484 
Afjricultural Chemistry. 
averajje of seasons, \Yo. have this amount supplied both in the 
form of ammonia-salts, and in that of nitrate of soda. We have 
it also with the admixture of minerals ; and a<jain when, besides 
minerals, the same amount of nitrogen is supplied indifferently 
in the lorm ol rape-cake alone, or a mixture of rape-cake and 
ammonia-salts. We have next, in Series 5 and G, the amount of 
nitrogen recovered, when less than the standard amount of nitro- 
gen was employed. And lastly Series 7 and 8, when more than 
the standard amount of nitrogen was used. 
Now, since season has a very gi-eat effect upon the amount and 
description of the increase obtained by nitrogenous manures, and as 
the whole of these series do not apply equally to the same years, it is 
obvious that niceties of variation cannot be discussed upon such a 
summary statement of results as is here given. The general fact is 
clear, however, that the proportion of the supplied nitrogen not 
recovered in the increase of crop, is, in all cases, very large. The 
proportion of loss is greater when tlie standard amount of nitro - 
gen is used alone, tlian when a liberal supply of minerals is also 
added. But it is seen, that even when only the standard amount 
of nitrogen is used (an amount which does not yield more in- 
crease than should be obtained under high farming on the land 
in question), and when to this is added a liberal supply of 
mineral constituents, still there is little more than 40 per cent, 
ol the supplied nitrogen recovered in the increased produce of 
corn and straw Avhicli is obtained. When, again, with the 
minerals, less than the standard amount of ammonia is employed, 
that is, less than is adequate torsive an amount of crop equal to that pro- 
duced by good farming, — we have, even in that case — a case which 
of course in practice could not be followed — little more than 50 per 
cent, of the supplied nitrogen recovered in the increase of crop. 
But when, with the mineral constituents, we add more than the 
standard amount of nitrogen, though not more than gave a still 
further increment of increase, we have little more than one-third 
of the nitrogen of the manure returned in the increase. 
It is seen, that with both wheat and barley, a large amount 
of nitrogen alone, applied as nitrate of soda, gives a worse result 
than a large amount of salts of ammonia alone. The nitrogen 
applied as rape-cake gave, in the case of wheat, nearly an equal 
result with that in ammonia-salts; when used with barley, it 
gave considerably less return in its increase than when applied in 
the latter form ; but the amount of rape-cake employed, was 
obviously far too great for the favourable maturing of tlie barley 
in the average of seasons. 
As a final average it is seen that we have, including all these 
cases and extending over so many years, in the case ol loheat, 
only 39'9 per cent., and in that of barley only 43'1 per cent., of 
