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The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research, educationa

information and other services only to individuals and institutions that function without regard to race, color , sex, age, handicap or national origin.

U.S. DEPARTMENT OF AGRICULTURE, COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, IFAS, Florid a A. & M. UN IVERSITY COOPERATIVE

EXTENSION PROGRAM, AND BOARDS OF COUNTY COMMISSIONERS COOPERATING.

E X T E N S I O NInstitute ofFood and AgriculturalSciences

Editor: Robert H . Stam ps Christine Taylor Wad dill, Dean, Coop erative Extension

Cut Foliage Grow erVolum e 15 , Num ber 2 AprilJune, 2000

The Bes t I r r i ga t i on Sys t em fo r Cu t Fo l iage Prod uc t ion

Robert H. Stamps1

We are frequently asked what is the best irrigation system to use for cut foliage production

This is, of course, a trick question since there is no such thing as a best system. When deciding

on an irrigation system design many factors should be considered , including:

< What crop(s) will be grown?

< Will production be in containers or in-ground? If in conta iners, what size? If in-ground

what is the soil type?

< Where will the crop(s) be grown outdoors or in a shadehouse or greenhouse?

< Is the irrigation system going to be u sed to apply only irrigation wa ter or will it be used for

cold protection and/ or to apply chemicals (chemigation, fertigation)?

< What is the water source and how is the water quality (alkalinity, etc.)?

< How much should you spend on an irrigation system given the value of the crop?

Wh a t c ro p ( s ) w i ll b e g ro w n ? Is foliar wetting a problem because of potential disease

problems? Examples of bacterial diseases that a re aggravated by foliar wetting are Pseudomona

leaf spot of Florida/ Holland/ Israeli ruscus (Ruscus hypophyllum) (reference 1) and Xanthomonas

leaf spot of English ivy (Hedera helix) ( reference 2). Micro irrigation (drip/ trickle/ spray-jet)

rather than overhead irrigation, should be used for these crops.

Wi ll p ro d u c t io n b e i n c o n t a i n e r s ? Most cut foliage crops that a re grown in container

are big enough in size and a re held long enough to war rant the use of micro irrigation. These

systems conserve water, energy and nu trients, and, as mentioned above, may help reduce folia

disease problems. However, micro irrigation systems are more costly to install and maintain

It is necessary to have high quality water and to perform regular maintenance for these types o

systems to be successful. (Reference 3 provides informat ion about micro irrigation systems.Many cut foliage growers are unaccustomed to container production and may forget to take into

1Professor of Environmen tal Hort iculture and Extension Cut Foliage Specialist, University of Florida,Institute of Food and Agricultural Sciences, Mid-Florida Research and Education Center, 2725 Binion Road,

Apopka, FL 32703-8504, Phone - 407/ 884-2034 ext. 164, Fax - 407/ 814-6186, E-mail -

rhs@gnv.ifas.ufl.edu.

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Cut Foliage Grow er, Vol. 15 , No. 2 , Page 2 AprilM ay 2000

consideration the limited water holding capacity of the restricted growing medium volume in

containers. Containerized plants may need to be watered more frequently than in-ground grown

plants that have more extensive root systems.

Most in-ground production occurs on sandy soils with low water-holding capacities and

relatively little latera l water movement. Therefore, irrigation systems must be designed to

uniformly wet the surface of the crop rootzone on an as-needed basis. Remember, water and

nutrients that are applied to non-crop areas (aisles, road, space between containers, etc.) are

wasted.

I s t h e c r o p g r o w n i n a s t r u c tu r e ? Water is used to cold protect crops like leatherleaf

fern (Rumohra adiant iformis) and sword fern (Nephrolepis exaltata) tha t are often grown under

artificial shade . Because of this, overhead irrigation systems with low angle sprinkler trajectories

must be used to apply water so that ice does not build up on the shade fabric and structure and

cause mechanical damage due to its weight. Further, fertilizer and pesticides are applied using

irrigation systems for these and many other cut foliage crops. Therefore, it is critical that these

overhead irrigation systems apply water un iformly. Knowing this, the question emerges, what

overhead irrigation system is the most uniform?

Perhaps you have already guessed that there is no one most uniform system, but there

are many systems with good uniformity. The Natural Resources Conservation Service ( formerlySoil Conservation Service), working for the St. Johns River Water Management District, tested

the uniformity of 148 overhead irrigation systems used for cut foliage production. They found

that only 16 systems (11%) had distribution uniformities (DUs) of 80%, the recommended

minimum, or greater. DUs are a measure of how evenly the water is distributed in the space

between a set of adjacent sprinklers and does not address uniformity of the entire irrigation

system. (For informat ion on how to determine DUs, see reference 6.) Although the overall

performance of the irrigation systems was disappointing, some useful information was learned

about the better performing systems.

Did the better performing systems use a particular sprinkler? No, the top performing

systems used Nelson R2000 sprinklers, or Rainbird 20A or 20AH sprinklers, or Weather Tec 1015

or 10-30 sprinklers. Could other sprinklers from these and other manufacturers have achieved

similar high marks? Of course, if the systems were designed properly.

What about orifice sizes? Orifice size varied from 13/ 128" to 20/ 128" (5/ 32") for the most

uniform systems. This range was essentially the same as for the 12 worst systems, those with

system DUs of less than 50%! Orifice size is only one factor used to design irrigation systems.

On the better performing systems, the orifice sizes were appropriate for the sprinkler types,

spacings, operating pressures and riser layouts used.

Was uniformity correlated to sprinkler spacing? No. Was uniformity correlated with

system pressure? No. Was uniformity associated with water application rate? No. Top

performing systems had application rates ranging from 0.10"/ hr to as high as 0.49"/ hr (a similar

but somewhat wider range than the twelve poorest performing systems). Then what did the topperforming systems have in common? They were competen tly designed, properly installed,

well-maintained and operated at the appropriate pressure.

Wa t e r q u a l it y co n s i d e ra t i o n s Irrigation wa ter quality is of concern regardless of the

system used to apply it because of the effects it can have on plant growth and quality (see

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Cut Foliage Grow er, Vol. 15 , No. 2 , Page 3 AprilM ay 2000

No te : Mention of a commercial or proprietary product does not constitute a recommenda tion

or warranty of the product by the author or the University of Florida, Institute of Food and

Agricultural Sciences, nor does it imply its approval to the exclusion of other products that may

also be suitable.

reference 4). Concerns about the chemistry of water alkalinity (total carbonates), pH and

salinity (electrical conductivity) transcend application method . However, as orifice sizes get

smaller, the need for higher qua lity water increases because of concern about system clogging.

Clogging can be physical (debris), chemical (scale) and/ or biological (algae and bacteria).

While most cut foliage crops are curren tly irrigated u sing impact sprinklers with large d iameter

orifices, those using and/ or plann ing systems with small orifice emitters shou ld pay par ticular

attention to concentrations of bacteria, carbonates, dissolved and suspended solids, hydrogen

sulfide, iron and manganese in their water. Water source concentrations posing a pluggingpotential and measures to deal with these problems are given in reference 5.

H o w mu c h s h o u l d yo u s p e n d o n a n i r r i g a t i o n s ys t e m ? Unfortunately, penny

wise and pound foolish is often the case when irrigation systems are designed and installed.

Poorly designed and/ or opera ted systems can result in serious cultural problems and difficulties

in controlling pathogens and pests. All new systems should be designed with systemwide

application un iformity and piping volumes (clear times) taken into considera tion. The amount

tha t should be spent is whatever it takes to properly design and maintain a system that will meet

all the needs of the crop and the grower . Remember, for many firms, the irrigation system is the

most used tool for producing saleable plants.

Wh e r e c a n yo u g o t o g e t h e l p d e s i g n i n g a n e w o r r e t r o fi t ti n g a n e x is t i n g

i r r i ga t i o n s ys t e m ? Try the local office of the University of Florida s Agricultural Extension

Office and/ or United States Department of Agricultures Natural Resources Conservation Service.

Another resource is system designers that a re members of the Florida Irrigation Society (FIS).

Members can be located by going to the FIS website ( fisstate.org) and checking ou t the ir list of

members for the region of the state in which you live.

There are also computer software programs available that can help you make irrigation

system design decisions. These programs run the gamut from useful utilities to full-blown

computer-aided design system programs for irrigation professionals. Prices, likewise, vary

greatly from free to thousands of dollars. These programs are available from irrigation system

supply companies and other sources. For example, Nelson Irrigat ion offers IRRICAD

(www.wwics.com/ ~ nelsonirr/ html/ irricad_design.html) and Senninger Irrigation sells Irri-Maker (www.senninger.com/ mm) . Senninger also has a free program (WinSIPP) that helps in

the selection and spacing of their sprinklers. Several other programs are available from the

California Agricultural Technology Institutes Center for Irrigation Technology

(www.atinet.org/ newcati/ cit/ good/ ). For other choices, point your Internet web browser to

www.wiz.uni-kassel.de/ kww/ irrisoft/ irrisoft_i.html. There Dr. Thomas-M. Stein has assembled

a searchable database conta ining 105 programs. And for those of you with skill at using

spreadsheet software (for example Corel Quattro Pro, Lotus 1-2-3, Microsoft Excel, or even

WordPerfect tables), much of the irrigation system piping design can be done using your

spreadsheet and a few equations to determine friction losses and clear times.

Water is an essential, limited, and precious resource that we should all strive to use wisely.

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Cut Foliage Grow er, Vol. 15 , No. 2 , Page 4 AprilM ay 2000

Refe rences

1. Chase, A. R. and R. H. Stamps. 1994. Controlling Pseudomonas leaf spot of ruscus

using tr imming and Kocide 101. Univ. of Fla., Inst. of Food and Agric. Sci., Coop.

Ext. Serv. Cut Foliage Grower9(1/ 2):14.

2. Henley, R. W., A. R. Chase and L. S. Osborne. 1991. English ivy. Univ. of Fla., Inst.

of Food and Agric. Sci., Cent ral. Fla. Res. and Ed. Cntr. Plant Research Note RH-91-15.

3. Haman, D. Z. and F. T. Izuno. 1989. Principles of micro irrigation. University of

Florida, Institute of Food and Agricultural Sciences, Florida Cooperative Extension

Service, Agric. Engineering Department Fact Sheet AE-24.

4. Hoadley, B. and D. Ingram. 1982. Water quality and woody ornamental plant

production. Univ. of Fla., Inst. of Food and Agr. Sci., Coop. Ext. Serv. Ornamen tal

Hort. Comm. Fact Sheet OHC-4.

5. Pitts, D. J., D. Z. Haman and A. G. Smajstrla. 1990. Causes and prevention of

emitter plugging in microirrigation systems. Univ. of Fla., Inst. of Food and Agr. Sci.,

Coop. Ext. Serv. Bull. 258.

6. Stamps, R. H. 1997. Measuring overhead irrigation system water application

uniformities and rates. Univ. of Fla., Inst. of Food and Agr. Sci., Coop. Ext. Serv. Cut

Foliage Grower12(4):17.

available on the World Wide Web at http:/ / edis.ifas.ufl.edu

available on the World Wide Web at http:/ / www.mrec.ifas.ufl.edu/ cutfol/ cfg.htm