theory that by means of it soil moisture is conserved, weeds elimi- 
nated, and the stand thickened by splitting the crowns. Experiments 
generally have shown that such treatment is injurious in that it 
weakens or kills ruany of the plants. 
Fig. 5. — Production of branch roots and distortions in Grimm alfalfa plants 166 days 
old. From the 49th to the 87th day the root systems were confined in small flower- 
pots. 
In many localities alfalfa roots are subject to considerable injury 
by rodents, such as gophers and mice. When they sever the taproot 
very close to the crown, as frequently happens, there is no opportunity 
for the plant to develop side roots, and it soon dies. If the taproot 
is severed several inches below the crown, the plant often survives 
and throws out branch roots, behaving much as a transplanted plant 
does. At Highmore, S. Dak., in 1912 and 1913, several Meclicago 
falcata plants had their main roots severed by gophers, yet these 
plants have continued to live, although much reduced in vitality. 
Medicago sativa plants failed to survive when the taproot was 
severed so near the crown. Malformations in roots maj T sometimes 
be caused by disease, the presence of which can only be determined 
by close examination. 
