LIMING- THE SOIL 



379 



meehanieal composition of limestone on sale in Pennsylvania 

 for 1920^: 



Table LXXXVI 



mechanical composition of some limestone offered for 



sale in pennsylvania in 1920. 



Limestone 



Amount Passing Sieve, Mesh 





10 



50 



100 



1 



100 

 100 

 100 

 100 

 100 

 100 



98 

 99 

 89 

 70 

 57 

 44 



92 



2 



88 



3 



73 



4 



58 



5 



50 



6 



34 







207. Gypsum and other soil amendments. — Gypsum, in 

 wMeh form calcium sulfate (CaS04.2H20) is usually applied 

 to soil, has been used for years and was popular long before 

 commercial fertilizers were available to any extent. The use 

 of gypsum was probably familiar to the Eomans. It fre- 

 quently goes by the name land plaster. It is widely distribu- 

 ted in nature and easily ground. Its beneficial effect has been 

 noted, particularly with clover and alfalfa, crops which re- 

 spond especially to potash. Its popularity has waned in recent 

 years, however, since its effectiveness on soils where it has 

 long been used has apparently decreased. This possibly has 

 been due in part to the acid residue that ultimately must re- 

 sult frQm the use of such material and to the failure to lib- 

 erate potassium— a property with which it has very gen- 

 erally been credited and which, when applied to some soils, 

 it may possess. The experimental work in this respect is 

 somewhat conflicting, possibly due to the fact that the con- 



*KeUogg, J. W,, Lime Seport; Penn. Dept. Agr., Vol. 4, No. 2, 

 II721. 



