THE EFFECT OF RUST INFECTION UPON THE WATER 
REQUIREMENT OF WHEAT 1 
By Freeman Weiss 
Formerly Agent, Office of Cereal Investigations, Bureau of Plant Industry, United States 
Department of Agriculture, and Assistant in Plant Physiology, University of Min¬ 
nesota, now Pathologist, Office of Cotton, Truck, and Forage Crop Disease Investigations 
INTRODUCTION 
During years of severe rust epidemics, such as those which the spring 
wheat sections of the northern Mississippi Valley and the prairie Provinces 
of Canada experienced in 1904 and 1916, and in other years, attempts 
have been made to estimate the loss suffered by the wheat crop as a 
direct result of the rust. Such attempts usually have been based upon 
the comparative yields in rust years and the average yield over a number 
of years in which rust was absent or not severe. It has not been pos¬ 
sible to compare directly, on a large scale, the yields of rusted and rust- 
free fields where variety, soil type, and growing conditions are similar, 
because during rust epiphytotics nearly all fields are too generally 
affected. Furthermore, as a characteristic sequence of weather condi¬ 
tions usually occurs in rust years, it has been impossible wholly to differ¬ 
entiate the effect of rust from that of climate. 
A scientific basis for apportioning the responsibility between the rust 
and the departures from normal weather is attainable only through the 
artificial maintenance of rusted and rust-free plots in which all circum¬ 
stances are otherwise similar, and by noting the effect on reduction of 
yield as the several growth factors are varied. The factors which most 
require this sort of investigation are those associated with fertilization and 
moisture content of the soil, but an examination of the literature of the 
cereal rusts affords only meager information in respect to each; 
As a beginning in this line of investigation, experiments were planned 
to determine the effect of rust infection upon the water requirement of 
the wheat plant and the influence of different conditions of nutrition on 
the water relations. It was believed that such data might be useful as a 
basis for separating the factors of climate and parasitism in the reduced 
yield of rusted wheat, particularly as regards the water requirement. 
It was desired further to compare the results of these cultures with those 
of soil-grown greenhouse and field plants in respect to the relation of fer¬ 
tilization to rust infection. Accordingly, this paper is divided into two 
parts, one of which deals with the effect of rust infection upon the water 
requirement, and the other with the influence of certain mineral nutri¬ 
ents on susceptibility to rust and injury from it. 
1 Accepted by the Office of Cereal Investigations, Bureau of Plant Industry, United States Department 
of Agriculture, July, 1922. Received for publication by the Journal of Agricultural Research Oct. 16, 
1923. Published with the approval of the Director, as Paper 416 of the Journal Series, Minnesota Agricul¬ 
tural Experiment Station. 
The investigation herein reported was conducted cooperatively between the Office of Cereal Investiga¬ 
tions, U. S. D. A., and the Department of Agriculture of the University of Minnesota. It was undertaken 
as a part of the general project on the effect of soil nutrients on the development of stem rust and orange 
leaf rust of wheat. 
(107) 
Journal of Agricultural Research, 
Washington, D. C. 
Vol. XXVII, No. 2 
Jan. i2, 1924 
Key No. G-351 
