﻿COPPER SPRAYS ON IRISH POTATO TUT; K US. 



17 



potatoes under them dug. The dirt was shaken from the vines and 

 the adhering roots, and the soil was wiped from the tubers. The 

 vines and tubers were then weighed together and separate weighings 

 of the tubers were made. From these data the percentage of tubers 

 in terms of the total weight of the vines plus tubers was calculated. 



Table 7. — Weight of potato vines' and tubers, Presque Isle, Me., /Hit. 



Variety. 



Date 

 weighed. 



B ordeaux-spray ed . 



Pickering-sprayed. 



No copper spray 

 (check). 





Vines. 



Tubers. 



Vines. 



Tubers. 



Vines. 



Tubers. 





July 26i 

 Aug. IS 2 

 Sept. 17 3 

 Aug. 2 1 

 Aug. 19 2 

 Sept. 14 3 

 Aug. 3i 

 Aug. 18 2 

 Sept. 13 3 

 Aug. 23i 

 Aug. 23 2 

 Aug. 29 2 

 Sept. 20 3 

 Sept. 21 3 

 ...do 



Lbs. 

 7.50 

 5.25 

 3.50 

 6.00 

 6.75 

 6.25 

 6.50 

 7.25 

 4.25 

 10.75 

 7.00 



Lbs. 

 3.00 

 5.75 

 8.50 

 2.75 

 6.75 

 13.75 

 2.75 

 6.75 

 8.25 

 4.00 

 5.50 



Per ct. 

 28.5 

 52.3 

 70.8 

 31.4 

 50.0 

 68.8 

 29.7 

 48.2 

 66.0 

 27.1 

 44.0 



Lbs. 

 7.25 

 7.00 

 3.25 



Lbs. 

 2.50 

 7.00 

 9.00 



Per ct. 

 25.6 

 50.0 

 73.5 



Lbs. 



9.75 

 5.25 

 2.50 

 6.00 

 6.75 

 4.75 

 8.25 

 8.25 

 4.00 

 8.50 

 5.75 

 5.00 

 2.25 



Lbs. 

 2.50 

 5.25 



11.25 

 2.75 

 6.75 



13. 00 

 2.50 

 8.00 

 8.00 

 2.75 

 4.00 

 5.00 

 7.25 



Per ct. 

 20.4 



Do 





Do 



«81.8 





31.4 



Do 









50.0 



Do 









8 73. 2 



Early Ohio 









23.3 



Do 









49.2 



Do 









f 66.7 





4 11.50 

 5.25 



* 4. 25 



M.0O 

 4.00 



5 3.00 



4 5.00 



4.00 



M.00 



4 8.75 

 10.50 



5 9. 50 



4 30.3 



43.2 



<48.5 



4 68.6 

 72.4 



5 76.0 



24.4 



Do 



41.0 



Do... 



50.0 



Do 



3.38 



7.38 



68.6 



6 76. 3 



Do... 





Do 































1 Date of first analysis. 



2 Date of second analysis. 



3 Date of last analysis. 



4 Barium-sprayed. 

 6 Nickel-sprayed. 



s The check vines at time of last analyses were dead or partly dead and therefore lighter than the 

 vines of the copper-sprayed plants. These figures are not comparable with the other data. 



The data presented in Table 7 show that when the potato vines 

 were growing, that is, while they were green, a higher propor- 

 tion of tubers to vines plus tubers was usually found in the copper- 

 sprayed than in the unsprayed plants. At the time the first weigh- 

 ings were made, as soon as the tubers were about an inch in diameter, 

 the influence of the copper sprays was shown. The results in Table 

 7 indicate that the stimulating effect of the copper is largely shown 

 by the increased weights of tubers rather than by increased weights 

 of the vines and that it is exerted early in their development. As the 

 tubers are the storehouse for the starch formed in the leaves, the per- 

 centage of starch in the tubers would naturally increase. At the 

 time the last analyses of the tubers were made the unsprayed vines 

 had partly dried and therefore were lighter than the corresponding 

 vines for the copper-sprayed plants. The data for these samples are 

 not directly comparable with the rest of the data. 



INFLUENCE OF STRENGTH AND NUMBER OF APPLICATIONS OF COPPER SPRAYS 

 ON COMPOSITION OF TUBERS. 



Several samples of tubers grown in New Jersey during the season 

 of 1920 were analyzed for solids and nitrogen. Some of the plots 

 from which samples were taken had received a 10-10-50 Bordeaux 

 spray ; others had received a 5-5-50 Bordeaux spray ; a third plot 

 had been treated with a 2^-2^-50 spray ; while some of the plots had 

 received no copper spray. The results for solids and nitrogen in 



