Guidelines “On - Farm Water Management For Horticulture Crops”
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
This Guide was prepared in the
framework of the project
“Good Agriculture Practices For
Sustainable Intensification Of The Small
Holder Horticulture Sector In Egypt”
Within the framework of cooperation
between
“Agriculture Research Center (ARC) Arab Republic of Egypt”
and
“Food and Agriculture Organization
(FAO)”
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Irrigation water use efficiency
The Irrigation water efficiency (WUE) is defined to:
1- Water use efficiency
2- Distribution efficiency
3- Field application efficiency
1- Water use efficiency
Water use efficiency = volume of product ÷ unit of water applied
This represents a combination of the irrigation system and agronomic efficiencies for a
crop.
2- Distribution efficiency
Distribution efficiency is the comparison between the amount of water at the supply
point and the amount of water that is delivered onto the field. The distribution efficiency
is defines as:
water delivered to irrigated field
Distribution efficiency = -----------------------------------------------------total inflow to supply system
3- Field application efficiency
Field application efficiency is the comparison between the amount of water delivered to
the field and the amount of water that is used by the crop. Field application efficiency is
defines as:
crop water use
Field application efficiency = --------------------------------------------water delivered to irrigated field
Using water more efficiently can result in significant cost savings and environmental
benefits. Therefore, water use efficiency is a term commonly used to describe the
relationship between water (input) and agriculture product (output). Thus, water
productivity might be measured by the volume of water taken into a plant to produce a
unit of the output. In general, the lower the resource input requirement per unit, the
higher the efficiency.
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Water use efficiency is also often used to express the effectiveness of irrigation water
delivery and use. Therefore we can defined irrigation efficiency as the ratio between the
water stored in the soil depth inhabited with active plant roots to the water applied by
the irrigation system (Table, 28). Thus, water applied by the irrigation system and not
being made available to be taken up by plant roots is wasted and reduces irrigation
efficiency. The major causes for reduced irrigation efficiency are drainage of excess
irrigation water to soil layers deeper than the depth of active roots. Leakage of irrigation
water to deep soil layers could result in pollution of the water table.
The cases of irrigation efficiency of 100 % are practically none existent even in the most
modern irrigation systems. Major difficulties in obtaining high irrigation efficiency stems
from the inability to obtain an accurate estimate of the quantity of water needed to
recharge the soil root zone depth and the lack of valid, real time information concerning
the actual soil depth of active roots.
Table (28): Irrigation efficiency under different methods of irrigation
Methods of Irrigation
Irrigation efficiencies
Surface
Sprinkler
Drip
Conveyance efficiency
40-50
100
100
(canal)
60-70
(well)
Application efficiency
60-70
70-80
90
Surface water moisture
30-40
30-40
20-25
evaporation
Overall efficiency
30-45
50-60
80-90
However, these efficiencies can be misleading and depend on soil type, moisture
conditions before irrigation, depth to groundwater, the crop being grown, management
practices, and quality of irrigation water. A technology that can lead to potentially high
efficiencies, such as drip irrigation, still has to be managed to take full advantage of that
potential.
Generally, improving water use efficiency or a crop water use index will require the
amount of water a crop transpires to be maximized and the losses that occur as the
water moves to the plant to be minimized.
Factors affecting water-use efficiency
1- Water delivery systems
Open canals, lined ditches and pipelines (Plate, 42) vary in their ability to convey water
and in the losses made. At macro level, the water conveyance system is a major factor
in determining water-use efficiency.
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Open canals
lined ditches
pipelines
Plate (42): Water delivery systems
2- Irrigation systems.
There are various methods for increasing water availability for transpiration. Factors to
be considered for maximizing the availability of water are improvement of water
movement in the soils, absorption by the roots and movement through the plant. The
amount of water required for irrigation can be estimated by sampling the soil at several
places in the field and estimating the moisture deficit. The water application is then
calculated allowing for the possible losses.
3- Crop shape and morphology.
When soil evaporation is low, crops with closed-leaf canopies (depending mainly on
genetic factors) have better water use efficiency.
4- Climatic factors.
The climate affects the physical processes controlling crop evapotranspiration and is
key to the management and minimization of water loss.
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5- Management.
Appropriate decisions aim to increase the amount of water available for crop production
and to improve crop growth characteristics in order to increase economic yield. Irrigation
water management can be significantly enhanced by the agricultural practices that
increase the soil's moisture-holding capacity or decrease evaporation, such as:
A- Conservation tillage
B- Cover crops
C- Conservation crop rotations
D- Field windbreaks
E- Using mulching
F- Using organic fertilizer
A- conservation tillage
Conservation tillage method (Plate, 43)
is Improved soil and water quality by
adding organic matter as crop residue
decomposes; this creates an open soil
structure that lead to the following:
 Lets water in more easily
 -Reducing runoff
 Conserves water by reducing
evaporation at the soil surface
 Optimizes soil moisture
 Enhancing crop growth in dry
periods or on droughty soils
Plate (43) : Conservation tillage method
B- Cover crops
Cover crops are grasses, legumes or forbs planted to provide seasonal soil cover on
cropland when the soil would otherwise be bare i.e., before the crop emerges in spring
or after fall harvest.
The advantages of cover crops to the efficient irrigation
 Improves water and soil quality by adding soil organic matter. This creates an
open soil structure which allows water in more easily, reducing runoff.
 Protects groundwater quality by preventing nitrogen from leaching into the water
table.
 Helps soil retain moisture for use by primary crops.
 Cover crops on the soil surface lead to reduce evaporation.
C- Conservation crop rotations
Conservation crop rotation (Plate, 44) is a system for growing several different crops in
planned succession on the same field, including at least one soil-conserving crop such
as perennial hay. Including a soil-conserving crop in the rotation reduces the risk of soil
erosion and runoff to nearby waters.
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D- Field windbreaks
Field windbreaks are linear plantings of trees/shrubs designed to reduce wind speed in
open fields, preventing soil erosion and protecting adjacent crops from wind damage.
The advantages of field windbreaks to the efficient irrigation:
-Reduces soil erosion from wind and protects water
-Increase water use efficiency due to micro-climate changes in temperature and
humidity Improves irrigation efficiency.
Plate (44): Using of cover crops for planting cabbage
to increase water-use efficiency
E- Using mulching
The use of mulches in agriculture should be standard practice. Researchers from many
agricultural experiment stations and private sector of Agriculture have shown striking
benefits from mulch applications on irrigation efficiency. The uses of mulches have
benefits as follow:
•Mulches conserve moisture by reducing the amount of soil water lost through
evaporation. Therefore, mulching can reduce the irrigation requirements of plants by
up to 70%, mainly by reducing evaporation of water from exposed soil surfaces
(Abu-Awwad, A.M. ,1998 and 1999).
•Mulches help maintain a uniform soil temperature. They act as insulators, keeping
the soil warmer during cool weather and cooler during the warm months of the year
which reduces water loss and reduces plant stress.
•Mulches minimize soil erosion and compaction from heavy rains and aid in water
penetration.
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•Mulches help with weed problems that lead to not seed weed germination and will
not compete the plants on water irrigation.
•Mulching helps hold water and reduce leaching loss, and improves the drought
resistance of plants. This is a significant benefit in non-irrigated areas.
Organic mulch materials
1) Buckwheat hulls: This material is fine textured and may blow around if used in windy
places.
2) Compost: An excellent mulch and soil conditioner that you can make at home by
composting various types of yard wastes such as grass clippings leaves, and plant tops
from vegetables and flowers.
3) Hay (leguminous): Used mostly in farm gardens since the material is more likely to be
available. No additional nitrogen is required.
4) Manure: Makes excellent mulch for use if partially decomposed. Aerate this mulch
before using to reduce the heat of decomposition.
5) Peanut hulls: Excellent attractive mulch that can be obtained in garden centers
located near peanut processing areas.
6) Sawdust: A very common mulch in areas where readily available. Its decomposition
will cause a nitrogen deficiency unless fertilizer is applied regularly. When available,
aged sawdust is preferable to fresh sawdust.
7) Straw: Used for winter protection and as a summer mulch in vegetable gardens. It is
highly inflammable and should not be used in high traffic areas.
F- Using organic fertilizer
Using composted soil conditioners improves soil structure, water infiltration, and water
holding capacity of the soil. Turf grown with the application of composted soil
conditioner can require up to 30% less water. This can increase root penetration,
resulting in deeper root systems that explore a larger soil area for moisture and
nutrients, reducing deep drainage and irrigation requirements (US Composting Council,
1996).
- In sandy soils, composted soil conditioners improve water retention and lateral root
distribution in the soil, improving plant access to soil water, and reducing deep drainage
and irrigation requirements. Composted soil conditioners are incorporated into the
topsoil, commonly before planting, to Improve soil structure and water holding capacity.
5- Economic considerations.
The cash return per unit of yield is central to improving efficiency.
Therefore, the economic component of the crop must be considered. Crop productivity
per unit area of land and water consumption per unit of yield must be taken into
account. Maximum cash return per unit volume of water in a given area is important in
crop selection.
6- Social and political factors.
They condition whether or not to give priority to increasing water-use efficiency in crop
production in a given area.
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Improving water-use efficiency
To maximize crop water-use efficiency, it is necessary both to conserve water and to
promote maximal growth as follow:
Conservation of water
 Reduce conveyance losses by lining channels or, preferably, by using closed
conduits.
 Reduce direct evaporation during irrigation by avoiding midday sprinkling. Minimize
foliar interception by under-canopy, rather than by overhead sprinkling.
 Reduce runoff and percolation losses due to over irrigation.
 Reduce evaporation from bare soil by mulching and by keeping the inter-row strips
dry.
 Reduce transpiration by weeds, keeping the inter-row strips dry and applying weed
control measures where needed.
 Use of organic fertilizers such as composted and soil conditioners. These have
been shown to improve the efficiency of water use by reducing evaporation,
improving water infiltration and storage, and reducing deep drainage.
 Use of mulching that increases the water-use efficiency.
Enhancement of crop growth
• Select most suitable and high-yielding crops for the region which well adapted to the
local soil and climate.
• Use optimal timing for planting and harvesting.
• Use optimal tillage (avoid excessive cultivation).
• Use appropriate insect, parasite and disease control.
• Apply manures and green manures where possible and fertilize effectively (preferably
by injecting the necessary nutrients into the irrigation water).
 Practice soil conservation for long-term sustainability.
 Avoid progressive salinization by monitoring water-table elevation and early signs of
salt accumulation, and by appropriate drainage.
 Irrigate at high frequency and in the exact amounts needed to prevent water deficits,
taking account of weather conditions and crop growth stage.
Poor irrigation efficiency can be caused by several things:
Low irrigation efficiency can be attributed to water mismanagement, in addition to
technical problems of conveyance, distribution or on-farm application, as well as poor
maintenance of irrigation structures as detailed in the following points:
• Not stopping the flow of water to the field when the amount of water needed has been
delivered
• Not knowing the exact quantity of water (head) flowing from the water source to the
field.
• Not knowing the soil moisture level at the time of irrigation
• Not knowing the water holding capacity of the soils being irrigated
• Not applying water based on the intake characteristics of the soil
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• Not knowing the daily water use requirements of the crops being grown
• Not using the proper set sizes for the available head of water
• Non-uniform slopes which cause poor water distribution across the field
• Excessive slopes which creates high runoff losses
Water-use efficiency of greenhouse crops in Egypt
Greenhouses can easily double the water-use efficiency of vegetable crops as crop
water requirements are easily managed under protected cultivation systems. Therefore,
Water-use efficiency values of greenhouse crops are generally much higher than for
open field crops in Egypt, due to the low water use and particularly to the high economic
value of vegetable crops grown out of season. Water-use efficiency will vary due to crop
season (autumn, winter, spring and summer) grown in greenhouse.
In greenhouse vegetable crops, the irrigation water-use efficiency (kg m-3, Water-use
efficiency), expressed as the ratio between marketable crop production and total crop
irrigation supply, is higher than in open field crops due to the low evaporative demand
inside the greenhouse that reduces water requirements and the higher productivity of
greenhouse-grown crops.
Water-use efficiency of greenhouse crops was increased under the following conditions:
• improved greenhouse structure
• increased length of growing season
• Recirculation of nutrients in substrate-grown crops
• Use the environment control (Heating, cooling, ventilation) inside the greenhouse.
GAP recommendations
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Using water more efficiently can result in significant cost savings and
environmental benefits. Thus, water productivity might be measured by the
volume of water taken into a plant to produce a unit of the output.
The major causes for reduced irrigation efficiency are drainage of excess
irrigation water to soil layers deeper than the depth of active roots. Leakage
of irrigation water to deep soil layers could result in pollution of the water
table.
water efficiently is depend on soil type, moisture conditions before irrigation,
depth to groundwater, the crop being grown, management practices, and
quality of irrigation water.
Water delivery systems, irrigation systems, crop shape and morphology,
climatic factors and management are the major factors in determining
water-use efficiency.
To maximize crop water-use efficiency, it is necessary both to conserve
water and to promote maximal growth.
• Water-use efficiency of greenhouse crops can be increased by improving
greenhouse structure, increasing length of growing season, recirculation of
nutrients in substrate-grown crops and using the environment control
(Heating, cooling, ventilation) inside the greenhouse.
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