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Best practices on irrigation
Joint Research Centre and Directorate-General for
Environment
Best practices in improving the
sustainability of agriculture
EXPO Milan, 6 July 2015
Daniele Massa and Alberto Pardossi
CRA-VIV
The views expressed are purely those of the authors and may not in any circumstances be regarded as stating an official position of the European Commission. Neither the European Commission nor any person action on behalf of the Commission is responsible for the use which might be made of this presentation.
Global agriculture and water use (ha x 106)
q Cultivated area (rainfed + irrigated) = 1,500
q Irrigated area = 300 (20%)
q Irrigated area for food production = 40%
q Irrigated area with salinity = 40%
<1700 m3/capita/year
<1000 m3/capita/year
2/23
General aspects
q Seasonal/annual irrigation water use:
• Field crops: 300 (e.g. beans) to 1200 mm (e.g. cotton)
• Protected crops (per year): 600 (e.g. leafy vegs.) to 1500 (fruit vegs.)
• Higher in soilless culture (open-loop hydroponics) than in soil
q Tendency to over-irrigate (+10 to +50%) results in:
• water loss
• nutrient loss (with drainage water) and pollution (e.g. nitrates)
• increased production costs (energy for pumping, fertilisers,…)
• crop water stress (due to waterlogging and hypoxia in the root zone)
• increased susceptibility to root diseases
1 mm = 1 L m-2 = 1 kg m-2 = 10 m3 ha-1
F 3/23
Water use efficiency (WUE)
0
10
20
30
40
50
60
70
WU
E (
kg
/m
3)
-
200
400
600
800
1,000
1,200
Open field Unheated plastic tunnel
Unheated greenhouse
Heated greenhouse
Heated soilless greenhouse
(closed cycle)I
(mm
); Y
(t/
ha
)
Yield
WUE
Irrigation volume
Irrigation management
& growing technology
4/23
Key elements of the BEMPs on irrigation
q Crop selection (species and cultivars)
q Soil management (tillage, amendments, etc.)
q Water treatment and storage (desalinization, etc.)
qDeficit irrigation (partial root drying, regulated d.i. )
qClosed-loop irrigation systems (substrate culture)
q Irrigation scheduling (ET models vs soil moisture sensors)
q Irrigation systems (drip vs overhead irrigation)
5/23
Approaches to efficient irrigation: Deficit irrigation
DEFICIT
IRRIGATION
Regulated deficit
Irrigation (RDI)
Partial root drying
(PRD)
http://www.pmsinstrument.com/winegrapes.htm
6/23
Deficit irrigation
7/23
Deficit irrigation
100 -
80 -
60 -
40 -
20 -
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
- - - - - - - - -
Yleaf (-MPa)
Expansion
growth
Net photosynthesis
8/23
Approaches to efficient irrigation Open vs closed irrigation systems
RainwaterGroundwater
Day-storage tankStorage tank
Drain water
Raw water tank
Mixer
Sector 1
Sector 3
Sector 2
Disinfectionunit
Fertigation
strategyDay-storage tank
21/70 9/23
Soilless-grown tomato: water and N balance) (Tuscany; 2 crops/year; yield @ 25 kg/m2)
• Water = 6,950 m3/ha
• N = 1,330 kg (N) • Water = 8,630 m3/ha
• N = 1,600 kg/ha (N)
• Water = 1,680 m3/ha
• N= 270 kg/ha N (17%)
Source: Incrocci, 2011 10/23
Soilless-grown tomato: water and N balance) (Tuscany; 2 crops/year; yield @ 25 kg/m2)
• Water = 6,950 m3/ha
• N = 1,330 kg (N) • Water = 6,950 m3/ha
• N = 1,330 kg/ha (N)
• Water = 0 m3/ha
• N= 0 kg/ha N
11/23
Approaches to efficient irrigation
Irrigation scheduling
• Irrigation timers (the standard method?)
• Determination of soil water balance (called ET-
based method in greenhouse and nursery crops)
• Direct measurement of moisture content in the
root zone with soil moisture sensors (SMS)
• Integration of methods 2 and 3
• Speaking-plant
12/23
Irrigation scheduling (dose and frequency)
Soil q So
Scheduling
Coefficient (KS)
Soil qET (mm)
Allowable
water deficit (AWD, mm)
Driving factor
ET - based IS
RZS –based IS
Dose = AWD · KS
Leaf area
indeX (LAI)
Root
depth
Salinity
(EC)
Texture I. efficiency
& uniformity
ET (mm
hedu
Water Crop Soil Irr. system
Climate
Frequency (time) Dose (mm)
13/23
1) Determination of available water in the root zone
Soil /substrate hydrology
0
20
40
60
80
100
Soil Soilless
56
15
14
40
10 20
20 25
Air phase
Easily Available
Water (EAW)
Unavailable
water (UW)
Solid phase
Volume of media explored by the crop roots
§ Soil: 250 to 500 L m-2 (mm) depending on root depth
§ Soilless: 10 to 50 L m-2 (mm)
% v
olu
me
14¤47
14/23
0 10 20 30 40 50 60 70 80 90 100
0
10
20
30
40
50
60
70
80
90
100
SOLID FASE
WATER
Air capacity
Easily available
water Total
available water V
olu
me
(%
)
Tension (hPa = cm of H2O)
AIR
300 1,000
SUBSTRATE
SOIL 15,000
15/23
1) Determination of available water in the root zone
2) Determination of the evapotranspiration rate
2.1) ET model: FAO equation.
(http://www.fao.org/docrep/x0490e/x0490e00.htm)
ET = kc · ET0
Kc: crop coefficient (ET/ETP). It incorporates crop
characteristics and averaged effects of soil evaporation.
ET0: reference or potential ET. It is assessed with
evaporation pan or based on weather conditions.
16/23
2) Determination of the evapotranspiration rate
2.2) ET model: plant transpiration under greenhouse.
• ET is mostly determined by leaf transpiration (T)
• T depends basically on leaf area (LAI), the intercepted radiation (Ic), air
temperature and relative humidity, which both determine the vapour pressure
deficit (VPD)
• Stomata regulation of leaf T is often limited (due to poor gh. ventilation)
VPDLAIBcI
AT ××+×=l
17/23
2) Determination of the evapotranspiration rate
2.2) ET model: semplified model for greenhouse.
Relationship between simulated and measured values of diurnal transpiration (Ed) in greenhouse
gerbera grown in substrate culture in different seasons (autumn, filled symbols; spring, empty
symbols). Transpiration was simulated using the Penman-Monteith equation or its simplified version
(regression model). (Carmassi et al., 2013)
0.0 0.1 0.2 0.3 0.4 0.50.0
0.1
0.2
0.3
0.4
0.5Y = 0.974 X - 0.001
R2
= 0.936
SEE = 0.023 kg m-2
h-1
MAPE = 15.9%%
Measured values (Ed, kg m-2
h-1
)
Pre
dic
ted v
alu
es (
Ed,kg
m-2
h-1
)
0.0 0.1 0.2 0.3 0.4 0.50.0
0.1
0.2
0.3
0.4
0.5Y = 0.957 X + 0.002
R2
= 0.939
SEE = 0.022 kg m-2
h-1
MAPE = 15.5%%
Measured values (Ed, kg m-2
h-1
)
Pre
dic
ted v
alu
es (
Ed,kg
m-2
h-1
)
P-M equation Simplified equation
18/23
3) Direct measurement of water-related parameters in the root zone
TDR
(Time Domain Reflectometry)
FDR
(Frequency Domain Reflectometry)
19/23
DIRECT MESUREMENT OF SOIL
MOISTURE DATALOGGERS
WATER BALANCE
PLANT GROWTH
IRRIGATION
SYSTEM
MANAGEMENT
RIGATI
CLIMATE
PARAMETERS
20/23
Approaches to efficient irrigation
Irrigation systems: drip vs overhead irrigation
www.wikipedia.com
Up to ≈ 100% distribution efficiency
www.fao.org
….especially
21/23
Conclusions on BEMPs
What?
q Advanced irrigation management (application of crop modelling and/or
sensing technology, deficit irrigation)
q Reuse of drainage water (closed system)
q Use of drip irrigation
q Other measures (crop selection, water treatment)
22/23
Why?
q Irrigation is generally inefficient due to: empiricism in irrigation scheduling,
use of saline water (large leaching fraction), etc.
q Over-irrigation causes pollution due to the leaching of agrochemicals (e.g.
nitrates, phosphates, plant protection products), soil erosion, etc.
How?
q Regulations
q Dissemination of best practices
q Education and training
Thank you!
European Commission: Joint Research Centre and
Directorate-General for Environment
Email: [email protected]
Websites:
http://susproc.jrc.ec.europa.eu/activities/emas/
http://ec.europa.eu/environment/emas/index_en.htm