NO-RUNOFF WATERING SYSTEMS
FOR FOLIAGE AND FLOWERING
POTTED PLANT PRODUCTION
M. R. Evans, J. E. Barrett, B. K. Harbaugh, and G.A. Clark
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences
University of Florida, Gainesville / John T. Woeste, Dean for Extension
The use of trade names in this publication is solely for the purpose of providing specific information. It is not a
guarantee, warranty, or endorsement of the products named and does not signify that they are approved to the
exclusion of others.
M. R. Evans is Assistant Professor and Extension Floriculture Specialist, Gulf Coast Research and Education Center (GCREC)-
Bradenton; J. E. Barrett is Professor of Environmental Horticulture, Environmental Horticulture Dept., Gainesville; B. K. Harbaugh is
Professor of Floriculture and G.A. Clark is Associate Professor and Extension Water Management Specialist, respectively, GCREC-
Concerns over water quantity and quality have
necessitated major changes in the way in which
water is supplied to ornamental potted plants.
Fueling these changes have been mandates by
regulatory agencies that require either all or
portions of the drainage water to be retained on the
producer's property and to prevent it from leaching
through the soil and into the ground water.
The major concern with drainage and irrigation
runoff exists with the fertilizer salts that may be in
the water and could potentially move into the
groundwater supplies, rivers and lakes. Therefore,
not only must water conservation be considered
when designing an irrigation system, but the reten-
tion of drainage and unused irrigation water must
also be planned. Because of the numerous modifi-
cations that can be made to any given design, it is
not possible to discuss all types of systems that
could be utilized in order to conserve and retain
irrigation water. However, the concepts discussed
and systems outlined in this publication provide
the basis for developing such a system.
When deciding upon the type of system to use,
many factors must be considered, and the planning
stage is critical. Crops being grown, types of con-
tainers in which the plants are to be grown, future
expansion plans, quality of irrigation water and
cost of the system versus value of the crops to be
produced are all important factors to consider. For
example, many seed trays and flats do not have
designs that allow the soil in the container to con-
tact the surface of a watering mat. Therefore, a
different system, such as ebb-and-flow, would be
better than a mat. Plants that are particularly
sensitive to high soluble salt levels should be grown
in a self-contained system in which water can be
collected and recycled in case leaching is necessary.
Fertilization practices must be adjusted when
using no-runoff watering systems. Since leaching
is not desired, regular flushing of fertilizer salts
will not occur. In subirrigation systems, water
moves from the bottom to the top of the pot.
Therefore, fertilizer levels and placement must be
adjusted to match the plant requirements, the irri-
gation system and management practices. Further,
watering frequency and volume will need to be
adjusted since water is not being lost through the
bottom of the pot.
A water test should be conducted to determine
the total soluble salt content, pH, and bicarbonate
level (often referred to as alkalinity) of the water.
Because leaching is not routinely conducted with
no-runoff systems, these variables must be con-
trolled to a much greater extent than is necessary
with overhead irrigation systems.
Some of the most common water quality prob-
lems encountered in Florida include high pH, high
bicarbonate and carbonate levels, high soluble
salts, microorganisms (bacteria, algae and fungi),
sulfur, iron and sand or other suspended materials.
If the water pH or bicarbonate and carbonate levels
are too high, acid injection into the irrigation sys-
tem may be necessary. The major effect that high
bicarbonates and carbonates will have in producing
potted plants is that they neutralize soil acidity
which tends to increase soil pH over time. Gener-
ally the recommended range for bicarbonates and
carbonates (reported as mg CaCO3/liter or ppm
CaCO3) in the irrigation water is 60 100 for plug
production, 80 120 for small pots and flats, 100 -
140 for 4- to 5-inch pots and 120 200 for 6-inch
and larger pot sizes. These numbers should only be
used as a guide since the plant being produced,
fertilizer type and the growing medium are all
important in determining the optimal range.
If acid injection is necessary, all parts of the system
must be compatible with the injected material.
Often it is best to have acid injected separately
from any fertilizer. Because each irrigation system
and water source may be different, the water
should be titrated in order to determine how much
acid is required to obtain the desired water pH and
If the irrigation water is high in soluble salts,
the water may need to be blended with water from
another source that has a lower salt level. Salts
may present a problem because of accumulation in
the growing media and subsequent damage to
plants or they may create operational problems for
the irrigation system since, through precipitation,
they can build up and create clogging problems.
Algae and bacteria may be a problem by growing
and accumulating within the irrigation system and
causing clogging. In addition some bacteria and
fungi present in the water may be plant pathogens.
Only opaque pipes, or translucent pipes coated with
an opaque paint, should be used in constructing the
irrigation system so that light required for algae
growth does not penetrate the pipe. Both liquid
sodium hypochlorite and Agribrom are labeled for
use in irrigation systems and may be injected into
the system to kill bacteria, algae, and fungi that
may be present in the water. The level of the in-
jected compound must be closely monitored as high
levels may cause plant damage. All chemicals
should be used according to the label.
Additional information concerning water quality
problems and potential solutions can be found in
the publication "Causes and Prevention of Emitter
Plugging in Micro Irrigation Systems" (Institute of
Food and Agricultural Sciences Bulletin 258,
Florida Cooperative Extension Service, April 1990).
Types of systems
Drip tube systems
Drip tube irrigation systems utilize 1 to 2 mm
(0.04 to 0.08 inch) inside-diameter tubing to supply
water directly to individual pots (Figure 1). The
tubing used for these systems is generally referred
to as spaghetti tubing. Spaghetti tubing is inserted
into 1.3 to 1.9 cm (0.5 to 0.75 inch) polyethylene
pipe which serves as the supply line for each bench.
The free end of the tubing is then held in the con-
tainer by a weighted emitter or with the use of a
small stake. Other systems may use multiple out-
let drippers with several supply tubes attached to
each outlet or individual pot drippers on the end of
each supply tube (Figure 2). The spaghetti tubing
Figure 1. Spaghetti tube Irrigation system with individual
spaghetti tubes per pot.
Figure 2. Spaghetti tube irrigation system with multiple
can be purchased pre-cut to specific lengths or cut
to the desired length from a roll of tubing. The
length of the spaghetti tubing and the pressure of
the water supply control the application rate from
each tube. Dishes or trays may be placed under the
pots to catch any irrigation water that might leach
through the soil. This not only prevents runoff, but
the retained water may be taken back into the soil
by capillary action and used by the plant.
Irrigation scheduling is easily automated with
the use of electric solenoid or hydraulic control
valves connected to simple clocks or irrigation com-
puters. Multiple daily applications of water are
often used to maintain adequate moisture levels in
the growing medium. Sufficient water should be
applied to uniformly wet the growing medium but
not enough to result in leaching. Since water drips
or trickles from emitters or tubing at one area
within the container, a uniformly mixed growing
medium which allows capillary movement of water
and fertilizer is necessary. If the growing medium
is too porous, water and fertilizer movement may
be limited to one side of the container leaving part
of the growing medium dry. Emitters have been
designed that provide a broader pattern of water
distribution to the medium surface and thus a
more even distribution of water to the pot.
Soluble fertilizers injected into the irrigation
water are often used with drip tube systems.
Attention to the solubility of nutrients or associ-
ated ions and reaction with existing elements in
the irrigation water is necessary to prevent
clogging of tubing and emitters. Controlled-release
fertilizers may also be used with this system alone
or in combination with soluble fertilizers.
Controlled- release fertilizers are generally incorpo-
rated into the growing medium. Since little or no
water runs over the medium surface with many
emitters, surface applications of controlled release
fertilizers may result in incomplete release of fertil-
izer or poor distribution within the pot. Advan-
tages of drip tube irrigation systems in comparison
to overhead systems include: conservation of water
and fertilizer by uniform distribution of water and
nutrients to containers; reduction of pumping or
water purchase costs due to water conservation;
reduction of foliar diseases and pest control costs
since water is not applied to the foliage and irriga-
tion does not wash pesticides from the plant; and
reduction or elimination of irrigation water runoff.
Disadvantages of drip tube irrigation systems com-
pared to overhead systems include: higher fixed
and operating costs; greater need for good quality
water; design limitations relative to existing struc-
tures or plumbing; increased labor requirements to
construct and maintain tubing and emitters; and
the lack of potential for the irrigation system to be
used for propagation, foliar feeding and frost
Ebb-and-flow irrigation has become the standard
irrigation system in Northern Europe and is becom-
ing more common in North America. It is generally
an easy system to use for growing plants but is the
most expensive of the no-runoff irrigation systems.
In ebb-and-flow irrigation the water level is raised
around the pots, which floods the air spaces of the
medium up to the height of the outside water.
The water is then drained from the benches and the
water remaining in the flooded lower portion of the
pot moves up into the medium by capillary action.
Plants do not need to be flooded very deeply.
Usually a depth of only about one-fifth the height of
the growing medium provides enough water to
thoroughly wet the medium. Also, the plants need
to sit in water only long enough to flood the lower
level of medium. Leaving plants sitting in water a
longer time does not increase the amount of water
the medium absorbs but does reduce the aeration of
the medium around roots at the bottom of the pot.
If one flooding does not provide adequate wetting to
the top of the medium, then more frequent irriga-
tions should be used rather than holding plants in
water for a longer time.
Ebb-and-flow irrigation is like all subirrigation
systems in that water moves up through the
medium and carries any salts with it which results
in a zone of high soluble salts in the upper layer of
the medium. Root growth is poor in this high salt
region. There is not a mechanism for leaching salts
out of the medium with ebb-and-flow irrigation, but
this is not usually a problem because the high salts
are located above the root zone. Since salts do con-
centrate in the medium, it is important to mini-
mize unwanted salts by using clean water, using
the lowest fertilization levels needed, and avoiding
fertilizer forms with ions, such as chlorine and so-
dium, that are not used by the plant.
Fertilization can be achieved with either pre-
incorporated slow release materials or with soluble
fertilizers in the irrigation water. Because there is
little downward movement of salts through the
medium, top dress applications of slow release
materials do not work well when only the ebb-and-
flow irrigation system is used. Soluble fertilizers
used in ebb-and-flow are similar to those used in
standard drip systems with leaching. When the
water level in the supply tank is low, the fertilizer
is premixed or injected at the desired concentra-
tion before the water is added to the tank.
The concentration of fertilizer in the water is much
less than used for the same crop in a drip system
with leaching. The actual concentration will vary
with individual grower practices but is generally
about one-half the level used with leaching. For
example, if a grower uses a 20-10-20 fertilizer at
300 ppm of nitrogen and switches to ebb-and-flow
irrigation, the same fertilizer at 150 ppm of nitro-
gen in the irrigation water would be close to the
desired level of fertilization.
The physical characteristics of media used with
ebb-and-flow irrigation and other subirrigation
systems are important. Very light and open mixes
do not work well because the reduced capillary
pores do not move water to the upper regions of
the media very well. The best media for ebb-and-
flow are usually a little tighter and heavier than
mixes used with drip systems. The tighter mix
provides for better water movement, but over satu-
ration is not a problem because water moves only
in the smaller capillary pores and the larger pores
remain open for good aeration. Generally, the
taller the pot, the tighter the medium needs to be
to adequately move water to the top.
Ebb-and-flow benches are constructed with alu-
minum frames and plastic liners, which have a
grid of channels to allow water flow along the
bench. There are some manufacturers of all alumi-
num benches, which are more durable but also
more costly. The benches should be mounted so
that they are level, and there are usually screw
type leveling mechanisms on each leg. The level
bench provides for uniform watering of all pots, and
the channels prevent pots from sitting in water
held in any low spots after the water is drained.
The benches come in standard widths and are
pieced together to obtain any desired length.
Benches can be fixed or rolling space- saver
benches with permanently-connected drain and fill
lines. Ebb-and-flow irrigation systems can also be
rolling table tops, which do not have fixed line
A consideration in the design of an ebb-and-flow
irrigation system is the size of the holding tank.
It is impractical to use one large tank that has
enough capacity to flood all the benches in a green-
house at one time. The tank would need to be very
large, and large amounts of water and fertilizer
would be wasted when the tank had to be emptied.
The tank is usually sized to irrigate 3 to 8 benches
at one time. The first zone is flooded, and, when
draining is started, flooding of the next zone is
started. This cycle is repeated until all plants have
been irrigated. The number of fertilizer solutions
available to be used at one time is limited by the
number of tanks installed. Many growers get along
with one tank where all the plants in a house need
similar fertilization. It is also easy to design the
system to flood with clear water and that is
discarded after use.
The filling and draining process can be handled
in different ways. Some benches are designed with
one tube connected in the bottom of the bench, and
the bench is filled and drained through the same
line. These benches usually take longer to drain.
Systems with separate fill and drain lines are avail-
able. The drain can be controlled manually or
mechanically, but this can be expensive and time
consuming. Benches with drains that open when
the water level reaches a desired height or with
drains that are open but drain slower than the
bench is filled, may be preferable. Drains can have
attached lines or they can be open below the bench.
In the later case, the water falls into a fixed trough
to run back to the holding tank. Some systems do
not have permanently connected fill lines. One
method is to use soft tubing that hooks over the
edge of the bench, similar in design to washing
machine drain lines. A more common arrangement
has polyvinylchloride (PVC) pipe running from
below and curving out over the end of the bench.
This design allows benches to easily roll under the
end of the fill line.
The principle disadvantage of ebb-and-flow sys-
tems is their initial cost. However, the relative cost
is not as great in new installations when compared
to the combined costs of installing other bench and
irrigation systems. The main advantage of ebb-
and-flow irrigation is the ease of use. Moving
plants is easy and does not require handling drip
tubes for each container. Keeping the benches
clean can be easier than with capillary mat sys-
tems, and there is not the need for replacing mats.
Flood floors are subirrigation systems similar to
ebb-and-flow benches, except that the plants are
grown on concrete floors. The principles of flooding
the plants, water uptake, and fertilization are the
same as in ebb-and-flow systems. Flood floors are
considerably cheaper than ebb-and-flow benches,
but are more difficult to install.
Getting proper drainage is the key to success
with flood floors. They do not have the channels to
move water away from pots and any low spots will
hold water. Poor drainage can result in problems
since plants in low areas will stay too wet and be
prone to disease problems. To promote water
drainage away from pots, the floors are given a
small uniform slope toward the drain. Standard
concrete construction and leveling techniques gen-
erally are not adequate for providing the desired
uniformity of the floors. It can be difficult to find
concrete contractors with the necessary skills for
installing flood floors. Additionally, the floor
should be constructed so that it can withstand the
weight of any equipment that may need to be
driven across the floor during production, shipping
The amount of area flooded at one time is
greater in flood floors than with ebb-and-flow
benches, so the tank and associated plumbing will
be larger and must be appropriately sized. Usually
flood floors are constructed with an entire green-
house bay being one zone. Most are built so the
water runs back to the tank from each zone.
However, they can be designed in staggered eleva-
tions, so the water flows from one zone to another
before going back to the tank.
Flood floors are most often seen in large opera-
tions, but they should be easily adapted to smaller
greenhouses. A good addition to flood floors is the
installation of hot water lines in the floors to
provide heating. Space utilization on flood floors
can be very good, but a common complaint is the
added labor in handling plants.
Trough systems are benches with tops that are
parallel rows of troughs rather than a solid surface
(Figure 3). The pots are not flooded as in ebb-and-
flow, but the water is delivered at the higher end of
the trough and runs in a stream to the opposite
end. The stream of water comes in contact with
the pots and water is taken up by capillary action
through the holes in the pots.
Figure 3. Trough Irrigation system with pots sitting in water
Trough benches are cheaper than ebb-and-flow
systems, and they allow for better air movement up
through the plant canopy because they are not a
solid surface. Due to the inflexibility in spacing
however, they work best for growers that produce a
large number of uniform sized plants. A common
problem is the need to reposition plants in the
trough so that each plant is contacted by the stream
of water. Some growers alleviate this problem by
placing a strip of capillary mat material in the
trough and, essentially, conducting capillary mat
Capillary mat watering systems
Capillary mat watering systems have existed for
many years in one form or another. The design is
generally simple and costs are low in comparison to
other watering systems such as ebb-and-flow or
spaghetti tubes. The basic design has been success-
fully adapted to numerous growing situations in
The basic design of the capillary mat system is
one that delivers water to a fibrous mat, usually 1/8
- 1/4 inch thick, that absorbs water. Pots are
placed on the mat and water moves from the mat
into the pot by capillary action (Figure 4). There
are numerous types of mats made from lint, cellu-
lose or other materials. The mat is placed on top of
a layer of plastic and covered with another layer of
opaque plastic. Opaque plastic, usually black, is
used in order to prevent algae growth on the mat.
The top layer may have holes cut where pots are to
be placed to allow contact between the mat and the
drainage holes of the bottom of the pot. Another
option is to use a perforated plastic that has small
pin-sized holes that allow water movement from
the mat to the pot. This option reduces light pen-
etration to the mat and roots are less likely to grow
into the mat. One disadvantage to this type of plas-
tic cover is that, if the water source is high in salts,
the salts tend to accumulate and block the holes.
The salt accumulation may be removed by brushing
the plastic or by spraying the mat with clean water.
In some cases the bench is slightly elevated at one
end and a catch trough is placed at the low end of
the bench. This allows for any water that may run
off the bench to be collected and recirculated.
Water is delivered to the mat through the use of
polyethylene drip tubes. Many types of tubes have
been successfully utilized. The water pressure
required will be dictated by the type of tube. Exces-
sive water pressure will rupture the lightweight
tubes whereas too low a pressure will result in poor
water delivery and distribution.
Mats have been used on benches and on ground
beds. The most important design factor is that the
L-BENCH CAPILLARY MAT
Figure 4. Capillary mat irrigation system as constructed for a
bed should be level or slightly graded. Otherwise,
low areas will receive too much water and high
areas will be too dry. Further, low areas will accu-
mulate water that can then become runoff.
When pots are initially placed on the mat, the
mat should be wet and the pots should be thor-
oughly watered using an overhead system to allow
for the establishment of capillarity. For subse-
quent irrigations using the capillary mat, enough
water should be applied through the polyethylene
drip tubes to fully saturate the mat but not enough
to allow runoff, unless catch troughs have been con-
structed to collect and recirculate any runoff. The
mat should not be allowed to dry. This may require
frequent water applications during the day depend-
ing on evaporation and crop use. If drying occurs,
the mat must be re-wet and the plants must be
overhead irrigated again to re-establish capillarity.
When mats are used outside or under saran, heavy
rains can leach fertilizer salts from the pots.
Therefore, when used outside, the mat system can-
not always guarantee that no fertilizer-containing
water will run off.
The growing medium should be heavy enough to
establish good pot-to-mat contact. If the medium
has large pore spaces, good water movement
through the medium may be inhibited. Further,
footed pots should be avoided because they can also
cause problems with water movement from the mat
into the pot.
An appropriate amount of a slow-release fertil-
izer should be incorporated into the potting mix.
Generally, with this type of irrigation system,
fertilizer use is more efficient and applications can
be reduced since leaching of fertilizer salts does not
occur. It is important to remember that water and
fertilizer management are closely related. There-
fore, the proper method and amount of fertilizer
application must be selected based on the needs of
the crop, the cultural conditions and the irrigation
system. There is no standard rule to determine
how much to reduce the fertilizer. This is an area
that requires grower trials. It is easier to add addi-
tional fertilizer than to deal with a high salt prob-
lem. If additional fertilization is required, it can be
provided by low volume top watering. Fertilizer
should not be fed through the mat system since
algae and root growth into the mats can become a
In summary, capillary mat irrigation systems
offer a simple and lower cost alternative to spa-
ghetti tubes or ebb-and-flow systems. The system
can result in as much as a 90% water savings as
compared to overhead watering. In addition, this
system will, particularly if used in a covered pro-
duction structure, eliminate runoff. The problems
with this system include potential clogging of water
delivery tubes, minimal flexibility in the fertiliza-
tion program, and limited ability to prevent runoff
in outside systems.
Sources of additional information
Clark, G.A., B.K. Harbaugh and C.D. Stanley.
1988. Irrigation of Container and Field Grown Or-
namentals Systems and Management Guidelines.
IFAS Extension Circular 808, Univ. of Florida,
Clark, G.A., D.Z. Haman and F.S. Zazueta. 1990.
Injection of Chemicals into Irrigation Systems:
Rates, Volumes, and Injection Periods. IFAS Bulle-
tin 250, Univ. of Florida, Gainesville, FL.
Haman, D.Z., A.G. Smajstrla and F.S. Zazueta.
1990. Chemical Injection Methods for Irrigation.
IFAS Extension Circular 864, Univ. of Florida,
Pitts, D.J., D.Z. Haman and A.G. Smajstrla.
1990. Causes and Prevention of Emitter Plugging
in Micro Irrigation Systems. IFAS Extension Bul-
letin 258, Univ. of Florida, Gainesville, FL.
COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOODANDAGRICULTURAL SCIENCES,John T. Woeste,
Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June
30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and institutions that
function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding 4-H and youth xi
publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-state purchasers *
Is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida 32611. Before publicizing *
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