Investigations at Lincoln, Nebraska. 



47 



third order were rare. In the second foot the branches became shorter, and 

 not infrequently, for considerable distances, none were over 0.1 to 0.2 inch 

 in length. Below 2.3 to 2.5 feet the number of roots decreased rapidly. 

 While many of them were very poorly branched and often gave rise to only 

 a few rootlets 0.1 to 0.5 inch long, in the course of several inches, most 

 of them were branched quite regularly at the rate of 5 or 6 laterals per 

 linear inch. These unbranched rootlets varied from 0.5 to over an inch in 

 length. 



At this time a comparison was made with the development of oats in the 

 lower crop plats. Due to a more fertile soil, as well as a more constant 

 and greater supply of available water in the surface 0.5 foot (12 to 15 per 

 cent), the crop was better developed (cf. tables 9 and 10). The plants which 

 were beginning to blossom were 2.6 feet in average height, although some 

 exceeded this by 0.5 foot. They had tillered more freely than the plants in 

 the upland and the stand was thicker. The poorer stand and growth in the 

 upland plats was probably due to the earlier planting and to differences in 

 soil fertility and water-content. 



In the lowland area the maximum root depth (3.7 feet) was somewhat less 

 than on the upland, although the working depth (2.7 feet) was greater. Little 

 difference was determined in degree of branching or in lateral spread. 



The relatively slower development of the 1920 crop as compared with 

 that of the more favorable growing-season of 1919 stands out strikingly. 

 On June 12, 1919, 49 days after oats were planted, the crop in the upland 

 area was 1.3 feet tall and had a working depth of 2.1 feet and a maximum 

 depth of 2.8 feet. At the lowland station plants 1.8 feet high had roots with 

 a working depth of 2.3 feet and a maximum depth of 3.3 feet (Weaver, 

 1920 : 134). Thus plants only 49 days old, during this more favorable season, 

 while not developed as far as the 80-day-old plants just described, were far 

 beyond the latter at the age of 60 days. 



A final examination was made a few days after harvesting the crop on 

 July 12. At this time the roots, except the deeper ones, were quite brittle 

 and the cortex greatly shrunken, indicating that much material had been 

 removed upward during ripening. Otherwise, the differences in the mature 

 root system from that described at the beginning of the blossoming period 

 are a somewhat greater working depth (2.7 to 2.8 feet) and an even more 

 thorough occupation of the soil-mass already delimited at the earlier exami- 

 nation. 



The period June 20 to July 12 was one very favorable for root growth. 

 Several well-distributed rains furnished an abundant water-supply to the 

 surface soils, while the deeper layers had 8 to 16 per cent of water constantly 

 available. On the lower crop-plats, moisture conditions were also favorable 

 (table 10). Here the roots of the matured plants had penetrated to maximum 

 depths of 4.3 to 4.8 feet, but the working level (2.8 feet) had changed little 

 since the previous examination 24 days earlier. Allowing for differences in 

 soil condition (although all root excavations in any plat were made within 

 a radius of a few meters), these findings agree only in part with those of 

 Rotmistrov (1914 : 24) that " towards the commencement of flowering the 

 development of the root system finishes, or the growth of the roots after 

 that to the attainment of maturity is insignificant." 



