MANURING, OF POTATOES. 25 

whole six stations have been averaged, and, in estimating 
profits, the calculations have been based upon the yield of 
the large or saleable potatoes only. 
The results Dr. Somerville finds to be as follows :—The 
artificials alone paid well, the average yield on these four 
plots being 8 tons 184 cwts. per acre, the average increase 
over the unmanured plot 3 tons 12# cwts., and the average 
net profit nearly £8 per acre. Of the four artificials used 
alone, that consisting of a mixture of 24 cwts. of sulphate of 
ammonia, 54 cwts. superphosphate, and 1 cwt. muriate of 
potash paid best, mainly on account of its relative cheapness, 
as there wa’ not very much difference in the yield on all the 
four plots. 
Where artificials were added to 12 tons dung, the average 
increase due to the former was 1 ton 2? cwts. (the dunged 
plot yielding 8 tons 24 cwts., and the plots receiving dung 
and artificials averaging g tons 51 cwts. per acre); and the 
net profit on the use of the artificials was here £1 12s. per 
acre. Itis noticeable that the average yield from dung and 
artificials was only 6% cwts. more than that from artificials 
alone, although in making this comparison it must be borne 
in mind that where the artificials were used in combination 
with dung, a smaller quantity of fertilising constituents 
was in four cases out of the five applied than when 
they were used alone. The average yield from 12 tons 
dung alone was 16 cwt. less than that from artificials alone. 
Twelve tons dung alone increased the value of the produce 
by £8 10s. 3d. per acre over the unmanured plot, which 
iiplies a rerurn of 145. 2d. per ton of dumg used, besides 
its residual effect. On two plots which received the same 
quantity of artificials, one of them receiving in addition 12 
tons dung, there was an average increase from the arti- 
ficials alone of £10 14s. 6d.,,and from the artificials with 
dung of £13 10s. gd. ; the increase due to the dung was there- 
flew 20S, 40. representing, a return of 4S. Sd: per ton’ of 
dung applied. : 
‘Ihe experiments showed that, as an addition to dung, all 
the dressings of artificials were profitable, the net returns 
Vdrying® irom 23S, to 47s. per acre. lad the potatoes been 
