Drip Basic Management

Yoram Krontal
Oct 2010
Irrigation management

How ?
When ?
How Much ?
The Soil, The Climate, The Plant.
Temperature Transpiration Radiation

Wind

Humidity
Evaporation

Drainage

Percolation
 Irrigation Goals
A. Complete the whole deficit throughout the
humid area
B. Air and volume should not be moved at the
same time
C. Water save
D. Prevent the accumulation of salts and fertilizers
in excess
E. Prevent lack of water in the soil
 SOIL AND WATER IN EQUILIBRIUM

• The water in the soil is in constant movement

• The soil particles are in contact with the water
• Porosity is the medium of water content.
 MODEL OF SOIL POROSITY

• The soil is a capillary system in

different diameters.
• Water movement is proportional
to the capillary system
diameters.
 Pc

• Capillarity – The angle of contact of Pc

the water with the surface creates less
pressure (Pc) then the atmospheric h
pressure (Pa), this makes the water
go up

Sand Silt Clay

45 30 45
40 40
% do diâmetro do volume total

% do diâmetro do volume total

% do diâmetro do volume total

25
35 35
30 20 30
25 25
15
20 20
15 10 15
10 10
5
5 5
0 0 0
0

0
00

00
10

10

00
10
10

10

10
10

10

10
Diâmetro Equivalente (µm) Diâmetro Equivalente (µm) Diâmetro Equivalente (µm)
 TOTAL ENERGY POTENTIAL OF THE WATER

Ψg + Ψsub + Ψm + Ψa + Ψp + Ψo = Ψt

Ψg – Gravity

Ψsub –Submergence

Ψm– Metric

Ψa–Pneumatic

Ψp– Pressure

Ψo– Osmotic
 Soil water holding capacity

Field Capacity: in empiric mode:

the humidity content of the soil a
few hours after irrigation.
Wilting Point: in empiric mode:
the humidity content of the soil
when the plant can not retrieve
water from the soil.
Available water: the strip between
field capacity and wilting point.
Soil Water Holding Capacity

50
Sandy soil Clay soil
45
40 Field
35 Capacity
Humidity (%)

30
25 Avaliable W ater
20
15
10 W ilting
5 point
0

Clay Content (%)

Soil Moisture in Drip
Irrigation

Dripper

SDI
Typical values of soil and water characteristics for
various soils
Type of soil Sandy Light Medium Heavy Heavy Very
medium heavy
Bulk density (g/cm3) 1.6 1.6 1.4 1.3 1.2 1.1

Field capacity (% w/w) 6 13 20 27 33 40

Wilting point (% w/w) 2 6 10 15 20 27

Water Deficit (% w/w) 4 7 10 12 13 13

Water deficit (% v/v) 6.4 11.2 14 15.6 15.6 14.3

Available water (m3/ha) 192 336 420 468 468 429

Depth 30 cm
 Soil Water Retention
Soil: Silt Clay (Loess)
Apparent density: 1.44
Field capacity by weight: 22.9 %
Wilting point by weight: 11.9 %
Water soil retention by weight: 22.9 – 11.9 = 11 %
Water soil retention by volume: 11 x 1.44 = 15.8 %
Soil volume in 1 ha at 30 cm depth: 10.000 m2 x 0.30 m = 3.000 m3/ha
Available soil water at 30 cm in 1 ha: 3.000 m3/ha x 0.158 = 474 m3/ha o 47.4 mm

Soil volume in 1 ha at 1 m depth: 10.000 m2 x 1.00 m = 10.000 m3/ha

Available soil water at 1 m in 1 ha: 10.000 m3/ha x 0.158 = 1580 m3/ha o 158 mm

What is the easily available water ?

 Water Requirement

1. Width of wetted band : 0.70 m

Depth : 0.50 m
Distance between drip lines : 1.80 m

2. In 1 ha (10,000 m2): with a drip line every 1.80 m  10000/1.8

= 5555 m of Drip lines
5555 m x 0.5 m of depth x 0.70 m of wetted band = 1944 m3 of
soil volume is wetted

3. The soil F.C. (Field Capacity) = 22.9% x 1.44 (Density) = 32.9%

water volume
The soil Wilting Point = 11.9 % x 1.44 = 17.1 %

Total Water Available = 32.9 – 17.1 = 15.8 %

4. Soil wetted volume = 1944 m3

5. % water available = 15.8 %

6. Available water in the wetted soil: 1944 m3 x 0.158 = 307 m3 /

ha or 30.7 mm

7. Easily Available Water Percentage: 40 %

8. Total Easily Available Water

307 m3 x 0.40 = 123 m3 / ha or 12.3 mm

9. Crop water requirement = 5 mm o 50 m3/ha

10. Irrigation frequency = Total Easily Available Water / Daily
Requirement

10. 12.3 mm /5 mm/day = 2.5 - days

11. 123 m3/ha / 50 m3/ha = 2.5 days

10. This data is the first REFERENCE data value

requirement for an irrigation program.
 Crop water requirements

The depth of water needed to meet the water

loss through evapotranspiration (ETcrop) of a
disease free crop, growing in large fields
under non-restricting soil conditions including
soil water and fertility and achieving full
production potential under the given growing
environment.
 Evaporation

Evaporation is the process whereby liquid water is

converted to water vapor (vaporization) and removed
from the evaporating surface (vapor removal). Water
evaporates from a variety of surfaces, such as lakes,
rivers, pavements, soils and wet vegetation.
 Transpiration

Transpiration consists of the vaporization of liquid

water contained in plant tissues and the vapor
removal to the atmosphere
 Evapotranspiration process
The combination of two separate process whereby water
is lost on the one hand from the soil surface by
evaporation and on the other hand from the crop by
transpiration. Evaporation and transpiration occur
simultaneously and there is no easy way of
distinguishing between the two processes.
 Pan evaporation method

The evaporation rate from pans filled with water is

easily obtained. In the absence of rain, the amount
of water evaporated during the period (mm/day)
corresponds with the decrease in water depth in
that period. Pans provide a measurement of the
integrated effect of radiation, wind, temperature
and humidity on the evaporation from an open
water surface.
(Evaporation x Kc) - (Effective rain + Applied
irrigation) = how much water is lost (mm)
 Penman-Monteith equation

In 1948, Penman combined the energy balance with the

mass transfer method and derived an equation to
compute the evaporation from an open water surface
from standard climatological records of sunshine,
temperature, humidity and wind speed.
Reference Evapotranspiration Values Comparison
between Class A Tank and Penman-Monteith
Methodology

14

12

10
Penman-Monteith
Tanque Clase "A"
8
mm

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 Plant Growing Phase

Plant Growing Phase Kc

Up to 40 days from Planting 0.4
Germination
25 – 50% leaf cover Per filling 0.45 – 0.65
50 – 75% Leaf cover Grand growth 0.7 – 0.9
75 – 100% Leaf cover Maturation 0.9 – 1.2
 Irrigation Schedule
Farm Nova Aliança
month Set.

Dados
Day Date Evaporation Rain Rain Kc irrigated mm
(m"m) (m"m) efetiva per day
Monday 27/08/2008 5 65 45 1 -40.00
Tuesday 28/08/2008 4.3 0 1 4.30
Wednesday 29/08/2008 2 0 1 2.00
Thursday 30/08/2008 1 0 1 1.00
Friday 31/08/2008 2 0 1 2.00
Saturday 01/09/2008 3 0 1 3.00
Sunday 02/09/2008 5 0 1 5.00
22.3 65.0 45.0 1.0 -3.24
Monday 03/09/2008 5.1 0 1 5.10
Tuesday 04/09/2008 4 5 0 1 4.00
Wednesday 05/09/2008 4.9 10 0 1 4.90
Thursday 06/09/2008 3.8 11 7.7 1 -3.90
Friday 07/09/2008 5.1 0 1 5.10
Saturday 08/09/2008 4.2 0 1 4.20
Sunday 09/09/2008 4.5 0 1 4.50
31.6 26.0 7.7 1.0 3.41
Monday 10/09/2008 4 0 1 4.00
Tuesday 11/09/2008 1 0 1 1.00
Wednesday 12/09/2008 2.5 0 1 2.50
Thursday 13/09/2008 3.6 0 1 3.60
Friday 14/09/2008 4 0 1 4.00
Saturday 15/09/2008 2.5 0 1 2.50
Sunday 16/09/2008 1 0 1 1.00
18.6 0.0 0.0 1.0 2.66
Monday 17/09/2008 4 0 1 4.00
Tuesday 18/09/2008 5 0 1 5.00
Wednesday 19/09/2008 2 0 1 2.00
Thursday 20/09/2008 1 0 1 1.00
Friday 21/09/2008 3 35 24.5 1 -21.50
Saturday 22/09/2008 4 0 1 4.00
Sunday 23/09/2008 2 0 1 2.00
21.0 35.0 24.5 1.0 -0.50
 Irrigation Calculation
Application Rate – how much water my system applies in 1 hour
Measurement in mm refers to water height and not to volume
1 mm = 1 L in m3 = 10000 L (10 m3) in 1 hectare
Emitter discharge 1
= = 1.11 mm/hr or 11.1 m3/ha/hr
distance between 1.8 x 0.5
x distance between
drip line drippers

• The irrigation requirement = 3.2 mm/day

• 1 mm = 1 L in m3 = 10000 L (10 m3) in 1 hectare
 Irrigation Calculation
• Irrigation requirement = 3.2 mm/day
• Irrigation interval = 2 days
• 3.2 mm x 2 = 6.4 mm
• Application rate = 1.11 mm/hr
• 6.4 / 1.11 = 5.7 hr or 05:42
 Monitoring

Do we really know how

to irrigate?
The Tensiometer
 Rain \ Irrigation (mm)
30
/0
4/

0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
20
06
02
/0
5/
20
06
04
/0
5/
20
06
06
/0
5/
20
06
08
/0
5/
20
06
10
/0

Irrigation
5/
20
06
12
/0
5/
20
Water stress

06
irrigation start

14

Rain
/0
5/
20
06
16
/0
5/
20
06
18
/0
5/
20
06
20

Ten. 30 cm
/0
5/
Soil Saturation

20
06
22
/0
5/
20
06
24
/0
5/
20
06
Adequate humidity

26
Ten. 60 cm

/0
5/
20
06
28
/0
5/
20
06
30
/0
5/
20
06
Ten. 90 cm

01
/0
6/
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06
03
/0
6/
20
06
0
1

0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9

Ptensiometer reading (bar)

 LYSIMETER

The use of lysimeters in sugar cane will contribute to the supply

of the correct amount of water to the crop, to flushing the
excess salts when needed, and to avoid leaching of fertilizers
such as nitrogen.