2, BULLETIN 1146, U. S. DEPARTMENT OF AGRICULTURE. 
When in 1917 it was found that the solids, starch, and nitrogen 
contents of tubers from copper-sprayed potato plants were greater 
than those of tubers from unsprayed plants, an investigation was 
begun in the Bureau of Chemistry to determine the effect of Picker- 
ing sprays, barium-water sprays, and standard Bordeaux sprays as 
compared with that of noncopper sprays on the yield and on the com- 
position of potatoes grown in different localities. The distribution 
of copper in the tubers, roots, stems, and leaves of the various 
sprayed and unsprayed potato plants was studied also. 
RESULTS OF PREVIOUS INVESTIGATIONS. 
YIELD OF POTATOES. 
Giddings (20),’ of the West Virginia station, fund that in 1909 
three applications of Bordeaux increased the yield of potatoes 53.5 
per cent and that in 1910 four applications increased the yield 39.3 
er cent. 
E In New York Stewart and his associates (46, 47,45) have conducted 
an extensive series of experiments to show the Benen: of Bordeaux 
spraying. In discussing the results obtained at the New York station 
in 1911 Stewart stated: ‘“ There was no late blight whatever, only a 
very little early blight and very little flea-beetle injury. The un- 
sprayed rows were affected by no disease of any consequence except 
tip burn and even of that there was only a moderateamount, * * *- 
yet spraying increased the yield at the rate of 98 bushels per acre. 
Plainly we have here a striking example of the beneficial influence of 
Bordeaux in the absence of disease and insect enemies.’ 
In 1912 Lutman (32) published data from Vermont showing that 
a greater yield of tubers was obtained from copper-sprayed potato 
plants at various stages of growth than from the unsprayed plants. 
Plants which received a Pickering spray, a Bordeaux spray in which | 
part of the copper sulphate had been replaced by iron sulphate, and 
a commercial spray containing copper also gave higher yields than 
the check plants. The increased yield seemed to be in proportion to 
the amount of copper present in the spray. The application of a 
spray containing silver did not increase the yield. Lutman sug- 
gested that the Bordeaux mixture acts asa stimulant, bringing about 
an increase in the quantity of starch produced daily. 
Clinton (8) in 1915 reported that homemade Bordeaux sprays used 
on potatoes in Connecticut uniformly increased the yields. Thé 
average increase for the sprayed plants during the 13 years that the 
tests were carried on was 36 bushels an acre. - 
In 1916 Lutman (33) reported the results he obtained in 1912 from 
using 5-5-50 Bordeaux and 24-24-50 Bordeaux on potatoes in Ver- 
‘mont. He concluded that “the amount of copper sulphate and lime 
used did not appear to be important providing the mixture was fairly 
strong. A little difference appeared in favor of the 5-550 combina- 
tion over the 24-24-50. Frequent and early sprayings did not seem 
favorably to affect the yield of tubers. Some of the plants were 
sprayed ten times but they produced little or no larger crops than 
did those plants sprayed less often.” .He stated further that the use 
* Italic figures in parentheses refer to literature cited at end of bulletin. 
