442 MANURING OF POTATOES. 

acre. This variation in the relative production with and 
without manure suggests the possibility that on poor land 
and with scanty manuring the yield of the different kinds 
of potatoes may approach more nearly to a uniform stan- 
dard, but that with liberal manuring a much wider variation 
in production may be manifested, according to the inherent 
capacity for growth of the varieties of potatoes grown. 
General Objects of the Experiments. 
In ordinary farm practice potatoes are rarely grown except 
with applications of farmyard manure, to which artificial 
manures may or may not have been added. This fact appears 
to have been kept in view in the preparation of all the 
schemes of experiments carried out by the various colleges, 
for all of them have been designed with evident relation to 
this practice. Hence the schemes of the colleges in relation to 
this point show a general uniformity of plan, which favours 
their easy comparison. In most of them there were plots to 
which farmyard manure was applied alone in the quantity 
usually given by farmers, along with plots to which, in addition 
to farmyard manure, there were applied dressings of artificial 
manures of various kinds and quantities, the main object 
being to discover which of these supplementary dressings © 
would give the greatest increase of crop, and which would 
prove most profitable. In most of the schemes plots were 
also included to determine whether full crops of potatoes 
could. be grown with artificial manures without farm- 
yard manure. In the Glasgow experiments throughout, and 
also in the Yorkshire experiments of 1899, one of.the chief 
objects aimed at was to determine whether small dressings 
of farmyard manure with supplementary applications of 
artificials would not prove more effective and profitable than 
the ordinary full dressings of farmyard manure applied alone, 
Along with these leading objects of investigation there were 
included in all the schemes a number of subordinate inquiries 
which related chiefly to the various forms and quantities in 
which the different kinds of artificial manures could be 
employed. In the Yorkshire and the Glasgow series an 
important section of the work dealt with the effects produced 
