EXPERIMENT STATION BULLETINS. 265 



TABLE NO. 7. 



Sprayed ivith Bordeaux Mixture Every Four Days. 



Yield per acre of merchantable tubers 8II/2 bu. 



Yield per acre of small tubers 2II/2 bu. 



Total yield per acre 103 bu. 



Gross returns per acre at 50 cents per bushel 140 75 



Gross gain in dollars per acre by spraying 20 25 



Increase in yield per acre by spraying 40.5 bu. 



Number of sprayings 14 



Total amount of lime used per acre 42 lbs. 



Total amount of copper sulphate used per acre 35 lbs. 



Cost of lime per acre 10 19 



Cost of copper sulphate per acre 2 45 



Cost of application 7 42 



Total cost of spraying per acre |10 06 



Net gain per acre 10 19 



According to the works of Millardet and Gayon,* the copper in Bor- 

 deaux mixture does not become soluble until the Hydrate of lime is 

 changed to the Carbonate of lime, this process taking about ten days. 

 In the above table it will be noticed that fresh Bordeaux mixture was 

 applied every four days, thus keeping the copper in an insoluble form. 

 The results go to show that it is not at all necessary for the copper to 

 be in solution in order to kill the spores and check the growth of Blight 

 (Phytophthora infestans). 



From the preceding tables it appears that the most profitable re- 

 sults were obtained from those sprayed every 10 days with Bordeaux 

 mixture or 6 times during the season (See Table No. 6). 



The lime experiment (See Table No. 3) is interesting from the fact 

 that it shows that the mere presence of some foreign substance on 

 the foliage helps very markedly in retarding the growth of the disease. 

 Further investigation along this line will be carried on during the com- 

 ing season. 



The condensed results of the experiment are fully shown in the table 

 below. 



♦Millardet et Gayon, La bouillie bordelajse Celeste, Jour. d'Agr prat 54e Ann. T. I, No. 8, Feb. 20, 

 1890, p. 272. 



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