68 The Sugar-Beet in America 
cropping, or the use of farm manure, tends to reduce the 
accumulation of these salts. 
\ 
ACID SOILS _ 
Soil acidity is not nearly so serious a problem in the 
sugar-beet areas of the country as is alkali, but in some 
districts it occurs. Sugar-beets, in common with most 
ordinary crops, require for their best growth an alkaline, 
or basic, reaction of the soil. This is not the condition 
mentioned above as alkali, but refers to the chemical 
reaction. Such important crops as alfalfa can hardly be 
made ‘to grow on an acid soil, since the bacteria that 
fix nitrogen in connection with growth on the roots of 
these plants require a basic reaction. Acid soils are 
most often found in humid regions where the basic ele- 
ments of the soil minerals have been leached out, leaving 
the acid part behind; in swamp lands where the decay 
of large quantities of vegetable matter also results in 
an acid condition due to the accumulation of organic 
acids. : 
An acid soil is indicated by the growth of a number 
of plants, among which are common sorrel, sour dock, 
and horsetail, also by the failure of alfalfa and other leg- 
umes to do well. Blue litmus paper and a number of 
other laboratory tests may be used in determining acidity 
and the amount of lime necessary to correct the condition. 
The kind of lime to use depends on conditions; burned 
lime and ground limestone both accomplish the result. 
Ground limestone, however, is usually cheaper and, if 
fine enough, is effective. 
