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Group Title: Circular
Title: Application volumes and wetting patterns for scheduling drip irrigation in Florida vegetable production
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 Material Information
Title: Application volumes and wetting patterns for scheduling drip irrigation in Florida vegetable production
Series Title: Circular
Physical Description: 11 p. : ill. ; 28 cm.
Language: English
Creator: Clark, Gary A
Smajstrla, A. G ( Allen George )
Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1993
 Subjects
Subject: Microirrigation -- Florida   ( lcsh )
Irrigation scheduling -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 8-9).
Statement of Responsibility: Gary A. Clark and Allen G. Smajstrla.
General Note: Cover title.
General Note: "February 1993."
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Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: ltqf - AAA6901
ltuf - AJN7895
oclc - 27943167
alephbibnum - 001813991

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February 1993


Circular 1041


Application Volumes and Wetting Patterns

for Scheduling Drip Irrigation in

Florida Vegetable Production


Gary A. Clark and Allen G. Smajstrla

















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











































































Gary A. Clark, Associate Professor of Agricultural Engineering, Extension Irrigation Specialist, University of Florida, Gulf Coast Research and
Education Center, Bradenton, FL; and Allen G. Smajstria, Professor of Agricultural Engineering, University of Florida, Agricultural Engineer-
ing Department, Gainesville, FL.








Introduction
Drip irrigation offers many ad-
vantages as a method of water ap-
plication. Water is applied to the
root zone of the plant at discrete
locations through emitters either
embedded into, embossed onto, or
attached directly to plastic tubing.
This water application method,
compared to overhead application
systems, reduces the potential for
foliar diseases and increases water
application efficiency. In addition,
liquid fertilizer may be injected
and applied as needed to provide
prescription water and fertilizer
applications in response to plant
needs, even under plastic mulch.
Drip irrigation is particularly ben-
eficial on sandy soils, which have
low water-holding capacities and
low cation exchange capacities.
However, without proper system
management, drip irrigation can
waste water and nutrients, or can
reduce yields.

Proper use of drip irrigation re-
quires that system designers and
managers know the soil hydraulic
characteristics, plant growth and
water use characteristics, and
evaporative demands. Irrigation
schedules must be developed con-
sidering these factors and must
conform to existing irrigation sys-
tem and cultural constraints. Be-
cause excessive water applications
leach plant nutrients out of the
crop root zone, the water manage-
ment program must be coordinated
with the fertilizer management
program. This bulletin discusses
those aspects of drip irrigation
scheduling specifically related to
the soil and drip tube characteris-
tics that affect water placement,
distribution, and availablility to
the plant.

Soil Properties
Soil properties play an impor-
tant role in irrigation scheduling
and plant water management. As


much as 30% to 40% of the soil vol-
ume is pore space, which is filled
with water at saturation. However,
because a soil has a wide range of
pore sizes, and water drains quickly
from large pores, following satura-
tion drainage occurs to the "field
capacity" (FC) level of the soil.
Plant extraction of water from the
soil occurs until the remaining wa-
ter is held so tightly that it is un-
available to the plant, and wilting
point (WP) of the soil occurs.


The "available water-holding
capacity" (AWHC) of the soil is de-
fined as the difference between WP
and FC (see Fig. 1). Soil water
content for a typical Florida sandy
soil may be 34%, 14%, and 8% by
volume for the saturation, field ca-
pacity, and wilting point levels, re-
spectively. The AWHC of this soil
would be (14% 8% = 6%) 6% by
volume. Available water-holding
capacity in typical Florida soils
ranges from 3% to 8% in sands to


WATER HOLDING CAPACITY

AND AVAILABLE WATER






"Sandy Soil"
Dry Saturated
Soil WP FC Soil

I I I I
Pore 0% 8% 14% 34%
Volume
Unavailable Available Drainage
Water Water Occurs



Available
= FC WP
Water (AW)

AW = 14% 8%

AW = 6%

AW = 0.72 in/ft


Figure 1. Water-holding capacity and available water example for a typical Florida sandy soil.


1


, ,*








10% to 15% in sandy loam and
sandy clay loam soils. Soils with
greater proportions of clay, silt, or
organic matter will have even higher
water-holding capacities.

The volume of water available to
the crop depends on the distribution
of plant roots and the water holding
characteristics of the soil. Irriga-
tions are generally scheduled when
an allowable fraction of the available
water above WP has been depleted
so that potential crop stress is
avoided. Typical levels of allowable
depletion may range from 30% of the
available water for sensitive crops to
70% for drought tolerant crops with
50% sometimes used as an average.
Therefore, in the previous example
of available water, irrigations would
be scheduled when the water con-
tent of the soil drops to 10% to 12%
rather than allowing the water con-
tent to drop all the way to the wilt-
ing point of 8%.

Drip irrigation systems deliver
water from drip emitters in slow
drips at discrete locations along the
irrigation tubing (see Fig. 2). Drip
emitters are located at regular inter-
vals such as 8, 12, or 16 inches.
Therefore, when drip irrigation
tubes or emitters are used, only por-
tions of the field are wetted by the
irrigation system. Because drip irri-
gation relies on the soil capillarity to
convey water from the emitter loca-
tion to the crop root zone, short run
times may apply the desired volume
of water, but the applied water may
not be positioned in a location avail-
able to the root system. This is com-
mon during the early stages of plant
development with immature root
systems. Therefore, during early
crop development, irrigations must
be run long enough to ensure that
the applied water is available to the
crop.

Soil capillarity is related to the
size of the pore spaces between the
soil particles and is an important
factor in water movement from drip


emitters. Although large capillaries
will transmit water more rapidly
than smaller capillaries, the
smaller capillaries will provide
greater lateral distribution of water
from the emitter. Sandy soils have
relatively large capillaries in com-
parison to clay or loam soils.


Horizontal water distribution
from point source drip emitters is
by soil capillarity; vertical move-
ment is influenced by both capillar-
ity and gravity. Therefore, water
distribution from drip emitters is
also affected by the irrigation run
time. In general, water and chemi-


Figure 2. Wetting patterns on a raised, vegetable production soil bed using drip irrigation.


Figure 3. Wetting front characteristics from a single dripper on a sandy soil.


DRIPPER







cals applied through the irrigation
system will be in greater concentra-
tions near the drip emitters. Figure
3 shows an example of the progres-
sion of the wetting front from a drip
emitter located on a sandy soil.
After 20 min of run time, the wet-
ting front had progressed 4 inches
from the drip emitter. Thus, as pre-
viously discussed, sufficient run
time may need to be scheduled in
order to move the applied water
laterally into the root zone of imma-
ture plant systems. After roots grow
into the areas wetted by the drip
emitters, schedules can be adjusted
accordingly.

Sandy soils generally have poor
water distribution characteristics,
with maximum lateral water distri-
butions ranging from 8 to 12 inches
from the emitter. This will depend
on how long the system is operated
and initial moisture conditions.
Pulsing the water application with a
series of on/off cycles may affect lat-
eral movement of water on some soil
types, but generally not on very
sandy soils. On heavy, fine textured
(loam or clay) soils, drip application
rates may exceed the infiltration
rate of the soil, resulting in ponding
or runoff of applied water. In gen-
eral, on sandy soils, closely spaced
emitters will result in greater uni-
formity of moisture distribution
within the soil profile. Individual
soils should be tested to determine
their lateral wetting capabilities to
aid in selecting an emitter spacing
and in irrigation scheduling. Field
instruments such as tensiometers or
other moisture measurement devices
should be used to check actual soil
wetting patterns and water distribu-
tions from irrigation schedules.

Run time per irrigation cycle is
also important. The total run time
required per day can be divided into
2 or 3 cycles per day depending on
the dripper, soil, plant, and irriga-
tion system constraints. Multiple,
short duration cycles (e.g. 15 min/


cycle) will minimize deep percola-
tion of applied water (Fig. 4A), but
may also confine the lateral distri-
bution of water near the dripper
and may not be long enough for liq-
uid fertilizer injections. As dripper
spacing increases, complete distri-
bution of applied water between
drippers will be reduced (Fig. 4B)
unless greater run times are used
(Fig. 4C), which could potentially
leach nutrients away from the plant
root zone.


Volume of Available
Water
The volume of water available to
a drip-irrigated plant will depend
upon water distributions from the
drip emitters, the soil water-holding
properties, and the size of the root
zone. Water distributions will be: 1)
hemispheres for short duration run
times with wide spacings (Fig. 5); 2)
vertical cylinders for long run times
with wide spacings (Fig. 6); 3) hori-


Row Direction ---


A Close spacing; Short run time
SDripper






Wetted Perimeter


B Distant spacing; Short run time


C Distant spacing; Long run time


Figure 4. Wetting patterns for different emitter spacings and run times (A) close emitter
spacing, short run time; (B) wide emitter spacing, short run time; and (C) wide
emitter spacing, long run time.


----~-- -- ----- -----~~-








zontal half-cylinders for closely
spaced emitters and short run times
(Fig. 7); or 4) rectangular blocks for
closely spaced emitters with long
run times (Fig. 8).

Distribution patterns 1 and 2
would be expected for widely spaced
emitters or short run times per irri-
gation. Each plant may have one or
more emitters, but the distribution
patterns may not overlap.

Patterns 3 and 4 would be com-
mon for vegetable or other row crop
drip systems with closely spaced
emitters.

The volume of available water
stored in each of these distribution
patterns must be known by the irri-
gation manager in order to develop
irrigation schedules and manage
the irrigation system throughout
the crop production season. Tables
1 through 4 provide the volume of
available water for each of these
patterns based upon the dimensions
of the wetted areas and the avail-
able water-holding capacity of the
soil.

For example, consider a veg-
etable drip irrigation system on a
sandy soil with an available water-
holding capacity of 5% and emitters
spaced 24 inches apart. The system
is operated to irrigate no deeper
than 12 inches, and also provides 12
inches of lateral wetting from the
dripper, providing a wetted pattern
similar to the hemispheres in Fig. 5.
Using Table 1, the available water
in the wetted pattern would be 78
gallons per 100 drippers. If each
plant was located next to a dripper,
then each plant would have about
0.78 gallons of water available from
that wetting pattern. If the system
were operated for a longer period of
time such that the lateral wetting
did not increase but the wetted
depth approached 2 feet, the distri-
bution pattern might approach the
cylinder shape shown in Fig. 6.


Figure 5. Hemisphere water distribution pattern from individual drip emitters operated for
short run times.


Figure 6. Vertical cylinder water distribution patterns from individual drip emitters operated
for long run times.


Drip Emitters Dripper Line









Wetted Volume




Radius




Depth




1







Using Table 2C, the available water
would become 235 gallons per 100
drippers, or 2.35 gallons per plant.

Now assume that the emitter
spacing is changed to 8 inches,
the wetted depth remains at 12
inches, and the wetting pattern
approaches the half cylinder
shown in Fig. 7. Using Table 3,
the available water would be 59
gallons per 100 feet. If plants
were spaced 24 inches apart, a 100
foot length of bed would contain 50
plants, and each plant would have
1.18 gallons of available water.
It is important to remember that
these examples assume that the
roots are distributed within the
wetted soil volumes and that the
plant has full access to the applied
water.

Evaporative Demand
and Volumetric Water
Use
Estimates of potential
evapotranspiration obtained
from calculations using measured
weather data, measured pan evapo-
ration, or from historical data bases
is reported in units of depth (inches)
of water use over the irrigated area.
This unit is appropriate for schedul-
ing irrigations with an overhead
irrigation system that also applies
water in inches. However, drip sys-
tems apply water in volume units
such as gallons per 100 feet of row
or gallons per plant. Therefore, it
would also be convenient to know
the crop water requirements in gal-
lons per plant or per 100 feet of row.
Tables 5 or 6 can be used to convert
from inches of crop water require-
ment or water application depth to
volume units. Table 5 converts
from inches of depth to gallons per
100 feet of plant row based upon
plant bed spacing. Table 6 converts
from inches of depth to gallons per
100 plants, and is based upon the
plant population in number of
plants per acre.


Figure 7. Horizontal half-cylinder water distribution pattern from closely spaced drip emitters
or line-source drip tubing operated for short run times.


Figure 8. Rectangular block water distribution pattern from closely spaced drip emitters or
line-source drip tubing operated for long run times.


tised Sod Bed


>"-,








For example, from Table 5 a
drip-irrigated tomato crop on beds
spaced on 6 foot centers with a crop
water use of 0.15 inches per day
would require a volume (V) of wa-
ter of 56 gal/100 feet of row per day.
Thus, if the field had 50,000 feet of
row, then 28,000 gallons of water
would be required each day.

Drip systems are normally 80%
to 90% efficient, with the actual
efficiency dependent upon system
design, operation, and cultural ar-
rangement. Therefore, it is impor-
tant to remember that additional
water is required to compensate for
losses due to system inefficiency.
If, in the above example, water was
applied daily at 85% efficiency,
then [28,000/0.85] 32,941 gallons
should be pumped each day.

Drip Tubing Discharge
Drip irrigation tubing discharges
water from small emission points
or orifices. The water discharge
rate is an important consideration
for scheduling and management
purposes. In many drip emitters,
the water discharge varies with
operating pressure, and tubing flow
rates are provided as either gallons
per hour (gph) per emitter or
gallons per minute (gpm) per 100
feet of tube length at a certain op-
erating pressure. Common dis-
charge rates range from 0.2 to 2.0
gph per emitter, or from 0.3 to 0.5
gpm/100 feet of lateral.

Choice of emitter spacing should
be based on plant spacing, expected
root distribution, and soil hydraulic
characteristics. For example, a
12-inch emitter spacing would be
appropriate for strawberry plants
spaced 12 inches apart on a sandy
soil. Although a wider spacing
such as 16 or 18 inches may be
used, irrigation run times must
be long enough to move water at
least 9 inches from the emitter for
plants between emitters. The ap-


Table 1. Volume of available water stored in the hemisphere distribution pattern shown in
Fig. 5 and based upon the available water-holding capacity of the soil and the wetted radius
from the dripper (in gallons per 100 drippers).
Available Wetted Radius (inches)
Water (%) 3 6 9 12 15 18
Gallons of available water per 100 drippers
3 0.7 6 20 47 92 159
4 1.0 8 26 63 123 212
5 1.2 10 33 78 153 265
6 1.5 12 40 94 184 318
7 1.7 14 46 110 214 371
8 2.0 16 53 125 245 423
9 2.2 18 60 141 276 476
10 2.5 20 66 157 306 529
11 2.7 22 73 173 337 582
12 2.9 24 79 188 368 635
13 3.2 25 86 204 398 688
14 3.4 27 93 220 429 741
15 3.7 29 99 235 459 794



Table 2. Volume of available water stored in the cylindrical distribution pattern of Fig. 6
and based upon the available water-holding capacity of the soil, the wetted radius from the
dripper, and: A) a 1-foot depth of wetting; B) a 1.5-foot depth of wetting; C) a 2-foot depth of
wetting; and D) a 3-foot depth of wetting (in gallons per 100 drippers).

2A) 1-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 drippers
3 18 40 71 110 159
4 24 53 94 147 212
5 29 66 118 184 265
6 35 79 141 221 318
7 41 93 165 257 371
8 47 106 188 294 424
9 53 119 212 331 476
10 59 132 235 368 529
11 65 146 259 404 582
12 71 159 282 441 635
13 76 172 306 478 688
14 82 185 329 515 741
15 88 199 353 552 794







plied water will move downward at
least 9 inches, which could be lower
than the effective root zone on
young plants. This may result in
leaching of plant nutrients at the
emitter locations.

The tubing discharge per emitter
can be converted to tubing discharge
per unit of length (ft) or per acre,
which is useful for irrigation system
design and scheduling purposes.
The following equation can be used
to convert emitter discharge rates in
gallons per hour (gph) per emitter to
gallons per minute (gpm) per 100
feet of tubing length.

Qgpm(100) = (20)(Qem)/Se

Where:

Qgpm(100) = the tubing water
discharge rate (gpm per 100 feet of
pipe),

Qem = the emitter water dis-
charge rate (gph/emitter), and

Se = the emitter spacing along
the drip tube (inches).

For example, a drip tube with an
emitter discharge rate of 0.3 gph
and an emitter spacing of 9 inches
would have a corresponding tubing
discharge of (20 x 0.3)/9 = 0.67 gpm/
100 ft.

Summary
Scheduling of irrigations for drip
irrigated crop production in Florida
is a dynamic process requiring con-
stant attention. Topics to consider
include soil and plant characteris-
tics, evaporative demand and crop
water requirements, scheduling
methods, drip tube characteristics,
and irrigation system characteris-
tics. Proper irrigation scheduling
must incorporate the application
characteristics of the system with
the requirements of the crop and the
water-holding characteristics of the
soil to achieve an operable and effec-
tive system. The steps to follow are:


2B) 1.5-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 drippers
3 26 60 106 166 238
4 35 79 141 221 318
5 44 99 177 276 397
6 53 119 212 331 477
7 62 139 247 386 556
8 71 159 283 442 636
9 79 179 318 497 715
10 88 199 353 552 795
11 97 219 389 607 874
12 106 238 424 662 954
13 115 258 459 718 1033
14 124 278 495 773 1113
15 132 298 530 828 1192



2C) 2-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 drippers
3 35 79 141 221 318
4 47 106 188 294 424
5 59 132 235 368 529
6 71 159 282 441 635
7 82 185 329 515 741
8 94 212 376 588 847
9 106 238 424 662 953
10 118 265 471 735 1059
11 129 291 518 809 1165
12 141 318 565 882 1271
13 153 344 612 956 1377
14 165 371 659 1029 1482
15 176 397 706 1103 1588








1. Determine the water require-
ments of the crop in units which
are consistent with drip irriga-
tion, such as gal/100 feet of lat-
eral, gallons per acre, or gallons
per irrigated block.

2. Determine the water-holding
characteristics of the soil in the
same units as the crop water re-
quirements.

3. Recognize the limitations of the
crop root zone and of the water
application capabilities of the ir-
rigation system.

4. Develop a water budget to main-
tain soil water storage with the
allowable depletion level for the
crop by considering the crop wa-
ter demands, the storage
amounts, and rainfall.

5. Check fields for soil moisture lev-
els using tensiometers or other
soil moisture measurement de-
vices in order to adjust irrigation
schedules to conform to actual
field conditions.

Related Publications
Clark, G. A., C. D. Stanley, and A.
G. Smajstrla. 1988. Micro-irriga-
tion on mulched bed systems:
Components, system capacities,
and management. Fla. Coop. Ext.
Ser. Bul. 245, Univ. of Fla.,
Gainesville.

Jones, J. W., L. H. Allen, S. F. Shih,
J. S. Rogers, L. C. Hammond, A.
G. Smajstrla, and J. D. Martsolf.
1984. Estimated and measured
evapotranspiration for Florida
climate, crops, and soils. Fla.
Coop. Ext. Ser. Tech. Bul. 840,
Univ. of Fla., Gainesville.

Pitts, D. J., D. Z. Haman, and A. G.
Smajstrla. 1990. Causes and pre-
vention of emitter plugging in mi-
cro irrigation systems. Fla. Coop.
Ext. Ser. Bul. 258, Univ. of Fla.,
Gainesville.


2D) 3-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 drippers
3 53 119 212 331 477
4 71 159 283 442 636
5 88 199 353 552 795
6 106 238 424 662 954
7 124 278 495 773 1113
8 141 318 565 883 1272
9 159 358 636 994 1431
10 177 397 707 1104 1590
11 194 437 777 1214 1749
12 212 477 848 1325 1908
13 230 517 919 1435 2067
14 247 556 989 1546 2226
15 265 596 1060 1656 2385



Table 3. Volume of available water stored in the half cylinder distribution pattern shown in
Fig. 7 and based upon the available water-holding capacity of the soil and the wetted radius
from the dripper (in gallons per 100 feet of row length).
Available Wetted Radius (inches)
Water (%) 3 6 9 12 15 18
Gallons of available water per 100 feet of length
3 2 9 20 35 55 79
4 3 12 26 47 74 106
5 4 15 33 59 92 132
6 4 18 40 71 110 159
7 5 21 46 82 129 185
8 6 24 53 94 147 212
9 7 26 60 106 165 238
10 7 29 66 118 184 265
11 8 32 73 129 202 291
12 9 35 79 141 221 318
13 10 38 86 153 239 344
14 10 41 93 165 257 371
15 11 44 99 176 276 397








Smajstrla, A. G., D. S. Harrison,
and F. X. Duran. 1984. Tensiom-
eters for soil moisture measure-
ment and irrigation scheduling.
Fla. Coop. Ext. Ser. Tech. Cir.
487, Univ. of Fla., Gainesville.

Smajstrla, A. G., B. J. Boman, G. A.
Clark, D. Z. Haman, D. S.
Harrison, F. T. Izuno, and F. S.
Zazueta. 1988. Efficiencies of
Florida agricultural irrigation
systems. Fla. Coop. Ext. Ser. Bul.
247, Univ. of Fla., Gainesville.

Smajstrla, A. G., B. J. Boman, G. A.
Clark, D. Z. Haman, F. T. Izuno,
and F. S. Zazueta. 1988. Basic
irrigation scheduling in Florida.
Fla. Coop. Ext. Ser. Bul. 249,
Univ. of Fla., Gainesville.

Smajstrla, A. G., F. S. Zazueta, G.
A. Clark, and D. J. Pitts. 1989.
Irrigation scheduling with evapo-
ration pans. Fla. Coop. Ext. Ser.
Bul. 254, Univ. of Fla.,
Gainesville.

Zazueta, F. S., A. G. Smajstrla, and
D. Z. Haman. 1987. Evapotrans-
piration estimation utilities. Fla.
Coop. Ext. Ser. Cir. 744, Com-
puter Series, Univ. of Fla.,
Gainesville.


Table 4. Volume of available water stored in the rectangular distribution pattern shown in
Fig. 8 and based upon the available water-holding capacity of the soil, the wetted radius
from the dripper, and: A) a 1-foot depth of wetting; B) a 1.5-foot depth of wetting; C) a 2-foot
depth of wetting; and D) a 3-foot depth of wetting (in gallons per 100 feet of row length).
4A) 1-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 feet of length
3 22 34 45 56 67
4 30 45 60 75 90
5 37 56 75 94 112
6 45 67 90 112 135
7 52 79 105 131 157
8 60 90 120 150 180
9 67 101 135 168 202
10 75 112 150 187 225
11 82 124 165 206 247
12 90 135 180 225 270
13 97 146 195 243 292
14 105 157 210 262 314
15 112 168 225 281 337



4B) 1.5-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 feet of length
3 34 51 67 84 101
4 45 67 90 112 135
5 56 84 112 140 168
6 67 101 135 168 202
7 79 118 157 197 236
8 90 135 180 225 270
9 101 152 202 253 303
10 112 168 225 281 337
11 124 185 247 309 371
12 135 202 270 337 404
13 146 219 292 365 438
14 157 236 314 393 472
15 168 253 337 421 505







4C) 2-foot depth of wetting.

Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 feet of length
3 45 67 90 112 135
4 60 90 120 150 180
5 75 112 150 187 225
6 90 135 180 225 270
7 105 157 210 262 314
8 120 180 240 300 359
9 135 202 270 337 404
10 150 225 300 374 449
11 165 247 329 412 494
12 180 270 359 449 539
13 195 292 389 487 584
14 210 314 419 524 629
15 225 337 449 562 674



4D) 3-foot depth of wetting.
Available Wetted Radius (inches)
Water (%) 6 9 12 15 18
Gallons of available water per 100 feet of length
3 67 101 135 168 202
4 90 135 180 225 270
5 112 168 225 281 337
6 135 202 270 337 404
7 157 236 314 393 472
8 180 270 359 449 539
9 202 303 404 505 607
10 225 337 449 562 674
11 247 371 494 618 741
12 270 404 539 674 809
13 292 438 584 730 876
14 314 472 629 786 943
15 337 505 674 842 1011







Table 5. Conversion from depth of crop water use or application to volume in gallons per
100 feet of bed length for different plant bed spacings.

Bed Spacing Crop Water Use or Application Depth
(feet) (inches)
0.05 0.10 0.15 0.20 0.25 0.30
Gallons per 100 feet of bed length
3 9 19 28 37 47 56
4 13 25 37 50 62 75
5 16 31 47 62 78 93
6 19 37 56 74 93 112
7 22 44 65 87 109 131
8 25 50 75 100 125 150
9 28 56 84 112 140 168
10 31 62 93 125 156 187



Table 6. Conversion from depth of crop water use or application to volume in gallons per
100 plants for different plant population levels in number of plants per acre.
Plant Crop Water Use or Application Depth
Population (inches)
(No./acre) 0.05 0.10 0.15 0.20 0.25 0.30
Gallons per 100 plants
100 1358 2715 4073 5430 6788 8146
150 905 1810 2715 3620 4525 5430
200 679 1358 2036 2715 3394 4073
300 453 905 1358 1810 2263 2715
400 339 679 1018 1358 1697 2036
600 226 453 679 905 1131 1358
800 170 339 509 679 849 1018
1000 136 272 407 543 679 815
1500 91 181 272 362 453 543
2000 68 136 204 272 339 407
3000 45 91 136 181 226 272
4000 34 68 102 136 170 204
5000 27 54 81 109 136 163























































































COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T. Woeste, Director,
in cooperation with the United States Department of Agriculture, publishes this information to furtherthe purpose of the May 8and 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 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 this publication, editors should contact this address to determine availability.
Printed 2/93.




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