320 Report of Expci iments on the Growth of Barleij, 
much as when a mixture of ammonia-salts and superphosphate 
was employed. This is a striking illustration of the slowness of 
the return from nitrogen supplied in farmyard manure compared 
with that in ammonia-salts or nitrate of soda. It is obviously an 
important question whether less or more of the at first unrecovered 
amount is lost by drainage, or otherwise, in the one case than 
the other ? or whether the residue from the one description of 
manure is more or less effective than that from the other? These 
points have already been referred to in some of their aspects, and 
will be further considered in the next Section (IV.) ; but data 
are still wanting for their full and satisfactory settlement. 
From a review of the whole of the data brought forward 
relating to the point, the practical conclusion may be drawn, 
that when an increase of barley is obtained by means of artificial 
manures, such as sulphate of ammonia, or nitrate of soda, or 
_ Peruvian guano, an increase of 1 bushel of grain (52 lbs.), and 
its proportion of straw (say 63 lbs.), 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 lb.), supplied in the 
manure — provided the amount applied be not excessive, and 
provided there be no deficiency of mineral constituents within 
the soil. 
These conditions will be fulfilled when barley, grown after 
dunged roots carted off, or after another corn crop, is manured 
by from 1^ to 2 cwts. of sulphate of ammonia, or If to 2^ cwts. 
of nitrate of soda, with 2 to 3 cwts. of superphosphate, per acre ; 
or, from 3 to 4 cwts. of Peruvian guano, containing 12 per cent, of 
ammonia, without superphosphate. 
When, however, rape-cake is used, rather more nitrogen in 
that form will be required to yield a given increase of the crop 
for which it is applied ; but when the increase is obtained by 
sheep-folding, or farmyard manure, very much less will be 
obtained in the first crop, in proportion to the nitrogen con- 
tained in the manure. 
In our Report on the growth of wheat for twenty years in 
succession on the same land, it was shown for that crop, as now 
it is for barley, that the quantity of increase obtained for a given 
amount of ammonia, or its equivalent of nitrogen, in manure, 
varied exceedingly according to the amount applied, to the 
provision of mineral constituents within the soil, and to the 
seasons. It was, however, stated, as a general practical conclusion, 
that, under the conditions the most camparable 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. Now, 
