8 BULLETIN 700, U. S. DEPARTMENT OF AGRICULTURE. 



(2) Fertile clay loam. This was of the same general texture as the 

 less" fertile soil, but owing to the presence of an adequate ground 

 cover the soil had not been subject to washing and erosion. It ap- 

 peared to be more mellow than the " infertile" clay loam and was 



darker in color. . 



The more important chemical properties at the time of the begin- 

 ning of the experiment were as follows : 



czzza rerf/'/e. so/7 

 ^" r'&r cesiT d/f fere nee. 



FIG. 2. Relative water requirements per unit dry weight for peas, native brome grass, 

 and wheat grown in infertile and in fertile soils of the same type. 



The chief difference chemically was in the total nitrogen content. 

 Also there was a wide difference in the humus content as determined 

 by incineration. The difference in the latter was largely responsible 

 for the contrast in the wilting coefficients of the soils, this factor 



