498 Report, of Experiments on the Growth of Wheat. 
soil, to which the farmer must look for the production of good 
crops of wheat ? 
In former papers in this Journal, we have pointed out that his 
chief means to this end was the adoption of a suitable rotation of 
crops — alternating with his corn the so-called "green," "fallow," 
or " fodder " crops, an important office of which it is to collect 
from natural sources, or to conserve on the farm in the form of 
manure, available nitrogen for the increased growth of the 
saleable cereal grains. We have further maintained that, as 
either by bare fallow, or a rotation of crops, with the consump- 
tion of the fallow crops and the retention of the straw on the farm, 
the accumulation of available mineral constituents will generally 
be in excess of the available nitrogen, it is the amount of the 
latter, rather than of the former, that will be the measure of the 
increased produce obtained by such means. 
Baron Liebig's former views of the means by which our cereal 
crops were to be increased were, however, directly opposed to those 
here stated. He assumed that fertility was quite independent of the 
ammonia conveyed to the soil ; that if only the necessary mineral 
constituents were supplied in sufficient quantity and in available 
form, our cultivated plants, Graminaceous as well as Leguminous, 
would derive sufficient ammonia from the atmosphere ; that the 
presence of ammonia in our manures was immaterial ; indeed, 
that the entire future prospects of agriculture depended upon our 
being able to dispense with ammonia in our manures, therefore 
with animal manures, and hence with the bulky farmyard 
manure, and substitute for it artificial preparations. 
Baron Liebig now fully admitting the inefficacy of the wheat- 
manure devised by himself, attributes its failure to the condition 
of insolubility in which the mineral constituents were provided 
in it ; and having formerly treated the investigations of Professor 
Way on the properties of soils with much ridicule, he now passes 
a well merited eulogium on the important experiments and dis- 
coveries of that gentleman and Mr. H. S. Thompson, and alleges, 
that since it has been shown that certain soluble mineral sub- 
stances become sufficiently insoluble when supplied to the soil, the 
want of the anticipated effect of his manures is completely explained. 
It is obvious, however, that those discoveries afford no explanation 
whatever of that failure ; for if insolubility were the only bar to 
efficiency, the same constituents supplied in the soluble form 
should have the effect which Liebig's wheat manure was designed 
to produce. They should, in fact, enable the wheat-plant to 
assimilate sufficient nitrogen from the atmosphere for large crops. 
But the results of direct experiment recorded in this and former 
papers, as well as the common experience of this country show, 
that those soluble mineral manures which are effective enough 
