COPPER SPRAYS ON IRISH POTATO TUBERS. ids 
1919 DATA. 
Arlington Experimental Farm, Va—The 1919 experiments at the 
Arlington Experimental Farm of the Department of Agriculture 
were conducted on the Early Rose and Irish Cobbler varieties of 
potatoes. All plots were sprayed four times, lead arsenate being 
applied to both unsprayed and copper-sprayed plots. The field was 
uniformly fertilized, using 4-8-4 mixture which was applied at the 
rate of 1,200 pounds to the acre. The tubers were analyzed the day 
they were dug. 
TABLE 2.—Yield and composition of tubers from copper-sprayed and unsprayed 
(check) potato plants, Arlington Experimental Farm, 1919. 
Yield 
from 
Variety. Treatment. 2rows, | Solids. |Nitrogen. 
each 100 
feet long. 
Pounds. | Per cent. | Per cent. 
Early Rose.....-.-- Nolcopperispray: (checks)\= suo; sasieeos casts aaeieioreyt= 50.0 13. 96 0. 293 
Don seseeh! it Bordeaux 4-4-50 (1 per cent copper sulphate)......-. 87.6 14. 30 -272 
DO eeeo css eet Pickering spray (0.5 per cent copper sulphate).-...-- 90.3 15. 83 ~325 
Trish Cobbler !-.--. INOICOPPErSprayalCHeCk:)a- seman eee nie sc sees ane 124.0 16. 41 - 346 
100) Aes 82 ees ease Bordeaux 4-4-50 (1 per cent copper sulphate).--...-- 134.0 18.14 .347 
JU eee eae | Pickering spray (0.5 per cent copper sulphate)..-...- 123.0 18. 57 . 364 
1 Average of 3 determinations given in each case. 
The data in Table 2 indicate that the copper sprays increased the 
yield for the Early Rose variety and the solids content of tubers of 
both varieties in a locality where late blight is unknown and where 
Bordeaux or other copper sprays are not employed generally. 
Seven States—The yield and composition of tubers from Bor- 
deaux-sprayed and unsprayed plants in seven States (Virginia, 
Maine, Minnesota, Pennsylvania, New York, Connecticut, and New 
Jersey) are recorded in Table 3. The analytical data are average 
figures for 62 samples. Data for Pickering-sprayed plots are 
included with the Arlington Experimental Farm results. The tubers 
analyzed were from sprayed and unsprayed potato plants grown in 
the various States under the direction of plant pathologists and were 
sent to the writer by express the day on which they were dug. Arsen- 
ical sprays were used on all plots. | 
The average increase in yleld per acre of potatoes was 25 per cent. 
The average increase of solids in the tubers was from 20.77 per cent, 
in the tubers from the check plots, to 21.99 per cent in those from 
Bordeaux-sprayed plants, an increase of 5.9 per cent. The average 
ficures for pounds of solids of the tubers per acre were 2,591 for the 
noncopper-sprayed and 3,430 for the copper-sprayed plants, an aver- 
age increase of 32.4 per cent or 48 bushels, due apparently to the use 
of copper sprays. It is important to note that the tubers from 
Virginia, Maine, and Minnesota, where practically no late blight 
occurred, showed the same general results as those from the other 
four States, where more or less late blight was noted. This means 
that prevalence of late bhg@ht was apparently not the important 
factor or necessarily a factor at all. The potato plants grown in 
