The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
(A revision of Bulletin 5)
COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida
Florida State College for Women
And United States Department of Agriculture
Wilmon Newell, Director
By A. P. SPENCER
Fig. 1.-Water for subirrigation flows into the main at the highest
corner of the field. Supply pockets are seen down the ends of the rows
Bulletin will be sent free to Florida residents upon request to
AGRICULTURAL EXTENSION SERVICE
BOARD OF CONTROL
R. P. TERRY, Acting Chairman, Miami
THOMAS W. BRYANT, Lakeland
W. M. PALMER, Ocala
H. P. ADAIR, Jacksonville
C. P. HELFENSTEIN, Like Oak
J. T. DIAMOND, Secretary, Tallahassee
STAFF, AGRICULTURAL EXTENSION SERVICE
JOHN J. TIGERT, M.A., LL.D., President of the University
WILMON NEWELL, D.Sc., Director
A. P. SPENCER, M.S., Vice-Director and County Agent Leader
J. FRANCIS COOPER, M.S.A., Editor
JEFFERSON THOMAS, Assistant Editor
CLYDE BEALE, A.B., Assistant Editor
E. F. STANTON, Supervisor, Egg-Laying Contest
RUBY NEWHALL, Administrative Manager
COOPERATIVE AGRICULTURAL DEMONSTRATION WORK
W. T. NETTLES, B.S., District Agent
H. G. CLAYTON, M.S.A., District Agent, Organization and Outlook Specialist
J. LEE SMITH, District Agent and Agronomist
R. S. DENNIS, B.S.A., Assistant District Agent
A. E. DUNSCOMBE, M.S., Assistant District Agent
R. W. BLACKLOCK, A.B., Boys' Club Agent
E. F. DEBUSK, B.S., Citriculturist
A. L. SHEALY, D.V.M., Animal Industrialist1
HAMLIN L. BROWN, B.S., Dairyman
N. R. MEHRHOF, M.AGR., Poultryman'
D. F. SOWELL, M.S., Assistant Poultryman
WALTER J. SHEELY, B.S., Animal Husbandman
C. V. NOBLE, PH.D., Agricultural Economist1
D. E. TIMMONS, M.S.A., Agricultural Economist, Marketing
CHARLES M. HAMPSON, M.S., Agricultural Economist, Farm Management
R. H. HOWARD, M.S.A., Asst. Agr. Economist, Farm Management
GRAY MILEY, B.S.A., Asst. Agr. Economist, Farm Management
R. V. ALLISON, PH.D., Soil Conservationist'
COOPERATIVE HOME DEMONSTRATION WORK
MARY E. KEOWN, M.S., State Agent
LUCY BELLE SETTLE, M.A., District Agent
RUBY McDAVID, District Agent
ETHYL HOLLOWAY, B.S.H.E., District Agent
ANNA MAE SIKES, B.S., Nutritionist
VIRGINIA P. MOORE, Home Improvement Agent
ISABELLE S. THURSBY, Economist in Food Conservation
CLARINE BELCHER, M.S., Clothing Specialist
NEGRO EXTENSION WORK
A. A. TURNER, Local District Agent
BEULAH SHUTE, Local District Agent
By A. P. SPENCER
The purpose of subirrigation is to control the moisture in
the soil so that plants will have at all times sufficient water
conveyed to their roots by capillary attraction without wetting
the blanket of surface soil of the field. The advantages of
this method are: The water supply is constant and regular.
The plants receive no excess water to encourage fungus and
other diseases. No crust forms on the surface of the soil. The
soluble fertilizers are not washed deep into the soil beyond the
reach of the roots as they are when heavy rains occur or when
quantities of water are applied to the surface.
The control of moisture in the soil is absolute if this system
of subirrigation is properly installed and operated and the con-
ditions are suitable for such a system.
Subirrigation is used more extensively in the Sanford and
Oviedo districts, along the southern border of Lake Apopka
0 M 4Ck
" ** ""300 to 500" t. O ,,
| ** ** .. 500to7500 ""RA I
...** btow 75 ft ,*
W 7 "-
Fig. 2.-Map of Florida showing areas .A
in which artesian water flow is encountered
at different depths. (Map supplied to 150by Stateph.
300 to 500 ft.
lIDIII 500 to 750 ft. "'N r -
bilow 754 ft
Fig. 2.-Map of Florida showing areas
in which artesian water flow is encountered
at different depths. (Map supplied by State
Acknowledgments: This is a revision of Bulletin 5,
brought up to date with the assistance and approval of
C. M. Berry, former county agent, and Ralph Dawson,
present county agent, of Seminole County.
Florida Cooperative Extension
and in sections of Manatee and Sarasota counties than in other
parts of Florida. The water is supplied by artesian wells from
100 to 1,000 feet deep. (Fig. 2.) A full description of the
artesian area may be secured from Florida State Geological
Survey, Tallahassee, Fla.
ESSENTIALS FOR SUCCESSFUL OPERATION ON SANDY SOILS
1. An abundance of water is necessary. This is usually sup-
plied by artesian wells obtained by driving iron pipes down
-into the artesian
stratum, and al-
lowing the water
to rise in the pipe
to a height some-
what above the
: p.. surface of the
i&-. ground. The wa-
-. ter can also be
_S. I brought to the
where it rises to
within easy reach
of the surface.
2. A subsoil or
floor, composed of
clay, marl, or
at a depth of
three to five feet
below the surface
to hold the water
Sand prevent its
3. A foot or
more of coarse
sand on top of
Fig. 3.-Showing installation of water main, t h e subsoil o r
with supply pockets. bottom of the
irrigated depth that will readily absorb and distribute evenly
the water to be used in grading the artificial water table.
4. A top soil of sandy loam that is neither too porous nor
too compact, and which will convey the water freely by capil-
5. Land that admits perfect drainage. It should have a fall
of about one inch to 100 feet.
6. Land that is level, without depressions or raised places.
SUBIRRIGATION ON MUCK SOILS
Subirrigation is used in muck soils where the muck is deep
and not underlaid with hardpan or marl. This applies particu-
larly to celery growing and the extent of its use depends on
the water table in the muck and the usual water supply.
Wherever the foregoing conditions obtain and wherever the
crops to be grown justify it, this system of subirrigation should
give satisfactory results, but if soil conditions are not suitable
or there is not an adequate supply of water some other irriga-
tion system should be installed. The system also supplies drain-
age and aeration.
MATERIALS AND CONSTRUCTION
The following list gives the materials necessary to construct
a subirrigation system for a unit of 21/2 acres. The lines of
lateral tile are 18 or 24 feet apart, the closer spacing being
preferable. BILL OF MATERIAL
Tiling 2 acres, tile spaced 18 ft. apart:
5,600 tile @ $32.00 M ............................................. $179.20
17 pockets @ $1.50 each ................................ ...... 25.50
17 pockets @ $1.75 each ............................................ 29.75
Sawdust (estimated) .................. .-..... ..... ........ 12.50
Cement (estimated) ............................... ........ 5.40
330 ft. 6" sewer pipe @ .18 ft. .................................... 59.40
34 nipples @ .10 each ..................... ........ ... ...... 3.40
Tiling 2% acres, tile spaced 24 ft. apart:
4,300 tile @ $32.00 M ...................................... $137.60
13 pockets @ $1.50 each ....................... ......... ...... 19.50
13 pockets @ $1.75 each ............................................ 22.75
Sawdust (estimated) ............................................. 10.00
Cement (estimated) -........ -................... ......... .... 5.40
330 ft. 6" sewer pipe @ .18 ft .................................... 59.40
26 nipples @ .10 each ............ ........... ....... ......... 2.60
Neither estimate includes cost of sand for mixing cement.
Both are for water discharging into open ditch.
For discharge into tile add 330 ft. 8" sewer pipe @ 32c ft., $105.60.
Cost of artesian wells varies in different localities from 40c
to $1 a foot. The cost of labor for laying the system varies
from $50 to $75 per acre.
Florida Cooperative Extension
The terra cotta or cement sewer pipes 12 inches in diameter
and 30 inches long are placed upright 20 to 24 feet apart. The
bottom ends are plugged with cement. These upright pipes
are known as the supply pockets. (Fig. 4.) They are connected
Fig. 4.-Supply pocket (left) and stop pocket (right) of terra cotta.
They are often constructed of concrete.
by 4 to 10-inch terra cotta water pipes, cemented tight at all
joints. This constitutes the water main (Fig. 3). The supply
pipe should have a lid or cover to prevent such obstructions as
rabbits, grass or other materials from falling into it and clog-
ging the line. (See Fig. 7.) From each supply pocket is laid
at right angles to the water main three lateral lines of tile.
These lines are made of ordinary 3-inch tiles, placed end to
end and not cemented. The tiles are then covered with saw-
dust, preferably cypress because of its durability, to a depth
of 6 inches. This layer of sawdust prevents sand from passing
through uncemented open joints. Or each joint may be covered
with a handful of sawdust or palmetto fibre or some other avail-
able material to prevent sand passing through the joints and
clogging the tile.
At the end of each lateral, opposite the main, a stop pocket
is placed. (Fig. 4.) The tile is connected with it in the same
manner as to the supply pocket.
Another hole is c(ut directly opposite in the stop pocket and
three tiles are laid to connect it with an open drainage ditch.
A 3-inch iron nipple 6 inches long is used to connect the outlet
tiles with the stop loockets. The stop pockets provide a means
for holding the water in the tiles when it is necessary, or the
water may be drained from the laterals into a large sewer pipe
placed directly below the bottom of the stop pocket. This will
give a covered outlet from the stop pocket, thereby avoiding an
open ditch. With this system it is advisable to use a cement
plug to be fitted into the outlet of the stop pocket with a pipe
handle, both elnds of the pipe to be open. This allows the water
flowing into the stop pockets to rise above the height of the pipe
handle and escape through the pipe handle into the sewer line.
The cement plug attached to the pipe handle as recommended
when the, outlet opens into a sewer pipe may be used also when
the outlet drains into an open ditch. In that case an ell should
be used instead of the iron nipple. It is not necessary to use
a partition in the stop pocket, since waste water will overflow
through the handle of the plug. This appliance also obviates the
necessity of reaching down into the stop pocket to remove the
plug. In such case the partition is not placed in the stop pocket.
LAYING THE WATER MAIN
The level of the land should be accurately determined by a
competent surveyor. The water supply or well (Fig. 1) is
located at the highest corner of the field to be irrigated. The
water main is laid from the well along the highest side of the
field at a depth of 16 to 24 inches and is allowed the natural
fall of the land, which may be preferably 1 to 3 inch fall to
100 feet. This slight fall gives the slow and uniform supply
of water to the laterals. The supply pockets are placed 18
to 24 feet apart in the main. All joints and connections are
made water tight with concrete consisting of three parts of
sharp sand to one of cement.
LAYING THE LATERALS
Two systems are used when connecting the laterals to the
supply pockets. In one instance one supply pocket supplies the
water to three laterals as shown in Figs. 5 and 7. This has
the advantage of requiring fewer supply pockets but the dis-
advantage that is difficult to determine which line is clogged
in case one lateral becomes clogged.
Florida Cooperative Exten'ion
Formerly all systems were installed with'a supply pocket for
each lateral line. While this is more expensive to install, it
obviates the difficulty in locating an obstruction that may get
Supply Pockets -
Fig. 5.-Plan of a subirrigation system in which one supply pocket
furnishes water to three lines of laterals.
furnshe w-18' to thee lie faeas
into the lateral, and there is likely to be more damage to the
supply pocket when more than one connection is broken at
the lateral joint when a lateral becomes plugged.
The tiles of the laterals are laid from the supply pockets
which are always located on the high side of the field along
the main. The union between the first tile and the supply
pocket is made with a nipple of 2-inch iron pipe 6 inches long.
Fig. 6.-Iron nipple fitted into tile.
One end of this nipple is fitted snugly into the end of the
tile and the other end is slipped into the supply pocket and
both are cemented water tight. The tiles fit together as closely
as possible. The joints are covered with sawdust or palmetto
fibre to keep out sand.
TO OBTAIN THE PROPER GRADE
Care must be taken to have the tiles properly placed. The
ditches in which the irrigation tiles are to be laid are dug one
foot wide and 18 inches deep and should have a fall of one inch
to 100 feet. This applies to an area where the average depth
to the hardpan varies from 15 to 30 inches. In areas where
the hardpan or impervious layer lies at a lower depth, the tiles
may be laid up to 50 inches or more below the surface. The
bottom of the ditch is made as even as possible and then
smoothed with a tiling scoop to give a good bed for the tile.
The proper grade is usually obtained with a surveyor's instru-
ment, or if an instrument is not available a less reliable method
is to allow water to flow slowly down the ditch and any eleva-
tions or depressions along the bottom can be detected. A tiling
scoop can be used to level the bottom until the water runs
slowly and regularly from one end of the ditch to the other.
Sometimes it is advisable to place a partition or gate in the
stop pocket to provide a safety appliance against overflow. This
Florida Cooperative Extension
is made by fitting
into the stop
pocket a vertical
having two holes
the size of the
opening in the
nipple. (See Fig.
8.) One of these
holes is placed on
a level with the
nipple, the other
nearer the sur-
face. This appli-
ance should al-
ways be installed
when it is desired
to hold the water
Fig. 7.-A concrete supply pocket for three laterals, in the tiles. Oth-
and a cover to prevent foreign matter from entering.
erwise, there is a
constant danger of raising the water table too high and
flooding the land. By placing the plug in the bottom hole
of this partition the water will rise as high as the upper
hole and then flow over and escape into the
TURNING IN THE WATER
When ready to set the land with young
plants, such as lettuce or celery, the outlet
holes of the stop pockets are plugged. The
water is then turned into the tiles, and is
allowed to rise until the surface of the soil
is evenly moistened, but not puddled. The
plants are then set in the moist soil, after
which the water supply is cut off. The plugs in
the stop pockets are removed and the surplus
water is allowed to drain away into the ditches.
This admits a circulation of air through the
tiles, which readily permeates the soil.
After this, the water is not again brought to
the soil during the life of the crop. As soon
Fig. 8.-A con-
crete stop pocket,
showing holes in
the center bar.
When the lower
hole is plugged,
the water rises to
the level of the
the surface of
as moisture is
needed the water is turned into the tiles and allowed to run
constantly unless the soil becomes too moist or periods of rain
occur. The water table is held about 18 inches below the sur-
face and the plants obtain moisture by capillary attraction.
The amount of water needed to hold the table at this height
is usually controlled by regulating the flow into the main line.
Its height is determined by the height to which the water rises
in the supply pockets. The depth at which the water table is
to be maintained depends on the nature of the crop. For ex-
ample, celery and lettuce require more water than tomatoes.
SIZE OF WELLS
Where flowing wells can be had, a 2 to 4-inch well is the
most desirable size. If increased water supply is needed better
results will be obtained from a number of such wells than
from one or more larger wells. One 2-inch well for every 21/2
acres of land is advised for vegetable growing or wherever a
liberal supply may be needed quickly. Where the well supplies
a wash house for a packing plant and consumes a larger amount
than is needed for irrigation, the size of the well should be
increased to 4 inches. The well is driven and cased with ordin-
ary iron pipes. Galvanized pipes should be used for the top
joint or the pipe above ground should be painted to protect it
DISTRIBUTING THE WATER TO A LARGER AREA
When only a small flow of water in each lateral is needed,
because of the kind of crop, recent rains, or a sufficient moisture
already existent, the area that may be watered from one well
may be increased by placing plugs having 1/2-inch holes bored
through them, in the nipples connecting the laterals with the
supply pockets. These reduce the flow into each lateral and
enable the well to furnish water to three or four times the
usual area. If, however, the soil is dry and liberal watering
is needed, the full 2-inch opening of the nipple should be used.
In case the water supply is insufficient the field can be watered
in sections, by placing a large plug in the main line at any
desired supply pocket until the soil is sufficiently moistened;
then plug the nipples leading into the laterals of the watered
area and allow the water to pass down the main into the next
area to be irrigated. The laterals should always be open at the
outlets to give a circulation of water through the pipes and soil.
Where it becomes advisable to reduce the amount of water
because of a limited supply, or of heavy expense in obtaining
Florida Cooperative Extension
it, a saving may be made by placing plugs with 3/4-inch holes
in the nipples of the stop pockets, thereby reducing the amount
of water flowing out of the laterals. This causes the water
to circulate less rapidly and increases the proportions absorbed
by the soil particles. In such cases, however, safety appliances
should always be provided in the stop pockets as there is danger
of flooding the surface if the small openings become clogged.
SUBIRRIGATION AS DRAINAGE
A subirrigation system, properly installed, provides a per-
fect subdrainage system during excessive rains, or whenever
the soil becomes too wet. It prevents water-logging, which
is so destructive to bacterial life in soil. In a few hours after the
heaviest rains it is possible to turn the land with heavy plows.
CROPS THAT MAY BE IRRIGATED
Subirrigation can be used for most truck and field crops
grown in Florida. It may be used in groves where the surface
and subsoil are suited, but roots of the trees may plug the tile.
In this case it will be necessary to re-lay the tiles every four
or five years.
Tomatoes, watermelons, cantaloupes and sweet potatoes are
not usually benefited by subirrigation. They prefer a drier soil
except during periods of continued drought. Celery and lettuce
require an abundance of water and are grown most successfully
in Florida where subirrigation is practiced.
Where the water supply is abundant it is easily possible
to give the crop too much water. Injuries from excessive irri-
gation are usually more serious and much harder to overcome
than those from lack of water. Plants start slowly or become
stunted. Many will actually die or become worthless, or they
may not mature early enough to obtain a good market.
The bad results produced by excessive irrigation are due
to driving the air out of the soil, filling the spaces with water,
and thus creating unfavorable conditions for soil bacteria. It
causes heavy loss of fertilizer by leaching, especially of am-
monia, which is readily soluble and expensive. Crops grown
on lands that are irrigated too heavily are usually sappy,
perishable, and lacking in good flavor. The soil is made com-
pact and more difficult to cultivate. Over-irrigated soil is
likely to become sour, which is detrimental to most crops.