Investigations at Peru, Nebraska. 



9 



Growth conditions during this period were rather unfavorable. Cloudy, 

 wet weather prevailed. At no time was the water-content of the surface 

 foot of soil less than 17 per cent above the hygroscopic coefficient. The tem- 

 perature of both air and soil was low. The maximum soil temperature of the 

 surface foot did not exceed 62° F. However, the period was free from frost, 

 the lowest air temperature being 37° F. 



The second examination of this oat was made May 29, 59 days after plant- 

 ing. The plants averaged 1 to 1.2 feet in height and the number of stalks, 

 including tillers, varied from 1 to 3. The first 7 to 9 inches of soil was filled 

 with a complete network of fine roots and rootlets. Most of these came 

 from a node a short distance below the surface and were branched freely 

 to the first and second orders. They penetrated the soil in all directions from 

 the base of the plant. The branches of all degrees seemed to grow upward 

 as readily as downward, and the tips of those extending upward very often 

 lay just beneath the soil surface. Indeed, it was not unusual to find even 

 some of the larger roots lying at a depth of only 0.5 to 1 inch. The horizontal 

 roots ran outward to a distance of 6 to 12 inches, and then some turned 

 downward. From each plant one or two of the main roots pursued a some- 

 what irregular course into the subsoil, often reaching depths of 3 to 3.4 feet. 

 The maximum penetration was 3.6 feet. These longer roots were rather 

 densely branched and rebranched, although not to so great a degree as those 

 nearer the surface. Branches of the first order sometimes reached a length 

 of 4 inches. The last 4 to 8 inches of the main roots were unbranched. Fig- 

 ure 1 a shows the two portions of this root system and also indicates how 

 splendidly the plant is equipped for absorption in both the upper and lower 

 layers of soil. 



The month of May was cool and dry, and during this second period of root 

 development all of the small cereals grew vigorously. 42 per cent of the days 

 were clear, and there were only 1.8 inches of rain. The day air temperature 

 averaged 65° F., the night temperature 53° F. Records of air temperature 

 were obtained, as at the other stations, by means of Friez's thermographs, 

 placed in appropriate shelters of the Weather Bureau type, with the record- 

 ing apparatus at a height of 4 inches above the soil surface. Livingston's 

 standardized, white, cylindrical, porous-cup atmometers were employed to 

 measure the evaporating power of the air. The cups were operated in dupli- 

 cate in the usual manner, with the evaporating surface only 3 or 4 inches above 

 the surface of the soil. Because of the cool weather, the average daily evapo- 

 ration was only 21 c. c. The soil temperature to a depth of 3 feet averaged 

 60° F. Although there was a deficit in rainfall of 3.6 inches below the mean, 

 the soil had been so thoroughly wetted during April that samples during May 

 showed an average available moisture-content of 16 per cent in the first 3 

 feet. The plants had a dark-green color and produced a luxuriant growth of 

 leaves. 



A final examination of oats was made July 1, 92 days after planting. The 

 height of the stalks, which averaged 1 to 3 per plant, ranged from 2.8 to 3.2 

 feet. The crop was about half ripe. In general, the form of the root sys- 

 tem was similar to that found at the second examination, except that it was 

 somewhat more extensive. The first 8 or 9 inches of soil were filled with a 

 mass of finely branched roots, many of which extended only a few inches, but 



