120 ROOT DEVELOPMENT IN THE GRASSLAND FORMATION. 



tended to the extreme depth of 5.7 feet. The ends of the wheat roots, 

 especially the last 1.5 feet, were much more branched than those of the 

 oats. 



Mankato, Kansas, lies still 60 miles farther east than the last station 

 and the unbroken land shows some exceedingly fine mixed prairies. It 

 lies near their eastern border, the rainfall being sufficient for an abun- 

 dant development of the tall-grasses and many accompanying her- 

 baceous societies, but not sufficient for these to entirely dominate the 

 short-grasses. Bulbilis dactyloides, Bouteloua gracilis, B. Ursula, etc., 

 normally form a layer in most places below the taller grass dominants, 

 and while sometimes absent they are sure to reappear on hillsides, 

 often in equal or greater abundance than the former. Where over- 

 grazing has occurred, the tall-grasses drop out more or less completely 

 and the area becomes carpeted with buffalo grass and grama, the 

 former usually predominating (plate 3, c). Of the tall-grasses, Agro- 

 pyrum glaucum frequently occurs in pure stands (plate 12, b), but is 

 still more frequently a part of a mictium. Andropogon furcalus, A. 

 scoparius, Kceleria crislala, Bouleloua curtipendula, EUjmus canadensis, 

 and in moister areas Panicum virgalum, are all abundant. Slipa 

 comala is absent. Amorpha canescens, Kuhnia glutinosa, Petalostemon 

 spp., Psoralea tenuiflora, and many other subdominants abound. The 

 vegetation was exceptionally well developed because of the high water- 

 content. 



A field of White Kherson oats was examined 6 miles northwest of 

 Mankato, on a broad, fiat hilltop, growing in Colby silt-loam. Al- 

 though the surface foot of this dark-colored soil was so dry that it 

 came out in great lumps, below this it was very moist to a depth of 

 more than 6 feet. At 1 .8 feet depth the characteristic whitish-streaked 

 layer of "hardpan" was encountered, but this, too, was thoroughly 

 moist and of no firmer texture than the soil above or below it. The 

 silt-loam subsoil was dark-colored to more than 5 feet. The land had 

 been farmed for several years; the preceding crop was corn. The oats 

 were disked in at the rate of 40 pounds per acre about the middle of 

 May. The stand was even and fairly thick and the crop at harvest 

 time 2.8 feet in height. Roots were examined on August 8. The 

 working depth was determined at 3.5 feet and the maximum root pen- 

 etration at 4.6 feet. 



About 2 miles further west a field of Turkey Red wheat was studied 

 on fairly level land which had been cropped for 30 years. Wheat had 

 grown on this land the preceding season. The stubble had been plowed 

 to a depth of 6 inches and the winter wheat drilled in at the rate of 60 

 pounds per acre early in September. At harvest time, July 4, the grain 

 was 2.8 feet tall, quite thick on the ground, and the yield was estimated 

 at 20 bushels. The soil was heavier and contained more clay than that 

 just described. It was moist nearer the surface but quite dry at about 



