Citation
Conservation of irrigation water in vegetable production

Material Information

Title:
Conservation of irrigation water in vegetable production
Series Title:
Florica Cooperative Extension Service circular 533
Creator:
Bennett, Jerry M.
Marlowe, George A. (George Albert)
Baldwin, L. B.
Affiliation:
University of Florida -- Florida Cooperative Extension Service -- Institute of Food and Agricultural Sciences
Place of Publication:
Gainesville, Fla.
Publisher:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Language:
English
Physical Description:
8 p. ; 23 cm

Subjects

Subjects / Keywords:
Irrigation water ( LCSH )
Plants -- Water requirements ( LCSH )
Vegetables -- Irrigation ( LCSH )
Spatial Coverage:
North America -- United States of America -- Florida

Notes

Funding:
Florida Historical Agriculture and Rural Life

Record Information

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 applicable rights reserved by the source institution and holding location.
Resource Identifier:
09858014 ( OCLC )
ABZ2767 ( NOTIS )
027254678 ( ALEPH )

Full Text

Circular 533



CONSERVATION
OF -..

IRRIGATION WAT

IN

VEGETABLE P6DUCTION
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Florida Cooperative Extension Service-Institute of Food and Agricultural Sciences
University of Florida, Gainesville John T. Woeste, Dean for Extension
University of Florida, Gainesville .John T. Woeste, Dean for Extension








CONSERVATION OF IRRIGATION WATER
IN VEGETABLE PRODUCTION
J. M. Bennett, G. A. Marlowe, Jr., and L. B. Baldwin*
Although Florida is fortunate to have a climate which provides an
average annual rainfall of approximately 50 inches, periodic short
and long term rainfall deficits often occur. During these periods of
low rainfall and reduced water supplies, the water available for
application to crops may be limited. It is important that we become
more aware of measures which are available to conserve our water
resources. These water conservation practices will probably play an
important role in the future of crop production. Many of the practi-
ces should be followed even when periodic water shortages have
been relieved, since they also often result in more efficient use of
both energy and crop nutrients. Obviously, however, economic
situations must be carefully evaluated by growers before new man-
agement procedures are implemented.
Numerous research and extension reports have been written by
IFAS faculty addressing vegetable irrigation, including proce-
dures and systems available for reducing the water required for
vegetable production. The purpose of this circular is to accumulate
and reference some of these research results so that readers desir-
ing information on a particular subject can consult the published
research reports.
Water Requirements of Vegetable Crops
Evapotranspiration (ET) refers to the amount of water which
passes through the leaves of a crop (transpiration) plus that which
evaporates from the soil surface (evaporation). Thus, the total
amount of water evaporated from the soil and leaves of a cropped
field is termed ET. It is important to realize that ET is not the total
amount of water required to produce a crop because it does not
include water lost through deep drainage (percolation), runoff, or
loss during conveyance of water to the crop. As a result, the amount
of water actually required to produce a vegetable crop is usually
greater than that used in the process of ET. Efficient irrigation
practices should, however, ensure that a large fraction of the water
pumped is delivered to the crop to meet ET needs. Methods which
reduce the loss of water from a field without affecting the amount of
water which is available for crop transpiration will result in water
savings without reducing yields.
*Assistant Professor, Professor (AREC Bradenton), and Associate Professor, respec-
tively, Institute of Food and Agricultural Sciences, University of Florida, Gainesville
32611.

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Evapotranspiration rates are dependent on many environmental
conditions and crop characteristics (15), but for average Florida
situations,ET rates and expected net irrigation requirements have
been calculated for many vegetable crops (15,24). Calculated ET
requirements range from 2.2 inches for a 30-day crop in Northwest
Florida to 22 inches for a tomato crop grown in Florida's lower east
coast region. The planting date and length of the growth period
result in ET values which vary considerably and the interested
reader is encouraged to consult the referenced reports (14,15,24).
Irrigation system application efficiencies, conveyance losses, perco-
lation, and run-off contribute to the amount of water actually
required to produce the crop (14). The amount of water required for
irrigation is also dependent on the ET needs of the crop, the amount
of water required for soil preparation, frost protection, etc., the
amount and distribution of rainfall, and the contribution from
ground water.


Water Conservation Measures
Many water conservation measures are available which should be
considered. Some of these measures can be implemented relatively
easily and inexpensively and are often also cost beneficial. A few
items are suggested below:
Transport water from source to field in pipes instead of open
ditches.
Use level land to reduce run-off and erosion.
Do not exceed field capacity when watering. Overwatering can
result in damage to certain crops.
Reduce run-off to a minimum.
Maintain water reservoirs and recycle when possible.
If water is short, grow high value, quick maturing crops.
Encourage root growth through good drainage and
proper water and fertilizer application.
Use mulch to save moisture and reduce weeds.
Use higher plant populations and well-balanced nutrient levels.
Supply irrigation water to match ET demands of the crop.
Know the rooting characteristics of the crop, when to irrigate,
how much water you are pumping, and the water retention
characteristics of your soil.
Control weeds and diseases.
Reduce bed heights if possible when using seep irrigation.
Reduce soil compaction.
The above suggestions reduce water loss without reducing the
amount of water actually transpired by the crop. The amount of

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water which can potentially be conserved in vegetable production is
quite large when you consider that the ET requirements are often as
low as 25% of the total amount of water applied (15).


Irrigation Systems
Research on vegetable crop irrigation suggests that one way to
improve water use efficiency is to consider other types of irrigation
systems. Numerous experiments have evaluated seep irrigation (6,
7, 10, 20, 21, 23), sprinkler or overhead irrigation (1, 2, 12, 20, 21),
drip or trickle irrigation (1, 2, 4, 5, 7, 8, 9, 12, 13, 16, 17, 18, 20, 21),
systems for conveyance and return of water (22), and subsurface
irrigation and drainage systems (3, 11, 25).
In 1977-78, overhead irrigation was practiced on 17% of the
tomato fields, while 80% of the acreage was seep irrigation (19).
Only 71% of the seep irrigated fields were continuously irrigated
and the remaining acreage was intermittently irrigated as neces-
sary.
When considering a type of irrigation system, it is also very
important to evaluate drainage needs (4,25). In many areas a drain-
age system may be just as important as an irrigation system. This
situation often favors seep irrigation which can also be applied
through facilities used for drainage.

Seepage and Subsurface Tile Irrigation
If water is the only variable considered, seep irrigation is one of
the most inefficient irrigation systems. Large amounts of water
may be required for maintaining the desired water table due to
water losses to runoff, deep seepage, lateral losses, and direct evap-
oration of water. In some areas, however, much of this "loss" returns
to the surface water system and may be available for reuse.
Seepage and subsurface tile irrigation systems which maintain
water tables at approximately 24 inches have produced maximum
yields of several vegetable crops (23). Soil moisture in the upper 0-6
inches of the soil is closely and inversely correlated with the depth to
the water table (10). Subsurface tile drainage and irrigation sys-
tems have resulted in 10% higher potato yields with 12% less water
when compared to conventional furrow systems (3, 11). Potential
yield increases are even greater if the increased land available for
production by eliminating the furrows is considered.
A subsurface tile irrigation and drainage system for tomato pro-
duction has been shown to require only 50% of the water normally
used by a ditch system without reducing yields (25). The difference
in water use was primarily a result of higher runoff with the ditch

3








system in addition to direct evaporation of water in the ditches. The
advantages and disadvantages of such a subsurface tile drainage
and irrigation system are (25):

Advantages
Excess water can be removed rapidly from the soil profile.
Conservation of water and pumping energy.
Less field work is required.
More land is potentially available for cropping.
Control of water application is easier and more precise.
Operating costs are much less than a ditch system.
Disadvantages
Difficult to maintain as high a water table as with a ditch system.
Ownership costs are more expensive than a ditch system. Total
costs (operating plus ownership) are slightly more expensive.


Drip or Trickle Irrigation
Numerous experiments comparing seepage irrigation to drip
irrigation have noted substantial differences in the amount of water
required to produce the crop (1, 7, 20, 21). The main reason for the
increased efficiency of a drip irrigation system is that it allows the
precise application of water in amounts corresponding to the ET
demand of the crop. Water is also delivered at points in the soil
which are readily accessible to the crop's root system. Drip irriga-
tion systems can conserve as much as 77% of the water normally
required with seep irrigation (7). Generally, if proper management
including proper fertilizer placement is practiced, vegetable yields
are just as good or better with drip irrigation when compared to
yields with other irrigation systems. As with any irrigation system,
however, there are both advantages and disadvantages to a drip
system. These characteristics have been identified by numerous
researchers and are listed and referenced below:

Advantages
Potential for water conservation (1, 2, 7, 12, 13, 16).
Supplemental fertilization through the irrigation system is
possible (2, 5, 8, 12, 16).
Water can be precisely supplied to meet the ET demands of the
crop (7, 12, 13, 16).
Small irrigation pumps are required, resulting in lower energy
needs (2, 12, 13).

4








For some crops, yields can be increased (1, 2, 7, 13).
Row middles remain dry and insect, weed, and disease control
is improved (13).
Pesticides can be injected through the system (12, 13, 17, 18).

Disadvantages
For some crops, yields may be decreased (7, 8, 20).
Non-uniform germination may be a problem (7).
Higher installation costs (7).
Drip systems are somewhat more complicated to install and
operate (13).
Clogging of emitters may occur (9, 13, 21).
Leaching of nutrients may be a problem if overwatering occurs
(9, 13, 21).
Soil water distribution is limited (8, 13, 16).
Ineffective for frost control (13).
Fertilizer placement may have to be altered from conventional
practices (20, 22, 24).
A drainage system is still required in many cases (4).
As with any irrigation system, the advantages of a drip system
must be weighed against the disadvantages. Changing economic
situations and water availability may alter future management
decisions regarding drip irrigation.


Conveyance and Return Systems
Recent studies have been conducted to evaluate a water convey-
ance and recovery system for seep irrigation (22). The system con-
veys water through a PVC pipe from a holding pond to the areas
requiring irrigation. Runoff water can be recovered and pumped
back to the holding ponds. Results indicated that water pumped
from a deep well was 38% of the total water required, while the
remainder was pumped from catch basins, stored rainfall, and
natural ground water seepage.
Advantages and disadvantages of a PVC pipe conveyance and
recovery system are as follows (22):

Advantages
Amount of water pumped from deep wells is reduced.
Energy requirements and pumping costs are reduced.
Increases the flexibility of the irrigation system for transport-
ing water.
Enables more acres to be irrigated with a given quantity of
water.

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Disadvantages
Larger capital investment.
Producers must learn how to manage the system.
The system may require increased pumping pressure beyond
the capacity of the existing pump used for open ditch irrigation.
At the present time investment in a water recovery system is very
costly and not profitable, but future water supply situations may
warrant consideration of such a system (22).

Overhead or Sprinkler Irrigation
Overhead sprinkler irrigation systems have been widely used and
are well-suited for many vegetable production situations. Overhead
systems are usually somewhat less efficient than drip irrigation but
considerably more efficient than seep irrigation. High winds and
low humidities can result in lower irrigation efficiencies due to
nonuniform distribution of water and large evaporation losses.
Most efficient use of sprinkler irrigation systems is generally at
night or on days of high humidities and low winds. A few advan-
tages and disadvantages of overhead sprinkler irrigation systems
are listed below:
Advantages
Useful for frost protection as well as irrigation.
Relatively simple to operate.
Less water is required when compared to seepage irrigation.
Less expensive than drip systems.
Can be used for cooling of the crop on hot days.
Can be adapted to many different crops, soils, and topographic
conditions.
Disadvantages
Nonuniform distribution of water due to wind.
Significant evaporation losses during periods of low humidity.
Cannot duplicate as a drainage system.
Requires more water than drip irrigation.
Larger pumps are required resulting in increased energy costs.
Water must be applied evenly over the entire field area, includ-
ing the soil between rows where few roots grow.
Each individual situation must be evaluated when considering
any change in previous management practices, but it is imperative
that we properly consider alternatives that are available for water
conservation during times of water limitations. At the present time,
some of the possibilities discussed may be economically unfeasible,

6








but severe water shortages may dictate future evaluation of certain
water saving procedures. Some water conservation methods can be
implemented in the short term with relatively low costs which can
be recovered rapidly. Other decisions, such as changing irrigation
systems, require long term evaluations with considerable costs
which may be recovered somewhat more slowly. Hopefully, the
interested reader will find answers to some questions by consulting
the referenced literature which addresses specific items.
Literature Cited
1. Bryan, H. H. 1977. Effects of irrigation method, plant popula-
tion, and alpha keto acids mixture on tomato yields. Proc. Tropical
Region A.S.H.S. 21:36-37.
2. Bryan, H. H., W. M. Stall, and J. D. Dalton. 1975. Response of
vegetables to drip and overhead irrigation on calcareous soils. Proc.
Fla. State Hort. Soc. 88:190-196.
3. Campbell, K. L., J. S. Rogers, and D. R. Hensel. 1978. Water-
table control for potatoes in Florida. Trans. Am. Soc. Ag. Eng.
21:701-705.
4. Csizinsky, A. A. 1979. Considerations in calculating and
reporting water application rates for drip irrigated lands. Braden-
ton AREC Research Report GC1979-13.
5. Csizinsky, A. A. 1979. The importance of irrigation frequency
and fertilizer placement in growing vegetables with drip irriga-
tion. Proc. Fla. State Hort. Soc. 92:76-80.
6. Csizinsky, A. A. 1979. Calculation of irrigation water for seep
irrigated land from riser flow rates. Bradenton AREC Research
Report GC1979-12.
7. Csizinsky, A. A. 1980. Yield and water use of vegetable crops
with seepage and drip irrigation systems. Agricultural Sci.
43:285-292.
8. Csizinsky, A. A., and A. J. Overman. 1978. Effect of drip
irrigation tube placement and type and quantity of fertilizer on
yields of broccoli and cauliflower with plastic mulch. Proc. Soil and
Crop Sci. Soc. Fla. 38:46-48.
9. Graetz, D. A., J. G. A. Fiskell, S. J. Locascio, and B. Zur. 1978.
Chloride and bromide movement with trickle irrigation of bell
peppers. Proc. Fla. State Hort. Soc. 91:319-322.
10. Hensel, D. R. 1964. Irrigation of potatoes at Hastings, Florida.
Proc. Soil and Crop Sci. Soc. Fla. 24:105-110.
11. Hensel, D. R., J. R. Rogers, and K. L. Campbell. 1975. Subsur-
face drainage and irrigation for potatoes on low flatwoods soils.

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Hastings ARC Research Report PR-1975-9.
12. Locascio, S. J. 1974. Tomato response to plug-mix, mulch, and
irrigation method. Proc. Fla. State Hort. Soc. 87:126-130.
13. Locascio, S. J., and J. M. Myers. 1979. Water and nutrient
application by trickle irrigation for vegetables. Veg. Crops Dept.
Report 27-1979.
14. Marlowe, Jr., G. A. 1977. A rationale for the determination of
irrigation needs for vegetable crops grown with seep irrigation.
Bradenton AREC Research Report GC1977-8.
15. Marlowe, Jr., G. A., and J. S. Rogers. 1976. Water use by
Florida vegetable crops. Veg. Crop Ext. Report No. 16-1976.
16. Orth, Paul G. 1978. Developing guidelines for drip irrigation
of row crops on shallow soils. Proc. Fla. State Hort. Soc. 91:310-312.
17. Overman, A. J. 1974. Nematicides in linear drip irrigation for
full-bed mulch of tomato. Proc. Soil and Crop Sci. Soc. Fla.
34:197-200.
18. Overman, A. J. 1976. Efficiency of soil fumigants applied via a
drip irrigation system. Proc. Fla. State Hort. Soc. 89:143-145.
19. Overman, A. J., and F. G. Martin. 1978. A survey of soil and
crop management practices in the Florida tomato industry. Proc.
Fla. State Hort. Soc. 91:294-297.
20. Persaud, N., S. J. Locascio, and C. M. Geraldson. 1976. Effect
of rate and placement of nitrogen and potassium on yield of mulched
tomato using different irrigation methods. Proc. Fla. State Hort.
Soc. 89:135-138.
21. Persaud, N., S. J. Locascio, and C. M. Geraldson. 1976. Influ-
ence of fertilizer rate and placement and irrigation method on plant
nutrient status, soil soluble salt, and root distribution of mulched
tomatoes. Proc. Soil and Crop Sci. Soc. Fla. 36:121-125.
22. Prevatt, J. W., C. D. Stanley, and W. E. Waters. 1980. Evalua-
tion of a water conveyance and recovery system for seep irrigation.
Proc. Fla. State Hort. Soc. 93:253-256.
23. Rogers, J. S., and D. S. Harrison. 1974. Crop response to
drainage in flatwoods. Proc. Fla. State Hort. Soc. 87:193-195.
24. Rogers, J. S., and G. A. Marlowe, Jr. 1975. Water needs of
Florida vegetable crops. IFAS-Water Resources Council Report
No. 2.
25. Stanley, C. D., J. S. Rogers, J. W. Prevatt, and W. E. Waters.
1982. Subsurface drainage and irrigation for tomatoes. Proc. Fla.
Soil and Crop Sci. Soc. (In Press).

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This public document was promulgated at a cost of $700.60, or
21.9 cents per copy, to provide information on water conservation
in vegetable production. 10-3.2M-82



COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORI-
DA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, K. R.
Tefertlller, director, In cooperation with the United States Department IFAS
of Agriculture, publishes this information to further the purpose of the
May 8 and June 30, 1914 Acts of Congress; and Is authorized to pro-
vide research, educational Information and other services only to Indi-
viduals and Institutions that function without regard to race, color, sex or national ori-
gin. 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, Gainesvllle, Florida
32611. Before publicizing this publication, editors should contact this address to deter-
mine availability.