Radiation and Light Use Effeiciency

8/2/2019 Radiation and Light Use Effeiciency

1/13

03/14/121

Radiation/Light Use Efficiency inRadiation/Light Use Efficiency in

Cropping SystemsCropping Systems

A.S. JADHAVDean, Faculty of AgricultureMPKV, Rahuri-413 722, Dist. Ahmednagar

Email: [email protected]

[email protected]


2/13

03/14/122

Topics CoveredAbsorbed radiation

Intercepted radiation

Transmitted radiationRadiation distribution in a crop canopy

Factors affecting radiation distribution withinplant community

Light use efficiency (LUE)


3/13

03/14/123

IntroductionIntroduction

Solar radiation is the source of energy forphotosynthesis.

Radiation in the 400 - 700 nm wavelength

interval supports photosynthesis in greenplants.

This region of the spectrum is referred as

photosynthetically active radiation (PAR).


4/13

03/14/124

Absorbed PAR is algebraic sum of the incomingand outgoing flux densities measured above andbelow a plant canopy (Aarar et al., 1989).

The measurements required above the canopy are

incident PAR flux density I0

excitant PAR flux density Rc

from the canopy (including

reflected by the but not absorbed prior to arriving at thetop of the canopy).

PAR flux density transmitted, Tc

through the canopy to

the soil surface and

PAR flux density reflected by the soil, Rs.

absorbed Par (APAR) of the canopy may becomputed as:

APAR = (I0 + Rs) - (Tc + Rc).


5/13

03/14/125

Intercepted PAR (IPAR) is the

difference in the PAR flux densityabove and below the plant canopy.

The two measurements required are

the incoming PAR flux densitytransmitted (T

c) through the canopy

to the soil surface:

IPAR = I0

- Tc.


6/13

03/14/126

When water, nutrients and temperature are

not limiting, the quantity of dry matter produced by a crop stand W (gm-2) can beexpressed as:

W = Sfet

Where, S is the daily mean solar radiation (MJm-

2day-1)

f is the seasonal mean fractional interception of

radiation by the canopye is the seasonal mean conversion coefficient

(gMJ-1)

t is the canopy duration in days


7/1303/14/127

During the season, fractional interception(f) is related to leaf area index (LAI) by

the equation:f = I - exp (-kLAI)

Where, k is an extinction coefficient

dependent on leaf angle and distribution.


8/1303/14/12

8

Reflection, Transmission andReflection, Transmission and

AbsorptionAbsorptionOn an average about 75 % of the

incident radiation is absorbed byplant canopyabout 15 % is reflected

and 10 % is transmitted.


9/1303/14/12

9

Radiation Distribution in a Crop CanopyRadiation Distribution in a Crop Canopy

Three aspects of solar radiation are biologicallysignificant. Intensity of radiation i.e. amount of radiant energy falling

on a unit surface area in a unit time.

Spectral distribution of radiation which governs thephotochemical process of photosynthesis.

Radiation distribution in time is important forphotoperiodic phenomenon.

The rate of photosynthesis depends on the availability

of photosynthetically active radiation intercepted bythe leaves.

The rate of transpiration from the plant canopy isalso controlled to a greater extent by the radiation

energy.


10/1303/14/12

10

Factors Affecting Radiation DistributionFactors Affecting Radiation Distribution

Within Plant CommunityWithin Plant Community

Transmissibilityof Leaves

Leaf Arrangement and Inclination

Plant DensityPlant Height

Angle of the Sun


11/1303/14/12

11

Light use efficiency (LUE)Light use efficiency (LUE)

Amount of dry matter produced (gm-2)

LUE = ----------------------------------------------------------

Amount of cumulative light absorbed (MJ m-2)

Pearl millet + pigeonpea and sunflower + pigeonpeaintercroppings are gaining popularity under rainfedconditions.

Intercropping advantages are maximized by complementaryinteraction between component crops due to minimal

intercrop competition (Willey, 1979). Intercrops intercepts PAR more efficiently compared to sole

crops under rainfed conditions.

It thus, improves light use efficiency ( Sivkumar and Virmani,1984 and Willey et al., 1986).


12/1303/14/12

12

Extinction coefficients (k)Extinction coefficients (k)

The k value is generally influenced byrow spacing,

plant population

plant arrangements.The k values were more under narrow row

geometry than wider row geometry

because of more interception of PARunder narrow rows.


13/1303/14/12

13

Radiation and Light Use Effeiciency

Documents

Transcript of Radiation and Light Use Effeiciency