THE CULTIVATOR. 
although the latter possesses a very sir king superiority 
in composition over common manure. We accordingly 
find in practice, that the comparative value of these 
different manures is very nearly the same that analysis 
indicates, when the average of experiment is taken. 
There are many other substances which chemistry 
points out as valuable for manure, which are found use¬ 
ful in practice. Many of these, however, if used singly, 
or mixed with only one or two others, often give un¬ 
certain results, frequently prove failures, and sometimes 
are a positive injury. Sulphate of ammonia, nitrate of 
soda, sulphate of lime, silicate of potash, and other salts 
have been known to produce extraordinary growth; 
but in other cases were valueless. So many causes con¬ 
trol their action, that this uncertainty must continue to 
exist. The soil maybe already supplied with them; 
drought may derange entirely their action; and other 
influences now unknown may produce a similar result. 
Common barn-yard and stable manure, though not so 
powerful, appears to be more universally benefical 
than any other from the certainty of its operation. 
This certainty is dependent on the great number of its 
ingredients. It contains a large portion of decaying 
vegetable matter derived from the pulverized hay con¬ 
sumed by the animal; it is rich in ammonia and other 
animal matters, resulting from the secretions; and it 
contains many salts derived from both these sources. 
Poudrette possesses nearly the same advantages; and 
guano, from its great quantity of animal matter and en¬ 
riching salts, rarely fails if properly applied. With 
single substances, however, there is great uncertainty, 
until experiment points the way. 
Wheat was found by H. Davy to contain more nitrate 
of potash than any other farm product; yet the author 
of British Husbandry says, “although it has generally 
occasioned an increase of straw, the yield of grain has 
not been improved, and the crops have in many instan¬ 
ces been found unusually subject to mildew. 55 Similar 
experiments, by the writer, have produced no favorable 
result. Hence we perceive that supplying, simply, an 
essential ingredient, does not always answer the pur¬ 
pose. Artificial guano, made by an observance of the 
analysis of the natural though useful, has not been found 
nearly so powerful as the latter. Nitrogen, supplied pro¬ 
perly to plants, causes a healthy and rapid growth; yet 
although this element exists uncombined as a compo¬ 
nent of the atmosphere, and in direct contact with the 
leaves of plants, they will perish for want of it before 
they will draw a particle of it from the air. Hence in 
all chemical deduction relative to manures, the ex¬ 
periments of the cultivator only are to be depended on, 
and to remain as the decisive test. Suggestions of in¬ 
calculable importance may come from theory, but prac¬ 
tice alone must prove their value. 
The importance of the analysis of soils, to determine 
deficient ingredients, and then to supply defects, has 
been already adverted to. Although its value thus ap¬ 
pears to be very great, and has been much extolled by 
chemical waiters and their imitators, yet there are dif¬ 
ficulties in practice which render extreme caution in 
drawing conclusions very necessaiy. The constituents 
of plants may indeed be determined with much accura¬ 
cy; and the different ingredients in manures, and their 
consequent adaptation to those plants, and of their com¬ 
paratively fertilizing effects, may be ascertained fre¬ 
quently in the laboratory. But the extensive diffusion 
of these ingredients through broad acres of soil, and the 
exceedingly minute proportion which some bear to the 
whole bulk of the soil, renders the determination of 
these proportions, if not the actual existence of the in¬ 
gredients, difficult if not impossible. A distinguished 
chemist told the writer, that for ordinary earthy sub¬ 
stances, the detection of a thousandth part required 
skilful analysis. Minuter portions of some constituents 
are more easily detected than of others. But suppose 
a ten-thousandth part the utmost limit for agricultural 
practice, a few instances will show the inadequacy of 
analysis in cases which may occur: 
A considerable portion of sulphate of lime or gyp¬ 
sum is found to exist in red clover, and other legumi¬ 
nous plants. Hence a reason that gypsum so eminently 
benefits the growth of red clover. And hence reason 
would here suggest, that to determine the fitness of a 
soil for clover, an analysis should be made; if it con¬ 
tain gypsum all is right, and the clover will flourish; 
but if not, then a dressing of this material must be ap¬ 
plied. This is the theory. Let us compare it with 
practice. A hundred pounds of gypsum to the acre has 
often doubled the clover crop; and a tenth part of that 
quantity, or ten pounds to the acre, will produce in some 
cases very sensible effects. After it is spread on the 
ground, and before any sensible effect is produced on 
the crop, the rain has usually dissolved it and carried it 
into the soil and among the roots of the young plants. 
It thus becomes intimately diffused through the soil. 
Now, will analysis detect its presence? If the soil is a 
foot deep, half a grain to a pound will indicate a hun¬ 
dred pounds to an acre. Yet thisffialf a grain to a pound 
is only one fourteen-thousandth part; though often pro¬ 
ducing a most luxuriant growth of red clover. A tenth 
part of that is only one hundredth and forty-thousandth 
part; yet this minute portion often is found to exert a 
very visible influence in growth; though far beyond 
the reach of ordinary analysis. A crop of clover of a 
ton and a half to the acre, contains only three times 
this amount, or thirty pounds of gypsum in its stems 
and leaves. 
Again; twenty pounds of muriate of ammonia ap¬ 
plied to an acre of rye added five bushels to the pro¬ 
duct.* But this is only one seventy-thousandth part of 
the soil. One hundred and forty pounds of guano 
added more than sixteen hundred pounds to an acre of 
hay. But this, manure, when diffused through the soil, 
constituted only about a ten-thousandth part; its pro¬ 
portion of phosphoric acid, forming about one-eighth, 
and a very important ingredient, would be about one 
eighty-thousandth part; its sulphuric acid would con¬ 
stitute less than a two-hundred-thousandth part, and its 
potash about one three-hundredth-thousandth part. I am 
not aware that many chemists claim sufficient skill to 
determine such small proportions in the soil; yet these 
experiments show their great practical influence when 
existing as added constituents. 
The ammonia of the atmosphere is considered by 
eminent chemists as holding a very important relation 
to the healthy and vigorous growth of plants; yet its 
presence has never been directly detected, and only 
indirectly by favorable opportunities when absorbed in 
snow or rain-water. Eminent and accurate experi¬ 
ments had not discovered even this until within a few 
years. 
It is not denied that a bright light may be thrown on 
the practice of agriculture by carefully conducted 
analyses of soils. The results of many examinations 
which have been made, show' frequently a very striking 
difference between fertile and barren soils. But these 
analyses were conducted with the most rigid care and 
accuracy by men of such skill and eminence as could 
hardly be expected to be at the service of any common 
practical farmer. And after all accurate experiments 
in cultivation would determine all that is necessary in 
many points of practice, and would in any case be 
needed as a test of the truth of the theory. 
It is to be hoped that chemists will continue to pur¬ 
sue their investigations on doubtful points, until cer¬ 
tainty, if possible, may be arrived at; and that all well- 
established facts may have as extensive application in 
farming as their value merits. But it must be admit¬ 
ted that there has been a disposition to take too much 
for granted, and to overstate the certainty of success in 
connecting chemistry with agriculture. The precision so 
striking in other sciences, and other applications of this 
science to variousarts, does not hold in case of the growth 
of plants, w hich, though governed by fixed laws, is too 
much controlled by circumstances and too much obscured 
from view, to be thoroughly understood. This growth 
is slow and imperceptible to the sight; plants are sur¬ 
rounded by an invisible air above ground, and are hid¬ 
den from view below ground; their surfaces receive 
* Johnston’s Lectures, Appendix, p. 29 
