SOIL AMENDMENTS 541 



462. Relative effectiveness of caustic lime and car- 

 bonate. In order to test the value of ground limestone 

 and other forms of calcium carbonate, experiments in 

 which it was compared with caustic lime have been con- 

 ducted at some of the experiment stations. Reports of 

 tests at the Pennsylvania Experiment Station, 1 in which 

 plats treated with slaked lime at the rate of two tons per 

 acre once in four years were compared with plats treated 

 with ground limestone at the rate of two tons to the acre 

 every two years, show that at the end of twenty years, 

 in every case, the total yields were greater on the plats 

 receiving ground limestone. After the treatment on 

 these plats had been continued for sixteen years, a de- 

 termination of nitrogen showed the upper nine inches of 

 soil on the limestone-treated plats to contain 2979 pounds 

 of nitrogen to the acre, and the slaked-lime plats to con- 

 tain 2604 pounds. It may be inferred from these figures 

 that the slaked lime caused a slightly .greater destruction 

 of organic matter than did the limestone. 



Patterson 2 also conducted experiments for eleven 

 years with caustic lime produced by burning both stone 

 and shells, and the carbonate of lime in ground shells and 

 shell marl. The average crops of maize, wheat, and hay 

 were all larger on the plats treated with carbonate of 

 lime. 

 . While these experiments show, at first glance, results 



1 Waters, H. J., and Hess, E. H. General Fertilizer Experi- 

 ments. Pennsylvania State College, Kept. 1894, Part 2, pp. 

 258-281. Also, Hunt, T. F. Soil Fertility. Pennsylvania 

 Agr. Exp. Sta., Bui. 90. 1909. 



2 Patterson, H. J. Lime, Sources and Relation to Agri- 

 culture. Maryland Agr. Exp. Sta., Bui. 66, pp. 127-130. 1900. 

 Also, Investigations on the Liming of Soils. Maryland Agr. Exp. 

 Sta., Bui. 110, pp. 16-21. 1906. 



