﻿2 BUL1J.TIN 1139, U. S. DEPARTMENT OF AGRICULTURE. 



The present study is not intended primarily to establish the maxi- 

 mum depth to which a wheat crop is capable of feeding. The pur- 

 pose is rather to determine and present the actual depth to which 

 the wheal crop has utilized the soil in a series of seasons, on a wide 

 range of soils, and under radically different cultivation methods. 

 The data are classified to show whether this depth was limited by the 

 depth of the soil itself, by the quantity of water available for storage, 

 by the physiological limitations of the crop, or by the character of 

 the season. 



The material was obtained in connection with the preparation of 

 United States Department of Agriculture Bulletin Xo. 1004, entitled 

 " Use of Water by Spring "Wheat on the Great Plains," by John S. 

 Cole and O. R. Mathews. All the members of the technical staff 

 of the Office of Dry-Land Agriculture Investigations from 1906 to 

 date have contributed to the publication by the data they have ob- 

 tained at the stations where they have been located. 



E. C. Chilcott, 

 Agriculturist in Charge. 



SOURCES OF INFORMATION. 



At the time the work of the Office of Dry-Land Agriculture Investi- 

 gations was inaugurated it w r as recognized by those in charge that a 

 measure of the water content of the soil would be of great value in 

 interpreting crop yields. For this reason frequent determinations 

 of soil moisture were made at the stations then in operation, on plats 

 receiving different cultural treatments. This work has been carried 

 on continuously at these stations and at all stations where experi- 

 ments have been subsequently started by the office mentioned except 

 one, where the character of the soil prohibits soil sampling by the 

 usual method. Moisture determinations have been made on all of 

 the principal crops, but at the stations where wheat grows well it 

 has been considered the basic crop and has been sampled more regu- 

 larly than any other. It should not be inferred, however, that wheat 

 is the most important crop at all the stations from which data are 

 presented. At some of them it is, in fact, of little importance, but 

 even at these certain data have been obtained on it for purposes of 

 comparison. The moisture reactions of spring wheat and winter wheat 

 have been found to be somewhat different. Spring wheat alone is 

 considered in this publication, as more moisture determinations have 

 been made with it than with winter wheat. Some of the stations 

 having the best soil-moisture records have been necessarily omitted 

 because the major part of their work has been with winter wheat. 



The data presented consist of moisture determinations at 17 sta- 

 tions in different portions of the Great Plains on three plats of spring 

 wheat, known as plats A, B, and C or D. The moisture history of 

 these three plats constitutes a total of 135 crop years, after omitting 

 years when some factor, such as hail, was responsible for crop dam- 

 age and years when the number of samples taken was not great 

 enough to determine the changes in moisture content of the plats. 



The plats indicated by the same letter receive the same cultivation 

 at all stations. They represent systems of tillage so different that 

 they should show maximum differences in their moisture relations. 



