• TABLE OF CONTENTS
HIDE
 Copyright
 Front Cover
 Table of Contents
 Introduction
 How much water is required?
 Soil water storage
 Capacity
 Limited irrigation and root...
 A water budget
 Soil moisture management
 Summary
 Reference
 Back Cover






Group Title: Florida Cooperative Extension Service circular 872
Title: Irrigation scheduling and management of micro-irrigated tomatoes
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00049220/00001
 Material Information
Title: Irrigation scheduling and management of micro-irrigated tomatoes
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 12 p. : ill. ; 23 cm.
Language: English
Creator: Clark, Gary A
Publisher: Florida Cooperative Extension Service, University of Florida
Place of Publication: Gainesville
Publication Date: 1990
 Subjects
Subject: Irrigation   ( lcsh )
Tomatoes -- Irrigation   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 11-12).
Statement of Responsibility: G.A. Clark ... et al..
General Note: Cover title.
General Note: "June 1990."
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Bibliographic ID: UF00049220
Volume ID: VID00001
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: oclc - 22901480

Table of Contents
    Copyright
        Copyright
    Front Cover
        Page i
    Table of Contents
        Page ii
    Introduction
        Page 1
    How much water is required?
        Page 2
        Page 3
        Page 4
    Soil water storage
        Page 5
    Capacity
        Page 6
    Limited irrigation and root zones
        Page 6
        Page 7
    A water budget
        Page 8
    Soil moisture management
        Page 9
    Summary
        Page 10
    Reference
        Page 11
        Page 12
    Back Cover
        Page 14
Full Text





HISTORIC NOTE


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
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida





June 1990
' p2.. June 1990


,-tral Science
Library

NOV 14 1990


Circular 872





i'


!University of Florida

Irrigation Scheduling
and Management
of Micro-Irrigated Tomatoes


GA. Clark
G.N. Maynard
C.D. Stanley
G.J. Hochmuth
E.A. Hanlon
D.Z. Haman










Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences
University of Florida / John T. Woeste, Dean







Contents
Page
Introduction .................................... ............ 1
How Much Water is Required? ........................2
Soil W ater Storage ............................................ 5
Capacity ......................................... ............. 6
Limited Irrigation and Root Zones ................6
A W ater Budget ............................................. 8
Soil Moisture Management.............................9
Sum m ary................................ ..........................
References .................................... ............. 10










Irrigation Scheduling of Micro-Irrigated Tomatoes

G. A. Clark, D. N. Maynard, C. D. Stanley,
G. J. Hochmuth, E. A. Hanlon, and D. Z. Haman'

Introduction
Irrigation scheduling is a decision-making process used to deter-
mine when to irrigate a crop, how much water to apply to meet the
needs of the crop, and how frequently the water should be applied to
conform to production system, cultural practice, soil, crop, and en-
vironmental constraints. Additional constraints such as power avail-
ability, regulatory agency restrictions, and others may influence irri-
gation scheduling, but these will not be discussed here.
Crops require irrigation to meet environmental and growth de-
mands when rainfall is not sufficient. Florida's sandy soils have low
water-holding capacities and consequently require frequent irriga-
tions to minimize stress caused by crop water deficits. This is
especially critical on shallow rooted crops where excessive irrigation
can leach nutrients out of the root zone. This increases costs due to
lost fertilizer and unnecessary pumping, as well as a possible loss in
production. However, if salt accumulation occurs within the root
zone, then an irrigation is desirable to leach out the excessive salts.
Therefore, proper irrigation scheduling is essential as a good manage-
ment practice. A general discussion of this topic is provided in Fla.
Coop. Ext. Ser. Bulletin 249 (Smajstrla et al., 1988).
This publication discusses irrigation scheduling as it applies to
micro-irrigated tomato crops grown on sandy soils in Florida. Reports
involving micro-irrigation of tomatoes will be discussed to provide the
most current information on this topic. Details concerning system
design, components, and basic operation are discussed in Fla. Coop.
Ext. Ser. Bulletin 245, Micro-Irrigation on Mulched Bed Systems:
Components, System Capacities, and Management, and Fla. Coop.
Ext. Ser. Agricultural Engineering Fact Sheet AE-72, Micro-Irriga-
tion in Mulched Bed Systems: Irrigation Depths.


SG.A. Clark is an Assistant Professor Extension Water Management Special-
ist, D.N. Maynard is a Professor Extension Vegetable Specialist, C.D. Stanley
is an Associate Professor of Soil Science; Gulf Coast Research and Education
Center, Bradenton; G.J. Hochmuth is an Associate Professor Extension
Vegetable Specialist, EA. Hanlon is an Associate Professor Extension Soils
Specialist, and D.Z. Haman is an Assistant Professor Extension Irrigation
Specialist; Gainsville; respectively, IFAS, Univeristy of Florida.









How Much Water Is Required?


This is a question which is not easily answered. Crop water re-
quirements are, in general, determined by the atmospheric demand
for water. Requirements for growth and development, transplant
establishment, frost/freeze protection, and other special needs will
not be discussed here. The atmospheric demand for water is generally
called evapotranspiration (ET), potential evapotranspiration (ETp)
or crop evapotranspiration (ETc). Detailed discussions of ET includ-
ing descriptions and measurement methods of the parameters
involved are provided in Fla. Coop. Ext. Ser. Bulletin 840 (Jones et al.,
1984) and Circulars 822 (Clark et al., 1989) and 827 (Clark et al.,
1989).
Potential ET (ETp) represents the amount or rate of water use, if
available, of an actively growing green surface of uniform height.
Fields of transpiring alfalfa or grass are good examples. Typical
values for ETp in south Florida range from 0.10 inches per day in the
winter to 0.19 inches per day in the early summer. Respective values
for north Florida range from 0.06 inches per day in the winter to 0.20
inches per day in early summer. As summer progresses the increase
in atmospheric cloudiness decreases ETp.
The actual crop water requirement, ETc, is generally less than ETp
depending upon the type of crop, cultural practice (bed spacing, crop
density, etc.) and stage of development. A crop coefficient, Kc, is used
to relate ETc to ETp. This relationship is
ETc = (Kc)(ETp). (1)
Crop coefficients are not available at this time for tomatoes in Florida,
but range from 0.2 during early crop growth to 1.0 with fully grown
plants for other crops such as corn, potatoes, and soybeans. The use
of crop coefficients is discussed in more detail in Fla. Coop. Ext. Ser.
Bulletin 840 (Jones et al., 1984).
The ET demand occurs over the entire surface area including
exposed row middles. This is important to consider with respect to the
crop water requirements and management of the irrigation system.
Unlike rainfall, micro-irrigation systems generally do not apply
water uniformly over the entire growing area and thus have different
management requirements. This will be discussed in more detail in
another section.
Irrigation requirements differ from crop water requirements in
that the application efficiency of the irrigation system is used.
Smajstrla et al. (1988) discuss the different efficiency types and levels
associated with irrigation systems used in Florida. The irrigation
requirement is equal to the crop water requirement divided by the









decimal value of the irrigation system application efficiency. For
example, a crop irrigated with a micro-irrigation system with a 90%
overall efficiency and a weekly crop water requirement of 0.95 inches
has an irrigation requirement of 1.06 inches per week.
To date, no studies have been conducted to determine the actual
water requirements of mulched, staked tomato crops. However,
several studies have been conducted which have investigated irriga-
tion rates and timing under Florida conditions (Locascio and Myers,
1974; Csizinszky, 1979; Locascio et al., 1981; Locascio et al., 1985;
Csizinszky et al., 1986; Clark et al., 1987a; Clark et al., 1987b; Haman
et al., 1988; and Clark et al., 1989). The study by Clark et al. (1989)
found that spring crop water requirements will be on the order of 10
to 15 inches and that fall requirements will be approximately 8 to 12
inches. These amounts will vary with seasonal conditions but provide
a first approximation to the water requirement. In addition, these
values do not include water required for plant establishment, main-
tenance, or system application inefficiencies.
Studies by Locascio et al. (1981) and Locascio et al. (1985) sched-
uled irrigations by using pan evaporation data. Irrigation amounts


GROWTH OF 'DUKE' TOMATO
(Data from Marlowe et al., 1983)
1.0 .....
0.9
cc 0.8 ./
M 0.7
2 0.6
XI
< 0.5
0.4
z 0.3
F / WIDTH
0 0.2
S.......... HEIGHT
0.1 / --- WEIGHT

0 2 4 6 8 10 12 14 16
WEEKS AFTER TRANSPLANTING

Figure 1. Growth characteristics of'Duke'tomato shown as thefraction of maximum
growth with respect to canopy width, plant height, and fresh weight.









were based on fixed levels of pan evaporation which were not varied
throughout the season. They found that applications amounts of 0.5
pan evaporation generally provided the best results. However, this
method does not consider growth differences of the plant as the season
progresses.
Marlowe et al. (1983) measured the growth and development
characteristics of'Duke' tomato plants. Some of their data are shown
in Figure 1. This figure shows a period of rapid growth around the
second to fourth week after transplanting. This is a period when
water and nutrients should be provided in sufficient amounts to meet
the requirements of the plant.
Clark et al. (1989) evaluated low and high irrigation application
amounts on micro-irrigated tomatoes grown on a sandy, flatwoods
soil in Bradenton, FL. Table 1 shows the relative daily irrigation
amounts for the two irrigation management levels over three crop

Table 1. Daily irrigation amounts scheduled during the different months of the season
and corresponding potential evapotranspiration (ETp) levels indicated by
measured pan data and historical data for the Tampa, FL area (Fla. Coop.
Ext. Ser. Bul. 205).

Month Irrigation Management Average Daily ETp Index

High Low Pan (0.75) Pan Historical
inches per day4

Fall '87'
Sep. 0.051 0.061 0.149 0.112 0.160
Oct. 0.089 0.090 0.152 0.114 0.139
Nov. 0.159 0.073 0.102 0.077 0.106
Dec. 0.199 0.088 0.090 0.068 0.084

Spring '882
Mar. 0.071 0.065 0.156 0.117 0.144
Apr. 0.147 0.084 0.217 0.163 0.185
May 0.207 0.116 0.232 0.174 0.203
Jun. 0.236 0.114 0.228 0.171 0.196

Fall '883
Sep. 0.047 0.039 0.152 0.114 0.160
Oct. 0.127 0.065 0.167 0.125 0.139
Nov. 0.161 0.070 0.112 0.084 0.106
Dec. 0.136 0.096 0.086 0.065 0.084

'Transplants were set on 24 Aug.
2Transplants were set on 19 Feb.
3Transplants were set on 23 Aug.
4Multiply inches per day by 27152 to convert to gallons per acre per day.









growth seasons. Ratios of irrigation level to pan evaporation vary
with irrigation management level. With high irrigation manage-
ment, ratios ranged from 0.3 0.4 early in the season to greater than
1.5 at the end of the fall seasons and around 1.0 at the end of the spring
season. Low irrigation management ratios range from 0.4 in the early
part of the season to 1.0 at the end of the fall seasons and 0.5 at the
end of the spring season.
The marketable yields of these management levels were similar
with each other as well as with a seepage irrigated comparison. The
high irrigation management level resulted in slightly greater propor-
tions of marketable large fruit than the low management level. An
intermediate management practice would probably provide favor-
able results.
Pan evaporation provides a good index of the atmospheric demand
for water, but must be incorporated with the crop and soil character-
istics to provide the most effective management plan. Pans can be
used on the farm and easily managed. Fla. Coop. Ext. Ser. Bul. 254
(Smajstrla et al., 1989) provides basic information regarding the use
of evaporation pans. The following sections will discuss the effects of
soil characteristics on irrigation management and how they can be
incorporated into the overall management plan.

Soil Water Storage
The soil has a finite capacity to hold and store water for crop use.
Florida's sandy soils have limited storage capacities. Soils have a
certain porosity or pore volume associated with them. The porosity
of sandy soils may be on the order of 30 to 35 percent. This means that
when saturated, 30 to 35 percent of the soil volume is water. Because
sandy soils are coarse-textured, when compared with silts and clays,
the pore spaces and capillaries are relatively large and result in poor
water holding capabilities. After a thorough saturation, the soil

Dry Saturated
Soil PWP FC Soil

1--------------I-1----------
Pore 0% 9% 16% 30%
Volume
I<- - -> I <- -> I <---- ----->
Unavailable Available Drainage Occurs
Water
Figure 2. Available water-holding capacity example of a "sandy" soil.








drains within a day or two to "field capacity" (FC). This is the amount
of water which the soil can hold against the influence of gravity after
drainage has occurred. The plant then extracts water from the soil
until the remaining water is held so tightly that it is unavailable to
the plant and permanent wilting occurs. This is called the "perma-
nent wilting point" (PWP).
The "available water holding capacity" (AWHC) of the soil is
defined as the difference between PWP and FC. A demonstration
typical of a sandy soil is depicted in Figure 2 where the saturation,
field capacity, and permanent wilting point levels are at 30%, 16%,
and 9% of pore volume, respectively. The AWHC of this example is
[(16% 9%)] 7% by volume. At FC the soil holds 16% water by volume
or 1.92 inches per foot of depth. However, at PWP the soil holds 9%
water by volume or 1.08 inches per foot of depth which remains
unavailable. Therefore, the available water holding capacity is 7% or
[(1.92-1.08)] 0.84 inches ofwater per foot depth of soil at field capacity.

Capacity
Available water holding capacity ranges from 0.40 to 1.00 inches
per foot (0.75 average) in sands to 1.25 to 1.75 (1.50 average) in sandy
loam and sandy clay loam soils.
The volume of water available to the crop depends on the root
volume of the crop and the water holding characteristics of the soil.
For example, a crop with a uniformly distributed root zone 10 inches
deep is grown on a soil with 0.84 inches of water available per foot
of depth. The available water for this example is then equal to
[(10/12 foot)(0.84 inches/foot)] 0.70 inches. An acre-inch is equal to
27152 gallons, therefore 0.70 inches is equal to [(0.70)(27152)] 19006
gallons.
Irrigations are generally scheduled when a critical fraction of the
available water has been depleted. This is used to avoid the PWP and
potential crop stress. Allowable depletion levels range from 33% to
67% of the available water with 50% used as an average. Therefore,
if in the above example a 50% allowable depletion was used, irriga-
tions would be scheduled when [(0.50)(0.70 inches)] 0.35 inches of
water had been depleted from the profile.

Limited Irrigation and Root Zones
Most of the previous discussion focused on irrigation applications
which were applied to the entire field area. When line-source micro-
irrigation tubes are used, only portions of the field are wetted by the
irrigation system. These types of irrigation systems deliver water in
slow drips at discrete locations along a piece of irrigation tubing. The








drains within a day or two to "field capacity" (FC). This is the amount
of water which the soil can hold against the influence of gravity after
drainage has occurred. The plant then extracts water from the soil
until the remaining water is held so tightly that it is unavailable to
the plant and permanent wilting occurs. This is called the "perma-
nent wilting point" (PWP).
The "available water holding capacity" (AWHC) of the soil is
defined as the difference between PWP and FC. A demonstration
typical of a sandy soil is depicted in Figure 2 where the saturation,
field capacity, and permanent wilting point levels are at 30%, 16%,
and 9% of pore volume, respectively. The AWHC of this example is
[(16% 9%)] 7% by volume. At FC the soil holds 16% water by volume
or 1.92 inches per foot of depth. However, at PWP the soil holds 9%
water by volume or 1.08 inches per foot of depth which remains
unavailable. Therefore, the available water holding capacity is 7% or
[(1.92-1.08)] 0.84 inches ofwater per foot depth of soil at field capacity.

Capacity
Available water holding capacity ranges from 0.40 to 1.00 inches
per foot (0.75 average) in sands to 1.25 to 1.75 (1.50 average) in sandy
loam and sandy clay loam soils.
The volume of water available to the crop depends on the root
volume of the crop and the water holding characteristics of the soil.
For example, a crop with a uniformly distributed root zone 10 inches
deep is grown on a soil with 0.84 inches of water available per foot
of depth. The available water for this example is then equal to
[(10/12 foot)(0.84 inches/foot)] 0.70 inches. An acre-inch is equal to
27152 gallons, therefore 0.70 inches is equal to [(0.70)(27152)] 19006
gallons.
Irrigations are generally scheduled when a critical fraction of the
available water has been depleted. This is used to avoid the PWP and
potential crop stress. Allowable depletion levels range from 33% to
67% of the available water with 50% used as an average. Therefore,
if in the above example a 50% allowable depletion was used, irriga-
tions would be scheduled when [(0.50)(0.70 inches)] 0.35 inches of
water had been depleted from the profile.

Limited Irrigation and Root Zones
Most of the previous discussion focused on irrigation applications
which were applied to the entire field area. When line-source micro-
irrigation tubes are used, only portions of the field are wetted by the
irrigation system. These types of irrigation systems deliver water in
slow drips at discrete locations along a piece of irrigation tubing. The








drip locations, emitters, are located at regular intervals (e.g. 8, 9, 10,
12, 18, or 24 inches).
Sandy soils have poor water distribution characteristics. Lateral
water movement may only be on the order of a maximum of 10 to 12
inches from the emitter, depending upon the application duration.
Therefore, closely spaced emitters will generally have greater uni-
formity of moisture distribution within the soil profile. Crops planted
on wider plant spacings can generally use the wider emitter spacings.
These systems have limited wetted soil volumes and thus smaller
reservoirs to hold soil water for crop use. This is discussed in greater
detail in Fla. Coop. Ext. Ser. Bulletin 245 (Clark et al., 1988) and Fla.
Coop. Ext. Ser. Agricultural Engineering Fact Sheet AE-72 (Clark
and Haman, 1988).
Consider a crop planted on 6-foot row centers resulting in 7260 row
feet per acre. A drip type of irrigation system is used with a close
emitter spacing (8 to 12 inches). The lateral wetting from the drip
tube is 9 inches to either side (providing an 18 inch wetted band). The
crop has a 10-inch-deep root zone, the soil holds 7% of available water
by volume, and a 67% allowable depletion will be used.
The bedded row feet per acre:
(43560 sq. feet per acre)/(6 foot row centers) =
= 7260 bedded feet per acre
The irrigated soil volume is:
(10 inch root zone) (18 inch wetted width)(7260 feet per acre)
(12 inches/foot)(12 inches/foot)
= 9075 cubic feet per acre
The soil water storage in the irrigated soil volume (@ 7%
available) is:
(0.07)(9075 cubic feet per acre)(7.48 gals per cubic foot) =
= 4752 gallons
At 67% allowable depletion, the depletion amount is:
(67/100)(4752 gallons) = 3184 gallons, or
(3184 gallons)
= 0.12 inches.
(27152 gallons/acre-inch)
The available water per acre (4752 gallons) in this example is very
different than the available water calculated in the previous section
(19006 gallons per acre), which assumed a complete root zone cover-
age. Furthermore, this example demonstrates that daily crop water









requirements in excess of 0.12 inches could result in short term daily
stresses if only one irrigation event per day is scheduled. Generally
these systems are operated for two to three short duration cycles each
day, depending upon the soil characteristics and the crop water
requirements. This type of management provides the necessary
water for the crop requirements and keeps it in the upper portion of
the soil profile.

A Water Budget
A water budget is an accounting or balance procedure used to help
schedule irrigations. This method takes into account the amounts of
water currently in the soil and any additions or deletions which occur.
This information is used to determine if an irrigation is required to
maintain the current soil water level above the allowable depletion.
The water budget method is:
Current Storage (CS) = Previous Storage (PS)
+ Effective Rainfall (ER)
+ Irrigation (I)
Crop Evapotranspiration (ETc). (2)
The values in Eq. (2) may be expressed in inches if the irrigation
and rooting systems are uniformly distributed over the production
area. If it is more convenient, they may be expressed in gallons per
acre or gallons per irrigated block. The latter method may be more
useful for micro-irrigated tomatoes grown on mulched beds.
The easiest place to start is with a full profile of water in the soil
at FC. This would be the initial level for PS. Effective rainfall is
actual rainfall minus runoff and minus drainage out of the root zone.
In some cases, mulched bed systems for example, many rainfall
events have low corresponding ER levels. This is because the actual
rainfall is not stored in the active root zone of the crop. Irrigation
water additions must be that which is available to the crop by
considering the application efficiency as was previously discussed.
The appropriate levels of PS, ER and I are added together to deter-
mine the available soil water.
Daily levels of ETc are subtracted from the available soil water to
obtain the current storage level. When current storage reaches the
allowable depletion level, an irrigation is scheduled to replenish the
profile to field capacity. After irrigation, the accounting procedure is
started again.
As an example, consider the previous situation of a micro-irrigated
tomato field with a 10-inch root zone, planted on 6-foot row centers,
and a lateral wetting of 9 inches to either side of the irrigation tube
(an 18-inch-wide band). The soil has an AWHC of 0.84 inches per foot









and an allowable depletion of 50% will be used. Rainfall is assumed
to be zero and ETc is uniform at 0.10 inches per day. The soil will
initially be at FC.
[This example converts water requirements to gallons per acre.]
The daily crop requirement (ETc):
(0.10 inches)(27152 gallons per acre-inch) =
= 2715 gallons per acre
[From the previous example, the soil water storage is 4752
gallons per acre:]
The allowable depletion @ 50% is:
(0.50)(4752 gallons) = 2736 gallons
Therefore, a water budget shows that the soil in this example holds
twice the daily requirement but at a 50% allowable depletion, daily
irrigations would be required.
If the above example was for a young crop with only a 6-inch deep
root zone the irrigation amount may need to be limited to keep from
causing deep percolation. The resultant irrigation may only provide
six inches of lateral wetting which gives a 12-inch wetted band. The
irrigated soil volume would be reduced to 40 percent of the original
example [(6/10)(12/18) = 0.40], and the available water at 50%
depletion would be 1094 gallons [(0.40)(2736 gallons)]. This would
require two and one half irrigations per day to maintain the irrigation
water in the managed root zone of the crop. If a little greater allowable
depletion could be used, two irrigations per day would be adequate.

Soil Moisture Management
Many times, roots are not uniformly distributed and are in greater
concentrations near the plant. Monitoring soil moisture levels can
help to determine if the soil moisture status is within a favorable
range and if the current irrigation management level is appropriate.
Tensiometers can be used to monitor soil moisture levels in the root
zone of the crop. Detailed discussions on the use oftensiometers are
presented in Fla. Coop. Ext. Ser. Circulars 487 (Smajstrla et al., 1984)
and 532 (Smajstrla and Harrison, 1984). Tensiometers positioned in
the active root zone of the crop can indicate if irrigation water is being
placed in the intended locations and if levels are excessive or suffi-
cient. They can also be used to determine when soil moisture levels
have been depleted to levels which require replenishment.
The use of tensiometers will vary with soil type. The readings
which indicate favorable moisture conditions on one soil will be









different on another soil. In general, field capacity on Florida's sandy
soils will be at tensiometer gauge readings of -7 to -9 centibars (cb).
Irrigations should generally be scheduled when readings are in the
range of-10 to -20 cb in the most active portion of the root zone. Some
crop/soil combinations may be able to go to -40 cb while other drought
sensitive crop/soil combinations may require frequent scheduling at
-10 to -12 cb.

Summary
This publication presents information on the scheduling of irriga-
tions for tomato production on sandy soils in Florida. Topics of
discussion included crop water requirements, soil characteristics,
limited irrigation zones, a crop water budget, and management of soil
water. Florida's sandy soils have poor water-holding and distribution
characteristics which must be used in the selection and design of the
irrigation system. Then, proper irrigation scheduling must incorpo-
rate the application characteristics of the system with the require-
ments of the crop and the water holding characteristics of the soil to
achieve an operable and effective system.
The steps to follow are:
1. Determine the water requirements of the crop and place into
units which are consistent with the method of irrigation man-
agement (inches, gallons, ...).
2. Determine and incorporate the water-holding characteristics
of the soil. These can be expressed as inches per foot of depth,
gallons per acre, gallons per 100 linear bed feet, or some other
convenient unit.
3. Be sure to realize the limitations of the root zone of the crop
and of the delivery capabilities of the irrigation system.
4. Develop a water budget by looking at the crop water demands,
the storage amounts, and external replenishment sources
(rainfall). From this budget determine the necessary irriga-
tion schedule to maintain soil water storage with the allow-
able depletion level for the crop.
5. Finally field checks of soil moisture levels can be used to
adjust irrigation schedules to conform to actual field condi-
tions. Tensiometers are a useful tool for these measurements.
For additional information on mulched bed systems and micro-
irrigation, refer to Fla. Coop. Ext. Ser. Bulletin 245 (Clark, et al.,
1988) and Fla. Coop. Ext. Ser. Fact Sheet AE-72 (Clark and Haman,
1988). These publications provide greater detail with respect to









determining bedded feet per acre, irrigated soil volumes, irrigation
application rates, and depths of irrigation.

References
1. Bennett, J.M., G.A. Marlowe and L.B. Baldwin. 1982. Conserva-
tion of irrigation water in vegetable production. Fla. Coop. Ext.
Ser. Cir. 533. Univ. of Fla.
2. Clark, G.A., D.Z. Haman, E.A. Hanlon, and G.J. Hochmuth.
1987a. Tensiometer control and fertigation of micro irrigated
tomatoes. Amer. Soc. Agri. Engr. Paper No. 87-2520. ASAE St.
Joseph, MI.
3. Clark, G.A., F.T. Izuno, P.H. Everett, andJ. Grimm. 1987b. Micro
versus seepage irrigation of tomatoes on sandy soils. Amer.
Soc. Agri. Engr. Paper No. 87-2525. ASAE St. Joseph, MI.
4. Clark, G.A., C.D. Stanley and A.G. Smajstrla. 1988. Micro-irriga-
tion in mulched bed systems: Components, system capacities
and management. Fla. Coop. Ext. Ser. Bul. 245. Univ. of Fla.
5. Clark, G.A. and D.Z. Haman. 1988. Micro-irrigation in mulched
bed production systems: Irrigation depths. Fla. Coop. Ext. Ser.
Agric. Engr. Fact Sheet AE-72. Univ. of Fla.
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COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTI-
TUTE OF FOOD AND AGRICULTURAL SCIENCES, John T. Woeste, director, in
cooperation with the United States Department of Agriculture, publishes this
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Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida
32611. Before publicizing this publication, editors should contact this address to determine availability.
Revised 7/90.




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