450 MANURING OF POTATOES. 

application as closely as possible to the maximum 
profit point. This view receives strong support from the results 
obtained in the Glasgow experiments of 1899. These 
experiments were carried out on two varieties of potatoes, 
one of which, the Up-to-Date, is known to be one 
of the most productive potatoes in cultivation, and 
one, therefore, on which large dressings of manure 
would be most likely to give a sufficient and a profitable 
increase cf crop. But cn both varieties of potatoes, on the © 
average of nine farms in the one case and of five in the other 
the addition of 6 cwt. of artificial manure per acre to a dressing 
of 20 tons farmyard manure produced only a small increase 
of crop, which, in Loth sets of experiments, had a value equal 
to about half the cost only of the artificials applied. The 
indication of all the experiments appears to be that under 
ordinary conditions an application of properly selected arti- 
ficial manures may be profitably applied to the potato crop 
along with 15 tons farmyard manure; but that when the | 
quantity of the latter exceeds 15 tons per acre the addition 
of ariificials is quite as likely to result in a loss asina 
profit. 
On the other hand, when the quantity of farmyard 
manure given to the potato crop does not exceed 10 or 12 
tons per acre, the evidence of the experiments 1s seme 
addition of artificials then becomes highly efficacious and pro- 
fitable. Thus, in the Durham series of 1897, when 12 tons of 
farmyard manure were employed, a large addition of artificials 
gave a profit of Ar 9s. per acre; while in the Yorkshire 
experiments of 1898 and in the Glasgow experiments of 1898 
and 1899, in all of which farmyard manure was applied at 
the rate of 10 tons per acre, the profits arising from the 
addition of artificials which cost from about AI 8s. to £1 178s. 
ranged between £1 8s. 3d. and £3 8s. 3d. per acre. It is 
obvious, therefore, that when the dressing of farmyard 
manure falls to 10 tons per acre it is insufficient of itself to 
produce a full potato crop, and artificial manures added to 
farmyard manure can then be relied on to give a very pro- 
fitable increase. 
