PRINCIPLES OF CROP GROWTH SIMULATION MODELLING

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PRINCIPLES OF CROP GROWTH SIMULATION MODELLING
Nitrogen-limited production
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The Rice System and boundary at field level
Radiation, CO2
O2
Temperature,
Nitrogen
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PROCESSES OF CROP GROWTH
I. N demand by crop

• Potential N demand
• Potential N uptake

II. N availability in the soil

• Indigenous soil N supply
• N fertilizer application

III. Nitrogen-driven crop growth

• Actual crop N uptake
• N translocation
• Effects of N limitations on crop growth

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I. N demand by crop
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Basic assumption crop strives towards maximal N
content
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Stem N content ? 50 leaf N content
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Panicle N content f(N in crop at flowering)
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1. Daily potential N demand by leaves
(NDleaf) NDleaf Nmax(Wleaf dWleaf) - Nleaf
(kg N ha-1 d-1) 2. Daily potential N demand by
crop (NDcrop) NDcrop NDleaf NDstem
NDpanicle (kg N ha-1 d-1)
3. Daily maximum N uptake by crop is
physiologically limited max is 8 kg N ha-1
d-1 gt Potential N uptake minimum(NDcrop,8)
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I. N availability in the soil
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Indigenous soil N supply

• Mineralization (SOM turnover)
• N in rain
• Biological N fixation

In ORYZA2000 no dynamic soil N modelling Soil N
supply estimated from 1. (total N uptake
in 0-N trials )/duration 2. fine-tuning by
model calibration At IRRI Soil N supply
0.5-0.8 kg N ha-1 d-1
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Fertilizer N supply
Fertilizer application x recovery
fraction Recovery fraction is calculated from
experiments
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Total soil N availability
1. Indigenous soil N supply 2. Fertilizer
application x recovery fraction
Unrecovered fertilizer N is either lost or
carried over to next seasons crop
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III. Nitrogen-driven crop growth
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Actual crop N uptake
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N redistribution
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Effect of N in crop on growth
1. Leaf photosynthesis
Van Keulen and Seligman, 1987 In
ORYZA2000 Adapted based on Shaobing Peng data
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2. Leaf expansion rate
Leaf expansion reduction factor f (actual N
leaf, maximum N leaf)
3. Accelerated leaf death rate
Accelerated leaf leaf death factor f (actual N
crop, maximum N crop)
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Input

• Weather data daily temperature, radiation
  gt Weather data file
• Management, additional fertilizer N
  application, fertilizer N recovery, soil N supply
  gt Experiment data file
• Crop characteristics, additional Max and min N
  contents of organs, Max N uptake, etc
• gt Crop data file

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Experimental data file
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------------------- 6. Nitrogen parameters

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--------------------- SOILSP 0.8 ! Indigenous
soil N supply (kg N/ha/d) (0.8) Table of
fertilizer rate (kg N/ha) (second column) versus
days after sowing in the seed-bed (!) (first
column) FERTIL 0., 0., 11., 0., 12.,
60., 13., 0., 29., 0., 30., 60., 31.,
0., 66., 0., 67., 60., 68., 0., 94.,
0., 95., 45., 96., 0., 366., 0. Table of
recovery fraction of Nitrogen in the soil (-)
second column versus development stage (DVS)
(first column) STANDARD VALUE RECNIT 0.0,
0.30, 0.2, 0.35, 0.4, 0.50, 0.8, 0.75, 1.0,
0.75, 2.5, 0.75
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Output

• Time course of leaf area index, biomass
• of various crop organs
• Time course of crop N contents and
• crop N uptake
• Yield, yield components

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IR72, Los Baños Dry season 1992
225 kg N ha-1 0
kg N ha-1
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Fraction leaf N ( kg kg1)
N content in leaves
Nmax
Nmin
225 kg N ha-1
Nmax
Nmin
0 kg N ha-1
Development stage
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IR72 1993 DS 17 treatments 0-400 kg N ha-1
Different splits