THE CHEMICAL COMPOSITION OF SOILS 





has been reported present in peaty soils. Acid soils 

 can be distinguished by their action upon blue litmus 

 paper, and the acidity can be readily corrected by the use 

 of lime or wood ashes. A soil may, however, give an 

 acid reaction and contain a fair amount of lime as a 

 silicate. Studies conducted by the Rhode Island Ex- 

 periment Station indicate that the areas of acid soils are 

 quite extensive. 



122. Soils in Need of Humus. Sandy and sandy 



loam soils that have 



been cultivated for a 



number of years to 



corn, potatoes, and 



small grains without 



rotation of crops or the 



use of stable manures 



are deficient in humus. Clay soils, as a rule, are not in 



need of humus so much as loam and sandy soils. The 



mechanical condition of 

 heavy clay is, however, im- 

 proved by the addition of 

 humus-forming material. 

 The addition of humus to 



FIG. 27. Humus from Old Soil. 



H 



N 



FIG. 28. Humus from New Soil. 



loam and sandy soils is 

 beneficial in preventing 

 drifting, because it binds together the soil particles. 

 There are but few arable soils, under ordinary cultiva- 

 tion, to which it is not safe to add humus-forming mate- 



