in Stackyard Field, Wohurn. 
5 
differ, this difference may be explained by the different character 
of the two cereals. 
It may appear at first sight strange that while the unmanured 
wheat only yielded 1 7 bushels per acre, the barley should yield 
23 bushels ; but if, instead of taking the bushel of grain as our 
measure, we take the total weight of the crops grown — straw 
and corn — we shall find very little difference in the weights. 
Wheat has a tendency to grow a larger proportion of straw to a 
given weight of grain than is the case with barley. If we take 
the highest yield of the two crops, in which the barley grew 
16 bushels per acre more than the wheat, the total produce — 
corn and straw — in the wheat amounted to 7,106 lbs. per acre, 
while in the barley it was 7,077. The manure has, therefore, 
done an equal amount of work in both cases, the same amount 
of dry matter has been produced, and the same amount of 
carbonic acid has been decomposed and carbon fixed in the 
plant. The only difference between them is, that, owing to the 
characteristic habits of each plant, one produces more straw in 
proportion to its grain than the other. 
One of the important facts brought out with gi'eat clearness 
in these experiments is the absolute impossibility of increasing 
the growth of the cereal crops by mineral manures in the 
absence of available nitrogen in the soil ; and it is tolerably well 
established that the nitrogen must be in the form of nitric acid. 
When, therefore, we use a salt of ammonia as a manure it 
requires to go through the process of nitrification in the soil 
before it is taken up by plants. Nitrogen as nitric acid being 
so valuable a substance as a manure for our corn crops, its 
economic application depends very much upon the price we pay 
for it and the amount of produce which can be obtained by its 
use. As the weights of the salts of ammonia and nitrate of 
soda used in these experiments are not those generally used in 
purchasing them in the market, it will make the matter more 
clear if the quantities used and the increase of crop obtained are 
calculated upon a basis of 112 lbs. 
The increase of wheat by means of the mineral and ammonia 
salts over the mineral manures alone was 13"8 bushels, which 
was obtained by means of 200 lbs. of salts of ammonia, yielding 
50 lbs. of ammonia. One cwt. of sulphate of ammonia yielding 
27 lbs. of ammonia would have increased the crop by 7^ bushels. 
Using the same mode of calculation for nitrate of soda, we find 
that 1 cwt. would give an increase of 6 bushels. With barley we 
find that 1 cwt. of sulphate of ammonia gives an increase of 10^ 
bushels, while the same quantity of nitrate of soda gives an 
increase of 9 bushels. If these results could be obtained in 
ordinary practice a very considerable profit would be made, I» 
