256 LIME 



element in plant growth, is used by some plants, notably 

 clover and alfalfa, in large quantities, and is frequently 

 lacking in soils in an available form. It has a distinct value 

 in many cases as a plant food, and lime compounds may very 

 frequently be direct fertilizers. 



Soil acidity, a condition corrected by lime, occurs in many 

 soils and is a natural result of cultivation and cropping. 

 Acids are produced in soils by the decay of organic matter; 

 by the selective action of plants which removes the base 

 from a salt and leaves the acid radicle free as an acid; and 

 by the adsorption of the base from a salt by hydrated silicates 

 and humus. Applications of potassium sulphate and potas- 

 sium chloride intensify this action. Soil acidity results when 

 there are not sufficient bases present to neutralize the acid. 

 Calcium carbonate is the principal base. 



Lime, properly so-called, is calcium oxide, but popularly 

 is any compound of calcium which will neutralize an acid. 

 Calcium carbonate and calcium hydroxide are the forms 

 ordinarily used. Whatever the original compound may 

 have been, the bicarbonate is the active one in the soil, 

 and is formed sooner or later from either the carbonate 

 or hydroxide. Hence no one compound is preferable. 



Lime acts on the soil by neutralizing acids and thus hasten- 

 ing decomposition of organic matter, increasing nitrification 

 and fixation of nitrogen — all bacterial processes. It also 

 prevents the acids from poisoning plants. Lime also frees 

 potassium and phosphorus from insoluble compounds, 

 improves the physical condition of soils, and checks plant 

 diseases. It causes potato scab, however, and prohibits 

 the growth of some crops. Too heavy applications of burnt 

 lime destroy organic matter unnecessarily and may destroy 

 seeds if applied too near seeding. 



The use of magnesian lime is not recommended. Waste 

 lime is good if care is taken in buying and using the various 

 forms. Gypsum is not particularly valuable. 



REFERENCES 



Penna. Agr. Expt. Sta. Report, 1899-1900, Pt. II, p. 15. The Agricul- 

 tural Use of Lime. 



Van Slyke. Fertilizers and Crops. 

 Wheeler. Manures and Fertilizers. 



