MANURING OF POTATOES. 449 

In examining these figures it may be proper first of all to 
dismiss from consideration all the experiments conducted on 
one farm only, also such very abnormal crops as those grown 
both in the years 1898 and 1899 on the Cheshire farm, where, 
presumably, the high yield was due to arich soil and to a 
vigorous and productive new variety of potato. Apart from 
these exceptional results an examination of the returns shows 
that the efficacy or otherwise of an addition of properly 
‘selected artificials to a dressing of farmyard manure is 
mainly dependent on the amount of the latter applied. The 
evidence on this point is derived solely from the Glasgow 
experiments, for in none of the others did the dressing of 
farmyard manure given to the crop exceed 15 tons per acre, 
and on most of them the quantity was either 9, ro, or 12 tons 
only. 7 | 
In the Glasgow expcriments ‘of 1897 the quantity was 
15 tonsper acre, but in the succeeding years two dressings were 
applied to different plots, one of ten tons and one of 20 tons 
per acre. In the Durham duplicate experiments of 1897 
15 tons were applied, as in the Glasgow experiments of 
fed weandeit may. be seem that artincials added to this 
quantity of farmyard manure produced in both series cf 
experiments a fair increase of crop, which repaid the cost 
of the manures and left a moderate profit, amounting in one 
Eacemtomas. 11d. im another to ros, 7d., and in a third 
to tos. 4d. per acre. It has to be remembered, however, 
that these represent the most profitable returns obtained in 
the experiments, and that on other plots to which different 
combinations of artificial manures had been applied the 
amount of profit was less, or an actual loss was incurred. 
There is a very distinct indication in all the results that 
when farmyard manure is applied to the crop in a quantity 
aslarge as 15 tons per acre, artificial manures must be carefully 
selected and used with skill if their employment is to 
prove profitable, and that even when so employed the amount 
of profit per acre to be got from their use is not likely to be 
great. At any rate the addition to 15 tons of farmyard 
manure of the quantities of artificial manures employed in 
these experiments seems to have brought the total manurial 
GG 
