climate change and crop productivityenvironmental and cultural factors affecting cotton growth and...

Environmental productivity indices for crop growth and development:Cotton as an examplePhotosynthesis

[email protected] of Plant and Soil sciences

Photosynthesis and Respiration and EnvironmentGoals and Learning Objectives:

• To understand the effects of multiple environmental factors on photosynthesis and respiration.

Photosynthesis and environment and Environmental Productivity Index (EPI) concept using cotton as an example crop.

Photosynthesis and environment and species variability and applicability of EPI concept.

Leaf and canopy aging and their relationship with photosynthesis.

Respiration and environment

• The next advance in field crop productivity will likely need to come from improving crop resource use efficiencies (e.g. radiation, water, nutrients, etc.), which are linked with overall crop photosynthetic efficiency.

• For this, there is an emerging agenda focused on genetic manipulation of the biochemistry of photosynthesis process to enhance crop canopy photosynthesis, and thus productivity and yield.

• However, progress is limited by the lack of connection between biochemical/leaf-level photosynthetic manipulation and crop performance, which is influenced by genetics and plant growth and developmental processes and environmental effects.

• Crop models which can incorporate the interactions and integrate across scales of biochemical organization might be the tools needed to accelerate the process in photosynthetic enhancement.

Racing towards Enhancing Crop Photosynthesis

Photosynthesis and Environment

You will learn:

• Effects of environmental factors on photosynthesis.

• How to quantify the effects of multiple environmental factors on photosynthesis.

• How to calculate potential photosynthesis under optimum conditions.

• Then, how to develop environmental productivity indices for various environmental factors to decrement the potential photosynthesis and to calculate actual photosynthesis.

Photosynthesis

• The process in which plants uses the energy fromsunlight to combine carbon dioxide (CO2) from theair with water to make carbohydrates plus oxygen.

Light, Plant6 CO2 + 6 H2O C6H12O6 + 6 O2

Water, Nutrients

H20 CO2

About 250 per sq mm

.

Environmental and cultural factors affecting Cotton growth and productivity

Temperature Atmospheric Carbon Dioxide Solar Radiation Water (Irrigation and Rainfall) Ultraviolet-B Radiation and Ozone Nutrients (N, P and K) Salt Stress Flooding (both short- and long-term Growth Regulators (PIX)

Global Atmospheric CO2 ConcentrationsMauna Loa, HI and South Pole

Year1958 1963 1968 1973 1978 1983 1988 1993 1998 2003

Atm

osph

eric

CO

2, p

pm

310

320

330

340

350

360

370

380

South Pole

Mauna Loa, HI

Time of the Day (Central Standard Time)0 2 4 6 8 10 12 14 16 18 20 22 24

CO

2 Con

cent

ratio

n, p

pm

340

360

380

400

420

440

23 July 1999Month of Year

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

CO

2 C

once

ntra

tion,

ppm

350

351

352

353

354

355

356

357

358

359

360

1990 at Mauna Loa, HI

High

Low

Radiation Conditions - Seasonal TrendsBakersfield, CA, Corpus Christi, TX and Stoneville, MS

Day of Year0 60 120 180 240 300 360

Sola

r Rad

iatio

n, L

angl

eys

0

100

200

300

400

500

600

700

800Bakersfield, CA

Corpus Christi, TX

Stoneville, MS

for Four US Cotton Producing AreasTe

mpe

ratu

re, °

C

Day of the Year0 50 100 150 200 250 300 350

-10

0

10

20

30

40-10

0

10

20

30

40

Days above Optimum = 0


Stoneville, Mississippi

Corpus Christ i, Texas

Long-term Average Temperatures

0 50 100 150 200 250 300 350


Bakersfield, California


Phoenix, Arizona

Precipitation - Seasonal TrendsBakersfield, CA and Florence, SC - 1991

Day of Year0 60 120 180 240 300 360

Prec

ipita

tion,

inch

es

0

1

2

3Florence, SCBakrsfield. CA

Seasonal Trends - Midday Leaf Water PotentialIrrigated and rainfed cotton, MSU North Farm -1995

Days after Emergence40 60 80 100 120

Mid

day

Leaf

Wat

er P

oten

tial,

bars

-25

-20

-15

-10

-5IrrigatedRainfed

Seasonal Trends Solar and UV-B RadiationMississippi State - 2001

Days0 100 200 300 400

UV-

B R

adia

tion,

kJ

m-2

d-1

0.00

0.01

0.02

0.03

0.04

0.05

Sola

r Rad

iatio

n, M

J m

-2 d-1

0

20

40

60

Solar radiation

UV-B Radiation

UV-UV-B/Solar Ratio: 0.00023323

Photosynthesis - Management Factors

Management factors such as fertilizer application amounts and timings affect nutrient uptake and leaf nutrient status and thus photosynthesis (Leaf N, P, K etc.,)

20 50 80 110 140

Leaf

N (g

kg-1

)

0

10

20

30

40

50

60

0 56112168

Days after planting

50 80 110 140

N (kg ha-1)

N study (2001) N study (2002)

FS FF FS FF

Cultural and Environmental FactorsSeasonal Trends – Leaf Nitrogen Concentration

Cultural and Environmental FactorsSeasonal Trends – Leaf Potassium and

Phosphorus Concentration

Leaf P

Days after Sedding

20 40 60 80 100 120 140

Leaf

P, %

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Laef K

Days after Seeding

20 40 60 80 100 120 140

Leaf

K, %

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6O N 50 N100 N150 N

How can we quantify environmental and cultural factor effects on plant processes – Photosynthesis?

Global Atmospheric CO2 ConcentrationsMauna Loa, HI and South Pole

Year1958 1963 1968 1973 1978 1983 1988 1993 1998 2003

Atm

osph

eric

CO

2, p

pm

310

320

330

340

350

360

370

380

South Pole

Mauna Loa, HI

Radiation Conditions - Seasonal TrendsBakersfield, CA, Corpus Christi, TX and Stoneville, MS

Day of Year0 60 120 180 240 300 360

Sola

r Rad

iatio

n, L

angl

eys

0

100

200

300

400

500

600

700

800Bakersfield, CA

Corpus Christi, TX

Stoneville, MS

for Four US Cotton Producing Areas

Tem

pera

ture

, °C

Day of the Year0 50 100 150 200 250 300 350

-10

0

10

20

30

40-10

0

10

20

30

40



Stoneville, Mississippi

Corpus Christ i, Texas

Long-term Average Temperatures

0 50 100 150 200 250 300 350


Bakersfield, California


Phoenix, ArizonaPrecipitation - Seasonal Trends

Bakersfield, CA and Florence, SC - 1991

Day of Year0 60 120 180 240 300 360

Prec

ipita

tion,

inch

es

0

1

2

3Florence, SCBakrsfield. CA

Seasonal Trends - Midday Leaf Water PotentialIrrigated and rainfed cotton, MSU North Farm -1995

Days after Emergence40 60 80 100 120

Mid

day

Leaf

Wat

er P

oten

tial,

bars

-25

-20

-15

-10

-5IrrigatedRainfed

Days0 100 200 300 400

UV-

B R

adia

tion,

MJ

m-2

d-1

0.00

0.01

0.02

0.03

0.04

0.05

Sola

r Rad

iatio

n, M

J m

-2 d-1

0

20

40

60

Solar radiation

UV-B Radiation

UV-UV-B/Solar Ratio: 0.00023323

20 50 80 110 140

Leaf

N (g

kg-1

)

0

10

20

30

40

50

60

0 56112168

Days after planting

50 80 110 140

N (kg ha-1)

N study (2001) N study (2002)

FS FF FS FF

Leaf P

Days after Sedding

20 40 60 80 100 120 140Le

af P

, %0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Laef K

Days after Seeding

20 40 60 80 100 120 140

Leaf

K, %

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6O N 50 N100 N150 N

Temporal trends in crop growth as affected

by environment

Quantifying the Effects of Environmental Factors on Photosynthesis

One way to quantify the effects of environmental factors on photosynthesis is to use environmental productivity Index (EPI) concept:

Actual (Photosynthesis) = Potential * Solar Radiation Index * Water Index * Temperature Index * Nutrient Indices (C, N, P, K) * UV-B Index, Salt stress Index, Flooding Index, Ozone Index, etc.,

First, we have to calculate the potential photosynthesis for a given species or cultivar. Potential photosynthesis is defined as the amount of photosynthesis that takes place at a maximum solar radiation under optimum environmental conditions (optimum water, nutrient, zero UV-B, temperature (27 °C) and in an actively growing canopy, no aging effect).


Then, we have to account for all the environmental factors that limit to obtain that potential.

Individual environmental factors affect the potential photosynthesis multiplicatively, not additively. For instance, if prolonged drought causes daily stomatal opening to cease, then no photosynthesis will occur, regardless of whether or not light, temperature or other factors are optimal for photosynthesis.

All the indices, ranging from 0 when it is totally limiting photosynthesis to 1 when it does not limit photosynthesis, represent the fractional limitation due to that particular environmental factor. Therefore, photosynthesis decreases as the effect of that particular stress becomes more severe.


This way, we could able to quantify the effect of all environmental factors limiting crop photosynthesis in multi-stress environments or in field conditions.


Database and Modeling Methodologies with Cotton as an Example Crop

Crop Responses to Environment - Tools

Naturally-lit Plant Growth Chambers

Soil-Plant-Atmosphere-Research (SPAR) Facility

Controlling Environmental Variables


Temperature = 30/22 °C (Average =27 °C)and in ambient (360 ppm) CO2 conditions.

SPAR - Data AcquisitionAtmospheric Carbon Dioxide Control

Time of day5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

CO

2 co

ncen

tratio

n, µ

L L-1

0

100

200

300

400

500

600

700

800

900

CO2 = 180 µL L-1

CO2 = 720 µL L-1

CO2 = 360 µL L-1


Measuring Gas Exchanges Carbon [CO2] Fluxes

Measuring Carbon FluxesCarbon Fluxes: Mass balance approach

During sunlit hours, by maintaining steady or constant CO2

concentration inside the SPAR chamber, we can calculate,

Net photosynthesis = Amount of CO2 injected – leak rate

Gross Photosynthesis = Net photosynthesis + Respiration

Suction

pump

Drying

agent

Drying

agent

CO2

analyzerDACS or

ComputerCompressed

CO2

Regulators/

Valves/flow meters SPAR

Canopy PhotosynthesisResponse to Solar Radiation

Time of the Day (Central Standard Time)0 2 4 6 8 10 12 14 16 18 20 22 24

PP

FD, µ

mol

m-2

s-1

0

500

1000

1500

2000

2500

Car

bon

Exc

hang

e R

ate,

mg

CO

2 m

-2 s

-1

-2

-1

0

1

2

3

4

5

6

7

360 µL L-1

Solar RadiationMaize, DAE 37

Estimating Potential Photosynthesis for Cottonas a Function of Solar Radiation

Solar Radiation, MJ m-2 d-10 5 10 15 20 25 30

Phot

osyn

thes

is, g

CO

2 m

-2 d

-1

0

50

100

150

200

250y = 10.7803*X - 0.1767 * X

2; r ² = 0.73

The Potential PHS (at 25 MJ) = 159.07 CO2 m

-2 d

-1

Weather Variables - Mississippi State - 1992Temporal Trends in Light Interception - 18 May = 0

Days after Emergence0 25 50 75 100 125 150

Ligh

t Int

erce

ptio

n, %

0

20

40

60

80

100

Square Flower Open Boll Maturity

Canopy Photosynthesis - Growing SeasonAccounting for environmental factors using EPI concept

Days after Emergence0 20 40 60 80 100 120 140 160

Phot

osyn

thes

is, g

CO

2 m-2

d-1

-50

0

50

100

150

200If the crop can intercept all the radiation

Intercepted Solar

Incoming Solar

Canopy Photosynthesis and EnvironmentResponse to Solar Radiation

Solar Radiation, MJ m-2 d-10 5 10 15 20 25 30

Envi

ronm

enta

l Pro

duct

ivity

Inde

x fo

r Pho

tosy

nthe

sis

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4y = 0.0678*X - 0.001111 * X

2, r

2 = 0.73

Canopy PhotosynthesisResponse to Atmospheric Carbon Dioxide

Carbon Dioxide Concentration, µL L-10 200 400 600 800 1000

Cano

py P

hoto

synt

hesis

, mg

CO2

m-2

s-1

0

1

2

3

4

5

y = 0.01235 *X - (0.00001222 *X2

) + (0.000000003976 *X3

)

Canopy Photosynthesis - EnvironmentResponse to Atmospheric Carbon Dioxide

Carbon Dioxide Concentration, µL L-10 200 400 600 800 1000

Envir

onm

enta

l Pro

duct

ivity

Inde

x fo

r CO

2 (CO

2 =36

0)

0.00.20.40.60.81.01.21.41.61.82.0

y = 0.004050 *X - (0.000004006 *X2

) + (0.000000001303*X3)

Canopy Photosynthesis - EnvironmentResponse to Temperature

Temperature, °C15 20 25 30 35 40C

anop

y Ph

otos

ynth

esis

, mg

CO

2 m-2

s-1

1

2

3

4

5

6

y = - 10.286 + 1.087 *X - 0.0192 *X2, r ² = 0.99

Canopy Photosynthesis - EnvironmentResponse to Temperature

Temperature, °C15 20 25 30 35 40

Envi

ronm

enta

l Pro

duct

ivity

Inde

xfo

r Tem

pera

ture

(T=2

7°C

)

0.2

0.4

0.6

0.8

1.0

1.2

y = -2.0247 + (0.2141 *X) - (0.003779 *X2); r ² = 0.99

Materials and Methods

Data collection: Pressure bomb

Leaf water potential

(LWP)

Canopy Photosynthesis - EnvironmentResponse to Water Deficits

Midday Leaf Water Potential, MPa-4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0Phot

osyn

thes

is, m

g C

O2 m

-2 s

-1

1

2

3

4

5

6

PPFD, 1600 µmol m-2 s-1 350 µmol mol-1 CO2

y = 6.0581 + (1.20327 * X); r ² = 0.64

Canopy Photosynthesis - EnvironmentResponse to Water Deficits

Midday Leaf Water Potential, MPa-4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0En

viro

nmen

tal P

rodu

ctiv

ity In

dex

for W

ater

Def

icits

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PPFD, 1600 µmol m-2 s-1 350 µmol mol-1 CO2

y = 1.3129 + (0.2608 * X); r ² = 0.64

PPFD, µmol m-2 s-10 500 1000 1500 2000C

anop

y Ph

otos

ynth

esis

, mg

CO

2 m

-2 s

-1

-1

0

1

2

3

4

5 0 kJ 8 kJ16 kJ

A

UV-B Radiation, kJ m-2 d-10 4 8 12 16C

anop

y Ph

otos

ynth

esis

, mg

CO

2 m

-2 s

-1

0

1

2

3

4

B

Canopy Photosynthesis – Environment

Response to UV-B Radiation

Response to Solar Radiation Response to UV-B Radiation

Canopy Photosynthesis - EnvironmentResponse to UV-B Radiation

UV-B Radiation, kJ m-2 d-10 4 8 12 16

Envi

ronm

enta

l Pro

duct

ivity

Inde

xfo

r UV-

B ra

diat

ion

0.0

0.2

0.4

0.6

0.8

1.0

1.2

y = 0.9835 -0.0002563*X - 0.002163*X2, r ² = 0.86

Canopy Photosynthesis - EnvironmentResponse to Fertilization - Nitrogen

Leaf N, %1 2 3 4 5

Phot

osyn

thes

is, m

g C

O2

m-2

s-1

1

2

3

4

5

6

7360 µL L-1 CO2PPFD = 1200

y = -1.9788 + (2.9243 * X) - (0.3096 * X2

); r ² = 0.79

Canopy Photosynthesis - EnvironmentResponse to Fertilization - Nitrogen

Leaf N, %1 2 3 4 5

Envi

ronm

enta

l Pro

duct

ivity

Inde

xfo

r Nitr

ogen

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

360 µL L-1 CO2PPFD = 1200

y = - 0.4029 + (0.5954 * X) - (0.0630 * X2

); r ² = 0.79

Canopy Photosynthesis - EnvironmentResponse to Fertilization - Potassium

Leaf K, %0 1 2 3 4Can

opy

Phot

osyn

thes

is, m

g C

O2

m-2

s-1

0

1

2

3

y = a*(1-exp(-b*x))

a = 2.5994, b = 1.7773

R2 = 0.96

Canopy Photosynthesis - EnvironmentResponse to Fertilization - Potassium

Leaf K, %0 1 2 3 4 5

Envi

ronm

enta

l Pro

duct

ivity

Inde

xfo

r Pot

assi

um

0.0

0.2

0.4

0.6

0.8

1.0

1.2

y = a*(1-exp(-b*x))

a = 1.0028, b = 1.4577

R2 = 0.96

Photosynthesis and EnvironmentModeling photosynthesis:Daily values of environmental variables such as temperature and

solar radiation (total as well as UV-B) as inputs (Physical inputs).Daily values of light interception (A separate model for solar

radiation interception).Daily values of leaf nutrient (N,P, K) status (Models for nutrient

uptake and leaf nutrient status).Daily values of leaf water potential as affected by precipitation

and irrigation (Model for water uptake and leaf water potential).Daily values of soil salt concentration (Model for salt

concentration). Soil oxygen concentration (Model for oxygen concentration

based on rainfall and irrigation).

Photosynthesis and Respiration and Environment

Actual photosynthesis:

Potential photosynthesis (159.07 g CO2 m-2 d-1)*EPI Indices (solar radiation, Temperature, Water stress, Nutrient stresses, UV-B radiation, salt, and flooding stresses) for various environmental factors.

Therefore, EPI is the way to quantify the effects of environmental factors on photosynthesis and thusproductivity of any crop.

Environmental Productivity Index (EPI)

Same concept can be applied for other crop growth and developmental processes.

The EPI concept has universal applicability and NOT location or crop-specific.

EPI also allows one to interpret and to understand stresses in the field situations.

If we know the factor that is limiting most at any point of time during the growing season, then we can make appropriate management decisions to correct that limitation.

Environmental Productivity ConceptEnvironment - Photosynthesis

Application of Environmental Productivity Index Concept to the Real-

World Situation

Environmental Factors Impacting Photosynthesis, Productivity and Growth of

Crops in a Single Season

Let us examine the environmental variables impacting crop growth

and development in a single growing Season:

Location: Mississippi State, North Farm

Year : 1992 cotton growing season

Cultivar: DPL 90

Fertilizer Applications: 80 lb N prior to planting

Irrigation/rain-fed: Rain-fed only

Pesticide and weed control: Standard best management practices

Weather Variables - Mississippi State - 1992Temporal Trends in Temperatures - 18 May = 0


Tem

pera

ture

, °C

0

10

20

30

40


Max. T

Avg. T

Min. T

Weather Variables - Mississippi State - 1992Temporal Trends in Solar Radiation - 18 May = 0


Sola

r Rad

iatio

n, M

J pe

r day

0

5

10

15

20

25

30

35


Weather Variables - Mississippi State - 1992Temporal Trends in Precipitation - 18 May = 0


Rai

nfal

l, m

m

0

20

40

60

80Square Flower Open Boll Maturity

Weather Variables - Mississippi State - 1992Temporal Trends in Wind Run - 18 May = 0


Win

d R

un, K

m p

er d

ay

0

100

200

300

400


Impact of Weather on Plant Growth - Mississippi State - 1992Temporal Trends in Mainstem Nodes - Simulated and Observed


Mai

nste

m N

odes

, no.

per

pla

nt

0

5

10

15

20

25

30

35


Simulated

Observed

Impact of Weather on Plant Growth - Mississippi State - 1992Temporal Trends in Plant Height - Simulated and Observed


Plan

t Hei

ght,

cm

0

25

50

75

100

125

150


Simulated

Observed


Let us assume the following crop conditions for leaf nitrogen, leaf K, and midday leaf water potential and weather variables such as solar radiation and use percent light interception to calculate an intercepted portion of the incoming solar radiation and temperatures for applying the EPI concept for one cotton growing season -1992.

Weather Variables - Mississippi State - 1992Temporal Trends in Temperatures - 18 May = 0


Tem

pera

ture

, °C

0

10

20

30

40


Max. T

Avg. T

Min. T

Weather Variables - Mississippi State - 1992Temporal Trends in Solar Radiation - 18 May = 0


Sola

r Rad

iatio

n, M

J pe

r day

0

5

10

15

20

25

30

35


Weather Variables - Mississippi State - 1992Temporal Trends in Light Interception - 18 May = 0


Ligh

t Int

erce

ptio

n, %

0

20

40

60

80

100




Phot

osyn

thes

is, g

CO

2 m-2

d-1

-50

0

50

100

150


Intercepted Solar

Incoming Solar

Photosynthesis and environmentSeasonal trends in Ultraviolet-B Radiation


UV-B

Rad

iatio

n, K

J m

-2 d

-1

0

2

4

6

8

10

Photosynthesis and environmentSeasonal trends in Leaf N, K and Water Potential


Leaf

N o

r K, %

0

1

2

3

4

5

Leaf

Wat

er P

oten

tial,

MP

a

-3.0

-2.8

-2.6

-2.4

-2.2

-2.0

-1.8

-1.6

-1.4

-1.2

N

LWP

K

Applying EPI Concept to Real-world Situation

1. First potential photosynthesis is calculated at optimum temperature, water, and nutrient conditions and 0 UV-B and at maximum solar radiation in an actively growing canopy. That is equal to 159.07 g CO2 m-2 d-1.

2. Then, using the functional algorithms or equations for Solar radiation, UV-B radiation, temperature, water stress, and nutrient stresses, EPI Indices for the environmental factors are calculated.

3. Finally, actual photosynthesis is estimated = Potential *EPI indices for various environmental factors.

Applying EPI Concept to Real-world Situation

Potential and

EPI for various

stress factors

Applying EPI Concept to Real-world SituationPotential photosynthesis = 159.07 g CO2 m-2 d-1 at 25 MJ m-2 d-1.

Then, actual photosynthesis = potential * EPI-solar radiation * EPI-UV-B radiation*EPI-temp * EPI-CO2 * EPI-water * EPI-leaf N * EPI-leaf K

Where:

EPI for solar Radiation = 0.0678*intercepted radiation – 0.001111*intercepted radition2

EPI for Temp = -2.0247 + (0.2141 *Temp) - (0.003779 *Temp2)

EPI for CO2 = 0.004050 *CO2 - (0.000004006 *CO22) + (0.000000001303*CO23)

EPI for Water = 1.3129 + (0.2608 * LWP)

EPI for N = - 0.4029 + (0.5954 * Leaf N)- (0.0630 * Leaf N2)

EPI for K = 1.0028 * (1-exp (-1.4577*Leaf K))

EPI for UV-B = 0.9835 – (0.0002563*UV-B) – (0.002163*UV-B2)



EPI I

ndice

s fo

r Var

ious

Env

ironm

neta

l Fac

tors

0.0

0.2

0.4

0.6

0.8

1.0

1.2

N

T

W

UV-B

SR

K



Phot

osyn

thes

is, g

CO

2 m-2

d-1

-50

0

50

100

150


Intercepted Solar

Incoming Solar



Phot

osyn

thes

is, g

CO

2 m-2

d-1

-50

0

50

100

150


Incoming Solar

Incoming Solar Intercepted Solar (Potential) Potential * UV-BPotential * UV-B * TPotential * UV-B * T * LWP Potential * UV-B * T * LWP * NPotential * UV-B * T * LWP * N * K

Variable Amount, MJ

Total Incoming Radiation 2842

Intercepted Radiation 1551

Percent Intercepted 55

Radiation Totals for the 1992 Growing seasonMississippi State – North Farm

Variable Amount, g CO2 m-2 season-1

Incoming R 19644

Intercepted R 11441 (100%)

Int. R * UV-B 10448 (9%)

Int. R.* T 10139 (11%)

Int. R.* W 9783 (14%)

Int. R.* N 8986 (21%)

Int. R * K 10841 (5%)

Photosynthesis – EPI ConceptAccounting for Individual factors

Photosynthesis – EPI ConceptAccounting for Multiple Factors

Actual amount

Variable Amount, g CO2 m-2 season-1

Incoming R 19644

Intercepted R 11441 (100%)

Int. R* UV-B 10448 (9%)

Int. R* UV-B*T 9153 (20%)

Int. R* UV-B*T*W 7551 (34%)

Int. R*UV-B*T*W*N 6292 (55%)

Int. R*UV-B*T*W* K 4576 (60%)

Applying EPI Concept to Real-world Situation1. Here, we have seen the demonstration EPI concept in

cotton for the whole growing season to estimate canopy photosynthesis.

2. Potential photosynthesis under optimum conditions; 159.07 g CO2 m-2 d-1.

3. Then, using the functional algorithms or equations for solar radiation, UV-B radiation, temperature, water stress, and nutrient stresses, and applying EPI indices for various environmental factors to estimate actual photosynthesis.

4. Finally, actual photosynthesis is estimated = Potential *EPI indices for various environmental factors.

climate change and crop productivityenvironmental and cultural factors affecting cotton growth and...

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