MANURING OF POTATOES. 445 

soil to enrich it and to add to its future fertility, and this 
residue, at the lowest computation, would certainly far more 
than repay the greater labour costs involved in the treat- 
Moi Ommtea larch  CrOp. a NX lLOseuter,. therelores having 
regard alike to the certainty of the action of farmyard 
manure and to the amount of increase of crop it produces, 
the results of all these experiments give ample support to 
the general practice followed by farmers of applying their 
farmyard manure to the potato crop. It follows also 
that where the manure from town stables and byres is pur- 
chased for application to the potato crop, at the prices at 
which it has been obtainable for many years, an exceed- 
ingly profitable return for the money expended on the pur- 
chase can be got in the first year alone, if the manure be 
utilized in the growth of potatoes. 
Influence of Quantity of Manure on the Return Obtained. 
It has been already pointed out that the amount of increase 
of crop produced by manures is greatly dependent on the 
variety of potato grown, but in the Glasgow reports attention 
has also been repeatedly called to the fact that the effect 
produced by farmyard manure also depends in a very marked 
degree on the quantity applied. This is shown in the 
results both of the 1898 and 1899 experiments recorded 
above, but the figures of 1898 may be selected for illustra- 
tion. Inthat year the average increase of crop produced when 
farmyard manure was appuied at the rate of 20 tons per acre was 
4 tons 19 cwt.2-qrs., while, when only the half ofthat quantity of 
farmyard manure was given, the increase obtained amounted 
to 3 tonsg cwt.2qrs. While the first 10 tons of manure applied 
were capable of increasing the crop by 3 tons 9 cwt. 2 qrs, 
the addition of a second 10 tons of manure was able to produce 
a further increase of only 1 ton 10 cwt. While every ton of 
the first 10 tons of farmyard manure gave an increase, there- 
fore, of 7 cwts. potatoes, every ton of the second 10 tons gave 
an increase of only 3 cwts. potatoes. At the price of £2 10s. 
per ton for the potatoes, each of the first 10 tons of farmyard 
manure gave a return in crop of the value of 17s. 6d., while 
each ton of the second 10 tons gave a return of the value of 
7s. 6d. only, or less than half as much. 
