Report of Experiments on the Growth of Wheat. 485 
of ammoniacal manures and nitrates constitutes one of the recog- 
nised sources of nitrogen for the growth of wheat, the practical 
question arises — how much increase may be calculated upon 
from the use as manure of a given amount of ammonia, or of 
an equivalent amount of nitrogen in some other available form ? 
Table XXXI. (see following page), brings together a vast 
amount of evidence on this point. It shows the amount of am- 
monia in manure (or of niti'ogen as nitrate reckoned as ammonia) 
that was required for the production of 1 bushel (or 60 lbs.) 
increase of wheat grain, with its proportion of straw, on the most 
important plots, in each of the last 12 years of the experiments. 
As the productive effect of a given amount of ammonia depends 
very much upon the available supply of the necessary mineral 
constituents within the soil, and as artificial nitrogenous manures 
of course should not be, and seldom are in practice, employed if 
the supply of them be deficient, the Table is arranged to show, 
not the amount of ammonia required for each bushel obtained 
beyond the produce without manure, but over that by the mixed 
mineral manure, which being higher, leaves so much the less 
to be reckoned as increase due to the action of the ammonia 
supplied. Then, again, instead of taking the actual number of 
bushels of increase of dressed corn each year, which would repre- 
sent very different amounts according to the varying weight per 
bushel from year to year, the number of bushels is, in all cases, 
calculated by dividing the number of lbs. of increase of corn by 
60. For the purposes of the Table, therefore, every 60 lbs. of 
increase over the produce by the mixed mineral manure is sup- 
posed to represent 1 bushel. 
Many years ago, in papers in this Journal, we stated, as a 
provisional estimate deduced from the results of the experiments 
now under consideration so far as they had then proceeded, that 
the farmer might assume, for practical purposes, that he would, on 
the average of seasons, get 1 bushel of wheat and its proportion 
of straw beyond the produce of the soil and season, for each 5 lbs. 
of ammonia applied as manure for the crop. This estimate was 
founded upon results obtained where the mineral constituents 
were not unduly exhausted, and the amounts of ammonia sup- 
plied were not excessive ; that is, under conditions likely to accord 
with those most frequently occurring in common practice. 
The statement met with much ridicule from Baron Liebig - , 
who said that it was " a mere stroke of fancy." Whether 
the statement in question, or this condemnation of it, partakes 
most of "a mere stroke of fancy," may be judged by the record 
of facts given in this Section. 
50 lbs. of ammonia, or its equivalent of nitrogen, would be 
supplied in rather under 2 cwts. of commercial sulphate, or 1| 
