Irrigation in vegetables: technology and practice This article was written by Evan Christen, Jim Ayars, John Hornbuckle, and Mark Hickey. It was published in the Irrigation Australia Journal in Winter 2008, Volume 23 No. 2. It is an extract from “Technology and practice for irrigation in vegetables” published by the NSW Department of Primary Industries.

1. CRCIF
CRCIF
IRRIGATION IN VEGETABLES: TECHNOLOGY AND PRACTICE
Evan Christen, CSIRO Land and Water, Griffith, NSW; Jim Ayars, CRC for Irrigation Futures;
John Hornbuckle, USDA-ARS, California; and Mark Hickey, NSW DPI, Yanco, NSW
It is important to identify the best
irrigation practices that will allow the
vegetable industry to develop into
the future. To help achieve this, the
suitability and risks associated with
different irrigation systems have
been broadly ranked in the areas of
water quality, environmental
management and agronomic factors.
In general terms irrigation systems
with better water control
(drip/sprinkler) are more likely to be
sustainable and reduce the risks of
negative environmental impacts. For
pathogen control, the use of drip
irrigation and ultimately buried drip
irrigation is clear advantageous. Drip
irrigation does have some specific
problems if there are high suspended
solids in the water and if there is a
need to germinate seeds. Sprinkler
irrigation is very useful if dust control
and cooling are required. A recent project has helped describe the best practices for irrigating vegetables by
identifying the suitability and risks associated with different irrigation systems and ranking
Matching crops, soils, water, quality them in the areas of water quality, environmental management and agronomic factors.
and irrigation methods
There can be no definitive answer as
to which type of irrigation system is quality parameters, likelihood of based on the criteria have been
most suitable for vegetable minimising environmental described as high (H), medium (M),
irrigation as there are so many problems, and appropriateness for and low (L).
variables. In the following tables we efficient and economic crop To help achieve this, the suitability
have rank the three main irrigation production. The irrigation systems and risks associated with different
systems against the key criteria are broadly assessed against these irrigation systems have been broadly
related to irrigation for vegetables. criteria below. ranked in the areas of water quality,
The main areas of assessment for The potential for using a particular environmental management and
irrigation systems are against water system or risk associated with a system agronomic factors.
Table 1. Water salinity and irrigation system suitability*. All irrigation carries
Salinity Drip Sprinkler Furrow potential risks to the
Buried Surface Fixed, Traveller environment. These risks
centre pivot are exacerbated if reclaimed
Low H H H H M waters are used, due to
Moderate H H M** M M potentially high levels of
High M M L L L salts and nutrients. Apart
from soil salinity, the other
* Assuming all soils have reasonable drainage; if drainage is very poor, then drip should be
used.
main factors are surface
** Leaf burn becomes a problem. run-off and deep percolation.
IRRIGATION AUSTRALIA 19

2. CRCIF
Water quality Table 2. Pathogens, aerosols and risk of contamination.
Salinity. Managing soil salinity will Salinity Drip Sprinkler Furrow
be key to irrigation sustainability.
Irrigation systems with better water Buried Surface Fixed, Traveller
control are inherently better suited centre pivot
to managing salinity. Table 1 refers
to the management of soil salinity, Ingestion risk L M M H M
but leaf burn with sprinkler Contact risk L H H H H
irrigation may also be a problem
when using saline waters. Aerosol risk L L H H L
Pathogens and aerosols. Where
reclaimed water is used for
Table 3. Clogging, precipitation and corrosion risk, and irrigation system suitability.
vegetable production, risk of Water quality factor Drip Sprinkler Furrow
pathogens contaminating the Fixed,
product is one of the key Buried Surface Centre pivot
limitations. The risk of
contamination varies according to High suspended solids L L M H
the crop and irrigation system used.
High potential precipitates L L M H
Production and drift of aerosols is
also an issue (Table 2). High biological activity L L M H
Clogging, precipitation and
pH <6, >9 L L L M
corrosion factors. Depending on
the water source, there are varying Table 4. Risk of surface run-off with irrigation system and soil type.
risks of clogging, precipitation and
corrosion affecting the operation Soil type Drip Sprinkler Furrow
and longevity of an irrigation
system. Generally, furrow irrigation Buried Surface Fixed, Traveller
is least susceptible to these centre pivot
problems (Table 3).
Sand L L L M L
Environmental management Loam L L M H M
All irrigation carries potential risks
Clay L L H H H
to the environment. These risks are
exacerbated if reclaimed waters are Table 5. Deep percolation risk with irrigation system and soil type
used, due to potentially high levels
of salts and nutrients. Apart from Soil type Drip Sprinkler Furrow
soil salinity, the other main factors
are surface run-off and deep Buried Surface Fixed, Traveller
percolation. The risks of these centre pivot
occurring with different systems are
Sand M M H H H
outlined below.
Surface run off. Surface run off in Loam L L L H H
irrigated agriculture is caused by Clay L L L M M
applying more irrigation water than
can infiltrate into the soil, as well as Table 6. Soil type and system suitability for crop production.
by rainfall. This can be a limiting
factor to irrigation in some regions. Soil type Drip Sprinkler Furrow
Systems with good control of
application rate and amount and Buried Surface Fixed, Traveller
with high uniformity have lower centre pivot
likelihood of run off. Systems with
Sand L M H M L
high application rates, such as
travellers, make it hard to control Loam H H M M H
surface run off and excess drainage
Clay M M L L M
into low areas of the crop. Systems
that leave parts of the soil surface Table 7. System suitability for crop establishment.
dry reduce the risk of run off due to
rainfall (Table 4). Type of crop Drip Sprinkler Furrow
Deep percolation. Deep percolation
of irrigation water down past the Buried Surface Fixed, Traveller
root zone is the other main loss of centre pivot
water. Good irrigation management
Small seeded crops L M H L M
and scheduling are the keys to
minimising deep percolation. Deep Large seeded crops L H H M H
drainage can be much higher with
Transplants or cuttings H H M M M
furrow irrigation than when using
20 IRRIGATION AUSTRALIA

3. CRCIF
drip or sprinkler irrigation, mainly Table 8. Irrigation system and disease risk.
due to less uniform application than
with these systems. The risk of deep Crop type Drip Sprinkler Furrow
percolation on very sandy soils is
Buried Surface Fixed, Traveller
high with all types of irrigation
centre pivot
method. Even with the best irrigation
management, rainfall can cause Large surface area crops L H H M M
considerable deep percolation, so
irrigation is not recommended on Root crops L M M M M
sandy soils (Table 5). Cucurbits, tomatoes etc L H H H M
Agronomic factors Trees, vines, cane, fruit L H M M M
Soil–water properties. For good crop
Table 9. Irrigation system and dust control/cooling.
production there needs to be an
appropriate match between the soil Control level
physical properties controlling water
movement and retention and the Control factor Drip Sprinkler Furrow
irrigation system. This affects the
amount of water that can be stored Buried Surface Fixed, Traveller
centre pivot
in the soil after an irrigation, the
depth of wetting, wetting pattern Soil/sand blowing L L H H M
and aeration status. These factors
affect the ease of management and Dust control L L H H M
agronomic productivity of the land Cooling L L H H M
(Table 6).
Crop establishment. Establishment Table 10. Irrigation system and weed control.
of crops is a critical task in
horticulture; the irrigation system Control level
must be able to do this with a high
degree of success. Table 6 is suitable Weed control Drip* Sprinkler Furrow
for this assessment, except when
Buried Surface Fixed, Traveller
considering a buried drip system, in
centre pivot
which case it is very difficult to
achieve good seed germination in Traveller
any soil type. Table 7 outlines
irrigation system suitability for At germination H H L L L
establishing various categories of Mid – late season H H L L M
plant material.
Disease. Control of leaf and root *If using pre-emergent herbicides that require watering in, drip irrigation is generally unsuitable.
diseases, especially fungal diseases, is
affected by the irrigation system,
crop and soil type. In general, waterlogging. Broad assessments of surface. Drip in combination with
sprinkler systems increase risk of leaf irrigation systems and potential for plastic polythene mulch or the use of
fungal and bacterial infections, disease are given below (Table 8). transplants can be particularly
whereas furrow irrigation increases Dust control and cooling. Control of effective for controlling weeds.
the risks of root rots due to dust is important for some vegetable It is important to note that certain
production, to keep the crop clean. It pre-emergent vegetable herbicides
is also important that the harvested require ‘fixing’ into the soil with 10
product is dust free. In the same to 15 mm of overhead irrigation to be
category is the task of cooling, which most effective. This could preclude
is required for some crops. Sprinkler the use of drip if alternative
irrigation provides the best potential
herbicides cannot be used.
for controlling these factors as it wets
A broad assessment of irrigation
the entire surface area. A broad
assessment of irrigation system system potential for these factors is
To reach the decision-makers in the
potential for these factors is given in given in Table 10.
irrigation field, you should consider
Table 9. This article is an extract from
advertising in Irrigation Australia “Technology and practice for irrigation in
Weed control. With vegetable
Journal, the official journal of Irrigation vegetables” published by the NSW
production, minimal competition is a
Australia. high priority, and the weed control Department of Primary Industries. The
that can be achieved by different full report is available on the NSW DPI
For information on advertising rates, website at
systems is important. Drip systems
please contact Brian Rault at Hallmark offer the best potential, as they wet http://www.dpi.nsw.gov.au/__data/assets/
Editions, Tel (03) 8534 5000 or email little of the soil. Buried drip systems pdf_file/0005/201101/Technology-and-
brian.rault@halledit.com.au are even better, as they can be practice-for-irrigation-in-vegetables.
managed so as not to wet the soil pdf.
IRRIGATION AUSTRALIA 21