Hopkins, Cyril G.

Pettit, James Harvey

IDEALS @ Illinois

Collecting and testing soil samples

Illinois Digital Environment for Access to Learning and Scholarship Repository

UNIVERSITY OF ILLINOIS 
Agricultural Experiment Station 
URBANA, MAY, 1911 
CIRCULAR NO. 150 
COLLECTING AND TESTING SOIL SAMPLES 
(Third Edition, Octob er, 1913 ) 
By CYRIL G. HOPKINS AND J. H. PETTIT 
A san1ple of soil should be collected to represent a soil type 
rather than to represent any particular. field, for a field may in-
clude two or more different kinds of soil. One should study the 
field or farm sufficiently to be able to know the prevailing type or 
types of soil conceniing which he desires to secure infonnation 
based upon chemical analysis. 
After one has become familiar with the type to be studied, the 
sample is collected by taking borings from twenty or more different 
places, a few rods apart, in each of which the soil should appear to 
be truly representative of the type. The~e borings thoroly mixed 
should ~1ake a trustworthy composite sample for analysis. An 
auger about r 34 inches in diameter is the most satisfactory imple-
ment to use. If a considerable number of samples are to be taken, 
and particularly if samples of the subsoil are also to be secured, it 
is well to have the stem of the auger cut in two and a steel rod 
of good quality welded in to make the auger about 40 inches long. 
A wooden handle may be used or the stem end of the auger may 
be enlarged and threaded and a handle made by using two 6-inch 
pieces of .7'i -inch galvanized iron gas-pipe and a .7'i-inch "T." If 
the auger is to be used especially for examining and sampling soils, 
it is well to fil~ off the screw point and the vertical lips. 
Ordinarily, samples may well be taken in sets of three: the 
surface, or average plowed soil ( o to 6% inches) ; the subsurface, 
or that which can possibly be n1oved with a subsoil plow ( 6~,1 to 
20 inches) ; and the subsoil ( 20 to 40 inches) ; corresponding to 
about 2 million, 4 million, and 6 million pounds, respectively, of 
ordinary soil. The surface boring is made and the hole enlarged 
about .7'i inch in diameter, the soil all being saved. The subsurface 
boring is then taken and the hole again enlarged, but the extra soil 
2 
is not saved. Finally the subsoil boring is taken and the soil saved 
frmn only one half (one groove) of the auger. This provides 
about equal quantities of soil from each stratum. 
For the regular chemical analysis the sample of plowed soil rep~ 
resenting the surface stratum ( o to 6% inches) is by far the most 
important, and frequently this is the only sample that is analyzed. 
Perhaps the greatest importance which attaches to the subsurface 
and subsoil samples relates to the amount of limestone present or 
required. Very commonly the surface soil is practically neutral in 
reaction; whereas, the subsoil may be strongly acid in one class of 
soil types or ·it may contain an abundance of limestone in other 
soil types. If the subsoil is stro11gly acid, then it is very important 
that liberal applications of limestone should be made; otherwise 
the capillary waters rising from the subsoil in times of partial 
drouth will carry additional acidity into the surface soil, and if 
the surface soil contains no limestone, injurious results are almost 
certain to follow' especially with such sensitive crops as clover and 
alfalfa. But if the subsurface and subsoil contain limestone in 
solution, then as the water evaporates from the surface and the 
moisture in the subsurface and subsoil rises, the limestone will tend 
to correct any acidity existing in the surface stratum and thus 
prove beneficial to crops that are sensitive to acid conditions. 
In so far as the subsurface and the subsoil are concerned, it 
is usually sufficient to make thoro tests for acidity and for alkalinity. 
The latter condition is represented chiefly by the carbonates of 
calcium and magnesium. 
Following are directions for making these tests: 
Soil Acidity.-To test for soil acidity make a ball of fresh, moist 
soil, break it in two, insert a piece of blue litmus paper; and press ' 
the soil firmly together again. After a few minutes examine the 
paper. If it has turned pink or red, soil acidity is indicated. The 
intensity of color and the rapidity with which it develops indicates 
to some extent the amount of acidity. (Blue litmus paper can be 
obtained from most drug stores, and five cents' worth is sufficient 
to make fifteen or twenty tests. To keep the unused paper fresh 
it should be preserved in a stoppered bottle in a dark place.) 
It is especially important to test the subsoil for acidity, as 
already explained ; but to make a thoro examination, samples 
should be tested both from the surface and from the subsoil at 
several different places in the field. The tests should , be made by 
the landowner in the field rather than by th<: chemist in the 1?-~ 
oratory. 
The litmus paper test for soil acidity is long-established, trust-
worthy, and very useful. It can also be used for determining acid-
ity in other materials, as in acid phosphate or in mixed fertilizers 
that contain acid phosphate. Put two or three spoonfuls of the 
fertilizer in a glass, add half a glass of water, stir well, let settle, 
3 
and then insert a strip of blue litmus paper; the paper will be 
quickly reddened by the acid solution. 
Carbona;tes.-A positive test for carbonates in the soil precludes 
the presence of soil acidity, for carbonates, such as calcium and 
magnesium carbonate, are easily decomposed by acids, and serve 
as mild alkalis in the presence of which soil acidity cannot exist. 
To test for carbonates, make a shallow cup of a ball of soil and 
pour into it a few drops of concentrated hydrochloric acid. If car-
bonates are present, they are decomposed with the liberation of 
carbon dioxid, which appears as gas bubbles, producing foaming, 
or effervescence. With much carbonate present the action is rapid 
and abundant, but with mere traces of it, only a few bubbles appear. 
The same test may be applied to limestone, marl, etc., to ascer-
tain whether carbonates are contained in the tnaterial. Most lime-
stones and marls show some effervescence when brought into con-
tact with cold concentrated acid, but some nearly pure dolomitic 
limestones require the application of heat to properly develop the 
reaction. 
Five cents' worth of concentrated hydrochloric acid in a small 
glass-stoppered bottle is sufficient for many t~sts for carbonates. 
Of course, care must be taken not to get the acid on the clothing 
or skin. In case it gets on the fingers it should be washed off, or 
rubbed off with soil, as soon as possible. It is not especially dan-
gerous to handle, but will soon "eat" or ''burn" thru the skin if 
not removed or neutralized, which is easily done by rubbing with 
soil containing carbonates. 
In the case of carbonates as in the case of acidity, it is especially 
important that the subsoil be tested, for an abundance of carbonates 
only I to 3 feet beneath the surface serves as a store and protection 
especially in critical periods in the growth of such plants as clover 
and alfalfa. These plants may die during a few weeks of summer 
drouth if the rising capillary moisture carries acidity, while if it 
bring traces of calcium bicarbonate, they will be kept alive. 
SYSTEMATIC SOIL INVESTIGATIONS 
Attention is called to the fact that a full report of the general 
soil survey of Illinois is given in Bulletin I23 of this station, "The 
Fertility in Illinois Soils." The bulletin includes a colored map 
showing all the great soil areas of the state, hundreds of soil analy-
ses representing twenty-five of the most important and extensive 
soil types in Illinois, and typical illustrations of results obtained 
from different kinds of soil treatment and soil improvement on 
experiment fields in all sections of the state. Besides this the bul-
letin contains some definite information relating to the plant-food 
requirements of different crops, and the sources, the approximate 
cost, and the methods of using different plant-food materials. 
4 
Attention is also called to the fact that the detail soil survey of 
Illinois already covers forty-six counties. In this detail survey the 
extent, location, and boundary lines of every type of soil covering 
an area of ten acres are determined and mapped. Soil samples are 
collected from every type, and these are being analyzed and pot-
culture and field experiments are being conducted so far as possible, 
so that when the maps are published the reports may also include 
definite information relating to the stock of plant food in every 
type of soil on every farm in the state, together with tried methods 
for maintaining or improving its productive power. (Soil Reports 
Nos. r, 2, 3, 4, and 5, for Clay, Moultrie, Hardin, Sangamon, and 
LaSalle counties, have been published, and No. 6, for Knox county, 
is now in press.) 
If the landowner has no other source of information concern-
ing the composition of his soil, it is altogether advisable that he 
collect a composite sample of th~ surface stratum (made by mixing 
together borings taken from about twenty different places where the 
soil appears to be uniform and truly representative of the type) 
and employ a skilled commercial chemist to determine the total 
phosphorus and the total nitrogen content. In cas.e of naturally poor 
or abnormal soils it is well also to have determined the total 
potassium, total magnesium, and total calcium. 
The chief value of a chemical analysis is that it serves as an 
absolute foundation upon which methods of soil treatment can be 
safely based for the adoption of systems of permanent soil enrich-
ment, not for OJ.!.e crop or one year only, but for progressive im-
provement. 
No CHEMICAL ANALYSES FoR PRIVATE PARTIEs. 
The Agricultural Experiment Station. does not undertake to analyze samples 
of fertilize'rs, soils, or other materials for private parties: First, because the 
total annual appropriation for the investigation of all the soil problems of the 
state is less than 30 cents for each quarter-section of Illinois land, while to 
analyze a soil or fertilizer would cost many times that amount, thus rendering 
it impossible to . make such analyses for all; and second, because the Experi-
ment Station is established for the investigation of problems of public interest, 
and not for the inspection or control of private investments or enterprises. 
That farmers generally understand and appreciate the fact that the State 
Experiment Station cannot and ought not to make such analyses is evidenced 
by the fact that, with a fe'w exceptions, there has been no demand by Illinois 
citizens for such private work at public expense. That it would be impossible 
to do such work for all Illinois citizens is also evidenced by the fact that we 
have received as many as eleven samples of soil from one man with the re-
quest that they should all be analyzed. To attempt to do such work would 
only delay the progress of the systematic detail soil survey which, as already 
explained, is being made to cover every type of soil on every farm in the state. 
It will never be possible for the Experiment Station to analyze the soil 
from every field of every Illinois farm, but it is possible and practicable to 
map the soils of the state in detail, and then to analyze representative samples 
of every type, so that ultimately every farmer can know what type or types 
of soil cover his farm, what the average composition of each type is, what 
crops are ·best adapte'd to the different soils, and what kinds of soil treatment 
or management are required to maintain or to increase the crop yields. All 
samples . taken for analysis by the Station are collected by Experiment Station 
men connecte'd with the systematic investigation of the soils of the state. 


https://www.ideals.illinois.edu/bitstream/handle/2142/33008/1144872.pdf?sequence=2

Collecting and testing soil samples

Abstract

Similar works

Full text

Available Versions

IDEALS @ Illinois

Illinois Digital Environment for Access to Learning and Scholarship Repository