Terracing of farm lands

              *^c 3 State Library
NORTH CAROLINA GEOLOGICAL AND
ECONOMIC SURVEY
JOSEPH HYDE PRATT, STATE GEOLOGIST
BULLETIN NO. 17
TERRACING OF FARM LANDS
BY
W. W. ASHE
RALEIGH
E. M. UZZELL & Co., PXJBLIC PsiNTEBS
1908
TERRACING OF FARM LANDS
BY
W. W. ASHE
North Carolina State Library
Raleigh
NORTH CAROLINA GEOLOGICAL AND
ECONOMIC SURVEY
JOSEPH HYDE PRATT, STATE GEOLOGIST
BULLETIN NO. 17
TERRACING OF FARM LANDS
by
W. W. ASHE
RALEIGH
E. M. Uzzell & Co., Public Pkintees
1908
GEOLOGICAL BOARD
Goveenoe R. B. Glenn, ex officio Chairman
Henbt E. Fries....
-Raleigh.
Feank R. Hewitt..
' Winston-Salem.
Hugh MacRae Asheville.
Feank Wood Wilmington.
Edenton
Joseph Hyde Pratt, State Geologist
Chapel Hill.
LETTER OF TRANSMITTAL
Chapel Hill, N. C, March 1, 1908.
To His Excellency, Hon. Bobert B. Glenn,
Governor of North Carolina.
Sir.—The report by Mr. W. W. Ashe, Forester, on Terracing of Farm
Lands, which I have- the honor to submit for publication as Bulletin No.
17 of the North Carolina Geological and Economic Survey series, should
be of especial interest at this time when so much attention and thought
are being given to the subject of the conservation of our natural resources.
Yours respectfully,
Joseph Hyde Pratt,
State Geologist.
CONTENTS
PAGE
9 Preface
Introduction
Coastal Plain Region 12
Piedmont Plateau Region 13
Mountain Region 13
Value of the Soils of the Piedmont Region 15
Extent of Soil Erosion 16
Cause of Soil Erosion 17
Characteristics of Soils 20
Of)
Texture
Moisture Capacity 30
Humus
Effect of Erosion on Quality of Soil 31
Soils Subject to Erosion 22
Heavy Red Clays 33
Yellow Sand Clays 23
Mica Red Clays 34
Absorption of Water by 'Soils 35
Methods of Lessening Erosion 36
Dikes or Flat Dikes 36
Hillside Ditches 26
Terraced Land 36
The Mangum Dike 37
The McLendon Dike 37
Hillside Ditches 37
Terraces ^
Objections to' Terraces ~ 8
Construction of Terraces 39
Locating Terrace Lines 30
Use of Triangle 31
Building up the Terraces °'w
Levelling 33
Reclamation of Washed Land 3*
Summary 35
List of Publications 37
ILLUSTRATIONS
PLATE FACING PAGE
I. Sketch map of North Carolina showing the three physiographic
divisions and the distribution of the three geologic formations. 13
II. Deforested and terraced mountains in the Province of Shan-Si near
the city of Wu-T'ai-Hien, North China. This shows that soil
erosion and soil preservation are by no means problems local
to the Southern States. (Photograph, courtesy of Mr. Bailey
Willis) 15
III. Incipient or flat erosion largely confined to the shoulders of slopes.
Vertical gulleys are just beginning to form SO
IV. Characteristic erosion of the heavy red clays of the Piedmont pla-teau
region in which vertical V-shaped gulleys have been
formed. It is difficult to reclaim for farming purposes land
in this condition. The soil, however, is often good and some-times
can be reclaimed more profitably than new land can be
cleared 22
V. Characteristic erosion of the mica red clays and silt soils with the
formation of vertically walled gorges which has resulted in the
complete destruction of the soil for farming purposes 24
VI. a, A steep, well terraced slope in middle North Carolina. Although
the terraces are narrow, they are nearly level and erosion is
slight. (Courtesy of Bureau of Soils.) 6, Incomplete terraces
well located but too far apart, the rise between them being too
great. At least one intervening terrace should have been con-structed
28
FIGUBE
1. Triangle used in locating dikes; AB, base board 10 ft. 8 in. long;
AC and CB, side pieces 7 ft. 6 in. long; BE, cross-bar; L shows
the location of the level; plum bob hangs from C to middle of
AB; M is an inch-high wooden, projection 31
2. a, Terrace in process of formation, using level dikes and hillside
plowing. A, dike; B, lower slope or face of dike; C, upper or
ditch slope of dike, b, Completed or level terrace 33
PREFACE
The subject of terracing of farm lands is one that should be more
seriously considered by the farmers of North Carolina, especially those in
the Piedmont section of the State where the farm lands are more subject
to erosion. This is one of the methods that can be satisfactorily employed
in conserving the soil and, for certain areas, no better or cheaper means
can be devised. Where attempts have been made to use this method and
they have not resulted as favorably as expected, it has usually been that
sufficient care and attention were not given to the location and con-struction
of the terrace. They have been either too steep, too far apart,
or had too much grade on their upper sides.
These points in connection with terracing are discussed in detail in Mr.
Ashe's report and it is hoped that this short report at this time will be the
means of creating a more general use of terracing in the Piedmont
section.
Joseph Hyde Peatt,
State Geologist.
^JB^^^M^
INTRODUCTION
By Joseph Hyde Pkatt.
The subject of soil conservation is one of considerable importance to
the people of North Carolina, especially in the Piedmont section where
the soils are composed of heavy red clays, yellow sand clays and mica red
clays which are low in humus. As a general introduction to the subject
of the conservation of these soils by terracing, it may be well to give a
general outline of the physiography and geology of the State with special
reference to the Piedmont plateau section.
As one travels across the State of North Carolina, from its eastern
shores to its western boundary, it will be noticed that when about half the
distance has been passed, there is left behind a region which is very level
or gently undulating, the surface of which is covered with sand and loam
soils, from which hard rocks are almost entirely absent; and there is
entered another region, the surface of which becomes more and more hilly
until it culminates in the high mountains in the western portion of the
State, and that the soil is mingled more or less with hard, granitic, slaty
rocks. It will also be noticed that the geological formations of the
eastern half of the State are radically different from those of the central
portions of the State, which are in turn different from the mountain
regions.
These are the three great physiographic divisions in the State which
have been designated as the coastal plain, Piedmont plateau and moun-tain
regions respectively, whose boundaries in a general way are rather
sharply defined. The ages of the rock formations, instead of being con-tiguous,
are widely separated ; that covering the coastal plain being some
of the most recent formations while those of the Piedmont plateau are
amongst the oldest, with the exception of the limited red sandstones of
the Triassic areas.
These three physiographic divisions are indicated in a general way on
the map (PL I), together with the minor geologic rock formations of
the Piedmont plateau and mountain regions. In the coastal plain region
the formations have to be shown practically as a unit for the reason that
the rock formations lie one above the other so that, although there are at
least five successive geological periods, only the uppermost is exposed
except here and there in isolated places, and along the banks of such
~^-" !— *-*w^^^^^s—m
12 INTRODUCTION.
rivers as the Cape Fear and Roanoke, where these have cut down and left
high steep bluffs, exposing a number of geologic formations.
^Coastal Plain Region.—This region represents the most recent geologic
formations composed of gravels, sands, clays and marls arranged m
nearly horizontal layers with the finer material nearer the coast. Along
its eastern borders this region contains the sounds and bays, the sand
dunes and ridges, the swamps and marshes, and other characteristics of
a seashore region. Further inland it is gently undulating and has more
of the upland and less of the marsh and towards its western boundary the
swamps disappear almost entirely, the upland predominates and the sur-face
becomes more undulating and even hilly in places. The soils toward
the east are composed of fine sand and silt, while nearer the western
border of the region they 'contain a larger proportion of coarse sand or
gravel mingled with clay. The extent of this region is from Kaleigh
eastward to the coast, with its western boundaries roughly defined as
extending from the western part of Northampton through Franklin,
Wake, Cumberland, Chatham, Moore, Montgomery and Anson counties.
Along the western border of the coastal plain region there are occa-sional
outcrops of hard granites' and slates exposed along the beds of
streams, where the once overlying sands and clays have been washed away.
In the southeastern counties of this region limestone is exposed at the
surface along the banks of streams in a large number of localities.
With the exception of the extreme western portion of the coastal plain
region the subject of soil preservation is not a serious question on account
of* the character of the soil and the flatness of the land. The western
portion, however, has some problems to consider similar to the adjoining-
Piedmont region, as the land has become more hilly and the soils contain
a greater proportion of clay.
Piedmont Plateau Region,.—The Piedmont plateau region, extending
westward from the coastal plain region to the mountain region, is about
I-;, miles in width and has an average elevation approximating 900 feet.
Crossing this Piedmont plateau obliquely are a series of geologic for-mations
which arc in general parallel to the mountains and seashore.
The most eastern of these formations is a narrow belt of Triassic sand-stone
and shales which lias a maximum width of about 15 miles, and
extends from Oxford in Granville County across the State through por-tions
of Wake, Durham, Chatham, Moore, Montgomery, Richmond and
\ ,,,,„, counties. On the northeast of this sandstone and between it and
the coastal plain region there are considerable areas of granite extending
across portions of Wake, Franklin, Warren, Vance and Granville counties.
To the west there is an older formation of metamorphosed slates and
INTRODUCTION. 13
schists which cross through Person, Orange, Randolph, Montgomery,
Stanly, and Union counties and has a general width of from 20 to 40
miles. Just west of this there is an area of granites, between which and
the mountain region are gneisses, probably 'Archean. Near the western
boundary of the Piedmont plateau region is the second of the two sand-stone
belts which is much more limited in area than the one to the east
and extends from the Virginia line across portions of Rockingham and
Stokes counties, having a maximum width of from 4 to 5 miles.
It is this region that the question of preservation or conservation of soil
is of vital importance to the agricultural interests of the State and the
descriptions given in the following pages regarding terracing apply
largely to this Piedmont region, although they can be adapted to the
coastal plain and the mountain regions.
Mountain Region.—The mountain region includes the Blue Ridge,
Great Smokies, and the country between, which is cut across by 'the
numerous cross ranges separated by narrow valleys and deep gorges.
The average elevation of this region is about 2700 feet above the sea
level, but the summits of many ridges and peaks are over 5000 feet. A
considerable number of peaks reach a height of over 6000 feet, the highest
of which is Mount Mitchell with an elevation of 6711 feet. Over the
larger part of this region are to be found the older crystalline rocks,
gneisses and granites, probably Archean, which are greatly folded and
turned on their edges. On the western and eastern borders of this
mountain region approximately along the line of the Blue Ridge and
Great Smokies there are two narrow belts of younger rocks consisting of
limestones, shales, and conglomerates and the metamorphosed marbles,
quartzites and slates.
In this region, as in the Piedmont plateau, the rocks are decayed to a
considerable extent and thus have produced deep soils which vary in
character according to the rocks from which they have been derived. The
soils are for the most part porous and fertile, affording a luxuriant vege-tation,
in many places the slopes of the mountains being covered by heavy
virgin forests. Where the rocks that have decomposed contained a large
percentage of aluminous minerals, a large amount of clay has been
formed and such clay soils characterize a large portion of both the Pied-mont
and mountain regions. It is these soils that are very liable to
erosion.
X. C. GEOLOGICAL AND ECONOMIC SURVEY BULLETIN NO. \"J . PLATE II
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TERRACING OF FARM LANDS.
By W. W. Ashe.
VALUE OF THE SOILS OF THE PIEDMONT KEGION.
The soils of North Carolina constitute one of its chief natural assets.
Like the forests and the water power of the streams, they are natural
resources, which, when destroyed through short-sightedness or ignorance,
can be replaced only at enormous cost, and frequently not at all. For this
reason their preservation and utilization is of the utmost importance and
is essential to the development of the resources of the State, to their
maximum earning capacity. The conservation, therefore of such re-sources
for the welfare of the people of the commonwealth represents an
obligation which neither the State nor the individual should neglect.
Notwithstanding the rapid growth of cotton manufacturing and wood-working
establishments, agriculture still employs more persons than all
other industries. The value of its products in 1905 was $110 000 000
compared with $142,000,000 for the products of all other employments;
and there is every indication that hereafter the rate of increase in the
value of farm products will be no less than at present.
In the Piedmont section, where an exceptionally good local market is
being developed, this rate will undoubtedly increase, just as it has done m the larger manufacturing states, through the opportunities offered by
diversified farming. The values of the farming lands of the Piedmont
region are at present low, and their future appreciation will be propor-tional
to their earning capacity.
The rolling uplands of this region constitute the greatest portion of its
cultivated area. The alluvials, which form the bottoms along the streams
are of comparatively limited extent, but they are, where in o-00d condition'
far more productive than the upland soils. This is due partly to their
origin. The alluvials have been built up by the fertile sediments which
came from the hills before the timber was cut and the land 'cleared
Their enrichment comes then, in part at least, from the deposit of the
most fertile material which was washed by heavy rains from the slopes
The same process of erosion of the uplands continues to-day but with a
hundredfold more activity than existed before the forests were cut. When
the hills were forested this washing or erosion from the slopes was slight
being hindered by the leaf mould, which had accumulated and covered
16 TERRACING OF FARM LANDS.
the soil. In the change from "new ground" to "old mould field" the leaf has een exhausted, and the eroding power of the heavy r ns
Iter ni"
Jearly b0me ^^ ^ the muMy Streams- The r It not
" 7 ^^ Sl°PeS ^^ gUlHed
'
and -Poverishes all. no longer accumulates for the enrichment of the valleys • most for the valua e portion the silt and finely divided organic matters sw p
SttudtanTsMe StreamS
'
°r ^^°CCaSi0naIly Settle * **- - great mud banks. Th coarser sai](i and .
g d ited
vials injuring instead of enriching them, as was the case when only the fine black so,! was deposited. Thus erosion of the cultivated slope! de troys both slope and alluvial bottom, and what was under purely natural condemns a constructive process, has under the influence of man become menace The retaining of this fertile soil on the slopes where it is s
and silt" t 7 r^" th6ir Pr0ducti^; ^ssen the deposit of sand silt on the bottoms; and add to their earning power and value. Any system of management which will conserve the slopes will augment the earning power and increase the value of both hillside and valley!
EXTENT OF SOIL EROSION.
The erosion of soil from hillside farms probably assumes in middle ^orth Carolina greater importance than elsewhere in the United States
It is very active in portions of several of the other Southern States'
especially on the red clays of Northern Georgia and on the upland silts
of Mississippi and Tennessee. It demands greater consideration in Pied-mont,
JSorth Carolina, however, on account of the comparatively small
area of level land, necessitating extensive hillside tillage (see PI I) A very large proportion of the farming lands are situated on slopes, many
of them on steep slopes, from which erosion or soil transportation is con-tinuous.
Erosion thus becomes a problem that has to be considered on some portion of nearly every farm, while the difficulties of successfully
preventing or lessening it are augmented by the prevailing steepness of
the slopes. So general is it and so damaging in its effects that it is prob-ably
the most serious drawback to profitable farming on the « red clays »
It is difficult to determine the extent of loss occasioned by it, but on land of
moderate slope, it certainly amounts to several dollars an acre 1
- the loss
rapidly increasing as the slopes become steeper, the erosion more rapid
and more difficult to prevent, and the earning power of the land reduced
in consequence. This loss does not include the cost of maintaining dikes,
'On ,,„„ cultlvated by ,„,, ;rlter ,,„. yleldi wMh cotton
dollars ax> acre less from slop, land , from aearly ieyel land which dicl not erode
EXTENT OF SOIL EROSION. 17
or ditches, or the smaller yield on account of the land occupied by ditches,
but refers only to the smaller crop yield from land situated on slopes com-pared
with that from land in a level position (see Pis. Ill, IV and V).
It is evident, then, that when a large portion of a farm is hilly or
rolling and is subject to washing or erosion, the cost of maintaining a soil
which is tillable and free from gullies becomes a large drain upon its in-come.
The productivity is reduced by the constant removal of the most
fertile soil. The land owner must realize that every stream of muddy
water that flows from his fields lessens their fertility and, therefore, their
value.
When the soils are deep and the erosion slight, especially when it is
superficial or flat erosion, which is characteristic of the early stages on
the heavy clays, the injury is not permanent, since deeper plowing can
again give the necessary depth, and the addition of humus can replace the
dark colored top soil. But it is a costly process.
In the case of shallow soils, which are frequently eroded until the rock is
exposed, especially on the granites and the hardest gneisses of the middle
portion of the State, the soil, which has been washed away, can be re-placed
only by the slow decomposition of the underlying rock. When
much eroded, the value of such a soil is largely destroyed for farming
purposes.
Large V-shaped gullies, whether on deep or shallow soils, greatly lessen,
frequently permanently destroy, the value of the soil for farming (PI.
IV). There are thousands of acres of the red lands in middle North
Carolina which have been gullied in this manner, and their cultivation,
at least temporarily, abandoned. Fortunately much of it has been stocked
by volunteer pines, which not only have checked further erosion, but in
many cases have been the means of promoting the filling in of the gullies.
Such a system of managing farm lands, however, is economically bad.
It could exist as a system only where both land and labor were cheap, and
where fresh, newly cleared land was available to take the place of that
which has been abandoned on account of the gullies. This condition has
now ceased to exist. Labor can be more profitably employed than in
clearing new ground to replace worn and eroded fields. Moreover, the
land which has already been cleared is usually the best land, and even if
badly worn, its reclamation can generally be effected more cheaply than
new land can be cleared; while it is possible, when once reclaimed, to
maintain it by proper cultural methods, and greatly lessen or even pre-vent
future erosion.
Two other points should be considered. Forest land is just beginning
to have remunerative earning power. The steady rise in the value of
fiorth Car-r^
e LlDr*&
IS TERRACING OF FARM LANDS.
stumpage assures its continued appreciation. In many localities the pro-portion
of forest is already too low, and timber for farm use must be pur-chased.
It would seem sound policy to maintain in timber those areas
which, from steepness of slope, stoniness or shallowness of soil, are least
fit for farming.
Any addition to the area of uncultivated or waste land means more
idle capital upon which the expenses of taxes and interest must be borne
without return, while at the same time it is subject to continued depre-ciation.
A better management of smaller cleared areas, whose fertility
is carefully maintained, will yield more satisfactory financial returns.
This also affords a better indication of the fertility of the soil, more
favorably impresses settlers and prospective purchasers, and gives a farm
quicker sale and a better value.
CAUSE OF SOIL EEOSIOK
The cause of erosion is the failure of the soil, in a hilly country, to
absorb the rainwater which falls upon it.
2
If the rainfall is all absorbed,
as by a coarse sandy soil, which is largely the case in the sand hill por-tions
of Eockingham, Moore, Bladen, Cumberland, and Scotland counties,
there is no run-off and no erosion. As the soil becomes finer in texture,
more compact, and correspondingly less pervious, the rain is not absorbed
as fast as it falls, and the very smallness of the grains which form the
soil facilitates its transportation whenever there is sufficient slope. The
impact of the rain drops loosens the fine cohering particles of soil and,
unless absorption takes place, the drops gather into small streams taking
with them, as they flow, the finest particles of soil, while the larger and
heavier grains are left behind As soon as the streams gather power,
either by the added volume of water or by increased slope, they, likewise,
begin cutting loose and transporting the soil, and at a constantly accele-rating
rate, since the eroding and transporting action of water is in-creased
by the increase in its volume. It is also multiplied four times by
doubling the slope. That is, if one hill has twice the steepness of another
it will erode with four times the rapidity, provided, the soils are similar;
and it may also be stated that the difficulty of preventing erosion increases
at a yet higher rate. So rapidly does erosion increase with greater
velocity of the water, that whenever the velocity of a stream of water is
doubled, as by increase in slope and added volume, its transporting or
eroding power increases sixty-four times. For this reason the steeper
land erodes very much more easily than that of gentle gradient. Since
'i hi paragraph, with sonic changes, is taken from ;i paper by the writer, on Turbidity
of Potomac River. Bulletin 102, li. S. Geol. Survey.
CAUSE OE SOIL EROSION. 19
the steepest slope is usually on the middle of a hill, the most rapid erosion
takes place there. The heaviest transported material is deposited by the
slackened current on the more gently sloping base, or on the bottom lands,
while the lighter silt and clay is taken to the streams. For these reasons,
it is extremely difficult to prevent erosion of steep land which has a soil
like that of the micaceous clays and silts, deficient in binding power, yet
not freely permeable, or, which has a compact clay soil formed of small
particles which are freely moved when once loosened.
Erosion is more rapid in the Piedmont region than in either the coastal
plain or in the higher mountains. The nearly level topography and pre-vailing
sandy soils of the coastal plain are inimical to erosion (see PI. I).
In general, erosion is not active in the higher mountains, although the
steep slopes are favorable. This is due largely to the following reasons
:
(1) The prevailing soils are more sandy and, on account of their physical
texture, have a naturally high absorptive power for rainfall. The heavy
soils of the mountains, as the red clays, are in many places badly eroded.
The Eed Hill section of Mitchell County, the clays at Balsam Gap, the
Upper Valley of the Little Tennessee River, and the red clays of Cherokee
County, and elsewhere, have been more or less deeply seamed. (2) The
fact that grazing is extensively practiced and grass occupies so important
a place in the crop rotation contributes not a little to protect slopes.
The sod, after being grazed for several years, is plowed under and corn
planted upon it. This sod adds a large amount of humus which further
tends to promote permeability and maintain the absorptive power for
heavy rainfall. (3) In the high mountains, the coolness of the air and
the frequently high humidity are other important factors operating to
minimize the tendency to erode. These furnish conditions highly fav-orable
for the growth of grass; they likewise retard the destruction of
humus in the soil, which takes place by the natural process of nitrification
and oxidation. For this reason the humus of the soils of the mountains
is more stable than in the soils of the Piedmont. The climate determines
the condition which leads to its formation and likewise retards its decay
when once formed. This climatic favorableness increases with the alti-tude,
and is also greatest on northerly slopes.
These same reasons explain why erosion is mere rapid in the Piedmont
of the South than in the Northern States. The level surface of the Lake
States and the States of the Middle West presents fewer exposed features.
In the more broken region, of the northeast many of the widely distributed
soils are permeable. The deep freezing and thawing of winter increase
their porousness. The high humidity and cooler climate not only furnish
suitable conditions for the growth of grass, but the soils, being of lower
20 TERRACING OF FARM LANDS.
oxidizing power, tend to preserve the humus. An additional and import-ant
factor is, that, not only is the rainfall to which plowed land is ex-posed
less than in the southeast, but a considerable proportion is in the
form of snow much of which is absorbed from beneath as it melts. The
rainfall of the North is from 20 to 40 inches; that of Piedmont North
Carolina is from 45 to 55, one-third of it, 14 to 17 inches, falling during
the three summer months of June, July and August, in heavy summer
showers.
It is evident that the soils of the Piedmont are advantageously situated
for excessive erosion when compared with farming lands of the northern
portion of the Mississippi Valley and the northeast. The heavier, concen-trated
rainfall, light snowfall, long warm growing season, and high oxi-dizing
capacity of the Piedmont soils render them more exposed to erosion
than soils of the northeast with similar slopes; while the deficiency of
many of them in lateral cohesion, as the mica silts, is another favorable
factor.
These features, however, are those which give the soils of the Piedmont
their highest values. The long growing season renders possible the pro-duction
of two or even three crops of many kinds ; while the rainfall, if
conserved by storing in the soils, is usually amply sufficient for their
maturing and can be used beneficially in place of being a destructive force.
Their oxidizing capacity possibly explains their warmth and earliness,
Their ease of tillage proceeds from their friability, while their fineness of
grain is one of the important elements of their fertility.
CHAEACTBRISTICS OP SOILS.
The essential characteristics of a productive soil are that it shall have a
certain fineness of grain or texture; maintain an equable amount of
moisture ; and possess a suitable proportion of humus.
Texture.-—In general, soils of medium fine texture are the most de-sirable,
though not the strongest soils. They offer a large amount of sur-face
for root action, yet are capable of maintaining a high content of
available soil moisture. Soils of too close texture bake and puddle badly
and are difficult to work. The red clays are generally not too heavy to be
readily worked; the mica clays work easily. Soils which are too coarse
textured are leachy and dry.
Moisture Capacity.—A soil must not be too wet, as are moist undrained
bottoms. An excess of water causes lack of aeration of roots, and retards
the decay of humus. It produces the condition known as sourness. The
other extreme, a deficiency of moisture, checks growth. The upland soils
of the Piedmont suffer more from hick of moisture than from an excess.
N. C. GEOLOGICAL AND ECONOMIC SURVEY BLTLLETIN NO. 17. PLATE III
EFFECT OF EROSION ON QUALITY OF SOIL. 21
Their subsoil drainage is generally good, probably on account of the low
water table which normally stands in summer 40 to 60 feet below the
surface. Drainage is more deficient in the heavy red clays than any other
of the slope soils.
3 Nearly all of the Piedmont soils are dry during the
autumn, in spite of the usually heavy summer precipitation.
Humus.—It is by means of humus that the proper conditions are se-cured
for the development of soil bacteria, which are necessary to render
the soil's fertility available for the use of the growing crop. Humus is
also directly, or indirectly, through the growth of legumes, the source of
most soil nitrogen. It largely increases the water storage capacity of the
soil, especially the top soil, and likewise its permeability, tending to re-move
any excess of surface water, but retaining it until needed during
dry weather. It also loosens a clay soil so that it is more easily penetrated
by the roots of crops; it lessens puddling and baking of the surface, mak-ing
tillage easier and the need for it less frequent.
EFFECT OF EKOSION ON QUALITY OF SOIL.
The effect of erosion is to injure the texture of the heavier soils by
eroding the sandier surface soil. Since so large a portion of the rainfall
runs off, there is a decided loss in moisture, especially in the autumn
when it is badly needed. The humus and small clay particles being the
lightest constituents of the soil, are most easily borne off in the water.
The most evident characteristic of an eroded red clay field is its " raw-ness
" or deficiency in humus. The muddy water contains, in addition to
the humus and the fine particles of soil, a large amount of material in
solution. It has been estimated * that the amount of matter carried off in
solution in the Potomac river water, which, however, is not so muddy a
stream as those of the Carolina Piedmont, during the period of a year, is
equal to four hundred pounds of matter for every acre of farmed land
drained by the river, and the plant food in it is about equal to that re-moved
by a crop. The amount of fertilizer yearly added just about equals
the soluble matter so removed. While this soluble material is replaced
with about the same rapidity as removed, the fine particles of silt and clay
are replaced more slowly.
The conditions on the James Eiver in Virginia more closely resemble
those which exist on the streams of North Carolina. It has been esti-mated
5 that in a flood with a 10-foot crest 275,000 to 300,000 cubic yards
"Drainage of the Iredell clay soils is very deficient. The lands are too nearly level to
he subject to erosion.
* Bulletin 192, U. S. Geol. Survey, Potomac River Basin, p. 292.
6 Rept. Chief of Engineers, U. S. Army for 1885, part 2, p. 947.
22 TERRACING OF FARM LANDS.
of solid matter (earth and humus) are removed during twenty-four
hours. Since the water in the James Eiver attains or exceeds this stage
during at least 10 days of the year, in addition to many other days when
the turbidity of the water is very high, but the stage lower, there must be
from 3,000,000 to 4,000,000 cubic yards of soil washed yearly from the
farming lands on the James Eiver situated above Eichmond.
The Eoanoke Eiver probably bears as large an amount of solid matter
as the James Eiver. Only a small portion of its watershed, the Dan
Eiver, lies in North Carolina. The two North Carolina streams, of which
the best data are at present available showing the extent of erosion, are
the Neuse and the Yadkin rivers.
The influence of heavier rainfall, more broken topography and heavier
soil is noticeable in the greater erosion on the basin of the Yadkin than
on that of the Neuse. More than 850 pounds of soil are yearly washed
from every acre of land on the Yadkin Eiver above Salisbury.6 Of
this more than 125 pounds are organic matter, the balance being mineral
soil. In addition there is a large amount of plant food contained in the
matter in solution which amounts to more than 150 pounds a year from
each acre. More than 380 pounds of soil are yearly washed from the
Neuse above Selma. Of this, more than 50 pounds are organic matter.
The organic matter is humus, which must be replaced. In addition to
this solid matter there is a large amount of soluble salts washed out,
amounting to more than 100 pounds per year from each acre.
The soil and soluble matter yearly washed in the rivers from the Pied-mont,
North Carolina, with an area of about 12,000,000 acres, certainly
amounts to more than 4,000,000 tons, and the plant food in it has a
value of more than $2,000,000.
SOILS SUBJECT TO EEOSION.
While there is no soil type in the middle portion of North Carolina free
from erosion, it is more active in some types than in others. Since it is
primarily due to the failure of the soil to absorb heavy rainfall, which
instead collects into flowing streams, it is the fine-grained, closely textured
soils that are most subject to it. As the soil becomes more porous, by the
grains being larger, the rainfall is more quickly absorbed and a heavier
precipitation is required to produce a surplus and cause run-off. The
actual capacity of a clay soil or fine silt for water is greater than that of
a sandy soil, since its pore space is greater. The difficulty is, as King
"Amount of mineral matter eroded from the watershed of Yadkin and Neuse rivers is
based on the turbidity record of tin- TI. S. Geol. Survey. Organic matter based ou
analyses by N. C. Geol. Survey.
N. C. GEOLOGICAL AND ECONOMIC SURVEY BULLETIN NO. \"J . PLATE IV
X s
a X
X
ffi > 5
SOILS SUBJECT TO EROSION. 23
has pointed out, that a heavy rain, especially a summer shower on a dry
soil, quickly puddles the surface of the soil and the absorption of water
is checked until the air can be gradually expelled. This takes place far
more slowly on the heavy clays than on the open sands.
Erosion then, attains its maximum on steep slopes, with heavy clay
soils deficient in humus; and it is at a minimum on level sands.
The three classes of soil which are most subject to erosion are the heavy
red clays, the yellow sand clays, and the micaceous (isinglass) soils.
Each of these erodes in a characteristic manner.
Heavy Red Clays"—These clays are frequently nearly homogeneous in
texture, that is, have their grains nearly of a size, although they contain a
variable amount of coarse sand, the proportion of which is large in the top
soil of the loamy phases. In its early stages, erosion of the heavy red
clays takes place as broad shallow "washes," or "galls" especially on
shoulders of the slope, or the steepest points. Plate III shows character-istic
incipient erosion of this character. When constant tillage is taking
place, these are " galled," " washed," or worn spots of the fields, and they
are indicated chiefly by their unproductivity. A deficiency in humus is
often evident. Later stages of erosion seam these soils into parallel V-shaped
gullies which may ultimately descend from near the summit to the
foot of even moderately gentle slopes. Plate IV illustrates an advanced
stage of erosion, when value for agricultural purposes has been largely
destroyed.
Yellow Sand Clays (Cecil Loams in Part).—These erode in much the
same manner as the heavier red soils, but usually less easily. They are
not homogeneous in texture, but contain a considerable amount of coarse
sand with very fine-grained clay,
8 and generally have a naturally low
7 The behavior of the soils of Piedmont North Carolina towards erosion, seems to be
slightly affected by their origin. The clays, whether from hornblende-gneiss, diorite,
serpentine, gabhro, or other basic rocks, erode similarly to those from the granites and
acid rocks. Those soils richest in available potash and lime are usually more productive
than those deficient in these materials if physical condition is the same. They will
consequently often contain more humus and exhibit less erosion on gentle slopes. Other
qualities being the same, the texture is, apparently, the determining factor.
The red clays of the Piedmont are classified by the U. S. Bureau of Soils, as Cecil
clays. As they become sandier they are referred to lighter members of the Cecil series.
When they are derived from mica-schists, and contain a large amount of finely divided
mica, they are classified as Cecil silts, or Cecil mica loams. These are the mica red
clays. The soils derived from sericite and talc schists have much the same texture and
erode in the same general manner as the mica soils.
8 It is probable that the mixture of sand and clay in some of these soils is in the
same proportion as that used in the construction of the sand-clay road. Enough fine
clay is present to fill the interstices between the sand. Such a mixture was noticed by
Orris Brown of Norfolk, Va., to make a road, the surface of which was almost imper-vious
to rains, and the mixture has been found natural in many places in the Southern
States by the Oflice of Public Roads. Soils having their sand and clay content, about
g>4 TERRACING OE FARM LANDS.
humus content, Erosion is active even on the gentlest slopes, forming
V-shaped gullies much like those of the heavy red clays, but broader. The
heavv sand content of this soil is frequently deposited as a sand bar, or
fan over the more level land at the foot of the slope, or on the bottoms.
The sand-clay soils are not generally distributed, but occur most abund-antly
in the eastern part of the Piedmont where they are tobacco and
cotton lands. They extend in the Eoanoke Kiver section well down into
the coastal plain. A phase of these soils, which is much prized for farm-ing
is the grav loam or sand top soil with a clay subsoil.
Mica Red Clays (Cecil Silt Loams, etc.).-Clays of this type are more
seriously affected by erosion than any other soils of North Carolina. They
contain in addition to the mica, which is extremely finely divided, a large
amount of other silty particles which, with a lack of horizontal lami-nation
render the soil decidedly deficient in cohesive qualities. On ac-count
of their silty character, they are permeable soils, and, under good
tillage and with a large humus content, erosion is largely restricted to
uniform soil transportation—a considerable amount of muddy run-on-occurring
during heavy rains, but few definite gullies being formed.
When gullies once form, however, and are not promptly checked by proper
cultural methods, erosion proceeds rapidly even on most gentle slopes;
the gully deepens rapidly towards the drainage line and recedes on nearly
the same level to the initial point of erosion. On account of the loose,
friable nature of the silt and red micaceous soils they are readily under-mined
by running water and present in the later stages of erosion deep,
vertically walled gorges. Since the mica-schist, from which this is
derived, has decayed to a great depth, frequently to the natural drainage
plain at depths of 50 to 60 feet, the bottom of the eroded gorge lies on a
level with the draining stream. Plate V shows a characteristically eroded
gully in the mica clays. Immediately along the foot of the Blue Ridge
ITtto proportion of the sand-clay road mixture would have low permeability, and be
BUTLmTTTo cTarcontent, not only in this soil, but in the beavy red clays as
wen Und probably a much larger proportion in the yellow clays in the beeswax and In
SSwSad^oS) 11 extremely fine grained or colloidal In texture. This clay is so
S?SS"it settles with the greatest slowness even from perfectly quiet water. It is
Z;• cause of t£^haVacteristfc turbidity of Piedmont streams even during dry seasons
nS^*2y?SJ^"« ^S« areas of unconsolidated silts which erode
w,tn even greater facility than these soils. Since they are subject, however to only
nf ,,,Tn" r n thev are not affected by surface erosion. They are easily undermined
infrequent *»™^™£ rf dniwbnck to the maintenance of Irrigation
«tcS A iSTJS ofthe excessive turbidity of western streams during high water
" I,;,,,' "such soils, the silt burden In these streams at times -»"£*» u
muctL as r, per cent, Only in Mississippi and western Tennessee are
,
then to be
Sund in the east silt soils more disastrously affected by surface erosion than the mica-clays
of the Carolina piedmont.
N. C. GEOLOGICAL AND ECONOMIC SURVEY BULLETIN NO. \"J . PLATE V
j*r
*&+
Jm
V:
::\
CHARACTERISTIC EROSION OF THE MICA RED CLAYS AND SILT SOILS. VERTICALLY WALLED GORGES
ARE QUICKLY FORMED IN THESE LOOSE SOILS WHEN UNDERMINING ONCE BEGINS, RESULTING IN THE
COMPLETE DESTRUCTION OF THE SOIL FOR FARMING PURPOSES.
ABSORPTION OF WATER BY SOILS. 25
there are extensive areas of such soils. Similar areas, but smaller, occur
locally eastward to the very edge of the coastal plain. While usually not
distinguished from the other red clays, the presence of the mica or the
small particles of sericite or talc, the sparkle of which is very noticeable
in the soils when dry and reduced to dust, and the slightly greasy feel
which is also due to the mica or talc schist, will serve to identify them.
These soils are very friable and far easier to cultivate than the heavy
clays. They drain more freely and puddle more lightly, but form a heavy
sticky mud when wet; become dry relatively more quickly after heavy
rains; and crumble rather easily when dry; are warmer and earlier but
difficult to maintain at a high productive capacity on account of the rapid
oxidation of humus.
These three broad classes are the most extensively distributed types of
heavy soil which lie on slopes in middle North Carolina. As these soils
pass into sandy or gravelly phases, there is a corresponding increase in
permeability to rainfall and lessened erosion, though even the sandy loams
in the Piedmont, when underlaid by compact, less pervious subsoils (gray
topsoil with clay subsoil) erode to some extent because the porous topsoil
lacks depth. It is evident, therefore, that with few exceptions the soils
of the Piedmont erode whenever the slope is favorable.
Since erosion is primarily due to the failure of the soil to absorb rain-fall,
followed by rapid flow of the accumulated surface water, it can be
lessened by any means which will promote absorption or lessen the
rapidity of the run-off.
ABSORPTION OP WATER BY SOILS.
The usual means for promoting absorption of rainfall by soils are by
deeper plowing and by increasing the amount of humus in the soil. Both
of these practices are undoubtedly advisable in managing most lands.
Humus is secured by manuring or by plowing under a green crop. The
increase of the humus content is particularly demanded on the heavy
soils, although for certain crops it is inadvisable to add too large an
amount of organic matter. The texture of bright tobacco is injured by
an excess of humus, especially of legumes; rye humus is not injurious.
Corn may preceed tobacco on a legume humus. When present in large
quantities, humus produces, in the short growing season of most portions
of Piedmont North Carolina, too weedy a cotton stalk, delaying maturity
and lessening the amount of the top crop. This last condition, however,
is infrequently realized and on most soils devoted to cotton culture a very
large addition to the humus content can be made with the certainty of
increasing the yield of cotton as well as lessening the tendency of the soil
26 TERRACING OF FARM LANDS.
to erode. The excess of nitrogen in legume humus may be balanced for
cotton by the use of fertilizer deficient in nitrogen. It has recently been
pointed out by the Georgia Agricultural Experiment Station, from ex-periments
carried on in that State, that plowing deeper than 8 inches
tended to lessen the yield of cotton. Comparatively little land prepared
for cotton in North Carolina is plowed to that depth, however, and even
plowing to that depth could do much to increase the water-carrying
capacity of the soils subject to erosion. But, as a matter of fact, only a
small amount of land in the Piedmont is plowed even 6 inches deep, while
much of it is not plowed deeper than 4 inches. While it may be true that
it is not advisable to plow to a greater depth than 8 inches for cotton,
this is not true in regard to either corn or peas, which make greater
demands on soil moisture than cotton. The low yields of corn especially
can be attributed more largely to a deficiency of soil moisture than any
other reason. A wet growing season invariably means a heavy corn crop
on the uplands of the Piedmont.
METHODS OF LESSENING EEOSION.
With the heavy concentrated rainfall which frequently takes place in
the South, neither deep plowing nor an addition of humus can be relied
upon to prevent erosion, although on land with only a gentle slope they
considerably lessen it. Precipitations of 2 to 3 inches within an hour's
time are not infrequent in summer showers, and they occasionally fall on
earth which still contains a high percentage of water from previous rains.
Theoretically, a soil in good tilth, deeply plowed, and containing a large
amount of humus can absorb 4 to 5 inches of rainfall. The concentrated
precipitation, however, which occurs in the South, frequently so compacts
the surface that absorption is retarded and rapid run-off takes place, pro-ducing
erosion. This condition has necessitated various artificial methods
of soil conservation by terraces, hillside ditches, and dikes.
Dikes or Flat Dikes.—These consist of broad low mounds located
nearly on a level, the cultivated rows in tilled crops crossing them. They
are adapted only to land of gentle gradient.
Hillside Ditches.—These are channels supported by a strong embank-ment
on the lower side. They are used on land of steeper grade for re-ducing
erosion by collecting the water on strips between the ditches and
conducting it through the ditch at a reduced fall, and consequently with
lower eroding power, to a convenient hollow where the ditch empties.
Terraced Land.—In terracing, the land is built up in a series of steps,
the intervals between the steps or rises being nearly or quite level (Pis.
II and VI, A and B). Incomplete terraces are those in process of de-
METHODS OF LESSENING EROSION. 27
velopment, the rises being slight and the slope of the intervening strip yet
relatively steep. There is little or no run-off and no erosion from com-pletely
developed terraces.
There are two methods of diking used in North Carolina, neither un-fortunately
being very extensively employed. One is the Mangum dike
(called terrace) which is adapted to land of only the most gentle slope.
The other is the McLendon dike which can be used on somewhat steeper
land.
The Mangum Dike.—This dike should be 4 to 5 feet broad and not
less than one foot high on gentle slopes, the height increasing to 2 feet on
hillsides the slopes of which amount to one foot in fifty, the maximum
grade on which it should be used. It should have a fall of not more than
one-half inch to the rod. When tilled crops are planted, the rows which
cross the dikes obliquely should be so laid off as to have no greater fall
than the dikes.
The McLendon Dike.—Steeper slopes can be cultivated by use of this
dike. It is located on a level and built up very broad, 10 to 15 feet at
base and 18 to 24 inches high. The rows are run in cultivated crops on a
level, along the dike as well as on the intervening strips.
Dikes require strengthening every year as there is always some erosion
from the lower slope and the upper slope tends to become level. The fall
between two adjacent dikes should not exceed 3 feet.
Their use permits, when the surface will allow it, the cultivation of
large fields having gentle slope without division into smaller areas, which
is a necessary practice when terracing is required. There is no wasted
land, as is the case with ditching and terracing. Diking, as already
stated, is adapted only to the most gentle slopes ; while deep plowing and
a high content of humus to maintain mellowness and promote absorption
are necessary adjuncts. Diked land tends to develop into a terraced sys-tem
and would, if it were not that constant cultivation across the dike
prevented the building up of the outer face.
Hillside Ditches.—These ditches are located with a sufficient fall to
drain the water rapidly. Their spacing is closer the steeper the slope.
The ditches are reinforced by a strongly built dike on the lower side.
They limit vertical erosion, but erosion continues to take place in the
ditches.
On land of gentle slope, diking is superior to hillside ditches, while on
steeper slopes terracing is superior. Ditches are objectionable on land of
any character. On gentle slopes they increase the cost of tillage above
dikes and add a considerable proportion of waste land; on steeper slopes
they do not prevent erosion, since soil transportation, flat erosion (PL
28 TERRACING OF FARM LANDS.
Ill), proceeds continuously, constantly removing the finer particles of
soil and humus, and draining off the water, which is one of the most essen-tial
elements of fertility. An examination of many farms on which dik-ing
and hillside ditching are practiced leads to the conclusion that hill-side
ditching should be entirely abandoned, no matter how gentle the
slope of the ditch ; and that diking is applicable only to lands of the most
gentle gradient.
Terraces.-—It is usual to develop terraces gradually by means of high
dikes located on a level, or nearly so. In their method of construction
they are similar to hillside ditches, but are deficient in fall. Unfortu-nately,
most of the so-called terracing is not such, and is planned in such
a way that its efficiency is seldom greater than that of ditches laid off
with a fall of 1 to 3 feet to the hundred feet, a sufficient fall to remove
not only the water but a large amount of fine soil. Erosion continually
takes place and terraces fail to develop.
Terracing rightly planned and well executed is so infrequent as to be
noteworthy ; and this is especially so when the gradient of the land is at
all steep. There have been some well terraced farms in this State and a
few are yet to be seen, but too frequently they have been poorly planned
or poorly developed, and have failed to produce the results intended.
As is seen from PL II, soil erosion and soil preservation are by no means
a problem local to the Southern States, but is common to all countries
with heavy intermittent rainfalls, hilly lands and close soils. In China
the preservation of the soil on hills and mountain slopes has been effected
only by terracing. Slopes not so protected have been destroyed by less
than three centuries of continuous tillage. The question arises with us
as to how our slopes will look after 300 years of corn and cotton culture.
OBJECTIONS TO TERRACES.
The chief objections which can be urged against terraces are:
(1) There is a considerable proportion of waste land. This is less,
however, than with ditches.
(2) The banks harbor weeds. This is also the case to a less degree
than ditch hanks, sinco only one face is exposed for their growth.
(3) There is difficulty in getting a team from one terrace to another.
This can be obviated only by leaving a small strip at each end of the field
unterraced and kept in good turf. Turnings of the team can be made on
it. In California, hillsides are sometimes terraced for irrigation. This
requires the intervals between the rises to he well levelled, yet by means
of the slope at one end teams and farm tools are readily moved from ter-race
to terrace.
N. C. GEOLOGICAL AND ECONOMIC SURVEY BULLETIN NO. 1
7
'. PLATE VI
A. A STEEP, WELL TERRACED SLOPE IN MIDDLE NORTH CAROLINA. ALTHOUGH THE TERRACES ARE
NARROW, THEY ARE NEARLY LEVEL, AND EROSION IS SLIGHT. (COURTESY OF BUREAU OF SOILS.)
INCOMPLETE TERRACES WELL LOCATED BUT TOO FAR APART, THE RISE BETWEEN THEM BEING TOO
GREAT. AT LEAST ONE INTERVENING TERRACE SHOULD HAVE BEEN CONSTRUCTED.
CONSTRUCTION OP TERRACES. 29
These drawbacks are more than offset by the gain from increased
yield and the greater ease of maintaining soil in good tilth. It is possi-ble
that in some very heavy soils terracing might make soils too wet for
early spring plowing. If this should take place in any case it could
easily be corrected by blind drains, either of tile or of green pine poles.
CONSTRUCTION OF TERRACES.
Terraces are largely developed by means of erosion, the very agent they
are intended to lessen. The earth which is scoured from the slopes is
deposited at the foot of the slope unti] aggrading has proceeded so far
that erosion no longer takes place. The rapidity with which the deposit
accumulates before leveling has reduced the slope, shows the extent to
which erosion was taking place under open slope cultivation.
There are four very important stages in the development of terraces as
follows
:
First. To locate on a level, or nearly so, lines which follow the slope.
The rise between each line, on which the terrace will subsequently be
developed, should, at a maximum, not exceed 4 feet. The lines are approx-imately
parallel.
Second. To construct with plows a strong dike or embankment of
earth on the lines which have been located. A ditch is on the upper side
or inside of the dike. As earth eroded from the slopes accumulates in the
ditch it is used for increasing the height of the dike, until the leveling
process is completed. If Bermuda grass is abundant the dike should be
turfed with it. If it is not, red top or meadow oat grass should be used,
or even one of the hardier vetches to give protection during winter and
spring.
Third. To constantly watch and strengthen these dikes, especially
during and after rains, until they have become thoroughly consolidated
and turfed, or, until the slope has been greatly reduced by leveling. Holes
made by mice, moles, rats and sometimes muskrats must be carefully
noticed and stopped.
Fourth. To plow so as to turn the soil only towards the lower dike.
This facilitates the leveling, lessens the danger of breaks in the banks,
and prevents an undue deposit of the most fertile surface soil in the ditch
on the upper side of the dike as the. process of leveling by filling proceeds.
In order to develop terraces which are nearly level from the outer crest
of one terrace to the foot of the one above, the rise between the two
adjacent terraces should never exceed 4 feet, and on gentle slopes a rise of
3 feet is more advisable (see Fig. 2). When there is danger of an ex-cessive
accumulation of water it is preferable to have low rises and develop
30 TERRACING OF FARM LANDS.
temporary intermediate terraces which can be plowed tip when the. em-bankment
of the permanent terrace becomes well consolidated and turfed.
Many of the terraces on the State farm near Columbia, South Carolina,
on a sandy loam soil, rise more than 4 feet, and in spite of their steep,
almost vertical slopes, are so well turfed with Bermuda grass that they
hold with no indication of weakness. When it is considered necessary to
have a slight grade to the ditch on account of large collection of water,
the fall should not exceed J inch to a rod, and preferably £ inch. A fall
of this amount will remove a large quantity of water very quickly, yet
will allow some sedimentation of silt and clay, at least during moderate
rains. If a greater fall than this is allowed a ditch is developed. The
velocity of the water is too rapid to allow sedimentation except of gravel
and coarsest sand, while the silt and light organic matter, which are the
most valuable portion of the soil, are borne off in the muddy water to the
impoverishment of the land.
The work of locating terraces should begin at the foot of the slope.
The work of construction of dikes and ditches should begin with the upper
terrace.
Locating Terrace Lines.—The lines of terraces can be laid off either
with a surveyor's theodolite or transit ; or a more simple home-made tri-angle,
furnished with either plumb bob or level, can be used. The method
of laying off the lines of terraces with a transit requires no explanation.
It is important, however, that every land owner should know how to cor-rectly
lay off his own dikes. He can do it satisfactorily with the
triangle.
The triangle 10 should be made of sound, well-seasoned lumber with
straight edges, and should be sufficiently rigid to be handled without
bending (fig. 1).
On a base 10 feet 8 inches long, of 1 x 4 inch board, complete the tri-angle
by using two pieces 7 feet 6 inches long. The pieces should be so
nailed that it will be 10 feet along the top of the base board between the
inside of the two sides. It should be 7 feet -| inch on the inside of each
of the sides.
Lay off 3 feet 8 inches above the base board along the inner edge of the
sides and carefully nail a cross bar joining the two short sides so that its
upper edge will be exactly at the 3 foot 8 inch mark. This cross bar must
be a straight edge.
If a plumb bob is used, it can be hung from the angle made by the
hort sides. When the base is level it should hang in its center and this
10 Triangles of this kind ;i r<- used In the west for grading Irrigation ditches. See
Newells' Irrigation, p, 106,
CONSTRUCTION OF TERRACES. 31
should be marked. A vertical board from the base to the apex of the
triangle, with broad staples in it through which the plumb line can
swing, will limit the swing of the plumb bob and facilitate handling the
triangle.
If a level is used, it is fastened to the center of the cross bar. It should
be tested and adjusted before being fastened. If the cross arm has been
correctly put on, when the bubble is in the center of the level the base of
the triangle will be level. The level should be so fastened as to leave a
narrow edge of the top of the cross arm clear for sighting. A projecting
block one inch long should be nailed at the bottom of one end of the
base board (M of fig. 1). The projection of the peg on which the other
end rests should also be one inch. The block lessens the trouble with
stones, clods, etc. which would be in the way of the base board.
j^ 10 6 n
Fig. 1.—Triangle used in locating dikes. AB base board, 10 feet 8 incbes long. AG
and CB side pieces, 7 feet 6 incbes long. DE cross-bar. L sbows tbe location of the
level. Plumb-bob hangs from G to middle of AB. M inch-high projection.
Use of the Triangle.—If it is intended to lay off level lines for dikes
or embankments, the triangle is ready for use. Flat-topped pegs 6 to 8
inches long should be provided. One will be required each 10 feet;
though if the curves are large, intermediate ones can be removed as the
work proceeds.
The triangle is used in this way for level lines. A peg is driven until
its top is within 1 inch of the ground, or the height of the projection on
the base of the triangle. The end of the base of the triangle with no
block is placed on this peg. The end with the block is moved until the
plumb or bubble in the level shows the base to be on a level. A peg is
then driven at the point where the projecting block is, its depth being
adjusted until the triangle reads level. The triangle is then moved for-
33 TERRACING OF FARM LANDS.
ward the end without the projecting block being placed on the last pe«r and the operation is repeated. The tops of the rows of pegs will each pro-ject
1 inch above the earth and will be on a level.
If it is desired to lay off the lines for the embankment with a fall the
short sides of the triangle must be of different lengths. For a fall of 1
inch in 10 feet let the distance to the cross arm be shortened to 3 feet
? 11/16 inches on one side. For. a fall of i inch in 10 feet, let the dis-tance
be shortened to 3 feet 7 25/32 inches on one side of the triangle
Let the distance on the other side remain 3 feet 8 inches. The short end
should be marked. In laying off, the short end will be the higher, and the
slope will be from that end. The inch block shonld be at the long end The same method of laying off is followed which has already been
described.
The approximate rise between terraces is also determined by means of
the triangle Turn it at right angles to the terrace which has just been
laid off and level it carefully on pegs, letting one end of the base board
res on one of the line pegs. A sight along the cross bar towards the hill
will then locate a point 3 feet, or the height of the cross bar, above the
terrace line just located.
When there are outcrops of large tight rocks, the terrace should pre-ferably
be located to include them. If their projection above the surface
is slight, they may be located above the dike, since they will be so deeply
buned in the course of leveling as not to interfere with plowing If
their projection is such that they will not be covered to a depth of at least
one foot, they should be left below the terrace.
BUILDING UP THE TEREACES.
The method of dike or embankment construction is generally too well
understood to require explanation (see Fig. 2). Earth should be thrown
with the plow on the located line from both lower and upper sides. Large
loose stones can advantageously be piled along the located line before plowmg. The embankment should be built especially strong in the hol-lows
and "swags" where a large volume of water rapidly gathers fre-quently
with high momentum, and where both undermining and over-washing
are most likely to take place. It is frequently advisable to
strengthen such pouts at the upper convex side by making a facino- of
inch boards, driven vertically side by side into the earth. Where the em-bankmenl
dike rounds the crest of a sharp ridge, the deep concave bend on
the upper side is extremely likely to erode if the ditch of the terrace has
;""
r
r;
',
" t0 lL The wc;akeRt Point is at and just below the center of the
l '"'" 1 "*ew the -rod,,,,, power of the water, as it changes its course, is
BUILDING UP THE TERRACES. 33
greatest. A facing of boards will frequently be advisable bere. Stone
can often be used in place of boards.
Dikes sbould be constructed with the largest plows available. The field
should be plowed at the same time that dikes are made. This increases the
absorptive capacity of the soil and lessens the possibility of breaks in the
dikes, which are weak for the first year until thoroughly consolidated. In
plowing the strips between the dikes there are many short furrows. It is
preferable to locate these short furrows either in the middle of the strip
or against the upper dike. Since there is always some fall from the short
furrows, the drain from them, if they open against the lower dike, tends
to increase the quantity of water which accumulates against this dike.
This is more essential in laying off for tillage than in plowing.
The weak point in the current practice is that the ditch is given too
much fall and there is consequent failure of the filling or leveling process.
c
b
Fig. 2 a.—Terrace in process of formation, using level dikes and hillside plowing.
A, dike. B, lower slope or face of dike. G, upper or ditch slope of dike. b. Completed
or levelled terrace.
Frequently, after an interval of ten years, the ditch is yet open, being
scoured clean by each heavy rain; and, since the hillside slope has not
been materially reduced, destructive erosion is yet taking place. More-over,
unless filling takes place, ditches and dikes must be kept in repair
at considerable cost.
Leveling.—Leveling can be hastened by the use of hillside plows.
These differ from the plow in general use by having the mold board
reversible. This permits the earth from every furrow to be turned down
the slope. By using this plow the first furrow is turned into the ditch of
the lower dike, while the last is turned away from the base of the upper
dike. This greatly quickens leveling (see Pig. 2). An additional advan-tage
is that there are no furrows up and down the slope which are subject
to gully, and, since plowing is on a level, the draft is easier on the team.
There is also no dead furrow or balk.
34 TERRACING OF FARM LANDS.
There are three general types of plows which are adapted to work of
this character
:
1. The Walking Hillside Plow.—The mold board of this plow is re-versed
by hand at the end of each furrow. This permits plowing very
close to dike banks and is especially suited to small or narrow terraces.
This plow is usually made in a two-horse size. It is adapted to level as
well as slope lands, and can be used without turning the mold board if it
is desired to do so. When only one heavy plow is used, it should be one
of this character.
2. The Reversible Dish Plow.—These plows are sulky, made in two,
three or four-horse sizes. They cut deep and wide, but are not suited to
very stony land, since their cutting is on the principle of the disk harrow.
They do well, however, on heavy clays. They do not admit of plowing
quite so close to the dikes as with the hand plow. An additional point in
their favor is that having no landside, they do not tend to compact the
bottom of the furrow as do landside plows. The reversible disk plow is
extensively used in northern Georgia.
3. The Two-share Mold Board Plow.—This plow seems to be made
by only one American firm. It is adapted to a greater variety of soils and
conditions than the disk plow, and there is a place for it on every large
farm with an extensive area of gentle hillslide land. It is a sulky plow,
made in two and three-horse sizes, with two shares, right and left, either
of which can be raised by a lever enabling all the furrows to be turned
in the same direction.
RECLAMATION OF WASHED LAND.
There are two classes of eroded land. One can be reclaimed profitably
for farming purposes ; the other cannot. Land to be profitably reclaimed
must not be too deeply gullied; the soil must be of good quality, and
have so moderate a slope that it can be terraced. A satisfactory method
of filling gullies is to place in them small pine boughs with the stick por-tion
turned down the slope. Grain straw can be substituted for the pine
bough. Plow deeply the strip intervening between the gullies, lifting
the plow across the gullies; then harrow. Both plowing and harrowing
should be entirely on a level, never up and down the slope. Plant at once
in field peas, using, if broadcast, not less than 5 pecks to the acre. In
early fall turn under the pea vines and plant at once in rye. The fol-lowing
spring terracing should be begun.
Land which is too badly washed or too steep, too1 rocky or shallow-soiled
to be reclaimed for farming purposes, should be planted in trees.
The native pine is one of the most satisfactoiy trees. Seedlings 1 to 2
SUMMARY. 35
feet high taken from fence rows, old fields or very open woods should be
used. Lay off on a level deep furrows 5 feet apart. Plant the trees 5 feet
apart in the furrows, placing them no deeper than they stood at first.
Press the earth firmly around the roots of the trees with the feet. Plant
a row in the bottom of each gully. Red and black oak can be used in
place of the pine, or mixed with it. If a large number of tree seedlings
have to be used they can be cheaply grown. Write to the State Geologist,
Chapel Hill, N. C, for directions for growing seedlings and planting
trees on washed or other waste land.
' SUMMAKY.
Terracing is more than an artificial means of preventing erosion. Its
beneficial effects may be summed up as follows
:
1. A reduction in the constant cost and labor of maintaining a tillable
surface soil which is free from gullies.
2. An increase in general fertility.
a. By an addition to the available soil moisture through soil storage,
by lessening run-off, especially of summer rains.
~b. By an increase in the humus content. Humus is one of the chief
elements of fertility and is one of the means of storing moisture. It also
retains much of the valuable soil solution which is lost in a soil deficient
in humus.
c. By reducing the loss of soluble plant food and of the finer particles
of soil. A portion of this loss is yearly replaced by commercial fertilizer.
3. There is a corresponding increase in land values.
4. In addition to reducing erosion, there is another urgent requirement
of the soils of middle North Carolina. This is humus, the organic or
manural portion of the soil. On account of the much greater loss of soil
moisture by evaporation, this constituent must be larger in southern soils
than in northern soils of the same texture. Terracing conserves the
water, but the texture of the soil must be such that absorption of the rain-fall
must take place rapidly and without puddling or baking the soil.
Deep plowing in connection with this is also necessary to give greater
storage capacity, lest soils, after heavy rains, remain too wet for working.
Since few cattle are kept in the south, the manure is insufficient for
maintaining humus. In the cattle-raising sections the grass sod, grass
being one crop in the usual rotation which is plowed under, also adds a
large amount of humus. In Piedmont, North Carolina it is necessary to
plow under a green crop to secure this. The North Carolina Department
of Agriculture has issued several valuable papers on this subject. The
most valuable crops to plow under are legumes, which include clover,
36 TERRACING OV FARM LANDS.
peas, vetch, beans, or rye. Of these, perhaps crimson clover, cow peas,
and rye are best suited for middle North Carolina. They should be used
in connection with a definite system of rotation. The humus crop should
follow the cotton or tobacco crop, since an excess is often injurious to
these crops; deepest plowing should be for com, if it proves true that
this lessens the yield of cotton. Deep plowing means from 8 to 10 inches.
There is another aspect of erosion in which the land owner is less per-sonally
interested, though it cannot but affect him. A part of the silt and
sand from the slopes destroys his bottoms. The other portion of it is
swept past in the streams. Some settles in the reservoirs of dams and re-duces
the value of the water power of the streams and affects the indus-tries
dependent upon them. A portion settles further down in the chan-nels
of the navigable rivers, lessening their value and rendering naviga-tion
hazardous. While still another portion forms a part of the silt bars
in the harbors, reducing their depth and necessitating constant dredging
to maintain depth of harbor. The silt, clay and sand burden of the
streams of the Piedmont probably amounts to more than 4,000,000 tons
a year, the greater portion of which comes from the farms. The welfare
of the entire State demands that this enormous quantity of soil, rich in
humus, and in soluble plant food, be retained on the farms to maintain
their fertility and not permitted to be washed into the rivers to destroy
their earning value. Natural resources, when once destroyed, cannot be
replaced. The civilization of a people is determined by the advantageous
use they make of the gifts of nature.
PUBLICATIONS
OF THE
NORTH CAROLINA GEOLOGICAL AND ECONOMIC SURVEY.
BULLETINS.
1. Iron Ores of North Carolina, by Henry B. C. Nitze, 1893. 8°, 239 pp., 20
pi., and map. Postage 10 cents.
2. Building and Ornamental Stones in North Carolina, by T. L. Watson and
P. B. Laney in collaboration with George P. Merrill, 1906. 8°, 283 pp., 32 pi.,
2 figs. Postage 25 cents. Cloth-bound copy SO cents extra.
3. Gold Deposits in North Carolina, by Henry B. C. Nitze and George B.
Hanna, 1896. 8°, 196 pp., 14 pi., and map. Out of print.
4. Road Material and Road Construction in North Carolina, by J. A. Holmes
and William Cain, 1893. 8°, 88 pp. Out of print.
5. The Forests, Forest Lands and Forest Products of Eastern North Caro-lina,
by W. W. Ashe, 1894. 8°, 128 pp., 5 pi. Postage 5 cents.
6. The Timber Trees of North Carolina, by Gifford Pinchot and W. W. Ashe,
1897. 8°, 227 pp., 22 pi. Postage 10 cents.
7. Forest Fires: Their Destructive Work, Causes and Prevention, by W. W.
Ashe, 1895. 8°, 66 pp., 1 pi. Postage 5 cents.
8. Water-powers in North Carolina, by George F. Swain, Joseph A. Holmes
and E. W. Myers, 1899. 8°, 362 pp., 16 pi. Postage 16 cents.
9. Monazite and Monazite Deposits in North Carolina, by Henry B. C. Nitze,
1895. 8°, 47 pp., 5 pi. Postage 4 cents.
10. Gold Mining in North Carolina and other Appalachian States, by Henry
B. C. Nitze and A. J. Wilkins, 1897. 8°, 164 pp., 10 pi. Postage 10 cents.
11. Corundum and the Basic Magnesian Rocks of Western North Carolina,
by J. Volney Lewis, 1895. 8°, 107 pp., 6 pi. Postage k cents.
12. History of the Gems Found in North Carolina, by George Frederick
Kunz, 1907. 8°, 60 pp., 15 pi. Postage 8 cents. Cloth-bound copy 80 cents
extra.
13. Clay Deposits and Clay Industries in North Carolina, by Heinrich Ries,
1897. 8°, 157 pp., 12 pi. Postage 10 cents.
14. The Cultivation of the Diamond-back Terrapin, by R. E. Coker, 1906.
8°, 67 pp., 23 pi., 2 figs. Postage 6 cents.
15. Experiments in Oyster Culture in Pamlico Sound, North Carolina, by
Robert E. Coker, 1907. 8°, 74 pp., 17 pi., 11 figs. Postage 6 cents.
16. Shade Trees for North Carolina, by W. W. Ashe. In press.
17. Terracing of Farm Lands, by W. W. Ashe, 1908. 8°, 38 pp., 6 pi., 2 figs.
Postage h cents.
18. A List of Elevations in North Carolina, by Joseph Hyde Pratt. In
preparation.
19. The Tin Deposits of the Carolinas, by Joseph Hyde Pratt and Douglass
B. Sterrett, 1905. 8°, 64 pp., 8 figs. Postage 1+ cents.
20. The Loblolly Pine in Eastern North Carolina, by W. W. Ashe. In
preparation.
ECONOMIC PAPERS.
1. The Maple-Sugar Industry in Western North Carolina, by W. W. Ashe,
1897. 8°, 34 pp. Postage 2 cents.
38 LIST OF PUBLICATIONS.
2. Recent Road Legislation in North Carolina, by J. A. Holmes. Out of
print.
3. Talc and Pyrophillite Deposits in North Carolina, by Joseph Hyde Pratt,
1900. 8°, 29 pp., 2 maps. Postage 2 cents.
4. The Mining Industry in North Carolina during 1900, by Joseph Hyde
Pratt, 1901. 8°, 36 pp., and map. Postage 2 cents.
5. Road Laws of North Carolina, by J. A. Holmes. Out of print.
6. The Mining Industry in North Carolina During 1901, by Joseph Hyde
Pratt, 1902. 8°, 102 pp. Postage 4 cents.
7. Mining Industry in North Carolina During 1902, by Joseph Hyde Pratt,
1903. 8°, 27 pp. Postage 2 cents.
S. The Mining Industry in North Carolina During 1903, by Joseph Hyde
Pratt, 1904. 8°, 74 pp. Postage 4 cents.
9. The Mining Industry in North Carolina During 1904, by Joseph Hyds
Pratt, 1905. 8°, 95 pp. Postage 4 cents.
10. Oyster Culture in North Carolina, by Robert E. Coker, 1905. 8°, 39 pp.
Postage 2 cents.
11. The Mining Industry in North Carolina During 1905, by Joseph Hyde
Pratt, 1906. 8°, 95 pp. Postage 4 cents.
12. Investigations Relative to the Shad Fisheries of North Carolina, by
John N. Cobb, 1906. 8°, 74 pp., 8 maps. Postage 6 cents.
13. Report of Committee on Fisheries in North Carolina. Compiled by
Joseph Hyde Pratt, 1906. 8°, 78 pp. Postage 4 cents.
14. The Mining Industry in North Carolina During 1906, by Joseph Hyde
Pratt, 1907. 8°, 144 pp., 20 pi., and 5 figs. Postage 12 cents.
15. The Mining Industry in North Carolina During 1907, by Joseph Hyde
Pratt, 1908. In preparation.
VOLUMES.
Vol. I. Corundum and the Basic Magnesian Rocks in Western North Caro-lina,
by Joseph Hyde Pratt and J. Volney Lewis, 1905. 8°, 464 pp., 44 pi., 35
figs. Postage 32 cents. Cloth-bound copy 80 cents extra.
Vol. II. Fishes of North Carolina, by H. M. Smith, 1907. 8°, 453 pp., 21 pi.,
188 figs. Postage 30 cents. Cloth-bound copies 30 cents extra.
Vol. III. Mineral Resources of North Carolina, by Joseph Hyde Pratt. In
preparation.
Samples of any mineral found in the State may be sent to the office of the
Geological and Economic Survey for identification, and the same will be
classified free of charge. It must be understood, however, that no assays,
ok quantitative deteuminations, will ue made. Samples should be in a
lump form if possible, and marked plainly on outside of package with name
of sender, post-office address, etc.; a letter should accompany sample and
stamp should be enclosed for reply.
These publications arc mailed to libraries and to individuals who may
desire information on any of the special subjects named, free of charge,
except that in each case applicants for the reports should forward the
amount of postage needed, as indicated above, for mailing the bulletins
desired, to the Htate Geologist, Chapel Hill, N. C.
\TE LIBRARY OF NORTH CAROLINA
3 3091 00748 4199
J.