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Group Title: Bulletin - Agricultural Experiment Station. University of Florida ; 887
Title: Microirrigation for flowering ornamental crops in humid regions
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
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Permanent Link: http://ufdc.ufl.edu/UF00086513/00001
 Material Information
Title: Microirrigation for flowering ornamental crops in humid regions
Series Title: Southern cooperative series bulletin
Physical Description: 9, 1 p. : ill. ; 28 cm.
Language: English
Creator: Stanley, C. D
University of Florida -- Agricultural Experiment Station
Publisher: Agricultural Experiment Station, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1992
 Subjects
Subject: Plants, Ornamental -- Irrigation   ( lcsh )
Flowers -- Irrigation   ( lcsh )
Ornamental horticulture   ( lcsh )
Floriculture   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 9-10).
Statement of Responsibility: C.D. Stanley ... et al..
General Note: Cover title.
General Note: "Produced as a result of research conducted as a component of Southern Regional Research Project S-143: Trickle irrigation in humid regions."
General Note: "Printed 1/92"--P. 10.
Funding: Bulletin (University of Florida. Agricultural Experiment Station) ;
 Record Information
Bibliographic ID: UF00086513
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 26383291

Table of Contents
    Front Cover
        Front Cover
    Front Matter
        Front Matter
    Main
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
        Page 7
        Page 8
    Literature cited
        Page 9
        Page 10
Full Text

Microirrigation for

Flowering Ornamental Crops
in Humid Regions

C. D. Stanley, G.A. Clark, J.W. Prevatt, B. K. Harbaugh, and A. J. Overman


Southern Cooperative Series Bulletin 364
This publication was produced as a result of research conducted as a
component of Southern Regional Research Project S-143:
Trickle Irrigation in Humid Regions

Agricultural Experiment Station / Institute of Food and Agricultural Sciences / University of Florida / J.M. Davidson, Dean


Bulletin 887









































































C. D. Stanley is Associate Professor; G. A. Clark is Associate Professor; J.W. Prevatt is Associate Professor; B.K. Harbaugh is Pro-
fessor; and A. J. Overman is Professor; all are from the IFAS Gulf Coast Research and Education Center, 5007 60th Street East,
Bradenton, Florida.

Administrative advisor for project S-143 was J. R. Fischer, Dean and Director, South Carolina Agricultural Experiment Station, 104
Barre Hall, Clemson University, Clemson, SC 29634-0351.








Introduction
Irrigation of flowering ornamental crops is typi-
cally required for production of a high quality crop.
Traditional irrigation systems have not always ap-
plied water efficiently. In recent years, issues con-
cerning the irrigation of ornamental crops and
waste of available water resources have received
greater attention from producers, causing them to
consider improving irrigation system efficiency. Ad-
ditional incentives include regulatory limitations
on water supplies available for irrigation and the
impact of excessive irrigation on the movement of
applied nutrients and pesticides from the produc-
tion area into the environment. Improved irriga-
tion management and increased control over other
cultural practices are factors which producers must
consider when changing an irrigation system.

Perhaps the widest range of irrigation system
options for agriculture are available for production
of ornamental crops. These include subirrigation,
overhead irrigation, hand watering, and many
types of microirrigation. The nature of
microirrigation and its ability to address water
quantity limitations and to manage agrichemical
movement make it an attractive alternative to
more conventional irrigation systems.

Project objectives
Objectives of Regional Project S-143 have been to
perform research to address the design, manage-
ment, and cultural implications of using
microirrigation systems for horticultural crop pro-
duction. Overall goals were to improve productiv-
ity, management and acceptability of these systems
for commercial use. From initiation of the project
until 1990, the objectives have specifically been:

* to determine crop water requirements under
specific soil conditions for development of opti-
mum irrigation management (scheduling) tech-
niques;
* to develop management techniques and guide-
lines for injection of agrichemicals through
microirrigation systems;
* to develop specific design criteria and procedures
for microirrigation in humid regions including
effective cultural and management practices;
* to assess the costs, returns, and profitability of
microirrigation on selected crops.
This report will summarize the pertinent re-
search conducted under these objectives, specifi-


cally addressing the use of microirrigation for pro-
duction of flowering ornamental crops in humid re-
gions.

Microirrigation systems for
ornamental crop production
Microirrigation systems include line-source lat-
eral drip tubes, microsprayers, microsprinklers,
spaghetti tubes, capillary mats, and numerous
other emitter devices and systems. In general,
these systems have the localized application char-
acteristics operating with low pressure require-
ments. Volume of water applied is controlled by
the duration of operation as well as the emitter
characteristics. These systems apply water to lo-
calized zones and allow precise and controlled irri-
gation applications. With proper management,
low-volume applications can be precisely achieved.
Poor management can result in excessive applica-
tions, reducing system efficiency.

Field systems used with mulched beds have one
or more lateral drip tubes in each bed. The tubes
are placed under the plastic mulch either on the
soil surface or at shallow depths below the surface
as shown in Figure 1. Since upward capillary
movement of water is very limited in sandy soils,
installation depths of only 2 to 8 cm are recom-
mended for these soils.

Emitter or orifice spacing can vary from 10 cm to
a meter or more. Because lateral movement of wa-
ter in sandy soils is limited to 25 to 30 cm, emitter
spacings should be close enough to provide an even
distribution of water or any additive applied
through the irrigation system. Typical spacings
range from 22 to 56 cm on sandy soils. Greater
emitter spacings can be used on heavier soils which
provide greater lateral movement of water. For


SINGLE TUBE MULTIPLE TUBES
PER BED PER BED


Figure 1. Line source microirrigation for mulch-bedded row
crops (Clark et al., 1988a).


S' ITY Of HG~iiPAq s.;k yS































MICRO-SPAYERS

Figure 2. Microsprayers for irrigation of container plants (Clark
et al., 1988a).


more information on this type of system see Clark
et al. (1988b).

Several microirrigation systems are available for
use with container grown plants (Clark et al.,
1988a). These systems include microsprayers, spa-
ghetti tubes, and line-source drip tubes used with a
capillary mat. Required operating pressures will
range from 5 psi to 30 psi, depending on emitter
type and other system design factors. Therefore,
pumping power requirements are generally low.

Microsprayers (Figure 2) apply water as small
streams or sprays and are used extensively in pot-
ted plant production. Use in field-planted woody
ornamental production systems is also common.
These systems may be designed to apply water to
the foliage if crop cooling or foliar chemigation is
desired. However, if chemical precipitation on foli-
age is a problem, these systems should be designed
to avoid wetting the foliage. Emitter discharge
rates can vary from 0.02 to 0.2 m3 hr- with diam-
eters of coverage ranging from 1 to 7 m. This al-
lows precise water control in relatively small areas.

Spaghetti tube systems are also used with con-
tainer grown ornamentals. Spaghetti tube emitters
apply water as small streams or drips directly to
the individual containers (Figure 3). The inside di-
ameter of spaghetti tubing is small (0.09 mm to


A B


Figure 3. Spaghetti tube irrigation: (A) single tube, weighted drippers and (B) multiple outlet drippers (Clark et al., 1988a).







CAPILLARY MAT IRRIGATION SYSTEM


WATER SUPPLY
(DRIP TUBE)


BENCH


CAPILLARY MAT


Figure 4. Line-source microirrigation tubes used with a capil-
lary mat application system (Clark et al., 1988a).


0.18 mm) which provides a restricted flow path for
water control. The spaghetti tubing is cut to the
desired length and then one end of the tubing is
weighted or attached to a small stake and placed in
the container to be irrigated. The other end is in-
serted into the lateral, which conveys water from
the pump or water supply system.

Spaghetti tube systems are designed to deliver
water and chemicals directly to the pot media. This
eliminates irrigation of non-production areas and
increases application efficiency. Because water
movement in container media is controlled by both
gravitational and capillary action, damp, uniformly
mixed, and well-graded potting media is needed.
Use of these systems may require initial sprinkler
or hand watering to dampen potting media.

The use of line-source tubes with a capillary mat
system is shown in Figure 4. These systems apply
water to the capillary mat with the line-source tub-
ing. The mat then distributes the water to the
pots, and irrigation is accomplished by upward
movement of water through the potting media. As
with the spaghetti tube systems, damp potting me-
dia is necessary to establish capillarity. Therefore,
sprinkler watering may be necessary for this proce-
dure.


Chemigation should not be used with capillary
mat systems. These systems do not apply water
directly to the plants or pots; therefore, control of
chemical application rates and amounts is not pos-
sible. The use of controlled-release fertilizers
placed directly in the pots is recommended for nu-
tritional requirements.

Microirrigation systems have greater mainte-
nance requirements than conventional overhead or
surface irrigation systems. The small orifices and
emitter passageways of these systems are easily
clogged with small particles or growth of biological
organisms. Therefore, water treatment, filtration,
and periodic cleaning of the system are generally
necessary (Pitts et al., 1990).

Because water is applied so precisely, the
microirrigation systems can be managed for opti-
mal water conservation. As with the sprinkler and
spray systems, water should be limited to amounts
which will remain within the active root zone of the
crop. In addition to poor water conservation,
overapplications can leach beneficial nutrients from
the root zone.

Microsprayer systems are sometimes used for
crop cooling or frost and freeze protection. These
applications are generally limited to low height
crops with foliage in or near the spray from the
emitters.

Water requirements
Research was conducted to determine water re-
quirements of various flowering ornamental crops
with the goal of using the information to develop
microirrigation scheduling guidelines. Harbaugh et
al. (1982) studied water use of microirrigation ver-
sus overhead irrigation for cut-flower chrysanthe-
mum production. Their microirrigation production
system used three laterals per bed and used slow-
release fertilizer. Seasonal water application
amounts of 13.6, 20.3, 27.1, 33.9, and 40.7 cm were
compared. Figure 5 indicates that seasonal applica-
tion amounts above 27.1 cm showed no significant
increase with respect to stem yield and quality,
while irrigation treatments below 27.1 cm showed
significant reduction in stem yield and quality. A
comparison to water application recommendations
for overhead irrigation resulted in a 91% reduction
in water applied when the microirrigation system
was used at optimum application rates.





















C
f_ 40


Seai
Irrigatl


2
-*- 2
2
-9- 3
- 4


0 20 40 60
Days from Transplanting

Figure 5. Plant height progression for 'Manatee Y
chrysanthemums grown with differing microirrig
(Harbaugh et al., 1982).

The effect that variation in seasonal e
demand has on crop water requirements
tigated for cut-flower chrysanthemum p
with microirrigation (Harbaugh et al., 1
results of four seasons of irrigation rate
showed that an optimum daily irrigation
0.99 cm day-1 in the bedded area was rec
prevent production losses from occurring
An additional study (Harbaugh et al., 1E
sulted in a similar optimum microirriga
cation rate. However, the optimum rate
stantially higher than that determined i
lier study (Harbaugh et al, 1982) and de
the effect of differing seasons on water r
ments.

Stanley and Harbaugh (1984a) devel(
method for estimating crop water require
based on crop species, stage of develop
evaporative demand for potted chrysant
grown with microirrigation. Three local
greenhouse, saran shadehouse, and out!
shade) were used to provide a wide rang
rative demand. Daily evapotranspiration
pan evaporation (located in the growing
ment) and plant growth characteristics
height and width) were measured for in
groups of pots in the various locations.
regression analyses of the data resulted


requirement estimation equation (including crop
Canopy height and pan evaporation as independent
variables) that was used to schedule irrigation of a
subsequent crop regardless of location. Figure 7
illustrates the degree of fit for measured water use
versus the estimated water requirement for plants
grown in the three different locations. If estimated
amounts had predicted the measured amounts, all
points would have been located on the 1:1 line. Al-
though the regression equation tended to underes-
timate water needs for crops grown where evapora-
tive demand was high (outside, no shade), results
sonal showed a strong relationship between evapotrans-
Ion Rate piration, and pan evaporation and crop canopy
characteristics.
3.6 cm
0.3 cm A similar study of poinsettia water use (Stanley
7.1 cm
and Harbaugh, 1989) resulted in a water require-
3.9 cm ment prediction equation (R2=0.78) which included
0.7 c canopy height, canopy width, and pan evaporation
J as independent variables. When a subsequent crop
80 100 was grown to verify the prediction equation, al-
though there was a similar tendency to underesti-
'ellow Iceberg' mate water requirements for high evaporative de-
ation rates mand periods (Figure 8), the crop quality and yield
was not significantly different from plants irrigated
with adequate water throughout the season.
evaporative
was inves- In addition to direct water requirement determi-
roduction nation studies, microirrigation was used to investi-
985). The gate the use of leaf water potential as a plant pa-
studies rameter for estimating the effect that deficit irriga-
n rate of tion had on cut-flower chrysanthemum stem pro-
luired to duction (Stanley et al., 1982; Stanley et al., 1983).
g (Figure 6). Environmental parameters (air temperature, pho-
)86) re- tosynthetically-active radiation, and humidity)
tion appli- were used to develop regression equations to deter-
s were sub- mine the effect of irrigation rate on yield and qual-
in the ear- ity for cut-flower chrysanthemums.
monstrated
equire- Management of injected
agrichemicals
)ped a A major benefit of microirrigation systems is the
cements ability to apply specific agrichemicals in small
lent, and amounts corresponding to the crop requirements.
hemums These chemicals include soluble liquid fertilizers
tions (glass and pesticides for insect and nematode control.
side with no One common problem when applying chemicals
e of evapo- with microirrigation is the difficulty of achieving
n rates, uniform distribution throughout the crop root zone
environ- for bedded systems on sandy soils.
(canopy
dividual Overman et al. (1979) investigated the influence
Multiple of placement and number of microirrigation tubes
Sin a water (one, two, or three tubes) per bed on distribution of















SN


Y 0.32 + 4.49X 2.26X'
* R = 0.64


0.2 0.4 0.6


.1.2 1.4


krigation Rate (cm/day)
Figure 6. Effect of microirrigation rate on number of marketable chrysanthemums stems (Harbaugh et al., 1986).


applied nutrients for mulched and nonmulched pro-
duction of chrysanthemums on sandy soils. Results
showed that highest yields were achieved using
three tubes per bed. Yields compared favorably
with those for plots using conventional seepage
and/or overhead irrigation with preplant nutrient
applications. In-bed soil sampling indicated that a
more even distribution of nutrients occurred with
an increase in number of tubes.

Overman (1977) studied the application of
nematicides through microirrigation tubing instead
of using normal bed fumigation practices for field
production of cut chrysanthemums. The study in-
cluded evaluating the efficacy of two nematicides
(Vydate or Nemacur) for control of the sting nema-
tode. Results showed no significant difference be-
tween nematicides for nematode control and an av-
erage 20% increase in marketable yield over
nontreated plots. The effectiveness was attributed
to the use of three tubes per bed, ensuring even dis-
tribution of the chemicals. Three distinct advan-
tages of injecting nematicides through
microirrigation systems were presented: 1) remote
control of hazardous chemicals; 2) restriction of


nematode control to the crop root zone (reducing
total amount of chemical required); and 3) ability to
treat plastic mulch-covered beds if nematode prob-
lems develop during the growing season.

Microirrigation-applied pesticides for control of
nematodes, insects, and mites was studied to evalu-
ate the effect on cut-flower chrysanthemum produc-
tion (Overman and Price, 1983). Metam sodium,
oxamyl, and carbofuran were injected and evalu-
ated for control of stubby root and sting nematodes.
Flower weight was increased by 250% with metam
sodium application 10 days prior to planting.
Oxamyl was only effective when applied at weekly
intervals compared to continuous application (with
equal total amounts of active ingredient applied per
week), indicating a temporary higher concentration
was more important than continual presence in the
bed. Carbofuran was ineffective in nematode con-
trol. Oxamyl or acephate were evaluated for
leafminer control resulting in effective control with
oxymyl only. In a followup study, Overman and
Price (1984) concluded that cryomazine,
avermectin, or fenamiphos were all ineffective in
controlling nematode or insect pests for chrysanthe-


25r


1.5 -


0.5 F












1000



800



600



400




200


0 200 400 600 800 1000
MEASURED WATER USE (ml/pot/day)


Figure 7. Measured water use vs. estimated water requirements for potted chrysanthemums grown in three locations. Water re-
quirements estimates made using a water use prediction equation developed by Stanley and Harbaugh (1984a).


mum production when injected in a microirrigation
system. They concluded that if a producer were to
use injected pesticides, they must be carefully se-
lected. All are not as effective when injected as
when applied in normal granular or spray formula-
tion.

Culture and management
Adoption of microirrigation systems often in-
volves significant changes in standard cultural and
management practices associated with conven-
tional irrigation systems. This section discusses
research conducted to investigate these changes.

Fertilization methods can be significantly af-
fected by changes in irrigation practices. Various
rates, types and formulations of controlled-release
fertilizers were evaluated as potential components
in a microirrigation production system (Harbaugh
and Wilfret, 1980) for spray chrysanthemums
(Chrysanthemum morifolium Ramat.). Optimum


rates of total-N, with 34 kg N/ha as soluble 6-2.6-
6.5 (N-P-K) and the remainder as 14-6.1-11.6
Osmocote, were estimated to range from 489 to 501
kg per planted hectare. Other formulations or ra-
tios of Osmocote and urea formaldehyde fertilizers
at similar rates did not improve production or were
not comparable to the above Osmocote formulation
or to the commercial practice of weekly liquid fer-
tilization applied with sprinkler irrigation. A water
savings of 70 to 80% was obtained with the con-
trolled-release fertilizer microirrigation system
compared to overhead irrigation, while marketable
yields were similar to those obtained using liquid
fertilization with sprinkler irrigation.

Harbaugh et al. (1989) studied the use of soluble
liquid fertilizer applications injected through the
microirrigation tubing compared to the use of a con-
trolled-release fertilizer (Harbaugh et al., 1989).
Applying fertilizer through the tubing allows pre-
cise nutrient applications corresponding to the
crop's nutrient requirements. Production using








microirrigation was compared to overhead irriga-
tion using the same two fertilization methods. Re-
sults showed no significant yield or quality differ-
ences among any of the treatment combinations.
The investigators concluded that commercial pro-
ducers need not be concerned about yield reduc-
tions resulting from using microirrigation systems
regardless of the fertilization method used. How-
ever, the producer should make irrigation system
decisions based on cost considerations and limiting
factors such as water availability, water resource
protection, and the effect that microirrigation use
has on other cultural practices.

Fertilization requirements for potted chrysan-
themum production using a capillary mat
microirrigation system was investigated by
Rosenbaum et al. (1979). Soluble liquid fertilizer or
controlled-release formulations were used with ei-
ther a hand watering or capillary mat system for
flower production. Results showed that no signifi-
cant yield and quality differences were detected
among the treatments, and they concluded that the
capillary mat system was compatible with either
fertilization method. Similar results were reported
for potted poinsettia (Euphorbia pulcherrima
Willd.) production using either a hand watering or
capillary mat system with controlled-release fertil-
izer (Wilfret and Harbaugh, 1977).

The suitability of microirrigation for cut-flower
chrysanthemum production with respect to re-
sponse by different cultivars and culture (single or
pinched stem) was investigated by Harbaugh et al.
(1986). A study using five cultivars (grown as
single stem and pinched stem) showed virtually no


40 80
20 60


response difference between cultivars for market-
able flower production. Since growers commonly
grow many different cultivars to satisfy the market
demand, this study indicated that the use of
microirrigation should not limit cultivar choice.

When flower cuttings are planted in field beds,
sprinkler irrigation is commonly used to establish
the cuttings' root systems and to relieve heat
stress. A study was conducted to evaluate different
irrigation systems (microsprinkler, fogger, and line-
source microirrigation tubing) in combination with
an antitranspirant and/or plastic mulch to establish
chrysanthemum rooted cuttings (Stanley and
Harbaugh, 1984b). No benefit from using plastic
mulch or an antitranspirant was measured. In ad-
dition, no significant difference existed among irri-
gation systems, demonstrating that using
microirrigation tubing (three lines per bed) ad-
equately provided water for establishing trans-
plants and minimized the need for sprinkler irriga-
tion.

It has been shown that changes in plant water
status can affect the pest populations on selected
crops. Since microirrigation is a water conservation
management practice, the effect of reduced water
applications on leafminer and twospotted spider
mite populations for chrysanthemum production
was investigated (Price et al., 1982). A significant
inverse relationship was obtained between the
numbers of twospotted spider mites per unit leaf
area on 'Manatee Yellow Iceberg' chrysanthemum
and seasonal microirrigation rates ranging from
13.6 to 40.7 cm. These data indicate that using
relatively low irrigation application rates may not


120 160 200 240
100 140 180 220


MkASURED WATER REOUREMENT (n/pot/day)

Figure 8. Measured water use vs. established water requirements for potted poinsettia. Water requirements estimates made using a
water use prediction equation developed by stanley and Harbaugh (1989).







significantly reduce marketable yields, but may re-
sult in increased twospotted spider mite densities
requiring appropriate planning and control. There
was no significant response of leafminer densities
with irrigation rates.

Development of application schedules for
microirrigation systems requires not only determi-
nation of crop water requirements, as discussed
earlier, but also knowledge of the water-holding
and transmitting characteristics of the soil on
which the crop is grown. Sandy soils need special
attention since both of these characteristics can be
limiting. Stanley and Harbaugh (1980) studied
EauGallie fine sand to determine the lateral dis-
tance (0, 90, 180, and 270 cm) and depth (0 to 15,
15 to 30, and 30 to 45 cm) of movement of applied
water from either a one or three tube
microirrigation system (one tube/bed or three
tubes/bed) by monitoring soil moisture changes.
Results indicated that no significant change in soil
moisture occurred at any location for either tube
arrangement except directly beneath the tube at all
sampled depths. A followup study was conducted
(Stanley and Harbaugh, 1981) to determine the
maximum distance (ranging from 0 to 22.8 cm) that
chrysanthemum cuttings can be transplanted from
a microirrigation tube without affecting crop devel-
opment. Results showed that plant fresh weight
was significantly reduced when transplants were
placed 15 cm or farther from the tubing.

Economic considerations
Microirrigation has been shown to provide orna-
mental producers with expanded management op-
tions. However, since producers are in business to
make a profit, they must consider the economic im-
plications of using microirrigation systems. Past
economic and regulatory incentives have encour-
aged ornamental producers to evaluate the costs of
adopting alternative irrigation systems such as
capillary mat, tube weight (spaghetti tube), hand
water and sprinkler overhead as described by
Prevatt et al. (1979). Associated with the decision
to invest in alternative irrigation systems are con-
siderations of whether the system is adaptable to
available water resources (groundwater or munici-
pal) and whether the capital investment is a fea-
sible and profitable venture. These are manage-
ment decisions concerned with evaluating the alter-
native irrigation systems with respect to costs and
returns of each system. This study assumed no
production advantages among irrigation systems
and evaluated the systems solely on the basis of
fixed and operating costs.


The tube weight system had the lowest annual
fixed costs and the hand water system had the
highest variable costs, regardless of water source.
Costs for the capillary mat and overhead sprinkler
systems were affected by the water source. The use
of less water by the capillary mat more than offset
the higher cost of water when using a municipal
water supply, while the overhead sprinkler system
using lower cost well water had a lower annual
fixed and variable cost.

Growers contemplating building new structures
or installing new irrigation systems must compare
the fixed and variable costs of the different avail-
able systems. As water quantities become limited
and water pumping costs increase, cost savings as-
sociated with conservative irrigation systems will
likely increase in the future.

The replacement of an existing system, however,
requires a different evaluation. In order to change
from an existing to a new irrigation system, the
fixed and variable costs of the new system must ei-
ther be less than the total (fixed plus variable) costs
of the existing system or be less than the variable
costs of the existing system (assuming that the
fixed costs of the existing system have been satis-
fied). For example, a grower will not save money
by abandoning an overhead sprinkler system with
annual variable costs of $3,852 and replacing it
with a tube weight system that has annual variable
costs of $2,000 but with annual total costs of
$6,580.

In the future growers will adopt irrigation sys-
tems that produce favorable returns over costs.
Microirrigation systems are already cost competi-
tive for new installations and appear to be an in-
surance policy for future energy and water short-
ages.

Performing a cost analysis of irrigation systems
can be confusing and cumbersome as pointed out by
Prevatt et al. (1982). Making a decision based on
costs requires an understanding of how different
costs affect the operation. To assist with the cost
analysis, a microcomputer program was developed
that prompts the user for all necessary information
and arranges the input in a meaningful manner so
an informed decision can be made.

Irrigation system selection and/or replacement
decisions are based on costs, but more explicitly are
based on variable and fixed costs of the irrigation
systems under evaluation. Unless adjustment is








necessary for differences in product quantity or
quality, capacity, effectiveness, taxes, regulatory or
government incentives, etc., these decisions can be
made based on the accurate input information. The
selection decision among new irrigation systems is
based on the annual total costs (annual variable
plus fixed costs). Therefore, if cost is the only factor
considered, growers will choose the irrigation sys-
tem that has the lowest annual total costs.

Drip and overhead sprinkler irrigation systems
have been used for field production of cut-flower
chrysanthemums. An economic analysis of these
two irrigation systems was conducted by Stanley et
al. (1983). Results indicated that investment costs
were similar for either type of system when the wa-
ter source was groundwater, but higher for the drip
system when using a municipal water source. Fixed
costs were significantly higher for drip irrigation
compared to overhead for either type of water
source. Variable costs were higher for both systems
when using municipal water as opposed to a
groundwater source. Compared to overhead irriga-
tion, drip irrigation variable costs were higher us-
ing groundwater but lower with municipal water.
Overall, overhead sprinkler was more economical
using well water for a new system or replacing an
existing system. Given economic conditions during
1983, drip irrigation was economically justified only
as a new system choice when using municipal wa-
ter.

Directions of future work
Although a significant amount of work on
microirrigation of flowering ornamental crops has
been conducted, there are challenges that lie ahead.
This project will continue to support studies to in-
vestigate improved microirrigation scheduling and
chemigation practices, taking advantage of recent
advances in remote sensing and computer control
systems. In addition, the impact that
microirrigation management can have on water
quality requires further study to ensure protection
of natural resources. An increased effort will be
made to improve the efficiency of system designs,
and to make use of experienced human resources
creating expert systems for management and de-
sign of microirrigation systems. The ultimate goal
of this entire research effort will be to provide infor-
mation to the user of microirrigation systems that
will assist in management and production decisions
while achieving efficient use of available water re-
sources.


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