UNITED STATES DEPARTMENT OF AGRICULTURE 



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Washington, D. C. 



PROFESSIONAL PAPER 



March 31, 1923 



USE OF WATER BY SPRING WHEAT ON THE 

 GREAT PLAINS. 



By John S. Cole, Agronomist, and O. R. Mathews, Assistant Agronomist in 

 Dry-Land Agriculture, with an introduction by E. C. Chilcott, Agriculturist 

 in Charge of the Office of Dry-Land Agriculture Investigations, Bureau of 

 Plant Industry. 



CONTENTS. 



Page. 



Introduction . * 1 



Statement of the problem 2 



Source, character, and method of study of the data 3 



Daily rate of the use of water while the crop is growing rapidly 6 



Bate of the use of water as the soil moisture approaches depletion 11 



Rate of the use of water during the growing season 12 



Quantity of water used during the growing season 20 



Correlation between the use of water and the yield at individual stations 26 



General discussion of the results 30 



Conclusions 32 



INTRODUCTION. 



Since 1906 the Office of Dry-Land Agriculture Investigations has 

 been conducting experiments to determine the possibilities and best 

 methods of crop production on the Great Plains. Coincident with 

 this work and an integral part of it since 1907 has been the determi- 

 nation of soil moisture in cooperation with the Biophysical Labora- 

 tory of the Bureau of Plant Industry. The investigations have been 

 continuous, coordinated, and systematic at 24 field stations, 1 care- 

 fully located to be most representative of general as well as local 

 conditions. 



. While the data from a single station or a single year are valuable 

 in themselves, they are still more valuable in their contribution to 

 the mass of facts accumulated. Covering a long series of years, em- 

 bracing wide ranges of soils, climatic conditions, and crop adapta- 

 tions found from the northern to the southern Plains and from the 

 lowest to the highest altitudes within them, the mass of comparable 

 data that have been gathered has a value that while foreseen affords 

 possibilities of study that could hardly have been appreciated when 



1 The stations in Montana, North Dakota, Wyoming, Nebraska, and Kansas are con- 

 ducted cooperatively with the agricultural experiment stations of the respective States. 

 The stations in South Dakota, Colorado, Oklahoma, Texas, and New Mexico are operated 

 independently by the United States Department of Agriculture. 



21511°— 23 1 



