their development. By its physical effect lime produces good air and 

 moisture conditions for bacteria as above described. 



5. Lime materials promote the normal decay of soil organic matter 

 through their effects on the agencies of decay above described. The 

 normal decay of organic matter in soil prevents accumulation of 

 poisonous materials in soils which may be detrimental to plant growth. 



6. Lime cannot be depended upon to neutralize the toxic effects 

 of sodium carbonate or black alkali. 



THE NATURE AND FUNCTION OF GYPSUM 



Gypsum is the sulfate of calcium and therefore is not the same as 

 "lime" nor the same as any of the three agricultural forms of the 

 latter above described. The only thing which gypsum has in common 

 with the three lime materials named, from the point of view of chem- 

 ical composition, is that it, like the others, contains the element 

 calcium. Let us study its functions in soils. 



1. Gypsum exerts a similar physical effect to that of lime on the 

 clay and adobe soils (see above). 



2. Gypsum, like lime, serves as a source of the element calcium 

 (see above). 



3. Gypsum, like lime, stimulates the beneficial soil organisms in 

 the nodules on roots of leguminous plants like the peas, beans, vetches, 

 alfalfas, and clovers. 



4. Gypsum does not make "sour" soil "sweet." It will not 

 change an acid into a slightly alkaline soil as do the lime materials. 

 Gypsum possesses no alkalinity, and therefore will not be of assistance, 

 or act as a corrective to "sourness" or acidity in soils. 



5. Gypsum will neutralize the toxic effects of sodium carbonate or 

 "black alkali." 



LIME VERSUS GYPSUM 



The question comes to us frequently as to whether "lime or 

 gypsum" will correct a certain difficulty in soils. This confusion 

 of two distinct types of substances has done much harm, and the 

 reader is asked to read carefully the statements made above with 

 respect to each in order that errors may be obviated. As above noted 

 there is at least one very important function which lime performs in 

 the soil which gypsum cannot perform. If soils need correction for 

 acidity, the lime materials will do but not the gypsum. Too much 

 emphasis cannot be placed on this distinction. In fact, to be on the 

 safe side the use of lime is advised even in cases in which people with 



