JOfflALOFAGEIOlTlALlSEMCH 



DEPARTMENT OF AGRICULTURE 



Vol. VI 



Washington, D. C, June 26, 1916 



No. 13 



RELATIVE WATER REQUIREMENT OF CORN AND 

 THE SORGHUMS 



By Edwin C. Miller '^BW Vu* 



Assistant Plant Physiologist, Department of Botany, Kansas Agricultural Experiment ""T AMC.* 



Station <iA»l>P.N 



INTRODUCTION 



During the summers of 1914 and 1915 a physiological study of the 

 water relations of corn and the nonsaccharin sorghums was made at the 

 State Branch Experiment Station at Garden City, Kans. In connection 

 with other experiments it was thought advisable to determine the water 

 requirement of several varieties of these plants. The term "water 

 requirement," as used in this paper, means the ratio of the weight of the 

 water absorbed by the plant to the weight of the dry matter produced. 



EXPERIMENTAL METHODS 

 CLIMATIC DATA 



The instruments for recording the climatic conditions consisted of a 

 hydrograph, a thermograph, maximum and minimum thermometers 

 placed in a standard shelter 4 feet from the ground, a rain gauge, an 

 evaporation tank, and an anemometer which measured the wind velocity 

 at a height of 2 feet. 



A portion of the weather records for the two seasons averaged for five- 

 day periods is shown in Table I. These show that the climatic con- 

 ditions for the two seasons were in marked contrast. The summer of 

 1 91 5 was much cooler than that of 1914 and the rainfall for the months 

 of May, June, July, August, and September in 191 5 was approximately 

 three times that for the same months in 191 4. The evaporation during 

 5-day periods is shown graphically in figure i. 



The evaporation for each of the growing months with but one excep- 

 tion was much higher in 191 4 than in 191 5. 



CULTURAL METHODS 



The plants were grown in large metal cans made from 2 2 -gauge gal- 

 vanized iron. These cans were 24 inches in height with a diameter of 

 15 inches, and under the conditions of these experiments contained about 



Journal of Agricultural Research, 

 Dept. of Agriculture, Washington, D. C. 



(473) 



Vol. VI. No. 13 

 June 26, 1916 

 Kans. — s 



