14 



EXPERIMENTS IN CHECKING POTATO DISEASE [Sept. 1894. 



V._EXPERIMENTS IN CHECKING POTATO DISEASE. 



The Secretary of the Irit>h Land Commission in a Report, 

 dated June 23rd, 1894, to the Under Secretary to the Lord 

 Lieutenant, fiirnishei an account of a series of field experiments 

 carried out by the Agricultural Department of the Irish Land 

 Commission during the summer and autumn of 1893, for the 

 purpose of further testing the value of applications of a mixture 

 of copper sulphate and lime to the potato plant as a preventive 

 of disease. The experiments were arranged with a view to 

 obtaining information on the following points, viz. : — 



(1.) Should the potato plant be sprayed from above only, 



from below only, or both from above and below ? 

 (2.) Is it sufficient to thoroughly spray the potato plant once 

 only, provided that the dressing be applied when the 

 foliage is fully developed and immediately before the 

 earliest period at which the disease may be expected 

 in the locality ? 



It was further decided to test the efficacy of a mixture 

 containing 2 per cent, of copper sulphate as compared with one 

 containing but 1^ percent, of copper sulphate. 



In order that the experiments should be uniform and as 

 serviceable as possible to the Irish farmer, the Champion variety 

 of potato only was experimented upon, that being the variety 

 most generally grown for home consumption in Ireland. 



The experimental areas were divided into eight separate plots 

 of 20 perches, except in one set of experiments in which the plots 

 were slightly smaller. Four plots were tested with a 1 J per cent, 

 mixture in the following manner : — The plants on the first plot 

 received one dressing from above and below ; in the case of the 

 second plot the dressing was applied twice from above and below 

 the leaves ; while the plants in the remaining plots received two 

 dressings, one from above the leaves only, the other from below 

 the leaves. A similar course was adopted in dealing with the 

 four plots treated with the 2 per cent, mixture. 



The 2 per cent, mixture consisted of 2 lbs. copper sulphate, 1 lb. 

 unslaked lime, and 10 gallons water; the per cent, mixture 

 consisted of 1 J lbs., copper sulphate, | lb. unslaked lime, and 10 

 gallons water ; the proportion of lime used was amply sufficient 

 to neutralise all acid, and to precipitate all the copper. 



The first dressings were applied at the latter end of June, and 

 the second dressings about one month later. The amount 

 of dressing applied per acre varied from 100 to 160 gallons, in 

 proportion to the quantity of foliage to be treated. 



At the end of September the produce of one perch in each 

 plot was carefully dug and weighed; at the time of digging, 



