Water penetration in the gumbo soils of the Belle Fourche Reclamation Project

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

Contribution from the Bureau of Plant Industry
WM. A. TAYLOR, Chief

Washington, D.C. 4 Vv November 22, 1916

WATER PENETRATION IN THE GUMBO SOILS OF
THE BELLE FOURCHE RECLAMATION PROJECT.

By O. R. MatueEws, Assistant, Dry-Land Agriculture Investigations. i

CONTENTS.
Page. Page.
MRErOGUCtION el Voce gle ane lc lode Aes!) 1 | Rate of movement of water in loose, sat-
Description of the gumbo soil of the Belle (DULG MSO USA IS Ee eee Ree SADE pl TEN he 4
Fourche Reclamation Project ............- 2 | Rate of movement of water in wet soil under
Water capacity of the gumbo soil.........._. 3 heldvconditionsys: N00 8 0) oc oy ae Roe Ue 5
Productivity of the gumbo soil........._.... 3 | Penetration of water into dry soil in the field -. 6
Changes in the volume of the soil due to SUANINA DY te tet oe ye Ln ee Ai eh pe aCe 11
wettineandidmying. i yee 3
INTRODUCTION.

The readiness with which water penetrates into any soil determines
to a great extent the amount that will be available to crops. An ac-
curate knowledge of water movement within a soil often furnishes
an indication of the farm practices that will be most successful.
Thus under irrigation the rapidity of water percolation may deter-
mine in what way and at what time water may be most effectively
applied. On dry land a knowledge of moisture movement often
shows what results may be expected from different cultural methods
calculated to increase the quantity of water entering the soil.

_ The gumbo soil of the Belle Fourche (S. Dak.) Reclamation Proj-

ect offers problems in water penetration materially different from
those in soils of other types. These differences are due largely to its
peculiar physical characteristics.

This bulletin presents the results of certain studies of the penetra-

tion of water into the gumbo soils of the Belle Fourche project.
_ Knorr, working on the sandy loam soils at Scottsbluff, Nebr.,
found that plats irrigated in the fall were more moist and moist to
greater depths in the spring than plats not fall irrigated. When

‘Knorr, Fritz. Experiments with crops under fall irrigation at the Scottsbluff Recla-
mation Project Experiment Farm. U. 8. Dept. Agr. Bul. .133, 17 p., 5 fig. 1914.

99155°—Bull. 447—16

2 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE.

irrigated during the following summer, the moist soil absorbed water
much more readily than the dry soil. The dry soil required a longer
flow of water to saturate it to a depth of 18 inches than did the soil
containing more moisture. By irrigation, the water content of the
moist soil was increased to a depth of 6 feet, while the dry soil showed
no increase in water content below the second foot. Continuing the
flow of water on the dry soil in order to get water into the lower
depths was tried, but was discontinued for' the reason that the dry
soil absorbed the water so slowly that a large amount of the flow was
lost by run-off.

The results obtained by Knorr on the sandy loam soils and those
obtained from the experiments described in this paper on the gumbo
soils are strikingly different. They bring out clearly the impracti-
cability of trying to use the same methods on all soils. The character
of the soil is an important factor in determining the degree of suc-
cess of any method of water application.

DESCRIPTION OF THE GUMBO SOIL OF THE BELLE FOURCHE
RECLAMATION PROJECT. |

The soil of the Belle Fourche Reclamation Project is a very heavy
clay of the type classified by the Bureau of Soils as Pierre clay.

The United States Bureau of Soils, in a reconnoissance soil survey of
-western South Dakota, found that the soils of this type covered about
seven and three-quarter million acres in South Dakota, or about 30
per cent of the total area surveyed.? It is a residual soil, formed by
the decomposition of shale, the partly decomposed shale being found
at a depth of approximately 4 feet below the surface. This depth
varies considerably with the location.

Fine soil particles make up the greater portion of the soil. A
mechanical analysis of the surface soil of this type shows that soil
particles of the different sizes are present in the percentages shown
in Table I.

TasreE I.— Mechanical analysis of Pierre clay.%

|
Fine | Very fine :
sand. sand. Silt. Clay.

Medium
sand.

Coarse
sand.

Fine

gravel.

| ®

| Per cent.| Per cent. len cent. | Per cenit. | | Per cent.| Per cent.| Per cent. -
PeTCTEG Clave: sa BEG ne eee 0.2 1S a 1.4 | Seo 13.0 | 43.2 35.0 ie
| zi | 4

a Strahorn, A. T.,and Mann, C. W. Op. cit.

Analyses of the subsoil are not available, but the textures of the
second foot and third foot indicate that the percentage of clay at

1 Strahorn, A. T., and Mann, C. W. Soil survey of the Belle Fourche area, South
Dakota. U. S. Dept. Agr., Bur. Soils [Adv. sheets—Field Oper., 1907], 31 p., 1 fig.,
2 maps. 1908.

2 Coffey, G. N., and others. Reconnoissance soil survey of western South Dakota. U.S. -
Dept. Agr., Bur. Soils [Ady. sheets—Field Oper., 1909], 80 p., 2 fig., 7 pl., 1 map. 1911.

a a ee

WATER PENETRATION IN GUMBO SOILS. 3

- these depths may be somewhat higher than in the first foot. The

difference is not great, and as a whole the mechanical composition
of the first 3 feet may be considered uniform.

WATER CAPACITY OF THE GUMBO SOIL.

The water-carrying capacity of this soil is high, and the minimum
point to which crops can utilize the water is correspondingly high.
The soil, when filled, will carry about 30 per cent of water, of which
about 15 per cent is available for the use of crops. The character of
the soil is such, however, that the crops do not root deeply, owing
either to the lack of water in the lower depths or to the impervious
nature of the soil. In spite, therefore, of the large quantity of
water that can be obtained by the crop from the soil near the surface,
the shallowness of feeding materially reduces the quantity of water
actually available.

PRODUCTIVITY OF THE GUMBO SOIL.

The producing capacity of the soil is high. There is no evidence of
a deficiency of any mineral element essential to crop production.
When sufficient water is supplied, abundant crops are obtained. The
high productive capacity of this soil is evidenced by the yields ob-
tained on plats not irrigated in 1915, when the rainfall was unusually
iavorable both in amount and in distribution. The average acre
yields obtained were 72.2 bushels of barley, 36.2 bushels of winter
wheat, 57.6 bushels of spring wheat, 125.6 bushels of oats, and 44.5
tenes of corn.

CHANGES IN THE VOLUME OF THE SOIL DUE TO WETTING AND
DRYING.

The large amount of clay present makes this soil subject to extreme
changes in volume with changes in its water content. When the soil
is wet it swells and compacts; when dried it shrinks and cracks.
That the change in volume is great enough to cause a material
change in physical structure is shown by the results of the follow-
ing experiment, which was made for the purpose of obtaining a
measure of this change. -

The volume of oven-dried compact samples of soil was determined.
These samples were then immersed in water and allowed to expand
freely and the volume redetermined. The volume of the soil from
the first foot increased 2.2 times. The volume of that from both the
second and third feet increased 2.5 times.

These changes in volume, due to variations in moisture content,

result in the following structural differences:

When dry this soil is usually covered with a natural mulch about 2 inches
deep caused by the crumbling of the surface soil. Beneath this mulch is a
layer of soil honeycombed with cracks. The number of these cracks and the

A BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE.

depth to which they extend depend somewhat upon the manner in which the
soil has been dried. Where a close-drilled crop has been grown, they are small
and numerous and break the soil into small lumps to a depth of about 15 inches.
Beiow this depth the soil is generally compact and practically free from cracks,
no matter how dry it may be.

When the soil becomes wet it expands, and thus the cracks are closed. When
any excess of the expanding force in the cracked layer occurs, the whole force
of expansion in the uncracked area has the effect of crowding the soil particles
closer together. For this reason the wet soil is always compact throughout and
tree from open spaces.

Considering these structural differences between the wet and the
dry soil, it can readily be seen that the moisture content of the soil
may have a great influence upon water movement; but a study of
water movement in both the wet and the dry soil is necessary in
order to obtain information as to how water penetration takes place
under actual field conditions.

On the Belle Fourche project it has been found in field practice
that the water content of the surface soil at the time the water is
appled determines to a great extent the quantity that will be ab-
sorbed, especially when the water is applied rapidly. When both
the surface soil and the subsoil are dry, over an inch of rain, even if
it comes in a torrential manner, will be absorbed with very little
loss, because much of the water makes its way into the soil through
the cracks. On the other hand, when the surface soil is wet these
cracks are closed and a rain of as little as one-fourth of an inch may
be largely lost by run-off. Any rain falling on a wet surface must
fall very slowly in order to be absorbed.

That the condition of the surface soil determines the amount of
water absorbed is especially true when irrigation water is applied.
A comparatively small rain, by wetting the surface and causing the
cracks to close, often stops irrigation. There are times when it is
possible to irrigate successfully in the afternoon, when an attempt
to irrigate during the forenoon of the same day has resulted in the
run-off of practically all the water applied. _

These facts indicate that water movement through this soil when
wet is very slow.

RATE OF MOVEMENT OF WATER IN LOOSE, SATURATED SOIL.

In order to make actual determinations of the rate at which water
moves in this soil when it is saturated, the following experiment was
performed:

Sections of blotting paper were fitted, as bottoms. into a number of cans
that were open at both ends. Each can was filled with a composite sample
of a foot section of soil and then immersed in water. After the soil had
become thoroughly saturated the cans were removed from the water and placed
upon a screen. All the soil was then removed except a 3-inch layer in the bot-
tom of each can.

WATER PENETRATION IN GUMBO SOILS. 5

The time taken for an inch of water to pass through these 3-inch
layers of saturated soil was four hours for the first-foot sample and
12 hours for the second-foot sample. These results show that water
moves slowly in the saturated soil. The rate of movement in these
samples is not the same as that under field conditions, because in
the field the soil is confined and can not swell freely and is therefore
more compact than the soil in these cans.

RATE OF MOVEMENT OF WATER IN WET SOIL UNDER FIELD

CONDITIONS.

To determine at what rate water moves in the wet soil under field
conditions, the following experiment was performed on a plat that
had been fallow for several seasons. The soil in this plat was wet

Fig. 1.—Diagram showing the method used to obtain samples of undisturbed soil from
different depths by means of brass tubes.

and compact to a depth of over 3 feet. Samples were taken by
means of brass tubes 14 inches in diameter and 5 inches long, in the
manner shown in an i:

Kach of these tubes when removed was found to contain between
2 and 24 inches of soil. After being removed, the tubes were im-
mersed in water in order that they might become thoroughly mois-
tened. They were then placed in an upright position on a blotter
and filled with water. The rapidity with which water passed into
the soil was then recorded. In the tubes containing the soils from
the surface, water passed into the soil at the rate of about 1 inch
in 12 hours. In all the others the rate was uniformly much slower.
No differences in the rapidity of water movement were shown be-
tween any of the samples taken at any of the various depths below

6 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE.

3 inches. In all of the tubes containing soil taken from below the
first 3 inches the water level fell less than one-eighth of an inch in
48 hours, and part of this was due to evaporation.

The smallness of the tubes used may have caused some compact-
ing during the process of sampling; also the plat sampled was un-
doubtedly more compact than one that had not been continuously
fallowed. For this reason a part of the experiment was duplicated
on land that had been fallow for only a few months. Samples were
taken with tin cans 5 inches in diameter and with thin cutting edges.
By this means samples were taken from the surface and from depths
of 3 and 6 inches without any mechanical compacting of the soil in
sampling. -The penetration in these cans was then studied in the
same way as in the brass tubes. Water passed through the surface
3 inches at the rate of 1 inch in two hours. For the other sections
the rate was at least as slow as in the brass tubes. Evidently the soil
in the brass tubes was not compacted enough to make any material
difference in the rate of penetration except in the surface section.
Even in this section the difference in the rate was probably due in
part to the fact that in the field the surface soil in the second plat
was considerably looser than in the first one sampled.

The extreme slowness with which water passed into these sections
proves that water movement in a wet soil of this type in the field
is exceedingly slow. That this slowness is partly due to the natural
compacting of the soil by swelling is shown by a comparison of the
rate at which water moved through soil under natural conditions
with the rate at which it moved in a saturated soil that was allowed
to expand freely, as is shown in the first experiment. At any rate,
water movement in this soil when it is wet is so slow as to be prac-
tically negligible in field practice.

PENETRATION OF WATER INTO DRY SOIL IN THE FIELD.

The experiments already described indicated that in this type of
soil a dry condition was most favorable for water movement. In
order to measure the maximum water penetration in the soil, a num-
ber of experiments were made on a plat that was extremely dry. The
plat was covered with a very thin dust mulch. Beneath the mulch
the soil was cracked into very small lumps to a depth of 15 inches;
below 15 inches it was very hard, dry, and compact.

The first experiment in this series was made for the purpose of
determining the permeability of the soil at various depths. For this
purpose, borings 8 inches in diameter, extending below the surface to
depths of 6, 9, 12, 15, 18, 21, and 24 inches, were made. Two gallons
of water was then poured into each hole. A like quantity of water
was applied to an equal area at the surface by means of a tin can set
1 inch into the soil. .

WATER PENETRATION IN GUMBO SOILS. 7

The time required for the water to disappear from each hole and
the depth to which it penetrated, as measured both from the bottom

of the hole and from the surface of the ground, is shown in Table IT.

TABLE II.—Time required for 2 gallons of water to disappear from 8-inch holes
bored to different depths in the soil and the depth to which the water
penetrated.

Hole No.
Specidication
1 2 3 4 3 6 7 8
Depthvofiholenessns sis inches. -.] Surface. | 6 9 12 15 18 21 24
Time required:
IME TATTE SS ences ree pee ate 4 36 39 OOO ete eas BIA Sore Cea he ee espera
ETO MESH ERP oe ser eer ine version SP Mi uiarteasias elias he alee eee ee oh 18 23 30 24
Depth of soil penetrated ..-.-inches. . 16 19 16 10 6 43 5 6
Depth below surface to which water
MCMCLEALCd e 2 = celeeae inches. - 16 25 25 22 21 225 | 26 | 30

As the line of demarcation between the wet and the dry soil was
always very sharp, the exact depth of penetration was easily de-

NUMBER OF HOLE |

R
g
S
;
q

Wig. 2.—Diagram showing the time required for 2 gallons of water to disappear from
holes 8 inches in diameter bored to different depths in the soil and showing also the
depths to which it penetrated. The heavy lines indicate the lowest points reached
by the water from the different holes. The heavy figures below each hole indicate
the total distance from the surface and the light figures the distance below the bottom
of the hole.

termined. The plan of the experiment and the results are shown
graphically in figure 2.

A study of Table II and figure 2 shows that, at least for the cracked
area, the time required for the water to disappear depended upon
the distance from the surface of the point of application. No doubt,
this was because the water applied near the surface escaped through
eracks in the soil. That this was the case is shown by the wide dif-

8 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE.

ferences between the cracked and uncracked layers as to the time
required for the water to disappear. In all parts of the uncracked
area water disappeared very slowly.

Water penetrated to practically the same depth from the surface
in all the holes except the first and the last. In all the holes except
the first, water evidently penetrated to a point where further move-
ment took place with difficulty. That the water applied at the sur-
face did not reach the depth where movement was difficult was
doubtless due to the fact that the quantity of water was not sufficient
to reach that depth. The fact that the water from most of the holes
penetrated to a depth of from 21 to 25 inches below the surface
would indicate that a layer of impervious soil exists at that depth

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Fig. 3.—Diagram showing the depth of soil penetrated and the total distance from the
surface reached when water was Kept standing for 10 days in holes 8 inches in
diameter bored to different depths. The heavy lines indicate the lowest points reached
by the water from the different holes.

were it not for the fact that.water added at about this depth pene-
trated through as many inches of soil as did that introduced 9 inches
higher. The depth to which the water penetrated in all holes in the
compact layer indicates that the water movement throughout this
portion of the soil was very uniform. ;

A second experiment was made to determine the distance to which
water introduced into the soil at various depths would penetrate in
a given length of time. For this purpose a set of borings duplicating
those in the previous experiment was made, and water was kept
standing in each of them for a period of 10 days. At the end of that
time the depth to which the water had penetrated was measured.
The results of this experiment are shown in Table III and figure 3.

WATER PENETRATION IN GUMBO SOILS. 9

TaBLE II1.—Depth of soil penetrated and total distance from the surface
reached where water was kept standing for 10 days in holes 8 inches in
diameter bored to different depths.

Hole No
Specification. |
9 HO ety, ) Tak 12 13 ss ied 16
Depth of hole..._......._.- inches..| Surface. 6 9 12 15 18 21 24
Depth of soil penetrated - .-.- do.. 22 15 12 8 7 10 11 11
Depth below surface to which water
penetrated. 2) .2..-2..... inches. - 22 21 21 20 22 28 32 35

Water added at all points within the cracked area penetrated
almost exactly the same distance. In each case it penetrated through
the cracked soil and about 7 inches into the compact soil beneath.
Where water was applied below the cracked area the total distance
reached by water penetration varied with the depth below the surface
at which the water was applied. The distance that it penetrated into
the compact soil was quite uniform. That a constant, though ex-
ceedingly slow, movement of moisture did take place in the compact
layer is shown by a comparison of Tables II and III. These show
that for all the points within the compact layer the depth penetrated
‘when water was kept standing for 10 days was greater than when
it stood for a shorter period of time.

A third experiment was performed in order to determine as nearly
as possible the rapidity with which water movement takes place
within this compact layer and the depth in it to which varying
amounts of water would reach. A third series of borings was made
to a uniform depth of 18 inches. The amount of water added, the
time required for the water to disappear, and the depth to which it
penetrated are shown in Table IV and figure 4. The distance that
the water penetrated in each case was determined as soon as possible
after the water disappeared.

TABLE IV.—Time taken for various quantities of water to disappear and the
depths of penetration in each case from the bottoms of a series of holes 18
inches deep.

Hole No.
Specification. Tae aE ROR a SETI GS RERRET 7 SSS
17 18 19 PAD yh AL 22 23 24
Water added:
ARG SRE sie eee ani ose Ailes olin 1 2, il aeeeeaee INS BOE TAN mal Bae Nod ah RGU RAN tees corey | ce aR aay
MUTT S eae MEL ANSE AU Oe RT GOL ao 8 1 1 2 2) 4 a2
Time required to disappear
CONDI Cyr i yed es dpmie hal air Sa On Se eal 3 5 32 48 57 AU anand a
aoe Pe AS ET er eS cE 5 10 | 40 40 SO We oO las at ves upala Pee a
EET PSSE Gs Ah Sie ei ca ape es Sed On DS IS Sp a Mae FS cess col ale ee ae al ER eI eel aa Qe stl (RMA ele Ye 10
Depth te enetration below the bot- | |
tom of the hole ...........: inches. . 5 6 | 3 5 | 54 5s i. 62
oe of penetration below the sur- |
Bt Ais vers ia ian hy Meer: Sere, 2 ae UY inches 23 24 21 | 23 234 2334 23 243

a Three times.

10 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE.

The smaller quantities of water penetrated practically as deep as
the larger amounts that stood for a much longer time. In five min-

utes the water in hole No. 17 penetrated to a depth as great as was.

reached by that in some of the others in several days.

There is an apparent lack of consistency in the time required for
some of the larger quantities of water to disappear. This is due to
the fact that in some cases the amount of water added was sufficient
to raise the water level to a point that allowed it to escape laterally
through the cracked soil. This is shown also by the lack of differ-
ence in the depth of penetration of the different quantities. The
best measure of time and depth of penetration is found in hole No.
24, in which a supply of water was maintained by the addition of
2 gallons at three separate times. Ten days were required for the

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WATER ADDED /QZ
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WHE TO DISAPPEAR 572 PR euR SIR F9HR SEHR FPHR 10 DAIS

Fig. 4—Diagram showing the time taken for various quantities of water to disappear
and the depth of penetration in each case from the bottoms of a series of holes 8
inches in diameter and 18 inches deep. The heavy lines indicate the lowest points
reached by the water from the different holes.

disappearance of the entire quantity, but the total depth of pene-
tration during this time was only a little over an inch more than it
was from those holes in which water stood for a much less time.
These experiments indicate that while the water movement is com-
paratively rapid in the dry soil it is very slow in the wet soil.

Since there is no evidence of a layer of soil actually impervious to
water, it appears that the exceedingly slow movement of water is due
to the fact that the soil in contact with the water quickly becomes so
swollen and compact that further movement of water within it is
very difficuit. Penetration into the dry soil almost stops, not because
of the resistance offered by the dry soil itself, but on account of
the extremely slow movement of the water through the layer of wet
soil that is between the source of water supply and the dry soil.

ee A lt

SN ma gah nw

WATER PENETRATION IN GUMBO SOILS. 11

That this slow movement in the dry subsoil is due to the com-
pacting of the wet soil above is further shown by laboratory experi-
ments on dry soil under field conditions. It was found that where
the soil was allowed to swell freely the water would move at least
an inch in five minutes in the heaviest section of the soil. Since the
rate of movement under field conditions is so much slower, there is
no doubt that the compacting of the wet soil in the field is so great
that it renders any movement of water through it almost impossible.
Water movement in the dry subsoil is therefore limited by the rapid-
ity with which the water can make its way through the wet soil above.

SUMMARY.

Water movement in the gumbo soils of the Belle Fourche Recla-
mation Project may be summed up as follows:

On a dry soil, penetration takes places rapidly to a depth of about
2 feet because of the cracked condition of the soil near the surface.
After the layer of easily penetrated soil becomes wet, it becomes
so swollen and compact that it is nearly impervious, and further
water movement is very slow.

The fact that moisture can move only very slowly in the wet sur-
face soil would make it necessary to run water over the soil for a very
long time in order that any considerable portion might be absorbed.
This is not practicable, for the experiment with a dry subsoil showed
that water from the surface penetrated almost as deep in a few
minutes as it did in 10 days, so that the increase in the amount of .
moisture absorbed where the water stands for any considerable
length of time over that taken in when the soil is simply covered
would be so small as to be negligible. After a field has once been
covered with water little benefit can result from having water con-
tinue to stand on or flow over the soil.

It is interesting to note the radical difference in water absorption
between this soil and the sandy loam soil at Scottsbluff. The maxi-
mum rate of absorption is obtained on the wet soil at Scottsbluff and
on the dry soil on the Belle Fourche project. These diametric differ-
ences apparently are due to the physical differences between the two
soils and show clearly that a satisfactory practice on one type of soil
may not be equally successful under other soil conditions.

The results of these experiments and observations can easily be
applied in field practice, and recommendations for methods and prac-
tices may be based upon them.

The following points relative to the application of water by irri-
gation to these gumbo soils are clearly shown:

(1) Water should be applied only when the surface is dry.

(2) The quantity of water absorbed will depend upon the dryness and con-
sequent cracked condition of the surface soil.

12 BULLETIN 447, U. S. DEPARTMENT OF AGRICULTURE.

(3) After a field has once been covered with water, little further absorption
takes place, and no benefit can result from having water stand on or flow over
the soil for more than a few minutes.

(4) The depth to which the water will penetrate depends upon the depth
to which the soil has been dried and cracked.

‘The following points brought out in this bulletin apply to the cul-
tural practices for these gumbo soils under either irrigation or dry-
land conditions:

(1) No particular method of cultivation will be superior to others in infiu-
encing the quantity of water absorbed, since this depends upon the degree to
which the surface soil is dried and cracked. The soil after harvest is usually
so dry that penetration takes place very readily, and any ordinary quantity of
rain that falls is absorbed, regardless of the cultural treatment.

(2) Since the dry soil is naturally broken up to depths as great as would be
reached by either deep plowing or subsoiling, these operations can be of no great
benefit in water absorption.

(3) Some method, such as dynamiting, by which the soil below the cracked

area could be broken up, might result in a temporary increase in the depth to

which water could easily penetrate. The natural swelling of the soil, however.
would cause it again to become compact every time it was wet. This would
make it necessary for the operation to be repeated each year,. which would
involve an expense too great for this method ever to be considered seriously.

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