The document discusses the effects of greenhouse gases on crop production. It notes that certain gases in the atmosphere trap heat radiation, causing global warming. The main greenhouse gases from agriculture are carbon dioxide from fossil fuel combustion, methane from livestock and rice cultivation, and nitrous oxide from fertilizer and manure application. The document outlines both positive and negative impacts of increased greenhouse gases on agriculture, such as potential yield increases from higher CO2 levels but also risks from rising temperatures, drought, and diseases. Climate change is projected to significantly impact crop growth and production. Agriculture must also play a role in mitigating climate change by reducing its own greenhouse gas emissions.

1. B.Triveni
I.D No. TAM/2014 - 02
Dept. of Agronomy

2. EFFECT OF GREENHOUSE GASES IN CROP
PRODUCTION

3. Certain gases in the atmosphere acts as glass panes in
greenhouses and allow the small wave radiation to pass
through them but trap the long wave radiation which
comes after reflection from natural bodies.
These long wave radiations causes warming of
atmosphere. This phenomenon is popularly known as
global warming.
The gases responsible for this green house effect are
called green house gases.

5. Natural Greenhouse effect
The natural greenhouse effect causes the mean temperature of the Earth's
surface to be about 33oC warmer than it would be if natural greenhouse gases
were not present.

6.  Throughout the 20th century, the global average
temperature rose by about 0.50C.
 Global warming have profound effects on agriculture,
forestry, livestock and food security.
 Likely impacts of global warming led climate change.
 Climate change - changes in the Earth’s average state of
atmosphere or weather-over time scales ranging from
decades to millions of years.

8. Rice cultivation
23%
Manure
management
5%
Emission from
soils
12%
Enteric
fermentation
59%
Crop residues
1%
Contribution of GG’S emissions by different sectors of
agriculture in India

9. Three most important greenhouse gases produced by
agriculture
Carbon dioxide:
 Widespread combustion of fossil fuels
 Plant and animal respiration
 The decay of organic matter
CO2 is currently responsible for over 60% of the enhanced greenhouse effect.
Methane:
 Decay of organic matter under anaerobic conditions.
 Ruminant digestive processes and
 Manure storage and handling
Although there is less methane is the atmosphere, it is a more effective heat-trapping gas than CO2.

11. METHANE FLUX FROM SOIL SURFACE
WATER (EBULLITION) 3pathways.
1. Diffusion of dissolved methane
2. The emergence of bubbles
3. Plant transport by diffusion into the
roots and conversion to gaseous
methane in the cortex and aerenchyma
and subsequent release of methane to
the atmosphere through plant
micropores (Wassmann et al., 1993).

12. Denier van der Gon, 1996

13. Nitrous oxide:
 Soil cultivation,
 Fertilizer and manure application and
 The combustion of fossil fuels
 Organic matter produce NO2 emissions.
Soils and oceans naturally release NO2.
It is over 300 times more effective than CO2 in causing global
warming.

15. POSITIVE EFFECTS OF GREENHOUSE GASES
 Fossil fuel demand in the extreme latitudes would be reduced
because heating of our homes would be reduced.
 Some areas that are currently uninhabitable or unusable for
farm land might become suitable for these uses due to warming
and weather changes.
 Some areas could receive much more rainfall than they do
currently.
 Food production could be increased.
 There might be an increase in yield of some crops due to the
increase in the photosynthetic rate of plants to try to keep up
with the increased carbon dioxide in the atmosphere.

16. NEGATIVE EFFECTS OF GREENHOUSE GASES
 Increase in global temperatures will cause the polar ice caps and glaciers to begin
to melt. This will cause sea levels to rise.
 The rise and expansion of the sea would also allow storm surges and hurricane
waves to proceed further inland, causing more damage.
 Temperature increases can also lead to changes in weather patterns, precipitating
more frequent and severe storms.
 If too much drying occurs in areas, droughts could follow.
 Diseases which are currently restricted to tropical areas could spread to other areas
as they become warmer and more receptive to the agents which carry the
diseases.

17.  Increase in the average temperature of the
planet in the range of 1.1 to 6.4oc by the century.
 More intense tropical cyclones with higher
wind speeds coupled with heavier
precipitation.
 Faster, shorter, earlier growing seasons, heat
stress risk, increased evapotranspiration.

18. Six major impacts of climate
change:
 More carbondioxide
 Higher temperatures
 Water stress
 Extreme weather events
 Soil fertility and erosion
 Pest and diseases

19. CO2 enrichment:
Wheat : 7-11% increase in yield per 100 μmol mol-1 CO2
Rice : 30% increase in yield at opt temp. & then declined.
Soybean : 29±8% increase by doubling CO2
Maize & Sorghum : No or little effect

20. Rise in temperature
Wheat: 6-10% decrease with +10C (Shorter crop duration)
Rice : About 10% decrease with +10C indica type.
Lawlor and Mitchell (2000) suggested that 10C increase in
temperature during grain filling will typically shorten the duration by
5% and reduce grain yield and harvest index in the same proportion.

21. As any other human activity, agriculture is
concerned by these two priorities: agriculture
must play a role in climate change mitigation, by
i. Reducing its GHGs emission,
ii. Reducing its indirect emissions (e.g. through
reduce the use of synthetic fertilizers) and
iii. Storing carbon into soils (use soils as a CO2
sink).