﻿COPPER SPRAYS ON IRTSI# POTATO TUHKIIS. 



11 



1919 DATA. 



Arlington Experimental Farm, Va. — The 1919 experiments at the 

 Arlington Experimental Farm of the Department of Agri culture 

 were conducted on the Early Rose and Irish Cobbler variety 

 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. 



Variety. 



Early Rose 



Do 



Do 



Irish Cobbler i 



Do 



Do 



Treatment. 



No copper spray (chedk) 



Bordeaux 4-4-50 (1 per cent copper sulphate). 

 Pickering spray (0.5 per cent copper sulphate) 



No copper spray (check) 



Bordeaux 4-4-50 (1 per cent copper sulphate). 

 Pickering spray (0.5 per cent copper sulphate) 



Yield 





from 





2 rows, 



Solids. 



each 100 





feet long. 





Pounds. 



Per cent. 



50.0 



13.96 



87.6 



14.30 



90.3 



15.83 



124.0 



16. 11 



134.0 



18.14 



123.0 



18.57 



Nitrogen. 



Per cent. 

 0. 293 



.272 

 .325 

 .346 

 .347 

 .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 yield 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 

 figures 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 blight was apparently not the important 

 factor or necessarily a factor at all. The potato plants grown in 



