PRINCIPLES OF CROP GROWTH SIMULATION MODELLING

Water-limited production

The Rice System and boundaries –Water-limited production situation

Radiation, CO2, H2O O2 , H2O

H2O H2O

H2OH2O Root zone

Temperature,Wind speedVapor pressure

Root water uptake

Crop transpiration

Affectscropgrowth

I. Growth as affected by water availability in soil

Soil water tension (“drought”) affects: transpiration,

photosynthesis, leaf rolling, spikelet sterility, leaf

expansion, assimilate partitioning, rooting depth, leaf

death

II. Water availability as function of soil water balance

Soil water tension = f(soil water content) Soil water content = f (rain, irrigation, evaporation, transpiration, percolation, seepage, overbund flow)

PROCESSES OF CROP GROWTH

I. Growth as affected by water availability in soil

Leaf

Stem

Root

Drought-stress effects derived from pot experiments, IRRI (Wopereis et al., 1996)

New research in progressNieuwenhuis et al., 2002

1. Transpiration and photosynthesis

Principle of reduction in photosynthesis by single leaf caused by water-stress

• Rate of CO2 flow through leaf stomata is equal to rate of H2O flow

• Stomatal aperture determines both CO2 and H2O flow rates

• When water supply (soil) is limiting, stomata close => CO2 and H2O flow rates decrease proportionally:

Fact = (Tact/Tpot) Fpot

Rice variety IR72

leaf (Tact/Tpot)

Soil water tension

• Actual photosynthesis (Fact) = relative transpiration x potential photosynthesis (Fpot)

Potential production routines

• Actual transpiration (Tact) = relative transpiration x potential transpiration (Tpot)

• Penman-Monteith

• Makkink

• Priestley-Taylor

Penman Priestley-Taylor

Makkink

Geographic latitude X X

Surface reflection coefficient

X X

Angstrom coefficients

X

Radiation/sunshine X X X

Temperature X X X

Wind speed X

Vapor pressure X

Required input data for calculation of Tpot

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80 90 100 110 120

TIME

0

1

2

3

4

5

6

7

0 10 20 30 40 50 60 70 80 90 100 110 120

TIME

Potential transpiration (mm d-1)

Reference ET (mm d-1)

Penman

Makkink

ET and T,

Dry season 1992,

Los Baños

2. Leaf rolling

0

0.2

0.4

0.6

0.8

1

1.2

1 10 100 1000 10000

Leaf rolling factor (-)

Soil water tension (kPa)

Rolled leaves => less canopy photosynthesis;

less canopy transpiration

3. Spikelet sterility

Turner (1986): relationship between leaf

rolling – increased canopy temperature

T = 5 (1 – LRF) 1.6

LRF = leaf rolling factor

Spikelet sterility

4. Leaf expansion, partitioning and root depth

Wopereis et al. (1996): leaf expansion stops at

soil moisture potentials of 50 to 250 kPa:

reduced-leaf-expansion factor

Tuong et al.: expansion stops between 1.45 and

1404 kPa.

Less leaf area => less canopy photosynthesis Assimilates don’t go to leaves but are

redirected to roots => changed assimilate

partitioning and increased rooting depth

5. Accelerated leaf death

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1 10 100 1000 10000

Drought-induced leaf death factor factor (-)

Soil water tension (kPa)

Less leaves => less canopy photosynthesis;

less canopy transpiration

0

0.2

0.4

0.6

0.8

1

1.2

1 10 100 1000 10000

Reduction factor (-)

Soil water tension (kPa)

Leaf expansion,Partitioning,Root depth

Leaf death

Leaf rolling,Spikelet sterility

Leaf photosynthesis,transpiration

Summary effects of soil water tension; IR72

Summary effects of soil water tension

Less leaves

Reduced leaf expansion

Less canopy photosynthesis

Less biomass

Reduced partitioning to shoot

Reduced leaf photosynthesis, transpiration

Leaf rollingLess light interception

Spikelet sterility

Less grainsLess yield

Accelerated leaf death

Soil moisture tension

Less canopy transpiration

II. Soil water balance

Schematic representation of the factors involved in a water balance, indicating water storage and flow in the plant-soil-atmosphere system. E - evaporation;T - transpiration; P - precipitation;I - irrigation; R - run-on/off; D - drainage; C - capillary rise; S - moisture content in the root zone.

Water balanceupland soil

Upland and aerobic rice

Lowland rice

Water balance lowland rice soil

Water requirements in lowland rice

Daily

(mm d-1)

Season 100 d (mm)

Land preparation 175 - 750

Evapotranspiration- wet season- dry season

4 – 5

6 - 7

400 – 500

600 - 700

Seepage & percolation- heavy clay- sandy/loamy soil

1 – 5

25 – 30

100 – 500

2500 - 3000

Total season : 675-4450 mm Typical value : 1500-2000 mm

Water (mm) SP (mm d1)

Guimba 88

89

90

91

2197

1679

2028

3504

18.3

12.5

16.4

32.8

Muñoz 91 1019-1238 5.2-7.6

Talavera 93 577- 728 0.3-2.0

San Jose 97 2874 25.8

San Jose 96

97

1417 (DS)

1920 (DS)

9.6

15.2

PhilRice 01 600 1.1 (-> 4.4)

Water use; central Luzon

Puddled soils for lowland rice

Transpiration

Evaporation

Rainfall

Irrigation

Tension (1), content (1)

Tension (n), content (n)

Water in1, water out1

Water inn, water outn

n soil layers

N puddled layers

Soil water balance inputs

Rainfall Weather station

Irrigation Irrigation subroutine

Potential soil evaporation PenmanMakkinkPriestley-Taylor

Actual crop transpiration PenmanMakkinkPriestley-Taylor +Crop subroutine

Irrigation scheduling subroutine

• Irrigation is 0: purely rainfed• Irrigation is input data• Irrigation timing as function of threshold values in depth of ponded water on soil surface• Irrigation timing as function of threshold values in soil water content• Irrigation timing as function of threshold values in soil water tension• Irrigation applied at X days after disappearance of ponded water on soil surface

Three soil water balance models:• SAWAH: puddled or upland soils • PADDY: puddled soils• SAHEL: free-draining upland soils

Simulated output:• Soil water content in each soil layer• Soil water tension in each soil layer• Actual soil evaporation• Water flows between each soil layer

Soil water balance inputs -

soil properties:

• Number and thickness of soil layers (n)• Bund height• Maximum rooting depth (obstructive layer)• Groundwater depth• Initial states (water content per layer)

• Soil hydrological characteristics: - soil water retention curve - soil water conductivity curve

0

1

2

3

4

5

6

7

0 0.1 0.2 0.3 0.4 0.5 0.6

-12

-10

-8

-6

-4

-2

0

2

4

0 0.1 0.2 0.3 0.4 0.5 0.6

Soil water tension (pF= log(h))

Soil water conductivity (log(cm d-1))

Soil water content (cm 3 cm-3)

Clay

Sand

Soil hydrological

characteristics:

Water retention curve

(pF curve)

Conductivity curve

SAWAH PADDY SAHEL

Conductivity curve

Simple Rijtema X

Extended Rijtema X

van Genuchten X X

Power function X X

Retention curve

Driessen X

van Genuchten X X

Simple data (4) X X

Extended data (10) X

Options for soil hydrological characteristics

)2)(/11(

21/11

)1(

))1(()(

lnn

nnn

s h

hhKhK

nrs

rh

h/11)1(

)(

Van Genuchten equations

Retention curve

Conductivity curve

Ks = Saturated conductivity

s = Saturated water content

r = Air-dry water content

= parameter

n = parameter

l = parameter

Sand Clay

Air dry

(pF = 7)

0.001 0.22

Wilting point

(pF = 4.2)

0.03 0.34

Field capacity

(pF = 2)

0.30 0.48

Saturation

(pF = 0)

0.46 0.560

1

2

3

4

5

6

7

0 0.1 0.2 0.3 0.4 0.5 0.6

Soil water tension (pF= log(h))

Soil water content (cm 3 cm-3)

Clay

Sand

Simple data (4) retention curve

Crop model Water-limited Production

Photosynthesis

Assimilatepool Biomass

Leaves

Stems

Panicles

Roots

LAI

Developmentstage

Maintenancerespiration

Growthrespiration

Partitioning

Developmentrate

N leaves

Light

Transpiration

Soil water Soil-watertension

Evaporation Rain, irrigation

Temperature

Input

1. Weather data: daily temperature, radiation, (wind speed, humidity), rainfall => Weather file

2. Management, additional: irrigation application => Experiment data file

3. Crop characteristics, additional: drought response factors => Crop data file

4. Soil properties: layers, retention characteristics, conductivity characteristics => Soil data file

Experimental data file*---------------------------------------------------------------** 6. Irrigation parameters * Need only to be filled-in when PRODENV = 'WATER BALANCE'*---------------------------------------------------------------*** Select from the following options:*SWITIR = 0 ! No irrigation; rainfed*SWITIR = 1 ! Irrigation supplied as input dataSWITIR = 2 ! Irrigation at minimum standing soil water depth*SWITIR = 3 ! Irrigation at minimum soil water potential*SWITIR = 4 ! Irrigation at minimum soil water content*SWITIR = 5 ! Irrigation at X days after disappearance of standing water

** If SWITIR = 1, supply irrigation table, amount of irrigation ** (y in mm) for a given calendar * day (x), used if RIRRIT = 0., 20.,366., 20.

** If SWITIR = 2-5, supply amount of irrigation IRRI (mm) IRRI = 75. ! Irrigation gift (mm)

** If SWITIR = 2, supply minimum standing water depth WL0MIN (mm)** below which irrigation water is appliedWL0MIN = 10. ! Minimum standing water depth (mm)

** If SWITIR = 3-4, supply minimum soil water potential KPAMIN (KPa)** (for SWITIR=3) or minimum soil water content WCMIN (-) (SWITIR=4)** below which irrigation water is applied, and the soil layer to** which this potential applies SLMIN (-)KPAMIN = 50. ! Minimum soil water potential (Kpa)WCMIN = 0.30 ! Minimum soil water content (-)SLMIN = 4 ! Soil layer for which KPAMIN or WCMIN applies (-)

** If SWITIR = 5, supply number of days after disappearance of** standing water (WL0DAY) at which irrigation water is appliedWL0DAY = 3 ! number of days after disappearance of (-) INTEGER!!

Output

• Time course of leaf area index, biomass

of various crop organs

• Time course of soil water content and

soil water tension; evapotranspiration

• Yield, yield components

• Irrigation scheduling

Jakenan, Indonesia, IR64: biomass

Calendar day

40 60 80 100 120 140 160 180 200

Dry matter, kg ha-1

0

3000

6000

9000

12000

15000

18000WiTnS1, measuredWrTnS1, measuredWiTnS2, measuredWiTdS1, measuredWrTdS1, measuredWrTdS2, measuredWiTnS1, simulatedWrTnS1, simulatedWrTnS2, simulated

Irrigated

Rainfed early

Rainfed late

1996

(a) April-June 1995 (walik jerami season)

A M J J A

Water table depth, cm

-140

-120

-100

-80

-60

-40

-20

0

(b) December 1997-March 1998 (gogorancah season)

D J F M A

-140

-120

-100

-80

-60

-40

-20

0

20

measuredsimulated

(c) November 1998-February 1999 (gogorancah season)

Day of seeding

N D J F M

-120

-100

-80

-60

-40

-20

0

20

40

Jakenan, Indonesia: groundwater depth

0

20

40

60

80

100

90 100 110 120 130 140 150

Rainfed early; 20 cm depth

Day

kPa

0

20

40

60

80

100

120 130 140 150 160 170

Jakenan, 1996. WrTdS2, 20 cm

Day

Kpa Rainfed late; 20 cm depthkPa

Jakenan, Indonesia: soil water tension

Hyderabad, India

Irrigated and rainfedyield

0

2000

4000

6000

8000

10000

12000

14000

16000

0 50 100 150 200 250 300 350 400

Paddy yield (kg/ha)

Sowing date (day of year)

irrigated

rainfed

0

500

1000

1500

2000

2500

0 50 100 150 200 250 300 350 400

Irrigation (mm)

Sowing date (day of year)

Rainfall (mm)

Irrigation requirements and rainfall

0

10

20

30

40

50

60

70

80

150 160 170 180 190 200 210 220 230 240 250 260 270 280

0

200

400

600

800

1000

1200Irrigation (mm)

Irrigation sum = 1600 mmCumulative rainfall (mm)

Day of year

0

10

20

30

40

50

60

70

80

150 160 170 180 190 200 210 220 230 240 250 260 270 280

0

200

400

600

800

1000

1200Irrigation (mm)

Irrigation sum = 800 mm

Cumulative rainfall (mm)

Day of year

Hyderabad, India:Irrigation schedule

Percolation = 1 mm d-1

Percolation = 10 mm d-1