356 
Journal of Agricultural Research v 0 i. xxvii, no. 6 
From the data presented in Table V it at first appears that manure 
increased the susceptibility of the plants. But it is probable that this 
apparent increase of susceptibility was due partly at least to later 
maturity of the wheat, giving the rust a longer time to spread. The 
plants in the manured plats on the cabbage soil ripened 20 days after 
those in the control plats; those on the clover soil 10 days after those in 
the control plat; and those on the alfalfa soil 5 days after those in the 
control plat. There appears to be a complete correlation between the 
increase in percentage of stem rust on the Haynes Bluestem plants in 
the manured plats over that on those in the control plats, and the increased 
number of days required for maturity of the plants in the manured 
plats over those in the control plats. On the other hand, the percentage 
of infection in all of the control plats was 70, in spite of the fact that the 
plants in the different plats matured on different dates. The Bluestem 
in the control plat of the cabbage-soil series was mature on August 15, 
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60 
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Fig. 3.—Graph showing the percentage of stem rust on Haynes Bluestem and on the hybrid and percentage 
of drying and acre yield in bushels (7.2 bushels =100 per cent) of Haynes Bluestem grown in plats which 
had received acid phosphate at the rate of 2,000 pounds per acre plus varying amounts in pounds of sodium 
nitrate (N) and potassium sulphate (K) in the commercial fertilizer experiments in 1916 on University 
Farm, St. Paul, Minn. 
-stem rust on Haynes Bluestem. 
-stem rust on hybrid. 
---drying of Haynes Bluestem. 
-•-*-- yield of Haynes Bluestem. 
in the control plat of the clover-soil series on August 22, and in the control 
plat of the alfalfa-soil series on August 28. Up to August 28, therefore, 
the dates of maturity seemed to have no effect on the amount of rust. 
After this date, however, rust again spread rather rapidly on those 
plants which remained green, but it is impossible to say just how much 
effect delayed maturity had on the percentage of rust in this series. 
There is no definite correlation between fertilization and the percentage 
of infection of P. triticina , which is in sharp contrast with the results 
obtained on the commercial fertilizer plats. The hybrid appeared more 
susceptible than Haynes Bluestem, but the highest percentage of infec¬ 
tion, 35 for both varieties, was on unfertilized alfalfa soil. 
EXPERIMENTS WITH COMMERCIAL FERTILIZERS IN 1916 
The commercial fertilizer plats in 1916 were the same plats actually 
used in 1915. A resistant hybrid wheat was used instead of Iumillo, 
however, and potassium sulphate was used instead of potassium chlorid. 
