70 



SOILS: PROPERTIES AND MANAGEMENT 



However, our major premise does seem to stand in a 

 general way that a glacial soil, other things being 

 equal, contains a larger amount of the mineral plant-food 

 constituents, and ordinarily a smaller amount of such 

 materials as silica, iron, and aluminium, than does a 

 corresponding soil of residual origin. 



The following data 1 bring out the points already dealt 

 with in their fullest significance: 



PERCENTAGE OF P 2 O 5 , CAO, MaO, AND J 2 O IN SOILS OF DIF- 

 FERENT PROVINCES 



54. Effect of glaciation on agriculture. These differ- 

 ences between residual and glacial soils reflect on the 

 general fertility of the soils. In a comparison of thr 

 driftless area of Wisconsin with the glaciated parts, 2 

 only 43 per cent of the former is improved as against 

 61 per cent of the latter, while the value of the farms 

 on the glaciated soil averages 50 per cent higher. The 

 same general differences appear between the glacial and 

 residual soils of Indiana 3 and Ohio. 4 



1 Failyer, G. H., and others. The Mineral Composition 

 of Soil Particles. U. S. D. A., Bur. Soils, Bui. 54. 1908. 



2 Whitbeck, R. H. The Glaciated and Driftless Portions of 

 Wisconsin. Bui. Geog. Soc. Phil., Vol. IX, No. 3, pp. 10-20. 1911. 



3 Von Engeln, O. D. Effects of Continental Glaciation on 

 Agriculture. Bui. Amer. Geog. Soc., Vol. XLVI, p. 246. 1914. 



4 Ames, J. W., and Gaither, E. W. Soil Investigations. 

 Ohio Agr. Exp. Sta., Bui. 261. 1913. 



