438 
On the Continuous Growth of Wheat on the 
another plot, similarly manured, which receives these salts 
in the autumn ; and although the spring-sown ammonia has 
given the largest produce, still, the difference between the two 
crops is by no means what we might have expected from the 
known loss by drainage which took place in the autumn-sown 
manure. 
In the autumn of 1881 the soil of the various experimental 
plots was sampled to the depth of 27 inches. Between the 
application of the salts of ammonia in the spring and the time 
of sampling, only a small amount of drainage had taken place, 
but the nitric acid in the soil and drainage water did not 
account for the nitrogen which had been applied in the salts of 
ammonia, but had not been taken up by the crop, and it appears 
quite possible that a considerable destruction of ammonia may 
take place in a soil, which would be in a much drier state in 
the spring than during the autumn and winter. 
It was not until after the experiment had been carried on for 
8 years that the nitrate began to show a superiority over the 
salts of ammonia, as up to that period, in the case of every one 
of the crops the ammonia gave the largest yield, the excess 
amounting in 8 years to 4^ bushels per acre. During the next 
3 periods the nitrate was considerably in excess ; and over 
the whole period of 32 years the nitrate gave an increase, over 
the salts of ammonia, of not quite 4 bushels per acre, the pro- 
duce of the ammonia being 32|^ bushels, and that of the nitrate 
36:^ bushels per acre. 
The produce of the nitrate supplying 86 lbs. of nitrogen is 
exactly equal to that of the salts of ammonia supplying 129 lbs. 
of this substance, both giving 36^ bushels per acre ; and if we 
take the total crop grown by the two salts — which is by far the 
best measure of the power of a manure to produce growth — we 
find that the 86 lbs. of nitrogen as nitrate of soda produced 
6982 lbs., and the 129 lbs. of nitrogen in salts of ammonia 
6832 lbs. of total produce per acre. 
Although there is often a strong prejudice against the use of 
nitrate of soda, it is evident from this example that, when 
judiciously applied, its properties as a manure are much higher 
than those of salts of ammonia. We may add, that when used con- 
tinuously for 32 years its power to produce growth appears to 
increase, rather than to diminish, as during the last 16 years the 
total produce per acre of 9 A, in excess of the produce of 7 A — 
each receiving equal amounts of nitrogen — has been 7084 lbs. as 
against 5313 lbs. ; a difference of 1771 lbs. of total produce 
per acre per annum in favour of the nitrate. 
