Mar. lo, 1919 Organic Matter and Water-Holding Capacity of Soil 277 



The comparatively slight influence that the water-holding capacity of 

 the surface soil alone exerts upon the productivity finds an illustration 

 in the common observation that sandy loams provided with fine-textured 

 subsoils, when properly farmed, produce as heavy yields as clay loams. 



The moisture available to a crop, in so far as the character of the soil 

 determines the amount, depends upon the water-retaining capacity of the 

 whole soil section penetrated by the roots of the crop, and not chiefly 

 upon that of the surface stratum, and while cultural methods which lessen 

 the organic-matter content of this stratum lower its water-retaining 

 capacity, it forms such a small part of the whole moisture-retaining sec- 

 tion that any change in the moisture supply thus induced may be too 

 slight to have any distinct influence upon the productivity. 



SUMMARY 



The paper reports a detailed study of the moisture conditions found on 

 two adjacent Minnesota plots, both of which had a silt loam soil, very 

 unifonn in texture, but differing widely in content of organic matter as 

 the result of great differences in cultural treatment. 



During the cool, wet summer of 1915, when cultivated crops were 

 grown, the surface foot, and this alone, showed a very marked difference 

 in the moisture content, especially in the available portion, the soil the 

 richer in organic matter retaining the more water; but in the warmer and 

 somewhat drier summer of 191 8, when winter rye was used, much smaller 

 differences were found. 



It is concluded that in the case of a finer-textured soil, with a fine-tex- 

 tured subsoil and a comparatively level surface, the differences in the 

 watery capacity that may be caused by differences in manuring or in 

 cultural operations exert but little influence upon the productivity. 



LITERATURE CITED 

 (i) Alway, Frederick J. 



1913. STUDIES ON THB RELATION OF THE NON-AVAILABLE WATER OP THE SOIL 



TO THE HYGROSCOPIC COEFFICIENT. Nebr. AgT. Exp. Sta. Research 

 Bui. 3, 122 p., 37 fig. 

 (2) Klein, Millard A., and McDole, Guy R. 



I917. SOME NOTES ON THE DIRECT DETERMININATION OF THE HYGROSCOPIC 



COEFFICIENT. In Jour. Agr. Research, v. 11, no. 4, p. 147-166. Lit- 

 erature cited, p. 165-166. 

 (3) and McDoLE, G. R. 



19 17. RELATION OP THE WATER-RETAINING CAPACITY OP A SOIL TO ITS HYGRO- 



SCOPIC COEFFICIENT. In Jour. Agr. Research, v. 9, no. 2, p. 27-71, 

 4 fig. Literature cited, p. 70-71. 

 (4) 



1918. VARIATIONS IN THE MOISTURE CONTENT OP THE SURFACE FOOT OF A LOESS 



SOIL AS RELATED TO THE HYGROSCOPIC COEFFICIENT. In JOUT. Agf. 



Research, v. 14, no. 11, p. 453-480, 5 fig. Literature cited p. 480. 



