Investigations at Burlington, Colorado. 



71 



ance of the crop when compared with the plat of alfalfa was undoubtedly 

 due in part to the greater depth of moist soil. In the portion of the sweet- 

 clover field examined, the hardpan was 6 to 8 inches deeper than in the portion 

 of the alfalfa field where roots were excavated. Except for rare cases of 

 roots entering burrows, etc., none extended to depths greater than 2.8 feet, 

 where hard, dry soil occurred. However, most of the roots reached this 

 depth. As with alfalfa, they were furnished both with more numerous and 

 longer laterals than were those at Lincoln. In the first foot of soil the laterals 

 were often more superficial in position, a response no doubt due to the stim- 

 ulus of moisture in the superficial layers and its dearth at lower levels. The 

 tap-root branched profusely throughout its length almost to its very tip. 

 Tubercles were abundant, often occurring in large clusters. 



On August 25, when a final exmination was made, a long trench was dug 

 in such a manner that while one end extended in heretofore undisturbed soil, 

 the other reached into the territory of the former trench. As usual, the old 

 trench had been sunk a foot or two below the deepest roots, and this one 

 had been deepened still further (to about 6 feet) in order to examine the sub- 

 soil. It had been refilled with the mixed soil and subsoil. A marked dif- 

 ference in growth and vigor of the plants growing adjacent to the old trench 

 and those in the undisturbed area was noted. While those in the latter area 

 were only about 1 foot tall, the others were 1.3 feet high, more branched, and 

 of better color. Where the dry, hardpan layer occurred at 2.7 feet depth, root 

 penetration was limited to the soil above this layer. In general, the root habit 

 was very similar to that of the alfalfa already described, the number of 

 branches, their greater lateral extent and degree of rebranching being quite 

 unlike plants from the same lot of seed grown in the moist soil at Lincoln. 

 However, the plants growing at the sides of the old trench had extended their 

 roots into the loose soil, which had been fairly well moistened, due to heavy 

 rains, and, undoubtedly, to the entrance of run-off water from the surrounding 

 area. Here a few roots were traced to depths of 6.8 feet, while many extended 

 into the fifth and sixth foot of soil. In this new soil area the root develop- 

 ment was similar to that described for plants at Lincoln. 



Summary of Crop Development. 

 Crops grown at Burlington, Colorado, were, owing to the unfavorable 

 climatic conditions, thin of stand, and the above-ground parts much dwarfed. 

 Oats when mature averaged only 1.5, and wheat and barley 1.7 feet in height 

 respectively. Root-depth was limited by water penetration and did not 

 exceed 2.9 feet. Alfalfa and sweet clover, when 132 days old on August 

 25, were only a foot high and rooted entirely in the surface 2 to 2.7 feet of 

 son. Early spring environment, except for the low temperatures (especially 

 at night), was quite favorable to crop growth. The cereals tillered freely 

 and because of the rich soil all the crops grew quite too luxuriantly to suc- 

 cessfully endure the drought conditions of June and later summer. Because 

 of low water-content of both air and soil, all of the crops were from time 

 to time in a semiwilted condition. Many tillers from the cereals died, as did 

 also new roots put forth during intervals when the surface soil was moist. 

 The extraordinary development of long, widely spreading, and profusely 

 branching laterals, which thoroughly filled the soil above the hardpan layer 



