UNITED STATES DEPARTMENT OF AGRICULTURE 



t BULLETIN No. 1087 



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Washington, D. C. 



PROFESSIONAL PAPER 



November 3, 1922 



ALFALFA ROOT STUDIES. 



By Samuel Gak\'ee, Assistant Agrostologist, Office of Forage-Crop Investiga- 

 tions, Bureau of Plant Industry. 



CONTENTS. 



Page. 



Scope of the study 1 



Factors tending to produce modifi- 

 cations of root growth 2 



Soil conditions 2 



Climatic conditions 3 



Cultural factors 3 



Abnormalities due to injuries 6 



Varieties studied 9 



Conditions under vrhich varieties 



were grown 10 



Difficulties encountered in getting 



comparable data 11 



Page. 



Characteristic root sj-stems of some 

 of the well-known varieties of 



alfalfa 12 



Xonhardy alfalfas 13 



Common alfalfas 14 



Turkestan alfalfa 18 



Grimm alfalfa 19 



Yellow-flowered alfalfa 21 



Summary 24 



Bibliography 2T 



SCOPE OF THE STUDY. 



Only within recent years have the crown and the root characters 

 of alfalfa been extensively studied and their relation to environ- 

 mental factors carefiiUy considered. The physical reasons for an 

 alfalfa plant being resistant to cold or drought remain much in 

 doubt, but the studies of various investigators tend to substantiate the 

 general belief that they may be associated with broad, deep-set crowns, 

 w.ell-developed rooting rhizomes, and numerous branch roots. The 

 publicity that has been given to these particular features has created 

 the rather general impression that there is a much greater difference 

 in the crown and root characters of the hardy and nonhardy alfalfas 

 than actually exists. Plants with pronounced taproots are generally 

 well enough adapted to regions with relatively high mean tenipera- 

 tures, while plants with the more branching root S3^stems are less sub- 

 ject to winterkilling and to injury by rodents or cultivation. The 

 broad, deep-set crowns that are usually associated with the branching 

 root system are popularly considered a decided advantage in cold re- 



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