444 MANURING OF POTATOES. 

varieties of potato grown were seldom the same, and in the 
different series of experiments the dressings of farmyard 
manure applied varied not only in quality, but also in the 
quantity applied even on the same station. ‘The soils were 
of different character and the climatic conditions varied, not 
only at the several centres, but also in the successive 
seasons. In looking at these figures it is difficult to avoid 
a regret that the schemes of the several colleges should 
not have been made identical in regard to the variety 
of potato grown, and in the inclusion of at least one 
plot to which the same quantity of farmyard manure 
had been applied. in spite of the other conditions of 
variation an average result of much value could then 
have -been obtained. As the figures stand, tac wmaees 
useful information is to be found in the extremes of variation 
that occurred. The smallest increase obtained for each ton 
of farmyard manure applied was 34 cwt., while the largest 
was 13}? cwt. The effects generally produced would indicate | 
the latter result to be somewhat abnormal, and more com- 
monly the return for each ton of manure varied between 
4 cwts. and 8 cwts. potatoes. The average value of a potato 
crop, including not only large sized eating potatoes, and 
seconds or potatoes of seed size, but also the small and 
damaged tubers suitable only for feeding farm stock, 
may be fairly put at £2 10s. perton. On the lowest increase 
obtained in these experiments the money return for the farm- 
yard manure was therefore 8s. 1$d. per ton, and on the 
highest, £1 14s. 5d. While an exact average can hardly be 
fixed, it may nevertheless be fairly concluded that neither the 
maximum nor the minimum shown in these results 
represents the return that a farmer would be fairly entitled 
to expect for his farmyard manure on the average of a con- 
secutive series of years. If it be assumed that his average 
return would be more nearly represented by 6 cwt. per acre, 
he would then receive 15s. for every ton of farmyard manure 
applied to the potato crop. From that there falls to be 
deducted the expenses incurred in the handling and market- 
ing of the 6 cwt. extra yield, but on the other hand there 
would remain a large residue of farmyard manure in the 
