Feb. 9, 1924 
Effect of Fertilizers on Stem Rust of Wheat 
345 
After data had been obtained for several years from the field experi¬ 
ments, it became evident that the same amount of stem rust might not 
equally injure plants grown in different kinds of soil. It was suggested 
that plants very heavily fertilized with nitrogen might be especially 
liable to rust injury on account of succulence, weak straw, and high water 
requirement. Special investigations therefore were made on these 
phases of the problem. 6 
EXPERIMENTAL METHODS 
Field experiments and observations were made for eight years on several 
types of soil and in several localities in Minnesota. Some pot experi¬ 
ments also were made. Four of the years were “rust years” and four 
were not. 
The most extensive experiments were made on University Farm, and 
the Quinn farm, St. Paul. One series was made at Anoka; and observa¬ 
tions were made on the regular fertilizer plats of the Division of Soils 
at Morris and at Crookston. 
The soil on University Farm is the Hempstead silt loam. It varies 
considerably, but, in general, is well supplied with all necessary plant 
nutrients. It is described by Smith and Kirk (28) as follows: “The sur¬ 
face soil of the Hempstead silt loam consists of about 10 to 18 inches of 
black to dark brown silt loam, underlain by a subsoil consisting of brown 
to yellowish-brown-silty clay to silty clay loam, which extends to a 
depth of about 3 feet. Local variations include a somewhat open and 
loamy texture on the one hand, and a rather heavy and compact structure 
on the other. The substratum consists of a bed of rather clean gravel 
and sand.” The series at University Farm was on the heavier and com¬ 
pact type, while that on the Quinn farm was on the more open and 
loamy texture. 
The soil at Anoka is a loamy sand, often deficient in nitrogen. The 
following description is given by Smith et al. (29 ): “The Merrimac 
loamy sand consists of a brown to very dark brown loamy sand, 10 to 18 
inches deep, underlain by a brown loamy sand subsoil and substratum. ” 
The plats at Crookston were on loam which is very rich in organic 
matter and does not require artificial fertilizers. According to Mangum 
et al. ( 18 ), “The soil, to an average depth of 12 to 15 inches, consists of a 
dark brown to black silty clay which contains a very large percentage of 
organic matter. This material becomes slightly heavier as the depth 
increases and grades at about 12 inches into a heavy drab to gray silty 
clay, with a very finely stratified structure. ” 
The fertilizer plats were laid out on uniform, level soil in order to 
avoid errors due to lack of uniformity in chemical composition, and to 
the washing of fertilizers from one plat to another. During the first 
four years, the size of the plats was one square rod. Three-foot alleys 
separated them from each other. In 1918, 1920, 1921, and 1922 obser¬ 
vations were made on tenth-acre permanent fertilizer plats. Data on 
percentage of stem rust only were obtained from these plats. 
The general plan of the commercial fertilizer plats in 1915, 1916, and 
1917 on University Farm is shown in Table I. Modifications of this 
plan are indicated in the proper places. 
0 The results are published in the Journal of Agricultural Research in separate papers by Dr. Freeman 
Weiss and Dr. C. R. Hursh. 
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