318 Rq)ort of Experiments on the Growth of Barley, 
G years 2000 lbs., and during the last 14 years 1000 lbs. per acre 
per annum were applied. The rape-cake is calculated to contain 
4 75 per cent, of nitrogen. This estimate is not founded on direct 
analysis of the lots actually employed, but is deduced from our 
own and published results on various samples in the market. 
Adopting it, the 20C0 lbs. would contain '.)5 lbs. nitrogen = 115"4 
lbs. ammonia, and the 1000 lbs., 47'5 lbs. nitrogen = 57'7 lbs. 
ammonia. 
As the manure leaves a considerable residue for future crops, 
and would especially do so during the first 6 years, the calcu- 
lation of the whole of the nitrogen supplied, against the increase 
obtained during that period, does not show the total or final 
effect of the nitrogen so supplied ; whilst, during the succeeding' 
14 years, the figures will represent the result too favourably, 
in so far as a portion of the increase will doubtless be due to 
accumulation from the previous applications ; and this would 
probably be more considerable, and more effective, than in the 
case of the double supply of ammonia-salts (Series 11.). Accord- 
ingly, the figures show much more nitrogen applied for the 
production of a bushel of increase during the first 6, than during 
the last 14 years. 
As already explained, the increase is, as in the experiments 
with ammonia-salts, calculated over the produce on the corre- 
sponding plots without nitrogenous manure. This plan is, upon 
the whole, less open to objection than taking the increase in each 
case over the unmanured produce ; but a consideration of the 
results will show that it is by no means without objection. 
The general result is, that the experiments with rape-cake 
show less difference and less beneficial effect due to the mineral 
manures also used, than those with ammonia-salts. Thus, com- 
paring the results with rape-cake over the last 14, or the 20 years, 
with those of Series II., with ammonia-salts over the same periods 
(both manures being applied in double quantity during the first 
6 years), considerably less nitrogen, reckoned as ammonia, is 
calculated to have been required to yield a given increase with 
ammonia-salts than with rape-cake when superphosphate was also 
used, but considerably less with rape-cake than with ammonia- 
salts, when each was used without superphosphate. 
The fact is that rape-cake itself contains phosphates and other 
mineral constituents, which serve to render the nitrogen associated 
with them the more effective. It is obvious, therefore, that 
calculating the increase by the rape-cake alone over the produce 
without manure, and that by rape-cake and mineral manure over 
the produce by the corresponding mineral manure alone, gives a 
relatively too favourable result for the rape-cake where it is used 
alone, and too unfavourable where it is used with the mineral 
