76 



ROOT DEVELOPMENT IN THE GRASSLAND FORMATION, 



has been shown that such a soil layer, more or less definitely differentiated and 

 of variable thickness, does occur throughout much of the drier grassland area. 

 But no case has ever been found by the writer among native species, and 

 relatively few cases among crop plants, where the "hardpan" corresponded 

 with the depth of root penetration. Usually roots penetrate it without pro- 

 found modifications and it seems doubtful if it ever acts as a mechanical 

 hindrance to root development. The soil here is certainly no more compact 

 than the Pierre clay, through which roots penetrate with no apparent external 

 modifications. The fact that native short-grass roots, together with those of 

 many other species, are found regularly, and those of cultivated crops at least 



Table 7. — Root development of buffalo grass in pro > rie-plains-grassland formation. 



often, below this layer should be sufficient to throw much doubt upon the too 

 widely credited efficiency of "hardpan" in preventing water penetration. One 

 of two things must occur: either buffalo-grass roots penetrate and develop 

 normally several feet below the point where water is available for growth, or 

 water reaches depths (at least at intervals) far beyond the surface 1.5 or 2 feet 

 of soil. Very few published data are available on the water-content of short- 

 grass plains soils. Shantz (1911) concludes from measurements taken at 

 Akron from June 10 to September 10, and at Yuma, Colorado, for a shorter 

 period, that "soil-moisture determinations in this type of land show that even 

 during periods of more than normal rainfall available soil moisture is limited 

 to a few inches of the surface soil." Alway (1919), using Shantz's data, has 

 shown further that even during this season (1909) of excessive rainfall, the soil- 

 water approached or reached the hygroscopic coefficient at depths of 0.5 to 1, 

 1 to 1.5 feet, and in the fifth and sixth foot at certain periods during the grow- 

 ing-season. However, until a long series of soil-moisture determinations are 



