320 B.J. Choudhury Agricultural and Forest Meteorology 106 2001 317–330
3. Input data
3.1. Stand characteristics The input data needed for stand characteristics are
leaf area index L
o
and nitrogen content of foliage, stem and roots per unit ground area. Each of these
Table 1 Number of data values n, mean and standard deviation in parenthesis of canopy leaf area index L
o
and nitrogen content per unit ground area mmol N m
− 2
of foliage, stem and roots used in the calculations Crop
n L
o
Nitrogen content Foliage
Stem Roots
Maize 24
2.7 1.5 281 177
160 110 55 42
Sorghum 13
2.7 1.9 230 115
161 115 109 17
Rice Transplanted
9 3.5 1.7
327 139 127 88
39 17 Direct seeded
5 6.2 1.7
335 128 282 112
107 19 All
14 4.5 2.1
330 130 182 120
64 38 Table 2
The daily total incident irradiance S, mol m
− 2
per day, diffuse fraction of the irradiance f
dif
, radiation-use efficiency for net carbon accumulation RUE, mmol mol
− 1
and carbon-use efficiency CUE, mol mol
− 1
for maize, sorghum, and rice
a
S f
dif
Maize Sorghum
Rice RUE
CUE RUE
CUE RUE
CUE Elora T = 20
◦
C 59
0.19 28 4
0.67 5 25 3
0.65 3 18 15
0.67 4 50
0.28 28 4
0.66 5 25 3
0.64 3 19 14
0.66 4 47
0.32 28 4
0.65 5 25 3
0.64 3 19 14
0.66 5 40
0.42 28 4
0.65 5 26 3
0.63 3 20 13
0.65 5 33
0.55 29 4
0.64 6 27 3
0.63 3 22 12
0.64 6 22
0.88 31 6
0.62 7 29 4
0.60 4 26 11
0.62 7 19
1.00 31 7
0.60 8 29 4
0.58 4 27 12
0.61 8 Los Banos T = 26
◦
C 54
0.17 27 4
0.64 6 24 3
0.61 3 16 17
0.61 7 47
0.26 26 5
0.62 6 23 2
0.60 4 16 17
0.60 8 37
0.42 27 5
0.61 7 24 3
0.58 4 16 17
0.58 10 30
0.58 27 6
0.60 9 24 3
0.57 4 17 17
0.56 12 24
0.78 27 9
0.58 11 25 4
0.55 5 19 18
0.54 14 18
1.00 27 12
0.54 14 25 6
0.51 6 19 21
0.50 18 Kununurra T = 26
◦
C 38
0.18 25 6
0.61 7 22 4
0.59 4 14 21
0.57 12 34
0.25 25 6
0.60 8 22 3
0.57 4 14 21
0.54 13 25
0.41 25 9
0.57 11 22 4
0.54 5 14 23
0.51 17 19
0.58 25 12
0.54 14 22 6
0.50 6 15 26
0.47 22 14
0.81 24 18
0.50 19 22 10
0.47 9 16 32
0.43 29 11
1.00 23 25
0.45 26 20 12
0.40 12 15 41
0.37 38
a
The coefficients of variation of RUE and CUE are given in parenthesis for all canopies of maize n = 24, sorghum n = 13, and rice n = 14. The highlighted figures appear in Table 3.
stand characteristics changes during growth, and at any time they can vary with husbandry, cultivar of a
species and meteorological conditions prevailing dur- ing growth. It is desirable to have all the needed data
measured concurrently for a variety because while A
g
depends upon L
o
and foliage nitrogen content, R
m
T depends upon the nitrogen content of foliage, stem and
B.J. Choudhury Agricultural and Forest Meteorology 106 2001 317–330 321
roots. Estimating L
o
or foliage nitrogen content using data from different sources introduce uncertainty in
determining A
g
, and such uncertainty appears in de- termining R
m
T when shoot and root nitrogen con- tent have not been determined concurrently. However,
such desirable sets of data were very limited, and thus measurements from different sources have been
used to determine the needed stand characteristics. The impact of uncertainties in the input data on RUE
and CUE has been addressed by sensitivity analysis Section 4.3.3.
The L
o
and nitrogen content per unit ground area mmol m
− 2
of foliage, stem and roots used in the calculations are summarized in Table 1. These data
have been extracted from published tables and figures after enlargement to minimize error, or estimated
using allometric relations.
3.2. Incident irradiance The direct and diffuse incident irradiance have been
calculated from a model Choudhury, 2000 by pre- scribing the atmospheric conditions and times during
the day being cloudy at Elora 43.7
◦
N, 80.4
◦
W during July, Los Banos 14.2
◦
N, 121.3
◦
E during April, and Kununurra 15.7
◦
S, 128.7
◦
E during June Table 2. These locations and time have been chosen for hav-
ing RUE data and to capture the diversity of radia- tion regime which can prevail during growth of these
crops.
4. Results and discussion
