•366 Report of Experiments on the Growth of Barley, 
the soil, and to the seasons. It was, however, stated, as a general 
practical conclusion, that, under the conditions the most com- 
parable with those of ordinary practice, approximately 5 lbs. of 
ammonia, or its equivalent of nitrogen, were, on the average, 
required to yield 1 bushel increase of wheat, and its proportion 
of straw. 
In like manner the experiments with barley have shown a 
very wide variation in the amount of ammonia required to yield a 
given quantity of increase, according to the amount ap])lied, to the 
provision of initieral constituents witliin the soil, and to the seasons. 
Thus, with superphosphate and 200 lbs. of ammonia-salts per 
ncre per annum, for six years, 3'2G lbs., but with 400 lbs. 5 06 
lbs. of ammonia were required to produce 1 bushel increase of 
barley-grain and its straw. 
- Again, with 200 lbs. of ammonia-salts for twenty years, there 
were required — on three plots where it was used with superphos- 
phate 2'13, 2"41, and 2'10 lbs. ; on one plot where it was used 
svith salts of potash, soda, and magnesia, without superphos- 
phate, 3'59 lbs. ; and on one without any mineral manure at all, 
3'68 lbs. of ammonia to yield 1 bushel of barley and its straw. 
Lastly, with only 200 lbs. of ammonia-salts per acre per annum, 
and with superphosphate also applied, the difference in the 
amount of ammonia required to yield 1 bushel of increase was, 
according to season, from about 1^ lb. in the two most favourable, 
to 5"36 and 4'48 lbs. in the two least favourable seasons ; whilst, 
with only the same moderate amount of ammonia-salts, but used 
without superphosphate, or without any mineral manure at all, the 
•difference in result according to season was very much greater still. 
Notwithstanding these very considerable and very significant 
variations, it may be concluded, from a review of the whole of 
the data bearing on the point, that when an increase of barley 
is obtained by means of artificial manures, such as salts of 
ammonia, nitrate of soda, or Peruvian guano, an increase of 1 
bushel of grain, and its straw, may, taking the average of seasons, 
be calculated upon for every 2 to 2\ lbs. of ammonia (or its 
equivalent of nitrogen, 1"65 to 1'86 lbs.) supplied in the manure 
— provided the quantity applied be not excessive, and there be 
no deficiency of mineral constituents within the soil. When, 
however, rape-cake is used, rather more nitrogen in that form 
will be required to yield a given increase ; but when the increase 
is obtained by sheep-folding, or by farmyard manure, very much 
less increase will be yielded in the year of the application, in 
proportion to the nitrogen contained in the manure. 
Thus, whilst it was concluded that, on the average, about 
5 lbs. of ammonia (or its equivalent of nitrogen) were required 
to yield 1 bushel of increase of wheat, and its proportion of 
straw, it is now assumed that only 2 to 2 J lbs. of ammonia are 
