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. 



