Environmental and Cultural Factors
Limiting Potential Yields
Environmental Factors
Carbon dioxide
¾Atmospheric Carbon Dioxide
¾Solar Radiation
¾Temperature (Extremes)
¾Water
¾Wind
¾Nutrients (N and K)
¾Others, ozone etc.,
¾Growth Regulators (PIX)
K. Raja Reddy
Krreddy@pss.msstate.edu
Why are we concerned with CO2?
CO2
•
Atmospheric CO2 is essential for life on earth.
•
Plants grow through photosynthesis, a process that uses the energy from
sunlight to combine carbon dioxide (CO2) from the air with water to make
carbohydrates plus oxygen.
H2 0
Light, Plant, Water, Nutrients
6 CO2 + 6 H2O
C6H12O6 + 6 O2
•
The carbohydrates formed through photosynthesis feed not only the plants,
but also almost all other organisms on earth, including those that eat the
plants and those that eat the animals that eat the plants.
•
Now, as the atmospheric CO2 is rising, we are seeing almost parallel
decreases in atmospheric oxygen.
•
The oxygen concentration is so much higher than that of CO2 that the
decrease in oxygen from fossil fuel combustion is not a problem, but it
demonstrates the connections between these two critically important
atmospheric constituents.
A Hierarchy of Plant Responses to CO2 – C3 Plants
Atmospheric CO2
?
Stomatal Resistance
Photosynthesis
Transpiration
About 250 per sq mm
.
Direct effect of CO2 on canopy or
Microclimate Soybean Face Experiments
Photorespiration
Carbon Availability
Tissue Temperature
Tissue Water Potential
Growth and Development
Yield
Acock, 1990
1
Crop Responses to Atmospheric Carbon Dioxide
Atmospheric CO2 and Plant Responses
C3 example, cotton response
Of the 250,000 higher plant species:
C3 photosynthetic model
222,000 (89%)
C4 photosynthetic model
8,000 (3.2%)
Crassulacean Acid Metabolic
(CAM) photosynthetic model
20,000 (8%)
Canopy Photosynthesis, mg CO2 m-2 s-1
5
4
3
2
1
0
0
200
400
600
800
1000
Carbon Dioxide Concentration, ppm or µL L-1
Carbon Dioxide and Photosynthesis
Species Variability
Plant Adaptations to
Atmospheric Carbon Dioxide
Direct effect of increased CO2 on crop photosynthesis might
lead to higher global food production
¾ Weeds: Plants are NOT unique and UNIFORM in
stimulation of their photosynthesis by elevated CO2.
¾ Losses to Pests: Several recent studies show that insects eat
more high-CO2 grown material, because of decreased protein
levels.
¾ Climate: The connection between CO2 and climate is
increasingly well understood, with vast majority of evidence
indicating that continued build up of these radiative gases
causes gradual warming.
Plant Adaptations to Atmospheric Carbon Dioxide
Natural Ecosystems
In natural ecosystems, elevated CO2 has an effect similar to that on
crops; but the responses tend to be smaller or even absent.
And, features like:
¾
Recreational value: Since responses are NOT uniform; there
will be winners and losers. Evidence suggest that trees and
may be introduced species are being favored in a high-CO2
world, thus affecting the recreational and grazing value.
¾
Biodiversity: Rare or endemic species may be at a
disadvantageous position because of their poorly adapted
features.
Our Biosphere
is Changing.
What are the
driving factors for
this change?
2
Trends, Signs and Signatures from the Earth
Global Carbon Emissions- Sources
Global Carbon Emissions- Sources
Total
60
6000
5000
4000
Million metric tons of carbon
Million metric tons of carbon
7000
50
40
30
20
10
0
1750
3000
Annual carbon emissions, metric tons per person
Trends, Signs and Signatures from the Earth
1775
1800
Year
1825
Liquids
1850
Solids
2000
Gases
1000
Cement
Flaring
0
1750
1800
1850
1900
Year
1950
7
6
USA
5
4
3
Russia
Germany
Japan
2
Mexico
Global
China
Brazil
India
Nigeria
1
0
1950
2000
1970
1980
1990
2000
Year
Trends, Signs and Signatures from the Earth
Mean Carbon Emission Rates
Trends - World Population
6
Mean of 1991-2000
10
5
8
4
Population in Billions
Mean Carbon Emissions, metric tons per person
1960
3
2
World
6
4
Developing World
2
1
Developed World
0
1900
0
Global Nigeria
India
Brazil
China Mexico Japan Germany Russia
1920
1940
USA
1960
1980
2000
2020
2040
Year
Representative Countries
Trends, Signs and Signatures from the Earth
Trends, Signs and Signatures from the Earth
Atmospheric Carbon Dioxide Concentration
Atmospheric Carbon Dioxide Concentration
350
375
300
CO2 Concentration, ppm
Carbon Dioxide Concentration, ppm
400
250
200
350
325
300
275
250
1700
150
3000
2000
1000
0
1750
1800
1850
1900
1950
2000
Year
Years before the industrial Revolution (1850)
3
Trends, Signs and Signatures from the Earth
Trends, Signs and Signatures from the Earth
Global Carbon Emissions and Carbon Fixation
Atmospheric Carbon Dioxide Concentration
Trends, Signs and Signatures from the Earth
Trends – Atmospheric Carbon Dioxide – Monthly
400
Mauna Loa, HI
Barrow, Alaska
Cap Matatula Samoa
South Pole
Alert, Canada
Cape Kumukahi
Baring Head NZ
Christmas Island
Kermadec Island
Lo Jolla Pier
380
360
360
359
CO2 Concentration, ppm
Atmospheric Carbon Dioxide Concentration, µmol mol
-1
Atmospheric Carbon Dioxide Concentration – South to North
340
320
1990 at Mauna Loa, HI
358
357
356
Low
355
354
353
High
352
351
350
300
1957 1962 1967 1972 1977 1982 1987 1992 1997 2002 2007
Year
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
Month of Year
Trends – CO2 Concentration
Diurnal – Starkville, 27 July 1999
Global Circulation Models
Predictive Capabilities – Data Requirements
440
CO2 Concentration, ppm
23 July 1999
420
400
380
360
340
0
2
4
6
8
10
12
14
16
18
20
22
24
Time of the Day (Central Standard Time)
4
Trends, Signs and Signatures from the Earth
Trends, Signs and Signatures from the Earth
Greenhouse gases and Climate Change
Projected Global Carbon Dioxide Concentrations
Trends, Signs and Signatures from the Earth
Predicted Annual Temperature Increase
in GCMs for Doubled CO2 Scenario
Future trends in global carbon dioxide concentration and
associated climate change, if no interventions are made
(Adams et al., 1990)
Region
Climate variable
2025
2050
2100
Carbon dioxide
concentration
405-460
ppm
445-640
ppm
540-970
ppm
Global mean
temperature change
from the year 1990
0.4-1.1
oC
0.8-2.6
oC
1.4-5.8
oC
5-32
cm
9-88
cm
Global mean sea-level 3-14
rise from the year
cm
1990
GISS
GFDL
°C
Southeast
Delta
3.5
5.3
4.9
4.4
Northern Plains
Southern Plains
4.7
4.4
5.9
4.5
Mountain
Pacific
4.9
4.7
5.3
4.7
Historical Lint Yield - Causes and Effects
Trends That Shape Our Future
Relative Responses
CO2, NPK Use, Cotton Acreage and Yields
5
900
12000
10000
8000
6000
337%
700
35
30
Yield
600
25
500
20
CO2
400
15
NPK use
300
4000
200
2000
100
1860
10
4
360
340
320
Relative Response
14000
800
Yield
380
[CO2], µmol CO2 mol-1
16000
40
Area
US NPK Use, Million tons
18000
Cotton Lint Yield, kg ha-1
Cotton Harvested Area, ha (*1000)
20000
3
2
Genetics
61%
19%
300
1
280
0
1920
CO2
5
1880
1900
1920
1940
Year
1960
1980
0
2000
1930
1940
1950
1960
1970
1980
1990
2000
Year
5
Summary
¾ CO2 is a critical component of the atmosphere.
Suggested Reading Material:
¾ Increases in CO2 will have both positive and negative impacts
on agriculture and natural ecosystems.
1.
Climate Change and the Global Harvest. C. Rosenzweig and D.
Hillel. 1998. Oxford University Press, pages 1-69.
¾ The negative impacts expressed through climate change and
global warming affect not only agriculture but also other sectors.
2.
Climate change and variability by L. O. Mearns. In: Climate
Change and Global Crop Productivity, edited by K. R. Reddy and
H. F. Hodges. 2000. Pages 7-35.
¾ Overall, increasing CO2 is likely to cause serious problems.
3.
Agricultural contribution to Greenhouse gas emissions by D. C.
Reicosky, J. L. Hatfield and R. L. Sass. In: Climate Change and
Global Crop Productivity, edited by K. R. Reddy and H. F.
Hodges. 2000. Pages 37-55.
4.
Reddy, K. R. 2005. Climate change and global productivity of
goods and services. Souvenir, Sri Venkateswara University
College Golden Jubilee Celebrations, Sri Venkateswara
University, Tirupati. India, 163-168.
¾ It is extremely unlikely that terrestrial uptake of CO2 will be
sufficient to prevent these climate problems.
¾ A major adaptive response will be breeding or designing new
cultivars: heat-and-cold and drought resistance crop varieties that
may be better adapted to new climate (short-term fixes).
¾ Additional steps to limit CO2 emission by world’s nations is
another possibility (long-term strategies).
6