LIMING THE SOIL 371 



202. Effect of lime on the soil. — In heavy soils there is 

 always a tendency for the fine particles to become too closely 

 associated. Such a condition interferes with air and water 

 movement. The granular structure that should prevail is 

 somewhat encouraged by the addition of lime, especially the 

 caustic forms. In practice, however, the amounts of lime ap- 

 plied are generally too small to have much importance in this 

 respect. 



Chemically, lime brings about many complex changes in 

 the soil. Basic exchange is forced and certain mineral nu- 

 trients tend to become more available. The hydrogen ion 

 concentration is lowered and deleterious bases, such as alumi- 

 num and manganese, are forced back into less active combi- 

 nations. Oxidation processes seem also to be stimulated, thus 

 favoring the elimination of organic toxins, which often de- 

 velop when improper decay takes place. The charge that 

 quicklime in normal amounts produces a rapid and detri- 

 mental oxidation of the soil organic matter is probably an 

 over-statement. 1 While lime of all kinds promotes the oxida- 

 tion of organic matter, calcium oxide, when added in rational 

 amounts, is probably no more active over the term of the rota- 

 tion than calcium carbonate. 



Most of the favorable soil organisms and some of the un- 

 favorable ones, such as those that produce potato-scab, are 

 benefited by judicious liming. The bacteria that fix nitrogen 

 from the air, either alone or in the nodules of some legumes, 

 are especially stimulated by the application of lime. The 

 change of ammoniacal nitrogen to the nitrate form, which is a 

 biological phenomenon, requires active basic material. Other- 

 wise this necessary transformation will not proceed. The 

 decomposition of both carbohydrate compounds (fermenta- 

 tion) and of nitrogenous materials (putrefaction) depends on 

 lime, that the decay products may be favorable. 



1 Madntire, W. H., The Carbonation of Burned Lime in Soils; Soil 

 Sci., Vol. VII, No. 5, pp. 325-446, May, 1919. 



