234 
THE CULTIVATOR. 
August, 
have we evidence that it can be so carried out as to re¬ 
present the composition of the soil 7 A farmer has 
several hundred acres of soil; how many analyses are 
needed “ to cover all this ground?” Often on a small 
farm, if we can judge by the look of the earth, there 
are a half dozen varieties. There are frequently de¬ 
cided variations within a very small area ; and it rare¬ 
ly happens on farms that have been long under culti¬ 
vation, that one specimen of soil represents the whole. 
The soil that is annually worked over by the plow, is 
different from the undisturbed subsoil; and the latter 
may vary every few inches of its depth. How many 
analyses then must often be needed ! But it is said,— 
“ collect from various parts of the field, and thus get 
an average.” This is but making bad, worse ; for the 
analysis of such a mixture, only represents the compo¬ 
sition of the few pounds which have been sent to the 
chemist; but not that of the millions of lbs. that re¬ 
main in the fields. In very many cases—not indeed 
in all—the number of analyses that must be made, 
renders the whole thing impracticable. 
But admitting the soil of the whole farm to be uni¬ 
form in composition, what are the accidents that may 
vitiate analytical results ? It may easily happen that 
an egg or snail shell lodge in the identical specimen of 
soil selected for analysis—then the carbonate of lime 
may come out too high. The droppings of a dog or 
bird, will thus make a thousand acres rich in phos¬ 
phates ! 
Allowing, however, that such contingencies may be 
perfectly provided against, and that a competent chem¬ 
ist has made a bona, fide analysis of a' fair specimen of 
the soil—is chemical analysis, even of the most refined 
character, capable of giving constant results, on the 
same soil, or valuable results at all 1 In 1846 the 
Prussian “Landes (Economic Collegium” instituted a 
series of experiments “to determine in what proportion 
certain inorganic ingredients of the soil must be pre¬ 
sent in order to nourish definite plants.” To settle this 
question experimentally, it was concluded to select 14 
soils in various parts of Prussia, to have three speci¬ 
mens of each analysed under the direction of such 
chemists as Liebig, Rosd and others ; then to crop these 
soils from year to year with rape (Brassica napus) and 
peas, until they were so exhausted as to be able to pro¬ 
duce no more ; when it was proposed to analyse them 
again, and ascertain the loss they had incurred. £he 
42 analyses were communicated to the public, by Pro. 
Magnus in May, 1849, and are accessible to the English 
reader, in Liebig and Kopp’s Report on the Progress of 
Chemistry for that year. From these analyses, execu¬ 
ted by the most competent chemists that the world fur¬ 
nishes, results—what might have been expected, that 
three analyses of the same soil, carefully collected for 
the purpose, give variable results. In one soil, for ex¬ 
ample, one chemist found .009 pr. ct. of phosphoric 
acid; another .169 pr. ct., and the third ,832 pr. ct. In 
another soil, in one specimen is found a quantity too 
small to be weighed, a “ trace;” the 2d yields 1.028 pr. 
ct.; the 3d only .009 pr. ct. In another soil, two analy¬ 
ses agree in stating the presence of a pretty good sup¬ 
ply, one giving .456—the other .651 pr. ct., while ac¬ 
cording to the third analysis there is none! In ano¬ 
ther soil, on the other hand, two analyses agree that 
phosphoric acid is absent, while according to the third, 
it contains .229 pr. ct. Similar variations occur in the 
other ingredients. Which of these analyses shall 
serve as the basis of a prescription for improving the 
soil 1 The farmer is advised never to have more than 
one analysis made of his sick soil; if he gets three, 
they will give him more trouble than employing as 
many physicians of different schools when he himself 
is sick. Each one makes a different diagnosis, and de¬ 
mands a different prescription. 
Magnus calculates that the average harvest of rape 
seed and straw, from a “morgen,” contains 13 lbs. of 
phosphoric acid. The soil of a morgen taken to the depth 
of 9 inches, he calculates would weigh 1,944,000 lbs. 
13 lbs. is then 0.00066 pr. ct. of the weight of the soil. 
Chemical analysis is incapable of deciding as to 0.01 in 
the case of soils, scarcely as to 0.1 pr. ct. How many 
crops, and how many lbs. of phosphoric acid may be 
removed from the soil, and chemical analysis never be 
able to tell the difference ? 
Magnus further shows that from a soil in which the 
closely agreeing results of three analysts gave 0.0073 
pr. ct. of phosphoric acid, three crops of rape were 
gathered, in ’46, "47 and ’48, the last of which was 
greater than the first (no manure was used,) and the 
three crops, not including chaff, drew from the soil a 
greater percentage of phosphoric acid, viz., .018 pr. ct. 
of the soil, than the soil contained according to the 
three analyses—viz., .0073 pr. ct. Magnus remarks— 
“ It follows from this, that plants do not need to find in 
the soil any much greater quantities of a substance 
than is required to their development.” 
Every farmer who has employed guano successfully, 
knows that 400 lbs. per acre is a good application, of¬ 
ten making a crop double and quadruple in its yield. 
An acre contains 43,560 sq. ft. Taken to a depth of 6 
in.it has half this number = 21,784 cubic feet. As¬ 
suming a cubic foot of soil to average 80 lbs. in weight, 
(Johnston’s Lectures, p. 291 Am. ed.) we have then for 
an acre to the depth of half a foot, 1,742,400 lbs. of 
soil. 400 lbs. = 1-43561, = 0.00023 of the weight, — 
0.023 pr. ct. of the weight of an acre of soil. Peru¬ 
vian guano contains say 25 pr .ct. of phosphates = i of 
the whole. I of 0.023 pr. ct., is 0.0058 pr. ct. Am¬ 
monia averages 17 pr. ct. of the best guano, call it 20 
pr. ct. 1-5. 1-5 of 0.023 = 0.0046 pr. ct. These frac¬ 
tions then, 0.0058, and 0.0046, respectively represent 
the additions in per cents of phosphates, and of am¬ 
monia which an acre of soil receives in 400 lbs. of gu¬ 
ano, supposing the latter to be uniformly mixed to the 
depth of 6 inches. A ton of guano would add five times 
as much, viz., 0.029 pr. ct., and 0.023 pr. ct. 
Chemical analysis is utterly incompetent to discover 
these slight quantities. The addition of a ton of guano 
to an acre of soil, would make no perceptible difference 
in the results of an analysis ! But the farmer knows 
