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THE CULTIVATOR 
The Mineral Manure Theory. 
Analytical Laboratory, Talk College, 1 
Neiv - Haven . Conn .. Oct . ‘24, 1851. J 
Eds. Cultivator —'The subject which I have placed 
at the head of this letter, is not one which can be fully 
discussed in a single page of your journal; and yet it is 
one of so much importance that I desire to make a few 
explanations and statements, regarding the shape which 
it has now assumed among scientific men. When I men¬ 
tion the ‘‘mineral manure theory,” I speak of that view 
of manures which ascribes all, or nearly all, of their effi¬ 
cacy to their mineral constituents. 
The principal supporter, and indeed the originator of 
this theory, is Prof. Liebig. This distinguished chemist, 
distinguished no less by his clear and lucid style, than by 
his high scientific reputation, was for a time devoted to 
“ the ammonia theory,” excluding those mineral manures 
to which he now attaches so much importance. A few 
years since, however, he saw cause to change his ground, 
and has since held, that if we furnish mineral manures 
in abundance, plants will, without doubt, always obtain 
their ammonia, or rather their nitrogen, from the atmos¬ 
phere or the soil. 
In pursuance of this idea, he went so far as to com¬ 
pound, after careful study of ash analyses, specific min¬ 
eral manures for wheat, rye, oats, turneps, &c., which 
were to take effect upon all soils in a proper physical 
condition. The failure of these specific manures, which 
were patented in England, was, as many of your readers 
doubtless are aware, very decisive. I had supposed the 
subject rather at rest, but find that in the last edition 
of Prof. Liebig’s ‘-'Letters on Chemistry,” published so 
late as the commencement of the present year, he reite¬ 
rates his former views on this subject in a most decisive 
manner, and prophecies that our future agriculture will 
depend upon them , however much we may distrust and 
disbelieve them now. I have also had occasion to ob¬ 
serve quite recently, that some gentlemen of high stand¬ 
ing among our own scientific men, follow Liebig in this 
as well as in other theories. For these reasons I have 
thought it best to express my own opinions on this con¬ 
tested point, in order that our farmers may be aware, 
that all chemists do not hold to views which militate 
almost directly against the ordinary results of practice. 
My belief is, that when Prof. Liebig advocated ‘‘the 
ammonia theory,” he was nearer right than he is now, 
when he only admits the necessity of mineral manure. 
Not that he was right then, but that better results would, 
in most cases, be obtained by the farmer in the use of 
ammoniacal or nitrogenous manures alone, than by the 
use of mineral manures alone. We find land in all parts 
of the country, where strictly mineral applications, such 
as lime, plaster, marl, &c., fail to produce any very 
marked effect; but if upon any of our fields we apply 
guano, or sulphate or carbonate of ammonia, the charac¬ 
ter of the vegetation is at once changed, its color alters, 
its luxuriance and vigor increases, and in a great ma¬ 
jority ef cases the product is augmented. v 
Every farmer who has observed such matters intelli¬ 
gently, knows that the above statements are correct; 
indeed they have been so far applied in practice, that the 
quantity of ammonia which any manure contains, is 
Dec. 
taken as the highest standard of its value. A guano, 
for instance, with the usual percentage of ammonia, will 
bring twice as much as one which contains little ammo¬ 
nia, even though this deficiency is replaced by the most 
valuable possible mineral constituents. 
I must not be understood to say, that mineral manures 
are not valuable; on the contrary, I have the highest 
opinion of them, and recommend their application in 
almost all cases where my advice is asked; the mineral 
constituents of the plant are no less indispensable than 
its organic part, and if one or two of them are absent 
from the soil, the plant will not flourish. There are 
many instances of these special deficiencies, which special 
mineral manures alone will supply, and there are cer¬ 
tain mineral substances which have been found specially 
valuable; the most so of all these is phosphoric acid. 
Now, the phosphates, that is, the compounds of this acid', 
are not more necessary to the plant than are the alkalies, 
but the supply is far more apt to be scanty, and this— 
not its intrinsic importance to the plant—is the cause of 
its higher value to the farmer. 
The same principle applies when we say that nitroge¬ 
nous manures, of which ammonia is the most common 
form, are more valuable than any others known in agri¬ 
culture. They are volatile, easily decomposable, and 
very soluble; for all of these reasons they are extreme¬ 
ly apt to disappear most rapidly. These manures, then, 
are worth more to the farmer than any others, because 
they are most likely to be needed, and because their 
scarcity renders it somewhat difficult to obtain a full 
supply. I make these statements fearlessly, and confi¬ 
dently, although against so high an authority as Liebig. 
I should not presume to oppose him on mere theoretical 
grounds, but feel that I am here sustained by almost 
uniform practical results. 
It must be acknowledged that we have occasional in¬ 
stances reported, of plants grown upon soils nearly or 
quite destitute of vegetable matter; but in most of these 
that have fallen under my observation, the fact of the 
entire absence of vegetable, and particularly of nitroge¬ 
nous matter, has not been sufficiently established. The 
information that they give is neither entirely definite, 
nor well enough made out by continuous and careful 
experiments, to be set off against the immense array of 
facts brought forward in favor of the opposite view. 
Single experiments for a single year, must always be 
looked upon with distrust until amply verified, and it is 
by mainly trusting to such, so far as we are informed, 
that the exclusive mineral theory has been built up. 
The laboratory alone is pretty sure to go wrong when it 
attempts to prescribe rules for practice: the chemist 
must go into the field and study actual experience, if he 
would serve the farmer effectually. 
It has been my intention to experiment somewhat 
largely upon this particular subject, but in the last number 
of the Journal of theKoyal Agricultural Society of Eng¬ 
land, is a paper by Messrs. Lawes and Gilbert, that 
almost precludes the necessity of doing anything more. 
These gentlemen have been experimenting on a large 
scale during the last ten years, and their results are 
clearly and admirably set forth 
They took a field at the close of a four years rotation, 
when the manures added at the commencement of the 
