10G 
AMERICAN AGRICULTURIST. 
[April, 
terial, drawn into the plant from the soil by the 
sap, and left there by the evaporation of the sap 
through the leaves and bark 1 This is an inter¬ 
esting-point, as will appear when we state that 
the theory of manuring, as taught by most agri¬ 
cultural chemists, is based upon the supposition 
that the ashes are the most important part of the 
plant to be ooked after. 
The reasoning is somew'hat like this : “ The 
“ organic portions of the plants—constituting 
“say ninety eight parts in every hundred—are 
“ made up of four elements that are always abund- 
“ ant in the atmosphere; and from this source 
“ (the ai : r,) the plant can readily get their organic 
“elements. But the mineral elements of the 
“ ashes, or a part of them, are not always abund- 
“ ant in the soil. Therefore, the plant having an 
“ever abundant supply of the organic elements, 
“ we have only to look after supplying the inor- 
“ganic elements—that is, the minerals in the 
“ ashes.” 
This is the substance of the theory adopted at 
one time, and still partially adhered to, by Liebig, 
and by most agricultural chemists. The theory 
is at once beautiful and plausible, and it is hardly 
to be wondered at that it. is readily fallen in with 
by theoretical chemists generally, and by the 
novitiate in the science of agricultural chemistry. 
Starting w'ith this plausible theory, the efforts of 
agricultural chemists have been directed to as¬ 
certaining the composition of the ashes of various 
cultivated crops, and of the soils upon which they 
grow, to the end that the deficient mineral ele¬ 
ments may be supplied to the soil. 
The chemists have been strengthened in the 
above theory by finding in the ashes of the same 
plants grown on different soils, an apparent simi¬ 
larity in the kjnds and proportions of the various 
mineral elements. Thus: in 1000 ounces of 
the ashes of wheat, there have been found 
about 500 ounces of mineral phosphates; 250 
ounces of potash ; 120 ounces o’f magnesia ; 80 
to 85 ounces of soda ; 25 ounces of lime ; 7 ounces 
of iron ; and 3 ounces of sulphuric acid. 
Allowing these figures to represent the gener¬ 
al composition of wheat ashes, the conclusion has 
been, that of these minerals, (phosphates, potash, 
soda, etc.,) there must be in the soil, and availa¬ 
ble to the roots, for every ten bushels of wheat, 
about fi pounds of phosphates, 3 pounds of potash, 
1£ pounds of magnesia, etc.; and that in their ab¬ 
sence/the supplying of these several mineral 
elements in the proportions named, will furnish 
the necessary aliment for the wheat crop. For 
other plants, different mineral elements, or differ¬ 
ent proportions of those above named, are sup¬ 
posed to be essential. As stated- in a former 
volume, Liebig, and others, after adopting this 
theory, commenced prescribing special fertilizers 
which severally contained the supposed requisite 
mineral elements for the different crops. Thus, 
a manure for wheat contained, say 500 lbs. of 
phosphates, 260 lbs. of potash, 120 lbs. of magne¬ 
sia, 83 lbs. of soda, 25 lbs. of lime, etc.; while a 
turnip manure contained only some 60 lbs. of 
phosphates, 400 lbs. of potash, 50 lbs. of magne¬ 
sia, 108 lbs. of soda, 125 lbs. of lime, etc. Such 
specific manures were patented by Liebig him¬ 
self, we believe, but they utterly failed to pro¬ 
duce the expected results. The same theory is 
put forth by the present manufacturers of super¬ 
phosphate of lime, and importers of “ American ” 
and other phosphatic guanos, etc. That there is 
some defect in this theory, the hundreds of thou¬ 
sands of dollars, nay, the millions of dollars lost 
by farmers in the purchase and use of mineral fer¬ 
tilizers, during a dozen years past, bear abundant 
testimony. We venture the assertion that not 
one farmer in a thousand buys any of these spe¬ 
cific mineral manures beyond the second or third 
time. They have not proved profitable in prac¬ 
tice. 
Another idea growing out of the above theory 
was, and in some measure is yet prevalent, viz.: 
that since soils generally contain most of the min¬ 
eral elements found in plants, it is only necessary 
to examine the soil chemically, to ascertain w’hich 
element, required by the ashes of any particular 
plant, is absent, and then supply this one only. 
Thus, if a soil designed for ten bushels of wheat, 
contains abundance of phosphates, potash, soda, 
etc., but is deficient in lime, then all that is neces¬ 
sary is to supply the missing element. But since 
the ashes of ten bushels of wheat contain only 
5 to 6 ounces of lime, how natural the conclu¬ 
sion of the enthusiastic agricultural chemist that 
“ he expected to see the time when a man could 
carry to a field in his pocket all the necessary ma¬ 
nure to secure a crop of wheat.” We need only 
to say here, that after thousands of analyses of 
soils, this mode of ascertaining what mineral ma¬ 
nures are needed for a particular crop, is nearly 
abandoned by all except quacks and humbugs who 
have a personal end to secure by keeping up and 
propagating the theory. Analyses of soils are 
continued by scientific men for the purpose of 
scientific investigation, but not now as being of 
practical utility in the application of manures. 
But to come back to the question : are miner¬ 
al elements, in definite proportions, essential to 
the perfect development of plants 1 There are 
strong reasons for supposing that some of the min¬ 
eral elements are essential. We find certain of 
them always present, as for example, the ashes 
of wheat always contain more or less of phos¬ 
phoric acid, and it would seem necessary that 
this should be the case, with this or some other 
material consumed as food, since our bones require 
phosphorus, and this must come from the food we 
eat. The same may be said of lime. 
Still it is impossible to say that a wheat plant 
can not grow and perfect its seed without a def¬ 
inite proportion of phosphoric acid, or of lime, 
or of other mineral matter. Allowing phos¬ 
phoric acid to be essential, we assert, that—all 
the analyses yet made to thG contrary notwith¬ 
standing—it is still to be ascertained what is the 
exact amount of phosphoric acid necessary to 
the wheat plant; and so of the various other 
mineral elements found in plants. Further, it is 
yet to be shown that any soil, having the other 
qualifications requisite to produce a crop of wheat, 
does not contain an abundance of phosphoric acid 
and lime to supply the wants of the crop. This 
much is certain, that a soil of the ordinary depth 
may contain phosphoric acid enough for a hun¬ 
dred crops of wheat, and yet the skillful chemist 
may not be able to discover an appreciable amount 
of this element* 
All plants, and all animals (with the exception 
of the bones of the latter) are chiefly made up of 
the four organic elements. That several miner¬ 
* Allow an acre to yield 20 bushels of wheat every 
year for a century, yet the total amount of phosphorus 
extracted from thesoil would not exceed a pound for every 
4000 lbs. of earth, estimating the soil at one foot in depth. 
The chemist in analyzing 100 grains of soil would find 
only about one-fortieth part of a grain of phosphorus, 
supposing there were only a sufficient amount for the 
100 crops of wheat. This shows that a soil may contain 
phosphorus enough for alternate crops of wheat during 
200 years, and yet the amount be so small, comparative¬ 
ly, as not to be discovered in an ordinary chemical anal¬ 
ysis. And the same is the case with other mineral ele¬ 
ments. There may bo an abundance of them for all the 
wants, or supposed wants, of a great number of crops, 
and the quantity still be so small in comparison with the 
entire weight of a soil that their presence can not bo de¬ 
termined by the most delicate tests of chemistry. 
al elements are found in plants and in the bodies 
of animals, is not conclusive proof that these 
mineral elements are all needed there. A person 
may imbibe spring or well water containing, as 
it usually does, potash, soda, lime, etc., and these 
substances may be diffused all through the body, 
but the chemist on finding them in the blood 
or tissues, would not therefore consider them es¬ 
sential. A towel hanging down so as to touch a 
basin of sea water, would draw up a portion ot 
the fluid, and along with it a quantity of salt, 
magnesia, lime, etc.; but the chemist on drying 
and burning the towel, and finding in the ashes 
the magnesia and lime, would by no means pro¬ 
nounce them essential constituents of the towel. 
So the roots of a plant, standing in the soil, ab¬ 
sorb water which, like spring water, contains more 
or less of the mineral elements of the soil. The 
water evaporates from the leaves, leaving behind 
the mineral elements thus taken up. The chemist, 
on cutting, drying, and burning the plant, finds 
these mineral elements thus accidentally present. 
Their amount and proportions depend upon the 
character and composition of the soils, and the 
amount of water previously evaporated and still 
circulating in the plant at the time of its gather¬ 
ing. What we are aiming at is, to show the lit¬ 
tle reliance to be placed upon that system of ma¬ 
nuring which teaches to supply to the roots of 
the plant as fertilizers, those mineral elements 
which the chemist has chanced to find in the 
ashes of the plant. We do not yet know what 
mineral elements (how many or in what propor¬ 
tion) are to be considered essential to the growth 
and perfection of any one plant. 
Illustration .—Agricultural chemists have all 
along claimed that silica is absolutely necessary 
to give strength and stiffness to the straw of 
wheat,- oats, rye, etc. Prof. S. W. Johnson, in a 
lecture at the recent Agricultural Convention at 
New Haven, unsettled this theory, which has 
been considered one of the most firmly settled 
points of agricultural chemistry. Thus, he 
asked : If an abundance of silica gives the firm 
texture to the oat stalk, how is it that the leaves 
and chaff are so soft and pliable, when chemical 
analyses show that these contain three times as 
much silica as the firm straw! The answer would 
seem to be, that the silica has nothing to do with 
the strength of the straw, but that it is simply 
due to a close texture, and that the excess of 
silica found in the leaves and chaffisleft there by 
the larger amount of sap evaporated from those 
parts. Silica (sand) is abundant in all soils, and 
is carried up by the sap, freely. A plant may be 
soaked and washed in a weak solution of potash, 
and then iu one of hydrochloric acid, until all, or 
nearly all, of its silica and other mineral elements 
are removed, and it will still retain its form, tex¬ 
ture, and strength. How then can we consider 
these mineral elements essential to its structure 
or growth 1 
These considerations, but a small part of what 
might be brought forward, are, we think, enough 
to vitiate the present current theories in regard 
to the value of this or that mineral manure. The 
present theories are too defective,too unreliable, to 
be a safe guide for practice. We are thrown back 
upon experience as our main guide. Experience 
teaches us that organic manures, animal and veg¬ 
etable, and especially those containing much ni¬ 
trogen, are those most likely to benefit growing 
crops. There are exceptions, as in the case of 
lime, potash, and gypsum (“plaster,”) which on 
some soils are useful, and on others not. So far 
experience, or a trial of them, is our only guide 
for using them. We shall refer to these excep¬ 
tions again, in discussing their use and mode of 
