﻿WATER UTILIZATION BY SPRING WHEAT. 7 



there have been only a few moisture determinations that have been 

 considered as not providing a true indication of the moisture content 

 of the plat. 



The object of this study is not to determine the exact quantity of 

 water used from each foot section of soil each year, but rather to 

 determine the extent to which the moisture-storage capacity of the 

 soil has been utilized and the extent to which the stored water has 

 been removed at harvest. 



The moisture content of each foot of soil of each plat at every 

 determination during the season has been charted. By a study of 

 the diagram it can be determined quickly and with a considerable 

 degree of accuracy whether available moisture has been present in 

 any foot of soil during the growing season and whether the avail- 

 able moisture in any foot of soil has been removed. 



Figure 1 shows the moisture content of each individual foot of 

 plat B at Williston, N. Dak., in 1910. The successive determina- 

 tions of the moisture content of each foot have been connected by 

 lines. The resulting curves give a good history of the moisture con- 

 tent of each foot of soil for the season ; the dotted lines represent the 

 wilting coefficients of the several foot sections. 



The soil in the first foot at the time of the initial determination 

 was at its field carrying capacity. This moisture content was not 

 maintained by rainfall, and by harvest, July 26, the moisture of the 

 first foot had been reduced to the minimum point of exhaustion. The 

 second foot of soil possessed only a small quantity of available 

 moisture, and this supply was exhausted long before harvest. There 

 is no evidence to indicate that any available moisture was present 

 below the second foot, and results from other plats and from 

 this plat in other years show that it was dry as far as water avail- 

 able to crops is concerned. A point worthy of note is the fact that 

 the minimum point of exhaustion of the soil in the lower depths 

 more nearly approximates the wilting coefficient than in the upper 

 depths. The greater experimental error in the fifth-foot and sixth- 

 foot depths is indicated by the broken curves of those sections. The 

 fact that the crop suffered severely for lack of water was noted 

 several weeks before harvest. The extent of drought injury is in- 

 dicated by the low yield of 1.3 bushels per acre. 



The depth to which the crop used water that year was less than 

 2 feet. The storage capacity of the first foot of soil was all utilized 

 and that of the second foot only partly utilized. 



CLASSIFICATION OF DATA. 



The presence of available moisture in the soil each year and the 

 extent to which the moisture present has been used are divided into 

 five classes, which are indicated by symbols. These symbols are 

 designed to show at a glance the moisture history of any foot section 

 of soil for a season. The condition represented by each symbol is 

 as follows : 



(1) A condition where the soil has been filled with water to its field carry- 

 ing capacity at some time during the growing season and where all of the 



