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Agricultural Emissions and pollution

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Every country's economic, environmental, and social well‐being is intricately linked to a healthy, well‐performing agricultural sector. In our country it becomes more important as growth of the agricultural sector has been fluctuating for a long time. The economic survey (2019-20) indicates that contribution of agriculture to the Gross value added (GVA) has decreased from 18.2% in 2014-15 to 16.5% in 2019-20. However, agriculture is facing the triple challenge of increasing production to meet the growing food demand, adapting to changing climatic conditions, and reducing agricultural emissions (Greenhouse gases (GHG) and non-GHG emissions) from the fields, globally.

At the same time, India has expressed its determination in its climate pledges, and nationally determined contributions (NDCs), under the Paris Agreement. This is indeed for the first time when our government has also restated firmly to step up and strengthen its nationally determined climate action plans through a long-term strategy, which indicates India’s unwavering commitment to the global efforts in tackling climate change. In that context, it would be interesting to know that our country is the third-largest emitter of greenhouse gases (GHG) in the world after the USA and China and therefore, to reduce emissions at a global level, India has a vital role to play.

“Our population is 1.3 billion which is the world's second-largest but we are the seventh-largest country in total area (3.288 million sq km)”. Agricultural activities contribute significantly to the GHG emissions. Methane (CH4) and nitrous oxide (N2O) were the two main gases emitted by agricultural activity. In addition to methane and nitrous oxide, agricultural activities have been linked to the emission of other dangerous gases and pollutants. These include carbon dioxide, ammonia, hydrogen sulfide, and airborne particulate matter, which has been linked to health problems. The situation becomes more challenging when agriculture, with its allied sectors, is the largest source of livelihoods in India with almost 70 percent of its rural households are dependent primarily on agriculture for their livelihood. Consequently, scientists and policymakers are faced with the dual challenge of meeting the growing demand for food whilst also reining in on GHG emissions.

Population growth will lead to an increase in food demand, which will exert pressure on crop production and likely increase the agricultural crop residue. The different studies were carried out to estimate the atmospheric emissions of various pollutants from crop residue burning using the Intergovernmental Panel on Climate Change guidelines. In India 488 Mt of total crop residue was generated during 2017, and about 24% of it was burnt in agricultural fields. This resulted in emissions of 824 Gg of Particulate Matter (PM2.5), 58 Gg of Elemental Carbon (EC) and 239 Gg of Organic Carbon (OC). Additionally, 211 Tg of CO2 equivalent greenhouse gases (CO2, CH4, N2O) were also added to the atmosphere. Trend analysis in a Business As Usual (BAU) model shows that crop residue burning emissions will increase by 45% in 2050 having 2017 as the base year.

Northwestern India is known as the “breadbasket” of the country producing two-thirds of food grains, with wheat and rice as the principal crops grown under the crop rotation system. Agricultural data from India indicates a 25% increase in the post-monsoon rice crop production in Punjab during 2002–2016. NASA’s A-train satellite sensors detect a consistent increase in the vegetation index (net 21%) and post-harvest agricultural fire activity (net ~60%) leading to nearly 43% increase in aerosol loading over the populous Indo-Gangetic Plain in northern India. The ground-level particulate matter (PM2.5) downwind over New Delhi shows a concurrent uptrend of net 60%. An efficient crop residue management system is critically needed towards eliminating open field burning to mitigate episodic hazardous air quality over India.

Therefore, we should adopt sustainable approaches and propose an integrated crop residue management model to minimize the adverse impact of agricultural waste burning on human health and the environment. Also, we need more research to cut the amount of fertilizer application in cropping seasons without significant loss of crop yield in arable lands, which might be plant demand-based (precision farming), or adoption of some innovative approaches like biochar-based formulations in place of conventional blanket recommendation practices. Policy regulations are needed to cut the emissions from the agricultural sector and our Honorable Prime minister has also encouraged the scientific fraternity to look for the ways to reduce mineral fertilizer use. Techniques including better manure storage, precision nutrient application, and air-breaks between farms can all help decrease the effect of agricultural practices on air quality.

Agricultural Emissions and pollution

What is agriculture?

Agriculture is the practice of cultivating natural resources to sustain human life and provide economic gain. It is the backbone of the economic system of a given country. Healthy, sustainable and inclusive food systems are critical to achieve the United Nation’s sustainable development goal 2 (UNSDG2), ‘zero hunger’, by 2030. One of the most effective strategies for reducing extreme poverty, fostering shared prosperity, and feeding the estimated 9.7 billion people by 2050 is agricultural development. A fairly big percentage of the population has access to employment opportunities in agriculture in addition to providing food and raw materials.

Why agriculture is important for India?

India has 3.288 million square kilometres of land area, making it the seventh-largest and the second-most populous country in the world. India's geographic location is exceptional for agriculture because it offers a variety of beneficial conditions. The country is home to a vast agro-ecological diversity owing to its proximity to the highest mountain range in the world, the Himalayas, which extend to its north from Jammu and Kashmir to Arunachal Pradesh in the north-east, the Thar desert to its west, the Gangetic delta to its east, and the Deccan Plateau to its south. Central part of India is dominated by plateau area. Apart from variation in landform, the country has varieties of climatic conditions, and soil types. India's climate varies from humid and dry tropical in the south to temperate alpine in the northern reaches and has a great diversity of ecosystems. Various crops can be grown due to the country's extensive relief, diverse climate, and diverse soil conditions. All types of tropical, subtropical, and temperate crops are grown in India; however 2/3 of the nation's cropped land is devoted primarily to food crops. There are plain areas, fertile soil, a longer growth season, and significant weather variety. In addition to its exceptional geographic features, India has continually used science and technology to increase production. The development of various farming techniques in India has been influenced by these physical variations as well as other elements including the availability of irrigation, the usage of technology, and contemporary agricultural inputs like High Yielding Varieties (HYV) of seeds, insecticides, and pesticides. According to the Indian Council for Agricultural Research (ICAR), India is blessed with vast areas of productive land divided into 15 agro-climatic zones that have a diversity of soil types, weather patterns, and crop-growing potential. It is the second-largest producer of fruit and vegetables, contributing 10.9% and 8.6%, respectively, to global fruit and vegetable production. It is also the second-largest producer of rice, wheat, sugarcane, cotton, and groundnuts.                                                                               Eventhough the Indian economy has expanded and diversified, the contribution of agriculture to GDP has continuously decreased from 1951 to 2011. Despite reaching food security in terms of production, India is still home to over 190 million living below the poverty line and one-quarter of the world's hungry people. ICAR predicts that by 2030, there would be a 345 million tonnes increase in global food grain demand. India's growing population, rising average income and the consequences of globalisation will increase demand for a greater variety, quantity, and quality of food. In order to produce more nutritious food in larger quantities, a productive, active, broad, and sustainable agriculture sector must quickly emerge.

What are the main agriculture produce of India?
India is the top producer of milk, spices, pulses, tea, cashew and jute and the second-largest producer of rice, wheat, oilseeds, fruits and vegetables, sugarcane and cotton. The nation ranks second place globally in terms of rice production. Approximately 34% of the nation's total cropland is dedicated to the production of rice. 42% of the nation's total food crop production is consisted of rice. Wheat is the second most significant food grain grown in India. Wheat production in India has significantly increased as a result of the Green Revolution.

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What are the seasons of agriculture and harvest?
There are three main cropping seasons in India – kharif, rabi, and zaid. The crop harvest season determines the names of these three seasons. The sowing date, however, varies slightly from state to state depending on the weather and rainfall patterns. The cropping season in India starts in June and ends in October where monsoon crops are cultivated and harvested is known as kharif season. Rice and maize are the major kharif crops. The season where crops are sown in mid-November and harvested in April/May is called rabi season, eg. wheat, barley.  Since the Zaid crops are also called summer crops, they are sown and harvested between March and June. Eg. Pumpkin, Bitter guard and Cucumber.

What are the factors affect agriculture in India? 
Climate factors such as light, water, rain fall, temperature, air, relative humidity and wind affect agriculture in many ways. As of now, half of India’s agricultural output depends on rainwater.  Most of the agricultural land is irrigated by the southwest monsoon. A year without a good monsoon can cause significant damage to India’s financial stability and growth. With India’s geographical location and environmental surroundings, summer monsoons are crucial to its economy. Therefore, all changes to this season have a direct link with India’s GDP growth and economic stability. In many ways, the monsoon is the most critical season for the nation. Various physical factors in the natural environment such as topography, soil and climate also affect agriculture. Several studies have shown that the exposure to high levels of pollutants such as SO2, NO2, O3 and particulate matter (PM) can cause severe damage to crops thereby reduction in agriculture production (Agrawal et al., 2003; Balasubramanian et al., 2021).

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What is atmospheric pollution?
The World Health Organization (WHO) defines air pollution as the existence of any chemical, physical, or biological substance in the indoor or outdoor environment that alters the atmosphere's normal properties. It is one of the major problems that the human community faces now. The industrialisation and economic development of nations lead to the consumption of high levels of energy, by which the lack of proper planning results into air pollution due to the emission of hazardous compounds. Common causes of air pollution include motor vehicles, industrial facilities, household combustion units, and forest fires. Particulate matter, carbon monoxide, ozone, nitrogen dioxide, and sulphur dioxide are pollutants of great public health concern. Air pollutants may be conveniently divided into two categories. Primary pollutants, such as sulphur dioxide, nitrogen oxide and particulates, are emitted directly into the atmosphere. They are generally present in high concentrations in urban areas or close to large point sources, such as around thermal power stations, where they may have large effects on local farming communities. Secondary pollutants include tropospheric (ground level) ozone, and are formed by subsequent chemical reactions in the atmosphere. They often spread at high concentrations over hundreds of kilometers away from urban and other sources.

What are the seasons of agriculture and harvest?
There are three main cropping seasons in India – kharif, rabi, and zaid. The crop harvest season determines the names of these three seasons. The sowing date, however, varies slightly from state to state depending on the weather and rainfall patterns. The cropping season in India starts in June and ends in October where monsoon crops are cultivated and harvested is known as kharif season. Rice and maize are the major kharif crops. The season where crops are sown in mid-November and harvested in April/May is called rabi season, eg. wheat, barley.  Since the Zaid crops are also called summer crops, they are sown and harvested between March and June. Eg. Pumpkin, Bitter guard and Cucumber.

What is atmospheric pollution?
The World Health Organization (WHO) defines air pollution as the existence of any chemical, physical, or biological substance in the indoor or outdoor environment that alters the atmosphere's normal properties. It is one of the major problems that the human community faces now. The industrialisation and economic development of nations lead to the consumption of high levels of energy, by which the lack of proper planning results into air pollution due to the emission of hazardous compounds. Common causes of air pollution include motor vehicles, industrial facilities, household combustion units, and forest fires. Particulate matter, carbon monoxide, ozone, nitrogen dioxide, and sulphur dioxide are pollutants of great public health concern. Air pollutants may be conveniently divided into two categories. Primary pollutants, such as sulphur dioxide, nitrogen oxide and particulates, are emitted directly into the atmosphere. They are generally present in high concentrations in urban areas or close to large point sources, such as around thermal power stations, where they may have large effects on local farming communities. Secondary pollutants include tropospheric (ground level) ozone, and are formed by subsequent chemical reactions in the atmosphere. They often spread at high concentrations over hundreds of kilometers away from urban and other sources. 
7. What are the key pollutants that affect agriculture production?
Major primary gaseous pollutants affect plants
Sulphur dioxide (SO2)
Sulphur dioxide, when they are exposed to can be quite harmful to plants. Sulphur dioxide primarily enters the leaves through the stomata (microscopic apertures), causing either immediate or persistent harm. Uneven, blotchy white spots can appear on exposed leaves as they start to lose their colour. Red, brown, or black dots may appear on certain leaves. Plants may start to lose their leaves when enough pigments in the tissue are harmed or killed. Growth may be inhibited, and crop productivity is significantly reduced. In young plants, this is particularly obvious.
Nitrogen dioxide (NO2)
The leaves and young plants are the main targets of NO2. As the plant and tissue mature, its impacts become less significant. In comparison to winter, spring and summer are discovered to be the seasons when conifers are most sensitive to this gas. In comparison to juvenile needles, older ones are more vulnerable to the gas. The consequence is a reduction in the plant's photosynthesis rate. The widely recognized noticeable injury markings are chlorosis in angiosperm leaves and tip burn in conifer needles.
Ammonia (NH3)
Most common visible symptoms in conifers are black discolouration, usually sharply bordered tip burn and abscission of needles. A wet appearance that eventually turns black, intercostal necrosis, minor marginal and upper surface injury, discoloration of the upper surface, drying, and defoliation are visible symptoms in angiosperm leaves (Gheorghe et al., 2011).
Secondary pollutants 
Tropospheric Ozone (O3)
At high concentrations, ozone acts as a pollutant and is a constituent of smog. It badly affects plants, specifically the leaves and influences the photosynthetic activity that severely affects the development and translocation of crop biomass to the economic portions of plants during maturity stages. This drastically reduces the yield of crops. Its impact on plants was first noted in the Los Angeles region in 1944. According to research by the National Crop Loss Assessment Network (NCLAN), ozone in the environment is detrimental to crop yield (Lesser et al., 1990). Ground-level ozone causes more damage to plants than all other air pollutants combined. In terms of its regional and global effects on crops, ozone is regarded as the most destructive pollutant (Fuhrer et al., 1997). By entering leaf pores known as stomata and oxidising plant tissue during respiration, ozone damages plants. It also reacts with the plasma membrane or alters into a variety of reactive oxygen species (ROS). ROS can alter biological processes, which causes premature senescence of leaves and cell death (Long and Naidu, 2002; Ainsworth et al., 2016). Yellowing, flecking, and blotching in leaves, early maturation, and premature senescence are typical signs of ozone pollution. It obstructs pollen production, pollination, pollen germination and pollen tube growth. 
   Fig1.Different levels of ozone injury on common soybean, maize and wheat leaves

Ozone stimulates respiration, inhibits oxidative phosphorylation and changes membrane permeability. This damages the plant leaves and causes reduced survival.Various factors, including soil moisture, the presence of other air pollutants, insects or illnesses, and other environmental pressures, might intensify the effects of ozone. High temperatures and intense light enhance the chemical reactions that lead to the production of ozone, making it a typical contaminant of hot summer days. In comparison to single pollutants acting alone, complex combinations of pollutants, which may be particularly important in metropolitan and peri-urban regions, may have a substantially bigger impact on yields.                                 


 
Fig 2. Plant responses to ozone at various scales.
ASA: reduced ascorbate; Asc/Glu: ascorbate/glutathione cycle;  PS: photosynthesis; Metab. Ir and IIr: primary and secondary metabolites; ROS: reactive oxygen species (Feng et al., 2021)

 
Fig 3. O3 incurs large-scale physiological and yield-related damages in rice plants
Loss of crop yield due to ground level ozone is usually quantified with metrics based on the mean daytime ozone concentration (M7 and M12) and cumulative exposure (seasonally accumulated daytime ozone concentration above 40 ppb AOT40, SUM06, W126) (Tong et al., 2009). The relative yield (RY) calculated with the exposure/dose-response equations concerning the concentration metrics.
Index    Relative yield (RY)

AOT40 (ppbv)    
0.0000039*AOT40+0.94 (Mills et al., 2007)

M7 (ppbv)    
exp[-(M7/137)2.34]/exp[-(25/137)2.34] (Lesser et al., 1990)

                             
Fig 4. The relative response of five major crop species to O3 as predicted by the Weibullmodel3 (Heck et al., 1983)
Surface ozone induced crop damages in India
Multiple experimental studies showed the impact of surface ozone on rice and wheat crops in India and revealed a reduction in the yield of major crops (Sharma et al., 2019; Lal et al., 2017; Tomer et al., 2015; Ghude et al., 2015). Exposure to surface ozone has been associated to a 5% to 11% relative yield loss in the mean total production per year for winter wheat and a 3% to 6% loss for rabi rice in India from 2002 to 2007 (Debaje et al., 2014). Wheat was the most affected crop, followed by rice, according to a district-level calculation of the impact of ozone on cotton, rice, soybeans, and wheat crops in India for the year 2005 (Ghude et al., 2014). The results of a study done by Lal et al. (2017) indicate that the relative losses in wheat and rice crops increased after 2007. The Indo-Gangetic Plain (IGP), also addressed  as the "breadbasket of India," is facing the threat of declining crop yield as a result of rising surface O3 concentrations (Singh et al., 2017; Pathak et al., 2011), which will indeed have an effect on the nation's food security (Rai et al., 2016; Tiwari et al., 2016). One of the main causes of the reduction in agricultural production in the IGP region has been attributed to the rising levels of air pollution in the region's urban and rural areas (Kumar et al., 2018; Burney and Ramanathan, 2014).
 
Fig 5. All India total production loss of  kharif rice in million tonnes (top panel) and rabi wheat (bottom panel) for 1997—2018.

 
Fig 6. District wise production loss of kharif rice (left panel) and rabi wheat (right panel) for the year 2018.

8. What are the important publications of pollution vs agriculture production?
Agrawal, M., Singh, B., Rajput, M., Marshall, F. and Bell, J.N.B., 2003. Effect of air pollution on peri-urban agriculture: a case study. Environmental Pollution, 126(3), pp.323-329.

Ainsworth, E.A., 2017. Understanding and improving global crop response to ozone pollution. The Plant Journal, 90(5), pp.886-897.
Avnery, S., Mauzerall, D.L., Liu, J. and Horowitz, L.W., 2011. Global crop yield reductions due to surface ozone exposure: 2. Year 2030 potential crop production losses and economic damage under two scenarios of O3 pollution. Atmospheric Environment, 45(13), pp.2297-2309.

Debaje, S.B., 2014. Estimated crop yield losses due to surface ozone exposure and economic damage in India. Environmental Science and Pollution Research, 21(12), pp.7329-7338.

Gheorghe, I.F. and Ion, B., 2011. The effects of air pollutants on vegetation and the role of vegetation in reducing atmospheric pollution. The impact of air pollution on health, economy, environment and agricultural sources, 29, pp.241-80.

Ghude, S.D., Jena, C., Chate, D.M., Beig, G., Pfister, G.G., Kumar, R. and Ramanathan, V., 2014. Reductions in India's crop yield due to ozone. Geophysical Research Letters, 41(15), pp.5685-5691.

Heck, W.W., Adams, R.M., Cure, W.W., Heagle, A.S., Heggestad, H.E., Kohut, R.J., Kress, L.W., Rawlings, J.O. and Taylor, O.C., 1983. A reassessment of crop loss from ozone. Environmental science & technology, 17(12), pp.572A-581A.

Lal, S., Venkataramani, S., Naja, M., Kuniyal, J.C., Mandal, T.K., Bhuyan, P.K., Kumari, K.M., Tripathi, S.N., Sarkar, U., Das, T. and Swamy, Y.V., 2017. Loss of crop yields in India due to surface ozone: an estimation based on a network of observations. Environmental Science and Pollution Research, 24(26), pp.20972-20981.

Lesser, V.M., Rawlings, J.O., Spruill, S.E. and Somerville, M.C., 1990. Ozone Effects on Agricultural Crops: Statistical Methodologies and Estimated Dose‐Response Relationships. Crop Science, 30(1), pp.148-155.

Mills, G., Sharps, K., Simpson, D., Pleijel, H., Broberg, M., Uddling, J., Jaramillo, F., Davies, W.J., Dentener, F., Van den Berg, M. and Agrawal, M., 2018. Ozone pollution will compromise efforts to increase global wheat production. Global change biology, 24(8), pp.3560-3574.

Sharma, A., Ojha, N., Pozzer, A., Beig, G. and Gunthe, S.S., 2019. Revisiting the crop yield loss in India attributable to ozone. Atmospheric Environment: X, 1, p.100008.

Singh, A.A. and Agrawal, S.B., 2017. Tropospheric ozone pollution in India: Effects on crop yield and product quality. Environmental Science and Pollution Research, 24(5), pp.4367-4382.

Singh, A.A., Fatima, A., Mishra, A.K., Chaudhary, N., Mukherjee, A., Agrawal, M. and Agrawal, S.B., 2018. Assessment of ozone toxicity among 14 Indian wheat cultivars under field conditions: growth and productivity. Environmental monitoring and assessment, 190(4), pp.1-14.

Tomer, R., Bhatia, A., Kumar, V., Kumar, A., Singh, R., Singh, B. and Singh, S.D., 2015. Impact of elevated ozone on growth, yield and nutritional quality of two wheat species in Northern India. Aerosol and Air Quality Research, 15(1), pp.329-340.

Van Dingenen, R., Dentener, F.J., Raes, F., Krol, M.C., Emberson, L. and Cofala, J., 2009. The global impact of ozone on agricultural crop yields under current and future air quality legislation. Atmospheric Environment, 43(3), pp.604-618.

9. What are websites for agriculture info?
1.    Food and Agricultural organisation of the United Nations 
https://www.fao.org/home/en/
2.    The World Bank: Agriculture and food
https://www.worldbank.org/en/topic/agriculture
3.    National portal of India: Minister of Agriculture and Farmers Welfare
https://www.india.gov.in/topics/agriculture
4.    ICAR-Indian Agricultural Research Institute
https://www.iari.res.in/index.php/en/research
5.    National Bank for Agriculture and Rural Development
https://www.nabard.org/
6.    National Food Security Mission
https://www.nfsm.gov.in/
7.    Directorate of Rice Development
https://drdpat.bih.nic.in/
8.    Department of Agriculture and farmers welfare, Ministry of agriculture and farmers welfare, Government of India
https://agricoop.nic.in/en/all-india-crop-situation
9.    Agriculture knowledge resources and information system hub for innovations https://krishi.icar.gov.in/

10. What are the key agriculture data websites?
1.    Directorate of economics and statistics, Department of Agriculture and farmers welfare, Government of India 
https://desagri.gov.in/divisions-cell/special-data-dissemination-standards-sdds/

2.    Indiastat: Agriculture
https://www.indiastat.com/data/agriculture

3.    Agriculture knowledge resources and information system hub for innovations https://krishi.icar.gov.in/


4.    Tata Cornell Institute: A decade of transforming food systems for the future (TCI)

https://tci.cornell.edu/?projects=district-level-database-for-indian-agriculture-and-allied-sectors

5.    International crops research Institute for the semi-arid tropics (ICRISAT)
http://data.icrisat.org/dld/

11. Important references / classic papers
Avnery, S., Mauzerall, D.L., Liu, J. and Horowitz, L.W., 2011. Global crop yield reductions due to surface ozone exposure: 2. Year 2030 potential crop production losses and economic damage under two scenarios of O3 pollution. Atmospheric Environment, 45(13), pp.2297-2309.

Heck, W.W., Adams, R.M., Cure, W.W., Heagle, A.S., Heggestad, H.E., Kohut, R.J., Kress, L.W., Rawlings, J.O. and Taylor, O.C., 1983. A reassessment of crop loss from ozone. Environmental science & technology, 17(12), pp.572A-581A.
Lesser, V.M., Rawlings, J.O., Spruill, S.E. and Somerville, M.C., 1990. Ozone Effects on Agricultural Crops: Statistical Methodologies and Estimated Dose‐Response Relationships. Crop Science, 30(1), pp.148-155
Mills, G., Hayes, F., Jones, M.L.M. and Cinderby, S., 2007. Identifying ozone-sensitive communities of (semi-) natural vegetation suitable for mapping exceedance of critical levels. Environmental Pollution, 146(3), pp.736-743.

Mills, G., Sharps, K., Simpson, D., Pleijel, H., Broberg, M., Uddling, J., Jaramillo, F., Davies, W.J., Dentener, F., Van den Berg, M. and Agrawal, M., 2018. Ozone pollution will compromise efforts to increase global wheat production. Global change biology, 24(8), pp.3560-3574.

Van Dingenen, R., Dentener, F.J., Raes, F., Krol, M.C., Emberson, L. and Cofala, J., 2009. The global impact of ozone on agricultural crop yields under current and future air quality legislation. Atmospheric Environment, 43(3), pp.604-618.
 

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