286 
Mineral Manures and Manuring. 
The quantities of manure employed were much greater than 
was necessary, and such as could not be made to pay in practice, 
and it is evident that the soil possessed too small an amount of 
assimilable mineral food to bring the whole of the added nitrogen 
into operation. 
Plot. 
Mean of the 'Years 1856-78. 
yield per Acre. 
Hay alone. 
Mean of Years 1877-78. 
First 10 years. 
2nd 10 years. 
Hay alone. 
Hay and 
aftermath. 
Cwts. 
m 
Cwts. 
20 
Cwts. 
18f 
Cwts. 
285 
„ 4. |1. Superphosphate.. 
23i 
2U 
231 
425 
„ 4. (2. „ & ammonia 
331 
30^ 
37J 
54J 
„ 9. Superphosphate, alkalies! 
and magnesia, and am-> 
531 
m 
55 
„ 5. Ammonia alone (aboufl 
400 lbs. Ammonia salts/ 
22 
21| 
41 
„ 18. First 10 years unmanured,'\ 
2nd 10 years received 1 
the ash constituents in- 1 
eluding nitrogen of 1 
ton of hay j 
21 
33i 
37i 
55i 
Superphosphate alone raised the crop 8 cwts. ; combined with 
400 lbs. of ammonia-salts it increased it by 20 cwts., and upon 
the addition of alkalies the increase in yield rose to 44 cwts. 
Thus the addition of alkalies more than doubled the increase in 
yield obtained by superphosphate and ammonia alone. Who 
then can logically attribute to potash as a means of increasing 
the crops a lower value than to phosphoric acid. It is only 
the arbitrary and excessive quantities which are generally 
employed that make it unprofitable : even superphosphate 
would be unprofitable if we had to employ excessive quantities 
annually in order to obtain a continuous action. 
The strict deduction of Liebig's mineral theory is that a 
regular return to the soil of the minerals and nitrogen yearly 
taken out of it is sufficient to maintain its fertility. The results 
on plot No. 18 give a most positive practical proof of the truth 
of this doctrine of restitution. Reckoning as above, the 
unmanured field yielded 31 cwts. of hay and aftermath. For 
12 years the plot to which each year the mineral matter and 
nitrogen of 20 cwts. of hay was applied yielded annually 
55f cwts. The addition, therefore, of the mineral constituents, 
