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USDEPARTNENT OPAGRICUETURE © 
No. 6 
Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief. 
September 19, 1913. 
THE AGRICULTURAL UTILIZATION OF ACID LANDS 
BY MEANS OF ACID-TOLERANT CROPS. 
By FREDERICK V. COVILLE, 
Boteénist in Charge of Economic and Systematic Botany. 
INTRODUCTION. 
In the past 20 years farmers have witnessed the development of 
what may be called a lime-and-clover literature and the growth of a 
corresponding agricultural practice. The scientific researches of 
various investigators published from 1867 to 1888 had demon- 
strated that leguminous plants through the bacteria of their root 
tubercles were able to take nitrogen from the atmosphere and that 
when a crop of these plants was plowed under the land was enriched 
as if by a corresponding application of manure. 
In the northeastern United States the principal leguminous plant 
used in crop rotations had been red clover. ‘The scientific con- 
firmation of the popular belief that this plant had high value as a 
green manure greatly stimulated its use, the customary procedure 
being to plow under the clover turf after taking off one or two cut- 
tings for hay. It was found, however, that if the land is acid in 
its chemical. reaction red clover makes but feeble growth. If the 
chemical reaction is neutral or shghtly alkaline and other conditions 
are favorable, heavy crops of red clover are produced. This con- 
sideration greatly extended the practice of applying lime, in order 
to neutralize the acidity of the soil and thus increase the manurial 
use of clover in crop rotations, over large areas of the older lands 
of the eastern United States. 
It was found also that timothy, the chief hay grass of this region, 
was much longer lived and more productive in acid land when limed, 
and that wheat, one of the principal cereals, yielded much more 
heavily when treated in the same manner. Within the last few 
years the attempt in the acid East to cultivate alfalfa, the great hay 
crop of the alkaline West. has conveyed the same lesson in a still 
more striking manner. for alfalfa can not be grown satisfactorily in 
any soil, however fertile, which has an acid reaction. When grown 
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