114 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



depth of 2 feet and broke out with rather a columnar structure. At 2.1 

 feet occurred well-formed "hardpan" nearly a foot thick, below which 

 was the dry, light-colored, loose subsoil. The working depth of the 

 roots was found to be 2 feet, none extending deeper than 2.3 feet. 



A field of rye was also examined. Following a crop of milo, it was 

 planted on September 19 at the rate of 56 pounds per acre. It came 

 up very well in the fall, and reached a height of about 3.5 feet, 

 when it was plowed under for green manure on May 27, just when 

 it was in the late flowering stage. A rather pronounced "hard- 

 pan" occurred at 2.3 feet. Below this level the subsoil was streaked 

 and colored with magnesium or calcium compounds to a depth of 4.4 

 feet. This layer extended much farther below the 2-foot level than 

 in either of the preceding fields. The roots had a working depth of 

 3 feet, while some reached a maximum extent of 3.6 feet. 



Finally the roots of spring wheat were examined. Corn had been 

 grown on the ground previously. The wheat was planted March 12. 

 It was of good stand, with an average height at harvest of about 2.6 

 feet, but the yield was only 12 bushels per acre. The soil was in all 

 respects similar to that in the adjoining field of winter wheat,' only it was 

 moist to a depth of at least 7 feet. Indeed, it was so wet that it stuck to 

 the spade and at any depth could easily be pressed into a very coherent 

 lump. The "hardpan" was so thoroughly moist that it could not be 

 distinguished from the surface soil. The root development readily re- 

 sponded to the presence of the moist subsoil and reached a working depth 

 of 3 .4 feet . It may be noted that this is 1 .4 feet deeper than the working 

 depth of the winter wheat, which, under similar growth conditions, is 

 usually of greater extent than the former. The difference in maximum 

 penetration is even more marked, being only 2.3 feet for winter wheat 

 and 4.4 feet for spring wheat. The cause of the excess of soil moisture 

 in this field was due to seepage from a large irrigation reservoir about 

 150 feet distant from the place of root excavation. 



These data throw some light upon the root penetration of native 

 grasses, legumes, and other species of the short-grass plains vegetation. 

 Most of these deep-rooted species are plants with periods of life and 

 growth of extended duration. During wet phases of the climatic cycle 

 it seems almost certain that water must penetrate far into the subsoil. 

 Becoming gradually moistened and finally thoroughly wet, the "hard- 

 pan" offers little resistance to the downward penetration of water. At 

 the Colby Experiment Station it has been shown conclusively that under 

 cropping conditions the water-content varies to a depth of at least 6 

 feet, and similar conditions occur at Burlington, Colorado. Further 

 study, now that we are certain of the deep rooting habits of short-grass- 

 plains species, will in all probability show this to be the case in native 

 vegetation. 



A final examination of the root development of crop plants in short- 

 grass land was made at Limon, Colorado, 70 miles east of Colorado 



