Productiveness of Soils 99 



grown. What yields are secured? Are the differences in yields due 

 to the properties of the soil or to the way the soils are prepared or 

 the way the crops are cultivated? Is fall or spring breaking pre- 

 ferred? What reasons do farmers give for justifying fall breaking or 

 spring breaking? 



141. Sour, or Acid, Soils are very unfavorable to some 

 crops. Many soils are slightly acid, as will be found when 

 tested with litmus paper. They differ greatly in the 

 degree of sourness. Very acid soils are not favorable 

 for alfalfa, cotton, etc.; but, for corn and small grains, no 

 rule has yet been suggested. Soils that contain injurious 

 amounts of acid are found in swamps or in sandy uplands. 



141a. To Test Soils for Acid, use a small slip of litmus paper, 

 secured from the druggist. Place the paper against the moist soil, 

 and the color after some minutes will change. If blue, the soil is 

 alkaline; if red, it is acid. More reliable results will be secured if 

 the soil is extracted in distilled water, and then tested with litmus 

 or other indicator. 



141b. To Test Soils for Free Lime, drop a small lump into a 

 glass of strong vinegar. If lime is present bubbles will continue to 

 stream from the lump for some minutes. Soils with free lime pres- 

 ent are not acid. 



141J. Alkali Salts in a soil may be the cause of un- 

 productiveness. There are several kinds of very soluble 

 salts that accumulate in the surface soils, most fre- 

 quently in regions of low rainfall. Often the dwarfing 

 effect of alkali salts is confined to a lo'w place, a wet- 

 weather seep, or other place where a quantity of soil- 

 water is evaporated. These salts are formed in all soils, 

 but where the rainfall is abundant they are washed out 

 of the soil by percolating water. If the rain is all evapo- 

 rated from the surface, it will cause an accumulation of 

 these salts near the surface to such an extent that injury 

 to the plant results. Lime is sometimes beneficial on 

 such soils. 



