May 29, 1916 Root Systems and Leaf Areas of Corn and Sorghum 315 



CULTURAIv METHODS 



The soil in which the plants were grown is known as a sandy loam of 

 the Richfield series and shows very little difference in its texture in the 

 upper 10 feet. Tables VIII and IX give the moisture equivalent and the 

 wilting coefficient (i, p. 56-73) ^ for the soil at each foot to a depth of 

 10 feet on the plots which were used in 191 4 and 191 5, respectively. 



The plants were grown on plots which had been in Dwarf milo the 

 previous season. The land was plovv-ed in the fall to a depth of 6 inches 

 and then irrigated with approximately 8 to 10 inches of water or until 

 the soil was saturated to a depth of from 3 to 4 feet. It received no 

 further attention until spring, when it received several shallow cultiva- 

 tions, was then harrowed, and before planting was leveled with a float. 



In order that the plants might be under the same conditions, the corn, 

 kafir, and milo were planted in alternate rows on the same plots. On 

 May 23, 1 9 14, and on May 26, 191 5, the crops were surface-planted in 

 rows 44 inches apart. After the plants were a few inches in height the 

 corn in the rows was thinned to a distance of i^ to 2 feet between the 

 plants, BlackhuU kafir from i to i^^ feet, and the Dwarf milo from 8 

 inches to i foot. The plants were kept free from suckers at all times 

 during the growing season. The plots were scraped with a hoe as often 

 as was necessary to keep them free from weeds, but no other cultivation 

 was given. After the fall irrigation the plots received no water other 

 than that from the rainfall. 



The relative weights of the root systems and aerial portions of the 

 corn, BlackhuU kafir, and Dwarf milo were obtained from plants grown 

 in large sealed metal containers. These cans were made of 22-gauge 

 galvanized iron and were 24 inches in height with a diameter of about 15 

 inches; and in this experiment each can contained from 100 to no kgm. 

 of soil. The surface foot of the field soil was worked through a X-i^ich 

 mesh screen and then thoroughly tamped in the cans. This soil was 

 in good tilth, and for both seasons had a m.oisture content of 20 to 21 

 per cent (dry basis). This moisture content v/as kept approximately 

 constant during the growing season by weighing the cans every 48 hours 

 and then replacing the water that had been lost by the method used by 

 Briggs and Shantz (2) in their work on the water requirement of plants. 

 Different numbers of plants were grown in each can, as will be shown in 

 the tables that record the data for this part of the work. 



ISOLATION OF ROOT SYSTEMS IN THE FIELD 



The root systems of plants growing under field conditions were iso- 

 lated by a modification of the method devised by King (5).^ This 

 method, stated briefly, consists of the isolation of a prism of soil con- 



1 Referenceismadeby number to "Literature cited," p. 331. 



' The work of other investigators concerning the development of root systems will be mentioned in this 

 article only in so far as it is necessary to give a clear discussion of the experiments reported. The studies 

 that have been made by other investigators on the development of the root systems of agricultural plants 

 have been reviewed in detail elsewhere by the writer. 



