238 
Journal, of Agricultural Research 
Vol. VII, No. s 
As there will be seen from this map, there are five different types of 
soil, which occur very irregularly in both the upper and the lower block. 
The diagram superimposed on the map shows the arrangement of the 
plots, the distribution of Spongospora subterranea, the percentage by 
weight of the progeny infected with the disease, and the yield per acre. 
The seed used was of the Green Mountain variety and was carefully 
selected and treated with the usual strength of mercuric chlorid. The 
plots, which were numbered i to 15, inclusive, received treatment as 
follows: 1 
1. —Sodium nitrate, 20 pounds. 
2. —Control, with commercial fertilizer, 150 pounds. 
3. —Old horse manure, 2,400 pounds. 
4. —Control; no treatment. 
5. —New horse manure, 2,400 pounds. 
6. —Phosphoric acid, 24 pounds. 
7. —Ammonium sulphate, 20 pounds, and phosphoric acid, 24 pounds. 
9. —Potassium chlorid, 30 pounds. 
10. — Ammonium sulphate, 20 pounds. 
11. —Flowers of sulphur in drills, 90 pounds. 
12. —Flowers of sulphur broadcast, 90 pounds. 
13. —Calcium carbonate, 300 pounds. 
ib.—Sodium nitrate, 20 pounds. 
2b.—Control with commercial fertilizer, 150 pounds. 
4b.—Control; no treatment. 
7b.—Ammonium sulphate, 20 pounds, and phosphoric acid, 24 pounds. 
13b.—Ammonium sulphate, 20 pounds. 
14b.—Flowers of sulphur, 90 pounds. 
15b.—Phosphoric acid, 24 pounds. 
As will be seen from the foregoing outline of treatments, the effect of the 
common commercial-fertilizer ingredients, as well as of some of the well- 
known soil disinfectants, were studied on the plots either with or without 
commercial fertilizer. The treatments in all the plots were applied with 
the potato planter and at time of planting, except in the case of those 
marked “b,” which were applied on August 12, a few days after the first 
infections were noted, and each treatment was duplicated on what was 
known as the upper and lower blocks. 
Seven of the control plots received at the rate of 1,500 pounds of com¬ 
mercial fertilizer per acre, or 150 pounds each, and an equal number 
received no treatment. In the former the percentage of infection ranged 
from 15.1 to 35.4 and averaged 24.7 per cent, while the latter showed a 
greater variation, ranging from 4.9 to 36.5 and averaging 23.4, or a total 
average of 24.05 for the 14 control plots. None of the treated plots 
gave as high a percentage of infection as the average of the control plots, 
and those treated with sulphur at the rate of 900 pounds per acre gave the 
lowest percentage, the average of the four thus treated being 8.7 per cent. 
1 All plots marked "b" received treatment on August 12. 
