6 
On the Valuation of Unexhausted Manures. 
twenty and thirty years full crops of wheat and of barley have 
been obtained under this treatment. 
Analysis of the produce has shown that a large proportion of 
the nitrogen supplied in the manure has remained unrecovered 
in the increase of the crop produced by its use. Still, any 
reduction in the quantity annually applied was followed by a 
diminution in the amount of the crop ; or, if the application 
were entirely stopped, there was frequently little or no effect 
upon succeeding crops from any unexhausted residue. 
Analysis of the soil showed that a portion of the nitrogen of 
the manure which was not recovered in the increase of crop was 
accumulated within the soil. But there yet remained a large 
amount of the supplied nitrogen to be otherwise accounted for 
than either in the crop or in the soil. 
It was next determined that the drainage-water from the 
various plots of the experimental wheat-field, which was already 
pipe-drained, should be examined. Numerous samples of the 
drainage-water from the differently-manured plots, collected at 
different periods of the year, have, by their own desire, been 
supplied for analysis, independently, to Professor Voelcker and 
to Professor Frankland. Their analyses proved that the drain- 
age-waters frequently contained a large amount of nitrogen in 
the form of nitrates ; that the quantity of nitrates was the greater 
the greater the amount of ammonia-salts applied as manure ; 
and that (after autumn-sowing) the quantity was very much 
greater in the winter, than subsequently in the spring and 
summer. 
In one case, after a heavy dressing of ammonia-salts. Dr. 
Frankland found a quantity of nitrates in the drainage-water, 
which would correspond to a loss of nearly 18 lbs. of nitrogen 
per statute acre, provided an inch of rain had passed as drainage 
of that strength. On another occasion, after a heavy dressing 
of nitrate of soda. Dr. Voelcker found a quantity of nitrates in 
the drainage-water, which, reckoned in the same way, would be 
equivalent to a loss of about 13 lbs. of nitrogen per acre. 
Lastly, on this point, calculation led to the conclusion, that 
most probably the whole of the nitrogen which had been sup- 
plied as manure in the ammonia-salts or nitrate of soda, and 
which was not either recovered in the increase of crop, or 
retained by the soil in a very slowly available condition, was 
drained away and lost. 
When the manure employed contains or yields ammonia, what 
happens is, that the ammonia becomes more or less rapidly oxi- 
dated in the soil, and so converted into nitric acid, which is 
washed away in the drainage-water, chiefly in combination with 
lime, or soda, or both, if not in the mean time taken up by a 
