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From: Bhagirath Singh Chauhan, Prabhjyot-Kaur, Gulshan Mahajan,
Ramanjit Kaur Randhawa, Harpreet Singh, Manjit S. Kang, Global Warming
and its Possible Impact on Agriculture in India. In Donald L. Sparks, editor:
Advances in Agronomy, Vol. 123,
Burlington: Academic Press, 2014, pp. 65-121.
ISBN: 978-0-12-420225-2
© Copyright 2014 Elsevier Inc.
Academic Press
Author's personal copy
CHAPTER TWO
Global Warming and Its Possible
Impact on Agriculture in India
Bhagirath Singh Chauhan*, Prabhjyot-Kaur†, Gulshan Mahajan†,
Ramanjit Kaur Randhawa{, Harpreet Singh†, Manjit S. Kang}
*Crop and Environmental Sciences Division, International Rice Research Institute, Los Baños, Philippines
†
Punjab Agricultural University, Ludhiana, Punjab, India
{
Indian Agricultural Research Institute, New Delhi, India
}
Department of Plant Pathology, Kansas State University, Manhattan, Kansas, USA
Contents
1. Introduction
2. Greenhouse Effect and Global Warming
3. Agents of Global Warming
3.1 Carbon dioxide
3.2 Methane
3.3 Nitrous oxide
3.4 Water vapor
3.5 Ozone (O3)
4. Evidence for Climate Change and Impacts on Agriculture
5. Projected Climate Change in India
6. Impact of Global Warming on Agriculture and the Food Supply
6.1 Effect of elevated concentrations of CO2 on crop growth
6.2 Effect of ozone on plants
6.3 Effect of increasing temperature on crop growth
6.4 Interactive effects of changing climatic factors on crop production
6.5 Effect of climate change on the quality of produce
6.6 Agricultural surfaces and climate change
6.7 Soil erosion and soil fertility
6.8 Potential effects of climate change on pests
7. Key Adaptation and Mitigation Strategies to Reduce the Effects of Climate Change
7.1 Crop-based approaches
7.2 Crops and cultivars that fit into new cropping systems and seasons
7.3 Cultivars suitable for high temperature, drought, inland salinity, and
submergence tolerance
7.4 Cultivars that respond to high CO2 concentration
7.5 Mitigation of the impact of climate change
7.6 Other strategies
7.7 Policy issues for managing climate change
Advances in Agronomy, Volume 123
ISSN 0065-2113
http://dx.doi.org/10.1016/B978-0-12-420225-2.00002-9
#
2014 Elsevier Inc.
All rights reserved.
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8. Conclusions
Acknowledgment
References
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Abstract
Progress has been significant in climate science and the direct and indirect influences of
climate on agricultural productivity. With the likely growth of the world's population
toward 10 billion by 2050, demand for food crops will grow faster than demand for
other crops. The prospective climate change is global warming (with associated
changes in hydrologic regimes and other climatic variables) induced by the increasing
concentration of radiatively active greenhouse gases. Climate models project that
global surface air temperatures may increase by 4.0–5.8 C in the next few decades.
These increases in temperature will probably offset the likely benefits of increasing
atmospheric concentrations of carbon dioxide on crop plants. Climate change would
create new environmental conditions over space and time and in the intensity and frequency of weather and climate processes. Therefore, climate change has the potential
to influence the productivity of agriculture significantly. Climate variability has also
become a reality in India. The increase in mean temperature by 0.3–0.6 C per decade
since the 1860s across India indicates significant warming due to climate change. This
warming trend is comparable to global mean increases in temperature in the past
100 years. It is projected that rainfall patterns in India would change with the western
and central areas witnessing as many as 15 more dry days each year, whereas the northern and northwestern areas could have 5 to 10 more days of rainfall annually. Thus, dry
areas are expected to get drier and wet areas wetter. It is projected that India's population could reach 1.4 billion by 2025 and may exceed China's in the 2040s. If agricultural
production is adversely affected by climate change, livelihood and food security in India
would be at risk. Because the livelihood system in India is based on agriculture, climate
change could cause increased crop failure and more frequent incidences of pests.
Therefore, future challenges will be more complex and demanding. This chapter
focuses on the variability of climate change and its probabilistic effects on agricultural
productivity and adaptation and mitigation strategies that can help in managing the
adverse effect of climate change on agricultural productivity, in particular for India.
1. INTRODUCTION
Climate is the synthesis of weather conditions in a given area, characterized by long-term statistics (mean values, variances, probabilities of
extreme values, etc.) for the meteorologic elements in that area (World
Meteorological Organization, 1992). Generally, the quantities measured
are surface variables, such as temperature, precipitation, and wind. More
broadly, the “climate” is the description of the state of the climate system
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(IPCC, 1995). Climate variability reflects deviations in climate statistics
across a given period (a specific month, season, or year) from the long-term
climate statistics relating to the corresponding calendar period (World
Meteorological Organization, 1992).
Climate affects human life on Earth. It regulates food production and
water resources and influences energy use, disease transmission, and other
aspects of human health and well-being (National Research Council
(United States), 2010). Earth’s atmosphere is mainly composed of nitrogen
(N) and oxygen (O2), but these gases have little or no influence on radiation
coming from the sun or that emitted by Earth’s surface. The so-called greenhouse gases (GHGs), which include water vapor, carbon dioxide (CO2),
methane (CH4), nitrous oxide (N2O), and chlorofluorocarbons (CFCs),
however, absorb and reemit infrared radiation emitted by the surface of
the Earth and trap heat in the atmosphere. This amplified warming keeps
Earth’s surface warmer (about 33 C) than it would be without the presence
of GHGs (National Research Council (United States), 2010).
Then, what is climate change? According to the World Meteorological
Organization (1992), climate change represents a significant change, that is, a
change with important economic, environmental, and social effects, in the
mean values of a meteorologic element, such as temperature and amount of
precipitation during a certain period, for which the means are computed
across a decade or longer (World Meteorological Organization, 1992). In
the IPCC usage, climate change occurs because of internal changes within
the climate system or in the interaction among its components or because of
changes in external forcing, either for natural reasons or because of human
activities (IPCC, 1995). Projections of future climate change reported by the
IPCC generally consider the influence on the climate of only anthropogenic
increases in GHGs and other human-related factors (IPCC, 1995). Agriculture accounted for 10–12% of the total global anthropogenic emissions of
GHGs (IPCC, Working Group III, 2007).
2. GREENHOUSE EFFECT AND GLOBAL WARMING
According to the Free Dictionary by Farlex, greenhouse effect is the
phenomenon whereby Earth’s atmosphere traps solar radiation, caused by
the presence in the atmosphere of GHGs, which allow incoming sunlight
to pass through but absorb heat radiated back from Earth’s surface. Earth’s
atmosphere balances the absorption of solar radiation with emission of longwave radiation (infrared) to space. Not only does Earth’s surface primarily
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Table 2.1 Relative contribution of greenhouse gases to anthropogenic greenhouse
effect in the United States (EIA, 2008)
Carbon equivalent
Greenhouse gases
Million metric tons
Percentage
Energy-related carbon dioxide
5735.5
81.3
Methane
737.4
10.5
Nitrous oxide
300.3
4.3
Carbon dioxide from other sources
103.8
1.5
Hydrofluorocarbons (HFCs), perfluorocarbons
(PFCs), and sulfur hexafluoride (SF6)
175.6
2.5
absorb most of the short-wave radiation from the sun, but also it reradiates
some of this radiation as long-wave radiation. The atmosphere is more efficient at absorbing long-wave radiation, which is then emitted both back to
space and downward toward the Earth. This downward emission heats Earth
further. This further warming by reradiated long-wave radiation from the
atmosphere is known as the greenhouse effect. The amount of long-wave
radiation that is absorbed and then reradiated downward is a function of
the constituents of the atmosphere. Certain gases in the atmosphere are
particularly good at absorbing long-wave radiation and are known as GHGs.
These include water vapor, CO2, CH4, N2O, and CFCs. (Table 2.1). If the
makeup of the atmosphere changes and the result is an increase in concentrations of GHGs, then more of the infrared radiation from Earth will be
absorbed by the atmosphere and then reradiated back to Earth. This changes
the radiative forcing of the climate system and results in increased temperature of Earth’s surface, which affects crop growth and production. Global
warming results from the increase in greenhouse effect in the atmosphere. It
is a blanket of gases that wraps around the Earth and holds the heat in. CO2 is
the most common gas that causes global warming. The more the global temperature increases, the more the climate changes.
3. AGENTS OF GLOBAL WARMING
Human and industrial activities are mainly responsible for the rise in
the concentration of GHGs in the atmosphere. CO2, the most abundant
GHG, is mainly increasing because of fossil fuel combustion. Similarly,
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Global Warming and Its Possible Impact on Agriculture in India
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industrial processes cause CFC emissions. The increased agricultural activities and organic waste management are presumed to be contributing to the
buildup of CH4 and N2O in the atmosphere (Hundal and Abrol, 1991). The
GHGs produced by various activities are considered as the agents of climate
change; a brief description of these agents is given in the succeeding text.
3.1. Carbon dioxide
There is a large fixation of CO2 in agriculture, but its estimates are generally
not available because of the continuous consumption of its products by
human beings and other secondary consumers. In India, fixation of CO2
is assumed to be important because almost 190 million hectares of land is
being used for farming. The estimated dry matter production from agriculture in India is almost 800 million t year1 (Khan et al., 2009). This is equivalent to fixation of 320 Tg of C or 1000 Tg of CO2 per annum. Only a part
of this is retained over time, while the rest is released back to the atmosphere.
3.2. Methane
The total annual output of CH4 into the atmosphere from all sources in the
world is estimated to be 535 Tg year1 (Khan et al., 2009). India’s total contribution to global CH4 emissions from all sources is only 18.5 Tg year1.
The increase in annual load of CH4 in the atmosphere is much less than that
of CO2, but its higher absorption accounts for a major contribution to global
warming. Agriculture, mainly continuously flooded rice (Oryza sativa L.)
fields and ruminant animals, is the major (68%) source of CH4 emissions.
Global annual CH4 emissions from rice paddies are less than 13 Tg year1
and the contribution of Indian paddies to this is estimated to be only 4.2 Tg
year1 (Bhattacharya and Mitra, 1998; Sinha et al., 1998). Low CH4 emissions from rice fields in India are mainly because the soils of the major ricegrowing areas have very low organic carbon and are not continuously
flooded.
3.3. Nitrous oxide
N2O, which is present in the atmosphere at a very low concentration
(310 ppbv), is increasing at 0.22 0.02% per year (Battle et al., 1996;
Machida et al., 1995; Mosier et al., 1998). But, in spite of its low concentration and less rapid rise, N2O is becoming important because of its longer
lifetime (150 years) and greater global warming potential than CO2 (about
300 times more than CO2). Both fertilized and unfertilized soils contribute
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Bhagirath Singh Chauhan et al.
to the release of this gas. The estimates of total N2O released from Indian
agriculture are low because of relatively low native soil fertility and lower
amounts of fertilizer used than in many developed countries (Khan
et al., 2009).
The major contributor to global warming is the energy sector (which
includes fossil fuel burning), which is responsible for 61% of the total contribution toward global warming. Agriculture and its allied activities contribute to 28% of global warming, followed by the industrial sector (8%),
wastes (2%), and land-use changes (1%).
3.4. Water vapor
Water vapor is the most abundant and most important GHG because of its
contribution to the natural greenhouse effect (National Research Council,
United States, 2010). Its concentration in the lower atmosphere is controlled
by the rate of evaporation and precipitation. It is not considered a climate
forcing agent.
3.5. Ozone (O3)
Ozone is found in its highest concentrations in the stratosphere that extends
from 15 to 50 km in height. It is produced by the dissociation of O2 by ultraviolet light. It absorbs harmful ultraviolet radiation. However, the use of
aerosols, man-made halogenated gases, and CFCs has destroyed the ozone
layer in the stratosphere, contributing to global warming. The Montreal
Protocol, signed in 1987, has been ratified by 196 countries now. The ozone
layer has started to recover, but it may take decades for complete recovery
(Ebi et al., 2008). Near the Earth’s surface, however, ozone is regarded as a
pollutant, causing damage to plants, animals, and humans, and it is the main
component of smog (National Research Council, United States, 2010).
4. EVIDENCE FOR CLIMATE CHANGE AND IMPACTS
ON AGRICULTURE
During the past few decades, climate change, caused by global
warming, has received worldwide attention (Baer and Risbey, 2009).
The most significant change is the rise in the atmospheric temperature caused by increased concentrations of GHGs in the atmosphere. Between 1000
and 1750 AD, CO2, CH4, and N2O concentrations were 280 6 ppm,
700 60 ppb, and 270 10 ppb, respectively (IPCC, 2007a). More
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recently, however, these values have increased to 369 ppm, 1750 ppb, and
316 ppb, respectively.
The global mean annual temperature at the end of the twentieth century
was almost 0.7 C above that recorded at the end of the nineteenth century
and it is likely to increase further by 1.8–6.4 C by AD 2100, with a best
estimate of 1.8–4.0 C (IPCC, 2001, 2007a,b). The decade 1990–2000
was the warmest in the last 300 years and was 0.5 C warmer than the mean
temperature of 1961–1990. Warmer summers have included record hot
spells and high sunshine hours, and the warm winters have reduced the
number of frosts. The quantity of rainfall and its distribution are also greatly
affected by climate change and these are expected to increase the problems of
flooding and soil erosion. Moreover, the sea level has risen and snow cover is
also gradually decreasing due to glacier meltdown, especially near the poles,
and arable land is decreasing near coastal regions due to inundation.
The Panel on Advancing the Science of Climate Change, set up by the
National Research Council (United States) (2010), arrived at several conclusions, whose important ones were (1) that several different research groups
had shown that the planet’s mean temperature was 0.8 C higher during the
first decade of the twenty-first century than during the first decade of the
twentieth century; (2) that much of the warming during the past several
decades could be attributed to anthropogenic activities that released into
the atmosphere CO2 and other GHGs that trap heat and burning of fossil
fuels (coal, oil, and natural gas) for energy was the largest contributor to climate change; and (3) that agriculture, forest clearing, and certain industrial
activities also made significant contributions to climate change.
The United Nations Environment Programme (UNEP) and the WMO
established the IPCC in 1988 to periodically assess the state of the global
environment. A report of the IPCC during 2001 projected that the global
mean temperature above Earth’s surface would rise 1.4–5.8 C during the
next 100 years (IPCC, 2001).
Climate change is a well-recognized, significant, man-made, global
environmental challenge and agriculture is strongly influenced by it
(Hillel and Rosenzweig, 2011; Kang and Banga, 2013). A team of experts
from the Food and Agriculture Organization (FAO) concluded that each
1 C rise in mean temperature would cause annual wheat (Triticum
aestivum L.) yield losses in India of about 6 million tons (US$ 1.5 billion
at current prices), and, when losses of all other crops were taken into consideration, farmers were projected to lose US$ 20 billion each year (FAO,
Food and Agriculture Organization, 2008; Swaminathan, 2012). Such losses
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can happen as temperature can reduce crop duration; increase croprespiration rates; alter photosynthate movement from source to sink; affect
the survival and distribution of pest populations, thus developing a new
equilibrium between crops and pests; hasten nutrient mineralization in soils;
decrease fertilizer-use efficiencies; and increase evaporation (Kumar et al.,
2011). Indirectly, there may be considerable effects on land use that can
be attributed to snowmelt, availability of irrigation, frequency and intensity
of inter- and intraseasonal droughts and floods, and availability of energy
(Sharma and Chauhan, 2011). All of these changes can have tremendous
effects on agricultural production and hence on the food security of a region.
More flooding, droughts, and forest fires; decreases in agricultural productivity; and the displacement of thousands of coastal residents by sea-level
rise and intense tropical cyclones are the likely consequences of climate
change in Asia. A rise in mean temperature of 2 C above the normal could
mean that small islands, such as Tuvalu in the Pacific Ocean and Maldives,
Lakshadweep, and Andaman and Nicobar in the Indian Ocean, could be
submerged (Swaminathan, 2012).
Global warming is mainly brought about by rapid industrialization, combustion of fossil fuels, increased agricultural operations, deforestation, and the
increased number of vehicles (National Research Council, United States,
2010). The driving force behind these factors is the ever-increasing human
population. The global share of various countries in CO2 emissions is given
in Table 2.2 (Sathaye et al., 2006), and per capita emissions of C by residents
of various countries are shown in Table 2.3 (Sathaye et al., 2006). The United
States is the major contributor to CO2 emission; the US share was about onefourth of the total global emissions, whereas India’s contribution was about 4%
(Table 2.2). Per capita production of C was also highest in the United States
(5.4 t of C per person), followed by Canada (5.2 t of C per person) (Table 2.3).
India’s per capita C emissions were only 0.26 t of C per person.
5. PROJECTED CLIMATE CHANGE IN INDIA
Analysis of a representative rainfall series across the past 176 years for
India as a whole did not suggest any significant trend in rainfall change
(Sontakke, 1990). However, Rao (2007) analyzed the rainfall data of
1140 meteorologic stations in India, which showed a negative trend in rainfall among the stations situated in the southern states of India, southern peninsular areas, central India, and parts of the north and northeastern regions.
Positive trends in rainfall were observed for Gujarat, Maharashtra, coastal
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Global Warming and Its Possible Impact on Agriculture in India
Table 2.2 Global share of some countries in CO2 emissions (Sathaye et al., 2006)
CO2 emissions (%)
Country
1990
2003
Canada
2.19
2.39
China
10.41
14.07
France
1.80
1.63
Germany
4.24
3.35
India
2.63
4.07
Italy
1.91
1.85
Japan
5.54
4.79
Russia
9.67
6.38
United Kingdom
2.76
2.24
United States
23.04
23.06
Rest of the world
38.61
36.17
Table 2.3 Per capita carbon emissions from energy for the year 2003
(Sathaye et al., 2006)
Country
Carbon emissions (t person1)
Canada
5.19
China
0.78
France
1.86
Germany
2.78
India
0.26
Italy
2.21
Japan
2.58
Russia
3.06
United Kingdom
2.60
United States
5.44
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Bhagirath Singh Chauhan et al.
Andhra Pradesh, and Odisha. However, the parts of the country covering
eastern Uttar Pradesh, eastern Madhya Pradesh, the west coast, and greater
parts of northwest India did not show any changes. Among the rainfed districts, 40% of the stations showed a negative trend, 48% showed a positive
trend, and 12% showed no changes in rainfall.
Based on observations from 73 stations, an analysis of the mean annual
surface air temperature across India for 1901–1988 showed a significant
warming of about 0.4 C per 100 years (Hingane et al., 1985). This warming
trend was comparable to the global mean temperature change of 0.5 C in
the last 100 years. Later on, using the all-India mean surface air temperature
for 1901–2000 from a network of 31 well-distributed, representative stations, the trends in mean annual temperatures across the country were determined (Rupa Kumar et al., 2002). Warming trends were observed during
four seasons (winter, premonsoon, monsoon, and postmonsoon) with a
higher rate of temperature increase during winter (0.04 C per decade)
and postmonsoon seasons (0.05 C per decade) compared with the
premonsoon (0.02 C per decade) and monsoon seasons (0.01 C per
decade). The warming across the Indian subcontinent was mainly contributed by the postmonsoon and winter seasons. The monsoon temperatures
did not show a significant trend in most parts of India, except for a significant
negative trend across northwest India (De and Mukhopadhyay, 1998). The
diurnal temperature range has also decreased, with nighttime temperature
increasing at twice the rate of the daytime maximum temperature (Sen
Roy and Balling, 2005).
In a regional study in Punjab, Prabhjyot-Kaur and Hundal (2010)
reported gradual increases in minimum temperature across a recent
30-year period. The maximum temperature, however, showed no significant trend at most locations in the state. A 5-year mean of annual rainfallvariability analysis in Punjab revealed that rainfall decreased significantly
during the past five decades at the rate of 5.5, 3.4, 7.1, 4.3, and 5.5 mm
year1 at Amritsar, Gurdaspur, Ferozepur, Bathinda, and Sangrur, respectively, and rainfall increased significantly at 1.4 mm year1 during the past
108 years at Ludhiana (Prabhjyot-Kaur et al., 2011). However, no significant
trend in rainfall variability was observed in Kapurthala, Jalandhar,
Hoshiarpur, Rupnagar, Patiala, and Faridkot districts. The IPCC compiled
data on the magnitude of change in temperature, rainfall, and CO2 for different parts of the world, according to which CO2 was expected to increase
to 397–416 ppm by 2050 and to 605–755 ppm by 2070 (Watson et al.,
1998). By the end of the twenty-first century, there could be a change in
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Table 2.4 Changes in temperature and rainfall projected for India (Lal et al., 2001)
Rainfall change (%)
Temperature change ( C)
Year
Season
Lowest
Highest
2020
Annual
1.00
1.41
2.16
5.97
Rabi
1.08
1.54
1.95
4.36
Kharif
0.87
1.17
1.81
5.10
Annual
2.23
2.87
5.36
9.34
Rabi
2.54
3.18
9.22
3.82
Kharif
1.81
2.37
7.18
10.52
Annual
3.53
5.55
7.48
9.90
Rabi
4.14
6.31
24.83
4.50
Kharif
2.91
4.62
10.10
15.18
2050
2080
Lowest
Highest
precipitation of 5–25% across India, with more reductions in winter than
summer rainfall (Prabhakar and Shaw, 2008).
There is considerable uncertainty in the magnitude of change in rainfall
and temperature predicted for India. The relative increase in temperature has
been projected to be less in kharif than in the rabi season; rabi rainfall would
have a large uncertainty, but kharif rainfall is likely to increase by as much as
10% (Lal et al., 2001) (Table 2.4). Because of the large spatial and temporal
variability in weather factors in a region, the availability of more detailed
scenarios for different agroclimatic zones is desirable. There is also increasing
consensus that climatic variability will increase in the future, leading to more
frequent extremes of weather in the form of erratic monsoons and increased
frequency and intensity of drought and flooding.
6. IMPACT OF GLOBAL WARMING ON AGRICULTURE
AND THE FOOD SUPPLY
Agriculture is both a victim and an abettor of climate change (Kang
and Banga, 2013). Climate change plays a significant role in a nation’s food
security and economy, especially in a developing country such as India. For
example, Killman (2008) wrote (p. iii), “Climate change will affect all four
dimensions of food security: food availability, food accessibility, food utilization and food systems stability. It will have an impact on human health,
livelihood assets, food production and distribution channels, as well as
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changing purchasing power and market flows.” All agricultural commodities
are sensitive to climate change or climate variability (Kumar et al., 2011).
The rising temperature and CO2 and uncertainties in rainfall associated
with global climate change have serious direct and indirect consequences for
crop production and food security (Sinha and Swaminathan, 1991). It is
therefore important to evaluate the direct and indirect consequences of
global warming on different crops contributing to food security. Future agricultural strategies thus have to formulate a holistic approach in the coming
decades on productivity, sustainability, profitability, stability, and equity in
Indian agriculture. Dar and Gowda (2013) suggested that improved crop,
soil, and water management practices and stress-tolerant varieties should
overcome the detrimental impacts of climate change, which in turn would
lead to improved food security, livelihoods, and environmental security.
They further pointed out that negative effects of climate change on food
security can be counteracted by broad-based economic growth, particularly
improved agricultural productivity, and robust international trade in agricultural products that can offset regional shortages and agricultural productivity
investments.
The effects of changes in temperature, CO2 concentrations, and precipitation on crop productivity have been studied broadly using crop simulation
models (Parry et al., 2004). The combined effects of climate change may
have implications for dryland and irrigated crop yields. However, the effect
on production is expected to vary by crop and location and by the magnitude of warming and the direction and magnitude of precipitation change
(Adams et al., 1998). Projections by the IPCC and a few other global studies
are that, unless we adapt, there is a probability of a 10–40% loss in crop production in India by 2080–2100 as a result of global warming (IPCC, 2007a;
Parry et al., 2004; Rosenzweig and Parry, 1994) despite the beneficial aspects
of increased CO2 concentrations (Kumar et al., 2011).
6.1. Effect of elevated concentrations of CO2 on crop growth
CO2 is essential for photosynthesis and hence for plant growth. An increase
in atmospheric CO2 concentration affects crop production through altering
photosynthetic and transpiration rates. It is therefore important to assess the
combined effects of elevated atmospheric CO2 concentration and climate
change on the productivity of a region’s dominant crops (Haskett et al.,
1997). The direct effects of increased concentrations of CO2 are normally
beneficial to vegetation, especially for C3 plants, as elevated concentrations
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Global Warming and Its Possible Impact on Agriculture in India
enhance assimilation rates and increase stomatal resistance, which result in a
decline in transpiration and improved water-use efficiency in crops
(Farquhar, 1997).
Several simulation studies have been carried out to predict the likely
effects of elevated CO2 on crop yield. In northwestern India, for example,
yields of rice and wheat increased by 15% and 28%, respectively, at elevated
(doubled) CO2 concentrations (Lal et al., 1998). Similarly, Hundal and
Prabhjyot-Kaur (2007) reported a gradual increase in rice and wheat grain
yield from elevated CO2. The effects of elevated CO2 on simulated grain
yield of wheat under optimal and suboptimal (stressed) moisture conditions
are presented in Table 2.5 (adapted from Pandey et al., 2007). With the gradual increase in CO2 concentration from 440 to 660 ppm, yield increased
from 21% to 68% under optimal conditions, whereas, under suboptimal
conditions, similar responses were observed with slightly lower magnitudes
(19–57%). Thus, under climate change, CO2 enhancement may increase
crop productivity. Hundal and Prabhjyot-Kaur (1996) reported that, if all
other climatic variables were kept constant (normal), leaf area index
(LAI), biomass yield, and grain yield of rice increased with elevated CO2.
With an increase in CO2 from 330 to 600 ppm, an increase as high as
11% in LAI was reported, in addition to an 8% increase in biomass yield
and 9% in grain yield (Hundal and Prabhjyot-Kaur, 1996) (Table 2.6).
Rice grown under elevated CO2 had significantly more grains and grain
yield per unit land area than under ambient CO2 and open-field conditions
(De Costa et al., 2006) (Table 2.7). In the open-field treatment, rice was
grown under normal atmospheric conditions to detect whether the presence
of a chamber had any effect on the crop. The percentage of filled grains was
also significantly higher under the elevated CO2 concentration than under
Table 2.5 Change in simulated wheat yield due to varying CO2 concentration under
optimal and suboptimal (stressed) moisture conditions (Pandey et al., 2007)
Change (%) from
Simulated grain yield
base suboptimal and
(kg ha1)
optimal yield
CO2 concentration (ppm)
Suboptimal
Optimal
Suboptimal
Optimal
330 (base value)
3112
3837
–
–
440
3695
4630
19
21
550
4327
5687
39
48
660
4876
6465
57
68
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Table 2.6 Effect of CO2 increase on growth and yield of rice (Hundal and PrabhjyotKaur, 1996)
Deviation from normal (%)
Parameters
330 ppm (normal)
400 ppm
500 ppm
600 ppm
5.22
þ 1.9
þ 8.5
þ 11.1
Biomass yield (kg ha )
12495
þ 1.1
þ 6.1
þ 7.7
Grain yield (kg ha1)
7563
þ 1.5
þ 6.6
þ 8.7
Maximum leaf area index
1
Table 2.7 Number of grains, percent of filled grains, grain weight, grain yield, and
harvest index of rice grown under elevated (570 ppm) and ambient (370 ppm) CO2 in
open-top chambers and in open-field conditions (De Costa et al., 2006)
Treatments
Elevated CO2
Open-field
Ambient CO2
Grains (no. m )
47007 (11)
41793
42336
Filled grains (%)
82.9 (9)
72.1
76.0
24.9 (2)
24.0
24.5
Grain yield (g m )
871 (24)
723
783
Harvest index
0.47
0.41
0.45
Parameters
2
Grain weight (mg)
2
The values in parentheses represent percentage increase over ambient CO2 concentration.
the ambient CO2 concentration. Individual grain weight and harvest index,
however, did not differ significantly between the elevated and ambient CO2
treatments. Grain yield under elevated CO2 was 24% higher than under
ambient CO2 concentration. Panicle dry weight in the elevated CO2 treatment was significantly higher than that under the ambient CO2 and openfield treatments throughout the grain-filling period (De Costa et al., 2006)
(Table 2.8). This was attributable to the crop’s significantly higher panicle
growth rate during the early grain-filling period, that is, 54–67 days after
transplanting. The partitioning coefficient in the elevated CO2 treatment
did not exceed that of the ambient and open-field treatments during the
early and late grain-filling periods. In cotton (Gossypium spp.), an increase
in CO2 from subambient to ambient and then to elevated concentrations
resulted in a significant increase in total dry matter production by cotton
plants (Reddy et al., 2004) (Table 2.9). This response was mainly attributable
to increased boll dry weight and lint dry weight per boll.
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Table 2.8 Variation of partitioning coefficient and panicle dry weight at different times
after rice transplanting under elevated (570 ppm) and ambient (370 ppm) CO2 in opentop chambers and in open-field conditions (De Costa et al., 2006)
Days after transplanting
Elevated CO2
Ambient CO2
Open-field
Partitioning coefficient
54
0.14a
0.12b
0.15a
67
0.30a
0.33a
0.34a
0.49b
0.51a
0.47b
54
165a
118b
167a
67
693a
428b
418b
94
1036a
884b
833b
94
2
Panicle dry weight (g m )
Partitioning coefficient was calculated as ratio between panicle dry weight and total dry weight.
For each time (days after transplanting), horizontal means with the same letters are not significantly different at p ¼ 0.05.
Table 2.9 Effect of different CO2 concentrations on total dry matter, boll dry weight, lint
dry weight, and seed dry weight of cotton (Reddy et al., 2004)
CO2
Total dry weight Boll dry
Lint dry weight Seed dry weight
concentration (g plant1)
weight (g) (g boll1)
(g boll1)
Subambient
(180 ppm)
165c
5.6b
1.8b
2.7b
Ambient
(360 ppm)
233b
5.8a
1.8ab
2.8ab
Elevated
(720 ppm)
309a
5.9a
1.8a
2.9a
Means with the same letters within the same column are not significantly different at p ¼ 0.05.
The growth and yield response of black gram (Vigna mungo) to CO2 concentrations (550 and 700 ppm) was investigated and compared with ambient
CO2 concentration (365 ppm) using open-top chambers (Vanaja et al.,
2007). The growth parameters (root and shoot length, leaf area, and root
volume) were significantly greater at 700 ppm CO2 than at 550 ppm. Compared to the ambient (chamber) control, the increase in total biomass at 700
and 550 ppm CO2 was 65% and 39%, respectively (Table 2.10). The
increase in seed yield at 700 ppm (129%) was attributable to an increase
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Bhagirath Singh Chauhan et al.
Table 2.10 Yield parameters of black gram (of 10 plants) under 365, 550, and 700 ppm
CO2 (Vanaja et al., 2007)
Parameter values
Increase (%)
Parameters
550 vs.
700 vs.
700 vs.
365 ppm 550 ppm 700 ppm 365 ppm 365 ppm 550 ppm
Pods (#)
158
187
239
18
51
28
Pod weight (g)
35.6
66.5
78.2
87
120
18
Seed weight (g)
17.4
32.9
39.9
89
129
21
100-seed weight (g) 2.6
2.7
3.9
2
51
48
Harvest index (%)
28.5
38.7
39.5
36
38
2
Total biomass (g)
61.1
84.9
101.1
39
65
19
in the number of pods per plant and 100-seed weight, whereas the increase
in total seed yield at 550 ppm (89%) was caused by a higher number of pods
per plant and seeds per pod. The harvest index, a very important parameter
in pulses for breaking the yield barrier, increased to 36% and 38% at 550 and
700 ppm, respectively (Table 2.10).
In rice, mean biomass increment, leaf area duration, and net assimilation
rate increased with increasing CO2 concentrations (Baker et al., 1990)
(Table 2.11). In the same study, net assimilation rate decreased and leaf area
duration increased in rice with the progression of growth stages. Grain yield
increased by nearly 32% when the CO2 concentration increased from 330 to
660 mmol CO2 mol1 air (Baker et al., 1990; Table 2.12). The number of
panicles per plant was mainly responsible for the observed differences in
grain yield among the CO2 concentrations (Table 2.12). The number of
filled grains per panicle was the most variable yield component, whereas
individual grain weight was stable across different CO2 concentrations.
Therefore, it was concluded that grain yield depended mainly on the number of panicles on rice plants.
6.2. Effect of ozone on plants
Ozone is likely to have adverse effects on plant growth. Necrotrophic
pathogens can colonize plants that are weakened by O3 at an accelerated
rate, while obligate biotroph infections might be reduced (Manning, 1995).
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Table 2.11 Effect of CO2 enrichment on mean biomass increment (DW), leaf area
duration (LAD), and net assimilation rate (NAR) in rice in controlled-environment
chambers (Baker et al., 1990)
NAR
LAD
(g m2
LAD
NAR
2
1
DW (g) (m day ) day1) DW (g) (m2 day1) (g m2 day1)
CO2 concentration
(ppm)
19–44 days after sowing
44–71 days after sowing
160
1.2
0.37
4.9
1.3
1.0
1.4
250
2.1
0.50
6.0
2.2
1.2
1.8
330
2.5
0.55
6.1
2.7
1.2
2.2
500
2.5
0.51
6.5
3.9
1.2
3.2
660
3.2
0.65
6.7
2.0
1.4
1.5
900
3.9
0.76
7.1
3.8
1.6
2.4
Standard error
0.4
0.07
1.1
1.2
0.1
0.9
Table 2.12 Mean grain yield and components of yield of rice in controlled-environment
chambers (Baker et al., 1990)
CO2 concentration Grain yield Panicles
Filled grains
1000-grain
(ppm)
(g plant1) (no. plant1)
(no. panicle1)
weight (g)
160
1.4
3.6
22
17.4
250
1.3
4.6
17
18.2
330
1.9
5.4
19
17.9
500
3.0
7.3
23
18.1
660
2.8
6.0
25
18.4
900
3.3
6.4
28
18.1
Standard error
0.6
0.9
5.5
0.83
6.3. Effect of increasing temperature on crop growth
Increases in temperature increase crop-respiration rates; reduce crop duration, the number of grains formed, and crop yield; inhibit sucrose assimilation in grains; affect the survival and distribution of pest populations; hasten
nutrient mineralization in soil; decrease fertilizer-use efficiency; and increase
evaporation. In a simulation study, an increase in temperature by 2 C
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Bhagirath Singh Chauhan et al.
brought about a 3–10% decrease in grain/seed yield of kharif crops, such as
rice, groundnut (Arachis hypogaea L.), and soybean (Glycine max L.), and a
29% decrease in grain yield of rabi crops such as wheat (Prabhjyot-Kaur
and Hundal, 2006). Pandey et al. (2007) simulated grain yield of wheat
under incremental units of maximum temperature (1–3 C) using the
CERES-wheat model and found a gradual decrease in yield from 3546 to
2646 kg ha1 (8% to 31% less than the base yield) under optimal moisture
conditions (Table 2.13). Similarly, under suboptimal conditions, yield
declined from 2841 to 2398 kg ha1 (9% to 23% less than the base yield).
The reduction in wheat yield with an increase in maximum temperature
was mainly attributable to a reduction in the duration of anthesis and in grain
filling with a rise in ambient temperature, and vice versa (Aggarwal and
Kalra, 1994).
An increase in temperature from the greenhouse effect would decrease
cereal and groundnut production; however, the impact of changes in temperature would vary with the type of crop and the direction of the change
occurring. For example, if all other climatic variables were kept constant, a
temperature increase of 0.5, 1.0, 2.0, and 3.0 C compared with the normal temperature would advance the maturity of wheat by 3, 6, 12, and
17 days, respectively (Prabhjyot-Kaur and Hundal, 2010) (Table 2.14).
On the other hand, with a temperature rise of up to 1 C above normal,
heading of rice was not affected, but a further increase in temperature to
3 C prolonged heading and maturity by 4 and 5 days, respectively, compared with the normal temperature. Flowering in soybean was delayed up
Table 2.13 Change in simulated wheat yield due to varying temperature under optimal
and suboptimal moisture conditions (Pandey et al., 2007)
Change in simulated
Simulated grain yield grain yield relative to
(kg ha1)
base yield (%)
Change in maximum temperature
relative to base temperature ( C) Suboptimal Optimal Suboptimal Optimal
þ3
2398
2646
23
31
þ2
2668
3091
14
19
þ1
2841
3546
9
8
1
3190
4206
3
10
2
3358
4485
8
17
3
3641
4817
17
26
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Global Warming and Its Possible Impact on Agriculture in India
to 4 days and its maturity was delayed by 2 days (Table 2.14). Deviation
(increase) in temperature from the normal temperature greatly influenced
flowering and maturity in gram. With an increase in temperature of 3 C
compared with the normal temperature, for example, flowering and maturity in chickpea (Cicer arietinum L.) advanced by 23 and 24 days, respectively (Table 2.14). A study analyzed the relationship between the yield
of rice and minimum temperature across the range of 22.1–23.7 C using
a quadratic equation and reported that rice yield declined by 10% with each
1 C rise in minimum temperature and yield declined by 15% with each
1 C rise in mean temperature (Peng et al., 2004).
Reddy et al. (1992) reported that cotton plants grew faster at 30/22 C
(maximum/minimum temperatures) than at either higher or lower temperatures. However, the plants at 35/27 C had more boll weight than those
grown at 30/22 C and they were more advanced in fruiting-structure formation (Table 2.15). The time required to produce the first square was only
2 days longer at 40/32 C than at 30/22 C. At 20/12 and 25/17 C, squares
abscised at a very early stage, whereas the maximum number of squares was
Table 2.14 Effect of temperature increase on phenology of crops (Prabhjyot-Kaur and
Hundal, 2010)
Deviation from normal temperature (days)
Normala
þ0.5 C
þ1.0 C
þ2.0 C
þ3.0 C
Heading
223
0
0
þ1
þ4
Maturity
263
þ1
þ1
þ1
þ5
Anthesis
41
3
6
12
16
Maturity
82
3
6
12
17
Flowering
239
þ1
þ2
þ3
þ4
Maturity
294
þ1
þ1
þ2
þ2
Flowering
08
4
7
19
23
Maturity
99
5
8
16
24
Crop and phenological stage
Rice
Wheat
Soybean
Chickpea
a
Julian day (calendar day).
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Bhagirath Singh Chauhan et al.
Table 2.15 Effect of temperature on days to appearance of first flower bud (square),
days to first flower, and biomass of different parts of cotton seedlings at 56 days after
emergence (Reddy et al., 1992)
Day/night temperature ( C)
Parameters
20/12
25/17
30/22
35/27
40/32
Days to first square
(day)
38
33
27
24
29
Days to first flower
(day)
a
a
53
43
b
Stem biomass
(g plant1)
3.6 0.3
18.0 1.9 33.9 3.7 31.1
11.2
Leaf biomass
(g plant1)
9.0 0.7
22.7 2.0 33.7 2.0 31.5 9.6 19.8 2.1
Root biomass
(g plant1)
1.3
2.9
6.5
6.2
4.5
Boll biomass
(g plant1)
a
a
1.3 0.4
4.1 0.6
b
Square biomass
(g plant1)
0.04 0.01 0.61 0.1 2.27 0.3 2.70 0.3
b
Total biomass
(g plant1)
13.5 0.9
41.5 4.2
a
44.2 4.0 77.7 6.9 75.3
21.7
17.2 2.1
Squares were abscised at very early stage.
Flowers were not formed at final harvest due to slow growth.
b
obtained at 30/22 C. Fruit branches were four times greater at 30/22 C
than at 20/12 C, whereas maximum vegetative branches were produced
at low temperatures (20/12 C). Bolls and squares were produced at 30/
22 C, whereas a 10% boll and square loss was observed at 35/27 C during
the early reproductive period.
Hundal and Prabhjyot-Kaur (2007) studied the effect of temperature on
the growth and yield of rice and wheat. An increase in temperature
decreased the growth and yield of rice and wheat, but a decrease in temperature increased their growth and yield. Both the decrease in yield and the
increase in yield were more for wheat than for rice. Compared with normal
conditions, a temperature increase of 1.0–2.0 C caused a decrease of 4–9%
in the maximum LAI in rice (Fig. 2.1) and a decrease of 18–29% in wheat
(Fig. 2.2). Similarly, biomass yield decreased by 2–5% in rice (Fig. 2.1) and
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Global Warming and Its Possible Impact on Agriculture in India
Deviation in LAI and yield from normal (%)
30
25
Grain yield
Biomass yield
Max. LAI
20
15
10
5
0
−3
−5
−1
Normal
3
1
−10
−15
Deviation in temperature from normal (°C)
Deviation in LAI and yield from normal (%)
Figure 2.1 Effect of temperature change on growth and yield of rice using CERES-wheat
model (Hundal and Prabhjyot-Kaur, 2007).
50
40
Grain yield
Biomass yield
Max. LAI
30
20
10
0
−10
−3
−1
Normal
1
3
−20
−30
−40
−50
Deviation in temperature from normal (°C)
Figure 2.2 Effect of temperature change on growth and yield of wheat using CERESwheat model (Hundal and Prabhjyot-Kaur, 2007).
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Bhagirath Singh Chauhan et al.
by 14–23% in wheat (Fig. 2.2), and grain yield decreased by 3–10% in rice
(Fig. 2.1) and by 10–18% in wheat (Fig. 2.2). A decrease in temperature by
1.0–2.0 C increased the simulated maximum LAI by 3–5% in rice and by
12–28% in wheat, biomass yield increased by 4–10% in rice and by 9–16% in
wheat, and grain yield increased by 8–15% in rice and by 7% in wheat vis-àvis the normal conditions (Figs. 2.1 and 2.2).
A simulation study was conducted using the CERES-wheat model to
assess the effect of an intraseasonal increase in temperature on the yield of
wheat sown on different dates (Prabhjyot-Kaur and Hundal, 2010). The
simulation results revealed that, in general, an increase in temperature from
February to mid-March severely affected the yield of early-, normal-, and
late-sown wheat (Table 2.16). The temperature increase mostly affected
the yield of the early (October)-sown crop beginning in the fourth week
of January to the first fortnight of March, the timely (November)-sown crop
during February and March, the late (fourth week of November)-sown
crop during March, and the very late (December)-sown crop during
March and the first week of April (Table 2.16). A maximum of about a
17% decrease in grain yield occurred in the early-sown crop if the temperature increased by 6 C in the first fortnight of February. This was mainly
because of a reduction in grain-filling period caused by an increase in
temperature.
6.4. Interactive effects of changing climatic factors on crop
production
The ultimate productivity of crops is determined by the interactions of cultivars, soil constituents, water, temperature, day length, etc. Temperature,
solar radiation, and water directly affect the physiological processes involved
in grain development and indirectly affect grain yield by influencing the
incidence of diseases and insects (Yoshida and Parao, 1976). Rice grain yield
was positively correlated with mean solar radiation and negatively correlated
with daily mean temperature during the reproductive stage (Yoshida and
Parao, 1976). Relatively low temperature and high solar radiation during
the reproductive stage had a positive effect on the number of spikelets
and hence increased grain yield. Solar radiation had a positive influence
on grain filling during the ripening period.
The simulation results indicated that warm climate with decreasing radiation would affect the growth and yield of cereal crops. However, the harmful effects of increasing temperature on growth and yield could be
counterbalanced to some extent by the increasing CO2 concentrations
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Global Warming and Its Possible Impact on Agriculture in India
Table 2.16 Effect of intraseasonal temperature increase (maximum and minimum) from
normal on grain yield (% deviation from normal) of wheat sown on different dates using
the CERES-wheat model (Prabhjyot-Kaur and Hundal, 2010)
Temperature increase from normal ( C)
Time period
Date of sowing
þ1.0
þ2.0
þ3.0
þ4.0
þ5.0
þ6.0
3.4 3.7 7.6
11.5 13.0 17.2
þ1.7 1.6 1.8
3.9
7.7
7.3
Normal sown 0.5 2.7 1.5
(November 15)
2.0
1.3
1.9
Normal sown þ0.5 þ2.4 þ2.8
(November 25)
þ4.7
þ4.9
þ7.0
þ0.7 þ0.6 þ0.6
þ3.4
þ3.6
þ3.7
2.4 2.8 5.2
8.1
10.9 13.8
0.4 4.1 5.1
9.9
14.2 16.4
Normal sown 2.0 5.8 6.0
(November 15)
8.7
9.7
14.2
Normal sown þ2.5 þ1.1 þ3.4
(November 25)
0.6
2.6
3.3
0.5 0.4 1.7
2.3
3.1
3.6
2.3 4.6 6.8
13.8 8.2
10.4
2.7 3.3 6.0
9.5
13.0
First fortnight of Early sown
February
(October 28)
Normal sown
(November 8)
Late sown
(December 2)
Second fortnight Early sown
of February
(October 28)
Normal sown
(November 8)
Late sown
(December 2)
First fortnight of Early sown
March
(October 28)
Normal sown
(November 8)
9.5
Normal sown 4.8 9.3 10.1 14.2 16.0 20.8
(November 15)
Normal sown 0.5 5.4 6.7
(November 25)
3.3
16.0 19.4
2.3 1.6 6.8
7.6
12.5 17.7
Late sown
(December 2)
Continued
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Bhagirath Singh Chauhan et al.
Table 2.16 Effect of intraseasonal temperature increase (maximum and minimum) from
normal on grain yield (% deviation from normal) of wheat sown on different dates using
the CERES-wheat model (Prabhjyot-Kaur and Hundal, 2010)—cont'd
Temperature increase from normal ( C)
Time period
þ3.0
þ4.0
þ5.0
þ6.0
þ1.1 1.5 0.5
0.1
1.9
1.5
Normal sown 2.5 1.6 4.3
(November 15)
6.9
5.9
8.1
Normal sown 0.1 4.7 5.6
(November 25)
9.2
10.1 11.2
Date of sowing
Second fortnight Normal sown
of March
(November 8)
Late sown
(December 2)
þ1.0
þ2.0
5.5 6.6 12.3 14.5 19.1 21.4
(Hundal and Prabhjyot-Kaur, 1996). A study reported that in India, the
adverse effects of a 1–2 C rise in temperature could be absorbed with a
5–10% increase in precipitation (Abrol et al., 1991). A grain yield increase
of 20–30% might be possible on about 70% of the area in the rice–wheat
cropping system in India. In northern India, warming could offset some
losses in yield by early pod setting in winter grain legumes, such as chickpea
and lentil.
Mahi (1996) found that the maximum LAI, biomass, and grain yield of
wheat and rice declined when radiation decreased by 10% relative to normal
radiation but increased when radiation was enhanced by 10%. The simulation results suggested that the growth and yield of wheat and rice would
be influenced by increasing temperature. The adverse effects generated
by a high-temperature scenario might be lessened to some extent by a
decrease in radiation amounts. In Punjab, India, there are indications that
the amount of radiation is likely to decrease. As a result, the production
of wheat and rice could be adversely affected, depending upon the degree
of change in radiation amount in the coming years. The past increase in
CO2 experienced to date and the projections of its increase in the future will
no doubt counterbalance the negative effects of a rise in temperature on crop
productivity.
Increased CO2 concentrations could result in greater growth and grain
yield of rice and compensate for the yield reductions caused by warmer temperatures (Hundal and Prabhjyot-Kaur, 1996). Under all the scenarios of
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Global Warming and Its Possible Impact on Agriculture in India
increased CO2 concentrations (i.e., 400, 500, and 600 ppm), maximum
LAI, biomass, and grain yield of rice were favorably affected (Tables 2.17
and 2.18). The interactive effect of enhanced temperature and CO2 revealed
that adverse effects caused by an increase in temperature of up to 0.5 C
could be compensated for by concentrations of CO2 above 400 ppm
(Hundal and Prabhjyot-Kaur, 1996). A further increase in temperature of
up to 1.0 C did not decrease maximum LAI, biomass, and grain yield when
CO2 was nearly doubled (600 ppm) relative to the normal temperature. But,
in scenarios with nearly doubled CO2 concentrations of 600 ppm, temperature increases of more than 1.0 C above normal reduced the maximum
LAI, biomass, and grain yield of rice (Tables 2.17 and 2.18).
Table 2.17 Effect of CO2 and temperature on the deviation of leaf area index of rice
(Hundal and Prabhjyot-Kaur, 1996)
Deviation of leaf area index from normal (%)
Temperature ( C)
330 ppm (normal)
400 ppm
500 ppm
600 ppm
Normal
[5.22]a
þ1.9
þ8.5
þ11.0
þ 0.5
5.5
1.9
þ2.5
þ6.6
þ 1.0
9.3
6.1
4.0
þ1.7
þ 1.5
9.8
9.1
5.7
1.7
þ 2.0
12.3
11.9
7.8
5.5
a
Leaf area index at normal CO2 concentration and temperature.
Table 2.18 Effect of CO2 and temperature on the deviation of rice biomass yield from
normal (Hundal and Prabhjyot-Kaur, 1996)
Deviation of rice yield from normal (%)
Temperature ( C)
330 ppm (normal)
a
400 ppm
500 ppm
600 ppm
þ1.1
þ6.1
þ7.7
Normal
[12495]
þ 0.5
3.5
1.4
þ2.2
þ4.5
þ 1.0
6.0
1.4
þ2.2
þ4.5
þ 1.5
7.2
6.8
5.0
2.0
7.3
7.1
4.0
2.6
þ 2.0
a
1
Biomass yield (kg ha ) at normal CO2 and temperature.
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Das et al. (2007) conducted a preliminary study to test crop simulation
model ORYZA 2000. The model has been used to investigate the impact of
climate change (with changing temperature and CO2 concentrations) on
rice yields. The model predicted direct changes in yield by 10%, 46%,
and 72% for temperature changes of þ1, þ2, and þ3 C, respectively.
The data demonstrated that even with an up to þ1 C warmer climate than
the normal, production might increase by about 10% in an atmosphere with
doubled CO2 concentration. However, a further increase in temperature
could negate the effect of increased CO2 concentration.
The results of the simulation study for the interactive effects of increasing
temperature and CO2 concentrations revealed that the adverse effects of
increased temperature on the growth and yield of rice were counterbalanced
to some extent by the favorable effect of increasing CO2 (Hundal and
Prabhjyot-Kaur, 2007) (Table 2.19). Under enhanced CO2 concentration
of 600 ppm, a temperature increase of 2 C compared with normal reduced
maximum LAI by 5.5%, biomass by 2.6%, and grain yield by 2.8%. With a
temperature increase of 1 C over normal, a CO2 concentration of
>500 ppm was able to nullify the negative deviations in growth and yield,
but, when the temperature increased by 2 C, 600 ppm CO2 was needed to
nullify the adverse effect of temperature (Table 2.19).
6.5. Effect of climate change on the quality of produce
According to the IPCC’s Third Assessment Report, the significance of the
impact of climate change on grain and forage quality emerges from new
research. In a previous study, the amylose content in rice grain (a major
determinant of cooking quality) increased under elevated CO2 (Conroy
Table 2.19 Effect of increasing temperature and CO2 on change (%) in maximum leaf
area index (LAI), biomass yield, and grain yield of rice (Hundal and Prabhjyot-Kaur, 2007)
Temperature change from
Temperature change
normal (þ2 C)
from normal (þ1 C)
CO2 concentration
(ppm)
LAI
Biomass
yield
Grain
yield
LAI
Biomass yield
Grain yield
330
9.3
6.0
6.6
12.3
7.3
7.5
400
6.1
4.0
4.3
11.9
7.1
7.2
500
4.0
2.9
2.8
7.8
4.0
4.4
600
þ0.8
þ0.8
þ0.5
5.5
2.6
2.8
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et al., 1994). In another study, cooked rice grains from plants grown in highCO2 environments were firmer than those from plants grown in ambient
CO2 environments; however, the concentrations of iron and zinc, which
are important for human nutrition, were lower (Seneweera and Conroy,
1997). Moreover, the protein content of the grains decreased with combined increases in temperature and CO2 concentration (Ziska et al.,
1997). Studies have shown that higher CO2 concentrations led to reduced
plant uptake of nitrogen (N) and trace elements, such as zinc, resulting in
crops with lower nutritional value (Taub and Wang, 2008). This would primarily impact people in poorer countries, who are less able to compensate by
eating more food and have less varied diets (Kaur and Rajni, 2012). Reduced
N content in plants used for grazing may also reduce animal productivity
(e.g., sheep depend on microbes in their gut to digest plants, which in turn
depend on N intake).
In a study, the protein content of soybean grain decreased with increases
in CO2 concentration; however, because of increased grain yield, the total
quantity of nutrients accumulated in grain per hectare still increased with
high CO2 concentrations (Mulchi et al., 1992). In the same study, increases
in CO2 concentrations from 360 to 510 ppm increased grain oil from 20.4 to
22.3% and decreased grain protein content. The N content of plants is likely
to decrease with elevated CO2, implying reduced protein.
At the International Rice Research Institute, rice (“IR72”) was grown
under three different CO2 concentrations (ambient, ambient þ200, and
ambient þ300 mL L1 CO2) and two different air temperatures (ambient
and ambient þ4 C) using open-top field chambers (Ziska et al., 1997).
Increasing both CO2 and air temperature reduced grain quality (e.g., protein
content). The combined effects of CO2 and temperature suggested that, in
warmer regions (i.e., >34 C) where rice is grown, quantitative and qualitative changes in rice supply could occur if both CO2 and air temperature
continued to increase.
6.6. Agricultural surfaces and climate change
Climate change might increase the amount of arable land near the poles by
decreasing the amount of frozen land. As per IPCC Assessment Report (AR)
4 (Bindoff et al., 2007), the reduction in area in the ice sheets of Greenland
and Antarctica contributed greatly to sea-level rise from 1993 to 2004
(Table 2.20). Although the impacts of sea-level rise are local in nature,
the causes are global and can be attributed to nonlinearly coupled
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Bhagirath Singh Chauhan et al.
Table 2.20 Observed rate of global sea-level rise and estimated contributions from
different sources (Bindoff et al., 2007)
Rate of sea-level rise
(mm per year)
Source of sea-level rise
1961–2003 1993–2003
Thermal expansion
0.42 0.12 1.60 0.50
Glaciers and ice caps
0.50 0.18 0.77 0.22
Greenland ice sheet
0.05 0.12 0.21 0.07
Antarctica ice sheet
0.14 0.41 0.21 0.35
Sum of individual climate contributions to sea-level rise 1.1 0.5
2.8 0.7
1.8 0.5
3.1 0.7
0.7 0.7
0.3 1.0
Observed total sea-level rise
a
Difference (observed minus sum of estimated climate
contributions)
a
Data prior to 1993 are from tide gauges and after 1993 are from satellite altimetry.
components of the Earth system. Sea levels are expected to rise by another
1 m by 2100 though this projection is disputed (Bindoff et al., 2007). The
rise in sea level may decrease agricultural land area, particularly in Southeast
Asia. With increasing sea levels, erosion, submergence of shorelines, and
salinity of the water table could affect agriculture by inundating low-lying
areas. Future climatic changes will affect water availability for agriculture.
Apart from monsoon rains, India depends on rivers that emanate from
the Himalayas for water-resource development. As a result of global
warming, the increase in temperature may increase snowmelt and consequently snow cover will decrease. In the short run, snowmelt may increase
water flow in many rivers, which, in turn, may increase the frequency of
floods. In the long run, however, the receding snow line might reduce water
flow in these rivers. In climate-change scenarios, the onset of summer monsoon across India may become more uncertain and could be delayed. This
will influence not only rainfed crops but also water storage in irrigated areas.
CO2-induced warming is expected to raise the sea level as a result of
thermal expansion of the oceans and partial melting of glaciers and ice caps,
which, in turn, is expected to affect agriculture, mainly through the inundation of low-lying farmland and increased salinity of coastal groundwater.
The IPCC estimates of sea-level rise above present levels are 9–29 cm by
2030, with a best estimate of 18 cm, and 28–96 cm by 2090, with a best estimate of 58 cm (IPCC, 2007a). Preliminary surveys of the vulnerability of
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land to inundation were made on the basis of existing contoured topographic maps, in conjunction with knowledge of the local “wave climate”
that varies between different coastlines (Parry and Carter, 1988). On the
basis of the extent of land liable to inundation, 27 countries were identified
as being vulnerable to sea-level rise.
The most severe effects of climate change on agriculture are likely to be
from flooding. Southeast Asia, because of the extreme vulnerability of several large and heavily populated deltaic regions, would be most affected.
According to more than 20-year-old projections, a 1.5 m sea-level rise
would cause submergence of about 15% of all land (and about one-fifth
of all farmland) and render another 6% of the land more prone to frequent
flooding (UNEP, 1989). Altogether, 21% of agricultural production could
be lost. Estimates revealed that, in Egypt, 17% of national agricultural production and 20% of all farmland, especially the most productive farmland,
would be lost as a result of a 1.5 m sea-level rise. Island nations, particularly
low-lying coral atolls, would suffer the most. In the Indian Ocean, 50% of
the land area of the Maldives would be submerged as a result of a 2 m rise in
sea level. In addition to direct farmland loss from flooding, agriculture would
experience increased costs from saltwater intrusion into surface water and
groundwater in coastal regions. Deeper tidal penetration would likely
increase the risk of flooding, and recharge of aquifers with seawater would
need to be prevented.
In addition, indirect impacts of flooding would relocate both farming
populations and production to other regions, which is a serious concern.
In Bangladesh, for example, as a result of the farmland loss from an estimated
1.5 m sea-level rise, about one-fifth of the nation’s population would be displaced. It is important to emphasize, however, that the IPCC estimates of
sea-level rise are much lower (about 0.5 m by 2090 under the “businessas-usual” scenario) than 1.5 m (UNEP, 1989).
6.7. Soil erosion and soil fertility
Climatic changes are expected to affect soils in many ways. Global warming
is likely to cause soil degradation, which could influence soil fertility.
Because the ratio of carbon (C) to N is a constant, doubling of C should lead
to storage of extra N in soils as nitrates, thus providing higher fertilizing elements for plants and enhancing crop yields (Blanco-Canqui and Lal, 2010).
The average need for N could decrease and provide an opportunity for
changing costly fertilization strategies. Climatic extremes (e.g., flooding)
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Bhagirath Singh Chauhan et al.
would probably enhance the risk of erosion. The possible evolution of
organic matter in the soil is a highly contested issue. An increase in temperature would increase the mineral production rate and lessen soil organic matter content (Salinger, 1989) (Table 2.20).
High temperatures could increase the rate of microbial decomposition of
organic matter, thus adversely affecting soil fertility in the long run, but
increases in root biomass resulting from higher rates of photosynthesis could
offset these effects (Buol et al., 1990). High temperatures could accelerate
the cycling of nutrients in the soil and more rapid root formation could promote more N fixation (Hillel and Rosenzweig, 1989). However, these benefits could be minor compared with the adverse effects of changes in rainfall.
Increased rainfall in regions that are already moist, for example, could lead to
increased leaching of minerals, especially nitrates. In the Leningrad region of
Russia, an estimated one-third increase in rainfall would reduce soil productivity by more than 20% (Pitovranov et al., 1988). Large increases in fertilizer
applications would be necessary to restore productivity (Pitovranov et al.,
1988). Decreased rainfall, particularly during summers, could have a dramatic effect on the soil through the increased frequency of dry spells, leading
to increased proneness to wind erosion. Susceptibility to wind erosion,
however, depends in part on the cohesiveness of the soil, which is affected
by precipitation effectiveness, and wind velocity.
An experiment was conducted with free-air CO2 enrichment (FACE) in
paddy fields at Wuxi, China, to study the effects of elevated CO2 on the
availability of soil N and phosphorus (P) (Ma et al., 2007). Soil-available
N decreased with elevated CO2 by 47% in low N and by 29% in normal
N status at the rice tillering stage (Table 2.21). In this study, elevated
CO2 caused a significant increase in root biomass, which led to higher
N uptake by the rice plants. The enhanced C input by FACE increased soil
microbial use of N and this could be the reason for reduced soil-available N.
The results of the study also reported decreased extractable soil-available
N due to elevated CO2 during the early period of rice growth. Therefore,
N mineralization was increased and N uptake was decreased by elevated
CO2 concentration during the later growth stages. In the same study,
P uptake in rice was significantly increased by elevated CO2 under both
low N and normal N rates (Ma et al., 2007). Elevated CO2 caused a decrease
in soil-available P by 32% in low N and by 30% in normal N rates at the
jointing stage, but an increase of 22% and 21% at the heading stage and
an increase of 34% and 31% at the ripening stage were observed under
low N and normal N rates, respectively (Ma et al., 2007) (Table 2.22).
16.6 2.1
51.0 10.3
A
16.1 1.8
3
10
IR
11.5 2.1
10.8 0.7
10.7 2.2
10.7 2.2
mg kg1
—D76—
6
0
IR
10.3 2.4
11.5 2.8
10.8 2.5
9.8 2.3
mg kg1
—D123—
Abbreviations: A, ambient CO2; F, elevated CO2 (200 m mol mol1 higher than ambient).
Increasing rate (IR) ¼ (F A)/A 100.
D27, D49, D76, and D123 are the days after rice transplanting and equal to the tillering, jointing, heading, and ripening stages, respectively.
29
36.3 5.3
F
Normal N
16.4 3.7
33.4 5.1
17.9 0.8
A
47
17.6 0.6
F
Low N
mg kg1
IR
mg kg1
CO2 level
Fertilizer treatment
—D49—
—D27—
Table 2.21 Effects of elevated CO2 on soil-available N in 0–15 cm soil depth at four rice growth stages (Ma et al., 2007)
Content of soil-available N at different growth stages after rice transplanting
11
10
IR
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4.0 1.3
10.9 2.3
A
5.7 0.8
29.6
32.0
IR
4.3 1.8
5.1 1.8
4.2 0.9
5.1 1.0
mg kg1
—D76—
20.8
22.4
IR
4.1 1.0
5.4 1.6
4.0 1.4
5.3 0.9
mg kg1
—D123—
Abbreviations: A, ambient CO2; F, elevated CO2 (200 m mol mol1 higher than ambient).
Increasing rate (IR) ¼ (F A)/A 100.
D27, D49, D76, and D123 are the days after rice transplanting and equal to the tillering, jointing, heading, and ripening stages, respectively.
5.8
10.2 1.3
F
Normal N
4.8 0.3
9.3 1.8
3.3 1.0
A
11.3
10.4 2.3
F
Low N
mg kg1
IR
mg kg1
CO2 level
Fertilizer treatment
—D49—
—D27—
Table 2.22 Effects of elevated CO2 on soil-available P in 0–15 cm soil depth at four rice growth stages (Ma et al., 2007)
Content of soil-available P at different growth stages after rice transplanting
30.7
33.8
IR
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Elevated atmospheric CO2 enhanced soil P mineralization and availability of
soil P. This response was mainly because of higher root biomass. Elevated
CO2 was shown to increase phosphatase activity in the rhizosphere and exudates at elevated CO2 increased the availability of soil P. Besides acid phosphatase activity, exudation of citrate was also important in releasing
inorganic P from aluminum–iron complexes in soils of highly P-limited systems (Ma et al., 2007).
6.8. Potential effects of climate change on pests
Like crop plants, weeds would undergo the same acceleration of growth
cycle and also benefit from carbonaceous fertilization. Under high temperature, weeds with a C4 photosynthetic pathway have a competitive advantage over C3 crop plants (Yin and Struik, 2008). Most of the weeds in rice are
of a C4 type and elevated CO2 may give a competitive advantage to rice (a
C3 crop) over C4 weeds (Fuhrer, 2003; Patterson, 1995). In crop–weed
competition studies, in which the photosynthetic pathway was the same,
weed growth was favored as CO2 increased. For example, the infestation
of Phalaris minor Retz. (C3) in wheat (C3) would worsen with an increase
in CO2 concentration (Mahajan et al., 2012). Because of CO2 enrichment,
the wheat crop could gain greater biomass than P. minor under well-irrigated
conditions. Under water stress, however, P. minor may have an advantage
over wheat at elevated CO2 concentration (Naidu and Varshney, 2011).
In a study in the United States, weedy rice (Oryza sativa L.) responded more
strongly than cultivated rice to rising CO2 concentration with greater competitive ability (Ziska et al., 2010). These results suggest that weedy rice may
become a more problematic weed in the future in India.
In a study around three decades ago (Patterson and Flint, 1980), biomass
production in four plant species responded quite differently to CO2 concentrations (Table 2.23). In corn (Zea mays L.), 12 days after planting, plant biomass was significantly greater at 600 and 1000 ppm CO2 concentrations than
at 350 ppm. Twenty-four days after planting, however, biomass did not differ significantly among the three CO2 concentrations. Forty-five days after
planting, biomass was significantly greater at 350 ppm than at 1000 ppm. In
Rottboellia cochinchinensis (Lour.) W.D. Clayton, biomass was significantly less
at 350 ppm CO2 than at 600 ppm CO2 at all three harvests. In soybean,
increasing CO2 concentration from 350 to 1000 ppm increased the biomass
of 45-day-old plants by 72%. In Abutilon theophrasti Medic., biomass was significantly greater at 600 and 1000 ppm CO2 than at 350 ppm CO2 and this
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Bhagirath Singh Chauhan et al.
Table 2.23 Effect of CO2 concentration on dry biomass of corn, Rottboellia
cochinchinensis, soybean, and Abutilon theophrasti harvested at 12, 24, and 45 days after
planting (Patterson and Flint, 1980)
Biomass (g plant1)
Species
Days after planting 350 ppm CO2 600 ppm CO2 1000 ppm CO2
Corn
12
0.63b
0.73a
0.76a
24
6.96a
6.24a
6.63a
45
91.29a
89.49ab
80.08b
R. cochinchinensis 12
0.08b
0.16a
0.15a
24
2.10b
3.82a
3.50a
45
39.25b
47.47a
38.62b
12
0.34c
0.52b
0.61a
24
3.60c
4.68b
6.38a
45
50.55c
62.19b
87.09a
12
0.08c
0.27a
0.21b
24
1.94b
3.73a
3.65a
45
35.4c
47.96b
54.34a
Soybean
A. theophrasti
Different letters within a row are significantly different at 0.05 level (according to Duncan’s multiple
range test).
was true at all three harvests. Such responses of biomass production to CO2
concentrations indicate that the effects of CO2 also depend on the age or
growth stage of the plant.
In another study, soybean was grown at ambient and elevated CO2 concentrations (þ250 mL L1 CO2 above ambient concentration) with and
without the presence of a C3 weed (Chenopodium album L.) and a C4 weed
(Amaranthus retroflexus L.), to evaluate the impact of rising atmospheric CO2
on crop production losses caused by weeds (Ziska and Goins, 2006).
A significant reduction in soybean seed yield was observed with both weed
species relative to their weed-free control at each CO2 concentration. Interference from C. album caused a reduction in soybean seed yield relative to
the weed-free conditions; the reduction increased from 28% to 39% as CO2
concentration increased. There was a 65% increase in the mean biomass of
C. album at the enhanced CO2 concentration. Conversely, with A. retroflexus
interference, soybean seed yield losses decreased with increasing CO2 from
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45% to 30%, with no change in the mean biomass of A. retroflexus. In a weedfree environment, elevated CO2 resulted in a significant increase in vegetative biomass (33%) and seed yield (24%) for soybean compared with the
ambient CO2 concentration. Interestingly, the presence of both weeds
negated the ability of soybean to respond, vegetatively or reproductively,
to enhanced CO2 concentration. The results from this study suggested that
rising CO2 concentrations could alter current yield losses associated with
competition from weeds and weed control would be very crucial in realizing
any potential increase in the economic yield of agronomic crops (e.g.,
soybean) as atmospheric CO2 concentration increases.
Climate changes may also necessitate the adaptation of agronomic practices, which in turn influence weed growth. Weed management operations,
for example, chemical and mechanical, could be influenced by climate
change. Because of sudden changes in climate, environmental stress on crops
would increase and as a result the crop could become more vulnerable to
attack by insects and pathogens and less competitive with weeds. Climate
change increases the importance of conservation tillage practices and the
adoption of these practices requires knowledge of local conditions and an
understanding of the overall system dynamics. For instance, zero tillage as
a component of conservation agriculture in wheat and inappropriate fertilizer application in dry-seeded rice can increase weed infestation, which in
turn increases herbicide-use and/or reduces fertilizer-use efficiency. Temperature changes may cause an expansion of weeds, with some species moving to higher latitudes and altitudes (Mahajan et al., 2012). Irrigation water in
northwestern India is increasingly becoming scarce and many resourceconserving technologies are recommended to conserve irrigation water:
for example, zero tillage in wheat, bed planting in rice and wheat, and
dry-seeded rice. This will have consequences for weed abundance and composition. Hardy weeds, such as Rumex spp., may increase in wheat because of
increased adoption of zero tillage in wheat. Flooding is commonly the primary cultural means to suppress weeds in rice as water depths of a few centimeters can suppress germination and emergence of a majority of weeds in
rice (Chauhan, 2012a; Chauhan and Johnson, 2008, 2009a, b, 2010). Alternate wetting and drying in puddled and in dry-seeded rice-production systems may encourage weeds, such as Leptochloa chinensis (L.) Ness., Eleusine
indica (L.) Gaertn., Panicum repens L., Eclipta prostrata (L.) L., Eleocharis
spp., and Cyperus esculentus L. (Mahajan et al., 2009b). A dwindling supply
of irrigation water makes it difficult to maintain ponding in rice for effective
weed control. Under these circumstances, where farmers are not aware of
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Bhagirath Singh Chauhan et al.
alternative weed control, yield losses are to be expected. Therefore, strategies for weed management need to be changed according to the environmental conditions.
The risk of herbicide application for weed control may increase as a result
of environmental change. Problems of resistant weeds, herbicide toxicity,
and poor weed control with herbicide application may increase in the near
future. Herbicide efficacy could be affected by elevated CO2, which has
been shown to increase the tolerance of weeds of herbicide (Ziska and
Teasdale, 2000). Changes in temperature and CO2 concentration may alter
transpiration, the number of leaf stomata, or leaf thickness, which, in turn,
may affect the absorption and translocation of herbicides. In C3 plants, an
increased concentration of leaf starch under elevated CO2 may reduce herbicide efficacy. Higher CO2 concentration may stimulate belowground
growth relative to aboveground growth and may favor rhizome and tuber
growth of perennial weeds (Ziska, 2003). Such information suggests that
the problem of perennial weeds in rice and wheat may increase in the near
future. These weeds, however, could be controlled through integrated
approaches that combine preventive, cultural, and chemical control measures. Integrated weed management strategies need to be developed that target weed invasion, recruitment, and reproduction. Such strategies may
include a combination of optimal fertilizer schedule, summer plowing, crop
rotation, land preparation, plant geometry modification, stale-seedbed technique, and the use of weed-competitive cultivars (Chauhan, 2012b;
Chauhan et al., 2006, 2012a,b). Knowledge of weed ecology and biology
could be used as a tool for effective weed management in futuristic
climate-change scenarios. Timely efforts to fill research gaps in management
and weed interactions are needed for the sustainability of the rice–wheat
cropping system in India. There are compelling reasons for expecting climate change to alter weed management; therefore, integrated novel
approaches must be developed to assist farmers in coping with the challenges
of weed control.
Global warming would increase rainfall in some areas, which would lead
to an increase in atmospheric humidity and the duration of the wet season
(Kaur and Rajni, 2012). Combined with higher temperatures, these conditions could favor the development of fungal diseases. Similarly, because of
higher temperatures and humidity, incidences of insects and disease vectors
could increase.
Elad and Pertot (2013) had discussed the impacts of climate change on
plant pathogens and plant diseases. They explained that climate change
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Global Warming and Its Possible Impact on Agriculture in India
would affect the optimal conditions for infection, host specificity, and mechanisms of plant infection. They also pointed out that both pathogens and
host plants would be affected by the changing climate. The authors
suggested that climate-induced changes would affect the measures farmers
use to effectively control diseases and the viability of particular cropping systems in particular regions.
Sharma et al. (2007) reported that an increase in total rainfall
(69–260 mm) resulted in an epidemic of bacterial leaf blight (Table 2.24).
Plant diseases have a direct influence on crop productivity; however, limited
information is available on the impact of climate change on plant diseases
(Agrios, 2005; Elad and Pertot, 2013). The risk of yield losses from plant
diseases is likely to increase in the wake of climate change; however, such
production losses are rarely considered in climate assessments (Anderson
et al., 2004; Reilly et al., 2001). Climate change may have a direct influence
on the temporal and spatial distribution of plant diseases. Plant pathogens are
strongly affected by environment; therefore, the survival, rate of multiplication, vigor, sporulation, direction, distance of dispersal of inocula, rate of
spore germination, and penetration of pathogens can be affected in the
climate-change scenario (Kang et al., 2010). Research evidence has revealed
that elevated CO2 increased disease incidence or severity in some cases
(Eastburn et al., 2010; McElrone et al., 2005; Shin and Yun, 2010), but
decreased it in other cases (Hibberd et al., 1996; McElrone et al., 2010;
Pangga et al., 2004).
Table 2.24 Comparative performance of weather variables in the month of August
during some epidemic and nonepidemic years for bacterial leaf blight (BLB) of rice
in Punjab, India (Sharma et al., 2007)
BLB epidemic year
BLB nonepidemic year
Weather parameters 1976 1985 1991 1992 1999 1979 1988 1993 2002
Rainfall (mm)
260
245
107
251
69
50
70
65
25
Rainy days (no.)
13
10
10
12
4
5
7
3
5
30
16
18
20
15
8
18
2
7
15
17
10
19
10
9
2
2
8
6.6
7.0
7.6
5.9
7.9
9.7
8.3
10.7 6.3
Disease severity (%) 42
47
40
34
38
12
9
8
Temperature
Humidity
b
Sunshine (h)
a
a
No. of days with temperature between 25 and 30 C.
Number of days with RH > 80%.
b
2
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Bhagirath Singh Chauhan et al.
The implications of climate change relative to insects, crop protection,
and food security have recently been highlighted by Sharma (2013). He
pointed out that changes in geographic range and insect abundance would
be expected to increase the extent of crop losses, which would affect crop
production and food security. Global warming is expected to affect host–
plant resistance, biopesticides, natural enemies, and the synthetic chemicals
now used for integrated pest management (Sharma, 2013). The author
argued that climate change would cause increased problems with insecttransmitted diseases, particularly in developing countries, where the need
to increase and sustain food production is most critical.
Abiotic factors may have a direct effect on insect–pest population
dynamics. These factors may influence developmental rate, fecundity, survival, and voltinism (Bale et al., 2002). The rise in temperature associated
with global warming may decrease the survival rate of brown planthopper
and leaffolder in rice (Heong et al., 1995). The authors concluded that rising
temperature could change pest population dynamics of the rice ecosystem.
In another study, elevated CO2 (570 ppm) exhibited a positive effect on
brown planthopper multiplication and more than doubled its population
(45 hoppers hill1) at peak incidence compared with the ambient CO2
(380 ppm) during the kharif season of 2010 (Prasannakumar et al., 2012).
Drought and rainfall play significant roles in soil insects’ abundance
(Srivastava et al., 2010; Staley et al., 2007). Global warming could alter voltinism and this could be reflected in a change in geographic distribution
(Tobin et al., 2008). Elevated CO2 showed some impact on pest population
abundance by altering the nutritional value of plants and this could alter
insect abundance and increase the rate of herbivory (Dermody et al.,
2008; Rao et al., 2009). In a nutshell, climate change might alter the population dynamics of insects differently in different agroecosystems and
agroclimatic zones of India; therefore, more research is needed to understand these issues. The effect of climate change may be more on temperate
insects; it could expand their range. Research is needed to systematically
document major and minor pests by investigating metabolic alteration in
insects in response to changing environment, developing prediction models,
and studying evolutionary changes under modified environment
(Karuppaiah and Sujayanad, 2012). In conclusion, changes in the spectrum
of weeds, diseases, insects, natural enemies, and antagonists; high risk of
invasion by exotic and migrant pathogens and insects; extension of geographic range; noxious abundance of several species at higher altitudes;
increased overwintering; changes in morphology and reproduction; altered
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development; increased number of generations; loss of resistance in cultivars
containing temperature-sensitive genes; extension of the crop-development
season and its effect on pest synchrony; change in interspecific interactions at
different trophic levels; and decreased pesticide efficacy are some of the
impacts of climate change. Better understanding the direct and indirect
effects of climate change is crucial for developing pest-management
programs. The use of historical crop, climate, and pest-management data
vis-à-vis current conditions provides ample and immediate scope for understanding the effects of climate change and planning for adaptive, integrated
pest-management strategies. Another approach toward understanding of the
potential direct effects is to conduct studies under controlled conditions for
knowing how intrinsic population growth is related to temperature and
identifying relationships among temperature, phenology, and population
growth rates by the use of appropriate models. Assessing the changing pest
scenario, mapping regions vulnerable to pest risk, and evolving curative and
preventive pest-management strategies for climate stress should be emphasized among many approaches.
7. KEY ADAPTATION AND MITIGATION STRATEGIES TO
REDUCE THE EFFECTS OF CLIMATE CHANGE
Climate change, involving frequent changes in temperature, precipitation, and sea level and increased impact of GHGs, is bound to affect agricultural production. Potential changes in temperature and precipitation may
have a strong influence on Indian agriculture. There have been trepidations
about a possible increase in the El Niño current, which is thought to be a
major factor contributing to drought in India. These climate-change issues
call for greater understanding of crop–climate interactions and for developing crop–weather models to devise efficient agricultural production strategies (Lal et al., 2001).
India has hardly any scope for future horizontal expansion to meet the
increasing demand for food, fodder, fiber, fuel, and other products. Scope
exists only for vertical expansion. To overcome the problem of climate
change, agronomic management practices could play a significant role.
Agronomists will have to be in the forefront of the research agenda and must
develop cropping/farming systems and agronomic management practices
that would harmonize high production with ecological safety. They must
play a key role on a research team in formulating crop production technology practices in the wake of climate change. Agronomists have to decide
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which and how much each of the recommendations made by plant breeders,
soil scientists, entomologists, plant pathologists, etc., will make a technically
viable, socially acceptable, economically profitable, and environmentally
sound package for a particular crop in a cropping system. They must caution
against practices that can harm the system. Starting from the basics of the
soil–plant–water–atmospheric system to develop cultivation practices for
high productivity and fitting them into farming systems through multidisciplinary collaborative research, or a systems approach, is required.
Climatic variations are present throughout the world, but the impacts of
climate change are the most devastating in developing countries, such as
India, that have fewer resources than developed countries to cope with these
adverse affects. Sustainable food security is therefore difficult to achieve in
developing countries, especially in India, because of the ever-increasing
human population; higher demand for, and intensification of, resource
use; and increased per capita consumption (Rosenzweig and Parry, 1994).
With the emerging threats from climate change, there are many uncertainties as agriculture is sensitive to short-term changes in weather and to
seasonal, annual, and long-term climatic variations. Variations in meteorologic parameters, in combination with other parameters, such as soil characteristics, cultivars, and pests, have a paramount influence on agricultural
productivity (Pathak and Wassmann, 2009). The Fourth Assessment Report
(AR4) of the IPCC suggested that increasing trends of GHGs in the Earth’s
atmosphere could accelerate in the future, as a consequence of which, the
best estimates of increases in mean global surface temperature are likely to
be in the range of 1.8–4 C (IPCC, 2007a). Globally, mean precipitation
is projected to increase with great deviances regionally (Meehl et al.,
2007). It is therefore imperative to chart adaptation and mitigation strategies
to counter the effects of climate change on agricultural commodities. Mitigation and adaptation are measured on temporal and spatial scales on which
they are effective. Mitigation strategies aim at reducing GHG emissions into
the atmosphere, and adaptation strategies aim at enabling the plants to perform optimally under adverse climatic conditions through cultural and
genetic manipulations.
The benefits of mitigation activities will be evident in several decades
because of the longer duration of GHGs in the atmosphere, whereas the
effects of adaptation measures should be seen immediately or in the near
future (Kumar and Parikh, 2001; Lal, 2011). The effects or benefits of mitigation strategies are both global and local, whereas the effects of adaptation
strategies are local or regional. The purpose of mitigation and adaptation
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measures is to attempt a gradual reversal of the impact of climate change and
sustain development under the inescapable effects of climate change.
7.1. Crop-based approaches
Adjustment in sowing dates is a simple yet powerful tool for adapting to the
effects of potential global warming. Krishnan et al. (2007) demonstrated
potential outcomes by adjusting the sowing time of rice at two sites
(Cuttack and Jorhat in India) by simulating crop growth under different
climate-change scenarios. Improved agronomic practices, such as altering
planting dates, helped in minimizing the effect of high temperature responsible for yield instability in rice and wheat. Manipulation of planting dates
helped in reducing yield instability by keeping flowering from coinciding
with the hottest growing season (Mahajan et al., 2009a).
On several occasions in the last decade, South Asia witnessed adverse
effects of climatic variations, that is, terminal heat stress, on wheat productivity. For example, despite favorable weather conditions during the winter
of 2009–2010, an abrupt rise in night temperature during the grain-filling
stage in wheat adversely affected wheat productivity in the Indo-Gangetic
Plains (IGP) and other northern states of India (Gupta et al., 2010). The
results indicated that terminal heat stress on wheat in Punjab in
2009–2010 led to a mean yield penalty of 5.8% compared with the previous
year. However, yield losses reached 20% in a few districts of Punjab and
other transects of the IGP. The magnitude of losses varied depending on
planting time, cultivars, and other management practices.
Agronomic management of crops, such as method of sowing, can be an
effective adaptation strategy under the climate-change scenario. Bed planting of crops has proved successful in the wake of climate change as it results
in increased water-use efficiency, reduced waterlogging, better access
for interrow cultivation, weed control, banding of fertilizers, better stand
establishment, less crop lodging, and reduced seeding rates (Bhardwaj
et al., 2009; Chauhan et al., 2012a). In irrigated areas, zero tillage in wheat
cultivation has successfully reduced the demand for water and other
resources (e.g., diesel and herbicides) and zero-till systems are now considered a viable option to combat climate change. Intercropping is a time-tested
practice in the wake of climate change. If one crop fails because of flooding
or drought, the second crop provides minimum assured returns for livelihood security (Mittal and Singh, 1989). Large numbers of recommendations
have been made for different zones on crop substitution and cultivar
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replacement in the case of delayed onset of monsoon (Joshi and Kar, 2009).
In this approach, short-duration crops and cultivars replace long-duration
ones. In the case of early-season drought, possible options are replanting
with a crop and cultivar(s) suitable for late sowing and transplanting by raising seedlings or taking seedlings from other fields. For midseason drought,
viable options are forming dead furrows at convenient intervals (3–4 m) well
in advance of anticipated drought (within a month after seeding or immediately after intercultivation) to minimize runoff and store rainwater and
thinning the plant population either within rows or by removing alternate
rows in a sole crop or removing more sensitive crop in intercropping and
harvesting the crop for fodder and allowing the stubbles to grow for grain
(ratooning) as in the case of sorghum and pearl millet. For late-season
drought, however, options are limited. A crop on relatively deep soil can
be removed and a short-duration rabi pulse crop can be sown on stored soil
moisture with subsequent rain. In the case of sorghum and pearl millet,
ratooning appears to be ideal even at the time of late-season drought, especially in deep black soils (Venkateswarlu and Shanker, 2009).
7.2. Crops and cultivars that fit into new cropping systems
and seasons
With climate change, the IGP could continue to be the major contributor of
food grains despite the scarcity of irrigation water, provided new cultivars
are grown with judiciously selected cultivation schedules. The area has three
cropping seasons: rabi or winter season from October/November to March/
April, zaid or summer season from March/April to June/July, and kharif or
rainy season from July/August to October/November. Different cropping
systems could be practiced with the use of suitable cultivars for high yields
in this era of climate change, for example, dry-seeded rice/pigeon
pea/soybean/urad bean/cotton in kharif, potato/rape/mustard–wheat/
chickpea/lentil in rabi, and mung bean/soybean in zaid. For high profitability for farmers, essential-oil crops such as menthol mint and medicinal crops
could be substitutes for mung bean/soybean/cotton in the zaid season as
suitable cultivars of these crops are already available. For strategic reasons,
a water-guzzling crop like sugarcane should continue to be grown in the
Himalayan terai/foothill region. Again, for augmenting the liquid biofuel
supply, crops such as mustard can be cultivated in irrigated areas for high
yield. In this direction, a mustard crop could be grown twice in the rabi season if suitable short-duration, early-maturing cultivars become available in
the future. The cotton crop yields lint and oil; therefore, it could be grown
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on additional land during the kharif season. Potato should assume the role of a
staple food as it is a rich source of carbohydrates. India will need to produce
120 million tons of wheat, 25 million t of pulses, and 100 million t of oil
seeds (50 million t for biofuel purposes) by 2025 (Kumar, 2006). In the
climate-change scenario, the IGP should become a major supplier of these
commodities. Crop breeding programs with the objective of developing
climate-resilient (temperature- and drought-tolerant), high-yielding cultivars of the identified crops should be given high priority, so that the desired
kinds of cultivars become available in the wake of climate change.
A combination of conventional and molecular marker-assisted, mutational, and transgenic breeding approaches will be required to develop
the desired kinds of crop cultivars. Crop-based coordinated programs
need to begin as early as possible to develop climate-resilient cultivars.
Recently, the Indian Agricultural Research Institute (IARI), New Delhi,
released an early-maturing basmati (fragrant) rice and a wheat cultivar suitable for late planting (Swaminathan and Kesavan, 2012). It appears that the
desired kinds of cultivars can also be selected in some of the ongoing breeding programs. There will be a need for identifying areas where climatechange conditions already exist or are mimicked (e.g., Rajasthan, Madhya
Pradesh, and Uttar Pradesh border areas in the IGP) and/or setting up suitable environmental chambers for the purpose of screening large segregating
populations to make selections (Rupakumar et al., 2006). Climate-change
issues need to be converted from a “problem” into an “opportunity.”
7.3. Cultivars suitable for high temperature, drought, inland
salinity, and submergence tolerance
Cultivars that fit into an erratic rainfall season and are drought- and
submergence-tolerant, have high fertilizer- and radiation-use efficiency,
and can tolerate coastal salinity and seawater inundation are needed. Germplasm of wild relatives and local land races could be used for developing
climate-resilient crop cultivars. There is a need to revisit germplasm that
has tolerance of heat and cold stresses but has not been used in the past
because of low yield potential. Breeding cultivars that are tolerant of
high-temperature stress should receive utmost importance. Recently, for
example, Tao et al. (2008) identified rice hybrid Guodao 6 as heat-tolerant.
Genetic improvement of heat-tolerant genotypes, especially in pulses, by
identifying and validating markers for high-temperature tolerance with high
yield potential is one of the key technological processes that could be a
significant approach for adapting to climate change. Inclusion of abiotic
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stress-tolerant cultivars in cropping systems and the development and use of
new cultivars with increased resilience to drought and flooding and
increased resistance to heat shock is important for climate adaptation.
Improving the adoption and dissemination of short-duration crop cultivars
can enhance the ability of farmers to cope with variable climatic conditions.
One of the most predictable issues of CO2-induced global warming is the
melting of the ice caps and glaciers and the addition of excess water to the
sea, thereby leading to the submergence of coastal areas. Further, the coastal
areas of the world are most fertile and densely populated. Therefore, breeding of crops and cultivars that can be grown in saline soils could be an efficient adaptation strategy to offset the loss of agricultural land. Genetically
modified rice cultivars possessing genes for salinity tolerance have been bred
by transferring genes from the mangrove species Avicennia marina (Sultana
et al., 2012). Similarly, for developing drought-tolerant strains of rice and
other crops, Prosopis juliflora L. is being used as a donor of a gene for drought
tolerance (Swaminathan and Kesavan, 2012). With the change in climatic
scenario, corn could emerge as an alternative crop in the rice–wheat
cropping system, replacing rice. Temperate germplasm, being highly productive, could be used for the introgression of desirable genes into promising
tropical/subtropical backgrounds for the development of inbreds suitable for
different agroclimatic conditions.
Using FR13A, one of the submergence-tolerant donors, improved rice
cultivars with submergence tolerance have been developed (e.g., SwarnaSub1 rice, the first submergence-tolerant product using marker-assisted
backcrossing to introduce a major QTL locus, SUB1). Cultivars with the
SUB1 trait tolerate complete submergence at the seedling stage
(Iftekharuddaula et al., 2011; Septiningsih et al., 2009; Xu et al., 2006);
however, they are susceptible to anaerobic germination. Introgression of
SUB1 did not improve germination percentage under flooded conditions.
In this direction, Nipponbare (a japonica cultivar), possessing characteristics
amenable to underwater seedling establishment, exhibited greater seedling
vigor under submergence because of rapid shoot elongation and was even
found to be better than the internationally recognized submergence-tolerant
cultivar FR13A (Vu et al., 2010). Commendable work is going on in this
direction at IRRI and elsewhere to face flood-like situations in the future
at the germination stage of the crop.
Drought occurrence is likely to be more pronounced in rainfed areas.
Although the occurrence of drought is not as sudden as other weather hazards, its effect can be equally devastating, especially in developing nations. In
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India, significant progress has been made in the genetic dissection of
flowering time, inflorescence architecture, temperature, and drought tolerance in certain model plant systems and in comparative genomics in crop
plants. The Central Research Institute for Dryland Agriculture (CRIDA)
in Hyderabad has developed a sorghum cultivar (transgenic), “SPV 462,”
that possesses tolerance of water deficit and salt stress. The germination
potential of these transgenic seeds was several times higher when challenged
with salt and water stresses and the plants had a robust root system (root biomass and root length) (Maheswari et al., 2010). The scientific approach
toward drought mitigation involves the pinpointing of drought-prone areas
and the scientific management of such vulnerable areas with droughttolerant cultivars. A holistic approach toward the management of water,
land, crop, and other natural resources, coupled with drought-tolerant cultivars, can go a long way toward alleviating the adverse impacts of drought
(Sharma et al., 2010).
7.4. Cultivars that respond to high CO2 concentration
As projected by various models, the future climate will be rich in CO2 concentration and it is also clear that the vegetation will be positively benefited
by increased CO2 concentration (Farquhar, 1997). This beneficial effect will
be more pronounced for C3 plants, such as wheat, rice, barley, oats, peanut,
cotton, sugar beet, tobacco, spinach, soybean, and most trees. In all of these
plants, the elevated concentrations of CO2 will lead to higher assimilation
rates and an increase in stomatal resistance, resulting in a decline in transpiration rate and improved water-use efficiency in crops. Hence, plant
breeders need to develop cultivars that are able to benefit from the high
CO2 fertilization effect. IRRI, in collaboration with several countries, is
working to alter the photosynthesis of rice from the C3 to C4 pathway by
introducing cloned genes from C4 species (e.g., corn and sorghum).
7.5. Mitigation of the impact of climate change
Many mitigation technologies are available that can help cope with the
challenges of climate change with desirable results. Agriculture, forestry,
and fisheries/aquaculture have great potential for mitigating GHG emissions. According to the IPCC, the global technical mitigation potential
for agriculture will be between 5500 and 6000 million t CO2 equivalents
per year by 2030, 89% of which is assumed to be from sequestration of C in
the soil. Rice is a staple food for a large population in India and the crop
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occupies the largest area in India. The maximum emission of CH4 is from
the rice-growing areas. CH4 emissions from rice fields can be restricted
with the adoption of improved agricultural practices. Resourceconserving technologies, such as zero tillage in wheat and dry-seeded rice,
could play a major role in this direction. Zero-till systems have a direct
mitigation effect as they convert GHGs such as CO2 into O2 in the atmosphere and C enriches soil organic matter. In dry-seeded rice, because of
minimum anaerobic conditions, improved root growth and diversity of
aerobic soil organisms may help in mitigating climate change. Research
has shown that yields similar to those in puddled-transplanted rice can
be achieved with alternate wetting and drying (Mahajan et al., 2011).
However, alternate wetting and drying may lead to emissions of N2O,
which has greater global warming potential than CH4 does. However, this
problem could be reduced by adopting integrated nutrient-management
practices, which can help in mitigating climate change. Integrated nutrient
management involves, in general, a combination of organic, inorganic, and
biofertilizers in proportions that will keep the soil capable of producing at
an accelerated rate without suffering physical, chemical, and biological
damage. The advantages of integrated nutrient management are increased
N-use efficiency and increased yield. The application of urease, hydroquinone, and nitrification inhibitors, dicyandiamide together with urea, is an
effective technology for reducing NO2 and CH4 emissions from rice fields.
The use of neem-coated urea is another simple and cost-effective technology. Improved management of livestock and their diet could also assist in
the mitigation of GHGs. The use of improved food additives, substitution
of low-digestibility feeds with high-digestibility ones, concentrate feeding,
substituting fibrous concentrate with starchy concentrate, supplementation with molasses, and changing microflora of rumen could help in reducing CH4 emissions (Aggarwal, 2008). Efficiency of energy use in
agriculture could be improved by using better-designed machinery
(e.g., the Happy Seeder, a drill for dry seeding, zero-till drill, and bed
planter) that could increase fuel-use efficiency and help in the commercialization of wind and solar power potential, and the use of a laser leveler
could also lead to mitigation (Chauhan et al., 2012a; Lal, 2011). Changing
land use by increasing the area under biofuel-producing crops and
agroforestry could help in mitigating GHG emissions, but this has to be
considered with the goal of increasing food production for national security (Venkateswarlu et al., 2011).
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7.6. Other strategies
Many options exist in soil-, water-, and nutrient-management technologies,
which can contribute to both adaptation and mitigation. The addition of
crop residues and manure to arable soils improves the soil water-holding
capacity (Benbi et al., 2011). Soil C sequestration is a useful strategy in
the wake of climate change. Although it has limitations in tropical areas
because of high temperature, a substantial quantity of C can be sequestered
with the adoption of improved agricultural practices. There are two types of
C sequestration, soil C sequestration and sequestration into vegetation.
Tree-based systems can sequester substantial quantities of C into biomass
in a short period of time (Lal, 2004). The total potential of soil
C sequestration in India is 39–49 Tg year1. This amount includes the
potential of the restoration of degraded soils and ecosystems, which is estimated at 7 –10 Tg C year1. The potential of the adoption of improved
agronomic practices on agricultural soil is 6–7 Tg C year1. In addition,
there is also the potential of soil inorganic-carbon sequestration estimated
at 21.8–25.6 Tg C year1 (Lal, 2011). By providing shelter and shade, as
in agroforestry systems, the effects of extremely high temperatures may
decline (Cannell et al., 1996). The planting of multipurpose trees on
degraded lands helps in C sequestration. The agroforestry system protects
farmers from climatic variability and helps in reducing the atmospheric load
of GHGs. In India, much of the research done on in situ moisture conservation, energy efficiency in agriculture, and the use of poor-quality water
relates to rainfed agriculture. The watershed approach may prove successful
in rainfed areas and help in both adaptation and mitigation. For example, soil
and water conservation work, farm ponds, and check dams help moderate
rainwater runoff and minimize flooding during high-intensity rainfalls. Lal
(2004) estimated that, by arresting water and wind erosion, 3–4.6 Tg year1
of C could be sequestered. The withdrawal of groundwater from deeper
layers demands more energy and leads to GHG emissions in agriculture
(Hira, 2009). If surface storage of rainwater in dugout ponds is encouraged,
dependence on withdrawing groundwater might decrease. The conjunctive
use of surface water and groundwater is an important strategy to mitigate
climate change, especially where groundwater is not suitable for agriculture.
Innovative approaches in groundwater sharing may also contribute to an
equitable distribution of water and reduced energy use in pumping. Biochar
is another novel approach to sequester C in terrestrial ecosystems; several
associated products are in the process of being manufactured. India could
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produce almost 310 million t of biochar annually, whose application might
offset about 50% of C emissions (292 Tg C year1) from fossil fuels (Lal,
2005). The rice–wheat cropping system in the IGP of India produces substantial quantities of crop residues, and, if these residues can be pyrolyzed,
50% of the C in biomass could be returned to the soil as biochar, thereby
increasing soil fertility and crop yield by sequestering C (Lal, 2011).
In situ water harvesting can help increase the rainwater-use efficiency of
crops through water-conserving techniques such as compartment bunding,
ridges and furrows, strip cropping, mulching, and vegetative barriers to soil
moisture.
The diversification of sensitive agricultural production systems (e.g.,
rainfed agriculture) into less sensitive agricultural microenterprises (smallscale vegetable and fruit production, livestock rearing, bee keeping, etc.)
can enhance adaptation to the short- and medium-term impacts of climate
change (Aggarwal, 2008). Diversifying income through other farming activities, such as livestock raising, tree farming, pond aquaculture, agroforestry,
and silvicultural practices, is a viable and effective approach to combating
climate change.
7.7. Policy issues for managing climate change
In addition to the use of technological strategies in overcoming climate
change-related impacts on crop production, there must be a solid policy
structure and strong political determination on the part of governments
to effectively tackle climate change. A sound policy framework should
examine the issues of redesigning the social sector with a focus on vulnerable
areas/populations, liability during extreme weather events, the introduction
of new credit instruments with deferred repayment, and weather insurance
as a major vehicle to transfer risk. The role of community institutions and the
private sector in relation to agriculture should be a policy matter. Policy
initiatives toward access to banking; microcredit; insurance service before,
during, and after a disaster event; and access to communication and information services are needed in the envisaged climate-change scenario. The
establishment of an early warning system for emerging climatic risks, such
as drought, flood, heat and cold waves, and pest outbreaks, is desired. In
India and globally, climate change is now on the political and public agenda.
In India, particular attention is being paid to the impact of climate change on
agriculture, because it could have serious implications for the food security
of the country. Most scientists and policymakers now acknowledge that
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climate change will have far-reaching effects on livelihood and food security
unless significant steps are taken to deal with it effectively now. The key policy issues are (1) establishment of a “Green Research Fund” for strengthening research on adaptation, mitigation, and impact assessment; (2) facilitating
greater adoption of scientific and economic pricing policies for water, land,
energy, and other natural resources; (3) providing financial incentives for
improved land management; (4) ensuring food and livelihood security;
(5) establishing seed banks in highly variable and unpredictable environments, etc. In India, governments should invest more in water storage
and efficient water-use technologies. Investment should be made in technologies that allow aquifer recharge and microirrigation to increase the efficient
use of available water. More investment should be made in funding projects
on cultivars with tolerance of adverse climate and on land-use systems to
ensure adequate food production in the face of climate change.
8. CONCLUSIONS
Climate change is a reality. Elevated CO2 concentration may increase
crop growth and yield due to increased photosynthesis, decreased photorespiration, and decreased stomatal conductance. The increase in temperature,
however, may decrease grain yields of rice and wheat due to the shorter
duration of crop growth. The protein content of legume grains may decrease
with increased CO2 concentration. Elevated CO2 concentration may
increase the availability of soil N and P because of increased mineralization
and activity of phosphatase enzyme in the rhizosphere. C3 plants are likely to
compete even more vigorously than now against C4 crops and vice versa.
Increased temperature along with humidity may increase the occurrence
of insects and diseases. Because of the complexity of crop–environment
interactions, a multidisciplinary approach to the problem is required in
which plant breeders, crop physiologists, agrometeorologists, and agronomists need to interact to find long-term solutions in sustaining agricultural
production. There is a need for strategic research to enhance the resilience of
Indian agriculture, including crops, natural resource management, horticulture, livestock, and fisheries, for the development and application of
improved production and risk management technologies. In addition, there
is a need for technology demonstration of existing management practices for
enhancing the resilience of crops and livestock to climate change. Capacity
building of scientists and other stakeholders in agricultural research on climate
resilience may also help in developing solutions for climate change.
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ACKNOWLEDGMENT
We would like to acknowledge the help of Bill Hardy in providing comments on the
manuscript.
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