48 Development and Activities of Roots of Crop Plants. 



The grain yield of the crop-plats was not determined. 20 or 30 quadrats 

 were selected from each plat (Kiesselbach, 1918), and the total dry weight 

 of tops, including grain, obtained (cf. p. 76). 



The extent of shoot and root of the oats in both upland and lowland areas 

 during 1919 was almost identical with that of 1920, although the crop in 

 1919 reached maturity at the end of 75 days. 



Barley, Hordeum vulgare. 



The root development of barley growing in an adjoining plat was deter- 

 mined, as was also that of wheat, at the same intervals as for oats. At the 

 first examination, on May 1, the evenly developed crop had a height of 2.5 

 to 3 inches. Nearly all of the plants had a second leaf 1 to 2 inches long. 

 The general root habit as regards fineness of roots, branching, and lateral 

 spread is almost identical with that of wheat and oats, being somewhat inter- 

 mediate between the two. The maximum depth of root penetration was 

 10 inches and unbranched laterals 0.3 to 1 inch in length were fairly abundant, 

 except near the root ends. 



On May 15 the plants averaged 4.5 inches in height, some had 2 or 3 tillers 

 with the second leaf unfolding, and practically all had developed 3 or 4 leaves. 

 Plants of average size had from 5 to 11 roots. The longest reached a depth 

 of 2.2 feet, but most of them ended at about the 1.2-foot level. The general 

 working depth of the root system was 9 inches and the maximum lateral 

 spread 8 inches. The older portions of the root system were well furnished 

 with primary laterals varying in length from 1 to 1.5 inches, some of which 

 had secondary branchlets 0.3 inch or less in length. Young, entirely un- 

 branched roots ran off horizontally or obliquely to distances of 1 to 3 inches. 

 Where roots entered crevices in the soil, they were densely covered with 

 short branches and root-hairs. Below 11 inches only a few short branches 

 occurred. As in the other cereals studied, the glistening-white, deeper roots 

 often ran several inches without branching. 



An examination of the development of barley on June 3 showed that the 

 plants had made a marked growth of both tops and roots. They averaged 

 8 inches tall, although some were 11 inches. 5 or 6 leaves had developed on 

 each plant, and many had 1 to 3 tillers, the oldest being from one-third to 

 one-half as tall as the parent. The area to be occupied by the mature root 

 system was at this time fairly well delimited, except in depth. Of the 10 to 

 17 main roots on a plant, some descended only slightly outward and then 

 downward to a depth of 1.7 to 2.7 feet, the deepest reaching 3.2 feet. Many 

 others extended rather horizontally or obliquely for horizontal distances of 

 5 to 8 inches from the plant, the shallowest ending in the surface 3 inches of 

 soil. Thus, barley roots are somewhat nearer the surface at this stage than 

 wheat or oats. The most superficial, younger roots, and indeed nearly all 

 of those in the surface 1 or 1.5 feet of soil, were clothed with an abundance of 

 laterals, often as many as 15 per inch, and an inch or less (rarely more than 

 2 inches) long. Below 1.5 feet laterals were far less abundant, rather irregu- 

 larly distributed (3 to 8 per inch), and also much shorter. Secondary lat- 

 erals were in no case abundant, although some from a few millimeters to an 

 inch in length were found. The last 6 to 12 inches of the rapidly growing 

 roots, and especially the deeper ones, were entirely devoid of branches. 



