Understanding emissions from rice cultivation

Rice is conventionally grown in flooded soils as it can tolerate anaerobic conditions. Furthermore, the advantages of flooded soils include minimal weeds and irrigation needs, availability of nutrients like phosphorus, iron, manganese, silicon, and potassium, and consequently, less need for fertilisers (Kundu 2016).

Under flooded conditions, rice emissions occur when methanogen bacteria react with the organic matter present in the soil to produce methane gas (Conrad 2020).

Organic matter in anaerobic soil → CO₂ + CH4

Methane emissions from the paddy field are contingent on the duration for which the soil remains under water (anaerobic condition). Further emissions also depend on the area under cultivation, irrigated area, and irrigation regime (Vasudha Foundation 2019) as well as soil type.

Table 1. Types of rice cultivation regimes and their status in India

Source: MoEFCC. 2021. India: Third Biennial Update Report to the United Nations Framework Convention on Climate Change.
Ministry of Environment, Forest and Climate Change, Government of India.

Emissions from the top 12 riceproducing states in India

In India, rice is predominantly produced in 12 states: West Bengal, Uttar Pradesh, Punjab, Telangana, Odisha, Chhattisgarh, Tamil Nadu, Andhra Pradesh, Bihar, Madhya Pradesh, Haryana, and Assam. These 12 states collectively produced more than 100 million tonnes (MT) of rice on 36.5 million ha of land in 2019–20; the other 16 MT were produced across other regions (MoAFW 2021a).

West Bengal, Uttar Pradesh, and Punjab are the top three rice producers, contributing more than 34 per cent to the total rice production (MoAFW 2021a). Across states, there has been an improvement in rice productivity over time. However, Punjab leads the states in productivity with a yield of 4366 kg/ ha, followed by Andhra Pradesh and Tamil Nadu. Chhattisgarh, Odisha, and Bihar are the tail-enders, having rice productivity 50 per cent lower than Punjab.

Rice emissions vary across states due to differences in soil type as well as irrigation regimes (Figure 2), among other things. Eastern states like Bihar and West Bengal fall under the lower Gangetic plains and have alluvial and loamy soil. They receive an average rainfall of 100–200 cm per year with a groundwater depth of 2–10 metres below ground level (mbgl). The water retention quality of these types of soil is high, and therefore, rice cultivation occurs under deepwater, flood-prone, and continuous flooding irrigation regimes, which easily facilitate the anaerobic reaction by methanogen bacteria over a longer time duration and release emissions. Similarly, the northeastern state of Assam falls under the East Himalayan agro-climatic zone, with red loamy and alluvial soil, which has high water retention; it experiences rainfall above 200 cm and has a shallow water table of 2–5 mbgl (NITI Aayog 2024).

Figure 2. Rice water regimes across 12 rice cultivating states

Source: Pathak, H, A Bhatiya, N Jain, and P.K Aggarwal. 2010. Greenhouse Gas Emission and Mitigation in Indian Agriculture.

Andhra Pradesh, Tamil Nadu, and Telangana fall under the southern plateau, a semi-arid region, receiving 50– 100 cm rainfall and ground water table of 2–20 mbgl. While they have red and yellow loamy soil, they receive comparatively less rainfall. Hence, a major portion of the rice cultivation area falls under continuous flooding and single aeration irrigation regimes. Therefore, these states feature in the middle of the emission spectrum of the top-12 rice-producing states (Bansal 2024).

North-western states like Punjab and Haryana emit less methane despite having a 99 per cent irrigation rate. They fall under the agro-climatic zone of the trans-Gangetic plain with sandy and loamy soil (P.K. Gupta et al. 2009). They have a low soil organic carbon content, and the lowest water retention rate (Gogoi, Baruah, and Gupta 2008). They receive an average rainfall of 70–125 cm, and have a deep water table at 10–40 mbgl before the monsoons. Hence, the major portion of rice cultivation area falls under the multiple aeration regime, which has the lowest emission factor. However, these states pump more and more groundwater into the field to make it suitable for rice cultivation.

Based on the rice emission trends of the selected 12 states, taken from the GHG platform report, the eastern states of Assam and West Bengal have the highest emissions per hectare, followed by Odisha and Bihar, together contributing to 42 per cent of total rice emissions in the country (Figure 2). The soil quality, annual rainfall and depth of the water table impact the high emissions from these states.

Figure 3. Assam, West Bengal, and Bihar contributed highly to the emissions per hectare (CO₂e) in 2019

Source: Authors’ analysis
Note: The issue brief only considers methane emission from rice cultivation represented as CO₂e using GWP.

Alternate cultivation strategies

Conventional rice cultivation under irrigated condition involves land preparation, puddling to create a mud-like soil consistency, seedbed preparation for germination, transplanting seedlings into the main field after repeated puddling, and meticulous water management. This technique is not only waterinsensitive, but also time-consuming. Practising the conventional method of sowing over a long period of time has caused issues, such as dwindling of water tables, labour shortages during peak seasons, and declining soil health (Kaur and Singh 2017). This necessitates an alternate establishment strategy to ensure rice yield and natural resource sustainability.

Moreover, sustainable rice cultivation should ensure that interests of small-scale farmers and communities that depend on rice for food and income are safeguarded.

A few alternative rice cultivation methods have been established, which could help mitigate emissions while increasing yield and reducing labour requirements during the peak season, thus resulting in improvement in food security and farmers’ income. The alternative rice cultivation strategies that have the potential to reduce emissions include direct-seeded rice (DSR), system of rice intensification (SRI), alternate wetting and drying (AWD), and replacing urea with ammonium sulphate as noted in Table 2.

Table 2. Alternative rice cultivation strategies along with their economic implications

Source: Authors’ compilation
Note: The list does not represent all the rice emission mitigation strategies. However, these are the most popular and commonly used strategies across geographies. Other methods such as laser land-levelling exist.

We can observe from the table that alternate cultivation methods reduce emissions and have several other benefits such as water savings, low labour requirement, and low fertiliser requirement. They also increase farmers’ income in terms of cost savings as well as additional income due to an increase in yield.

As per India’s Third Biennial Update Report, currently, 0.03 Mha area is under SRI cultivation, while 0.041 Mha is under DSR.

State-wise emission reduction potential in alternative rice cultivation techniques

According to India’s Third National Communication to the United Nations Framework Convention on Climate Change (UNFCCC), the agriculture sector accounted for emissions amounting to 421 MtCO₂. The rice emissions were 73.4 MtCO₂, 17.4 per cent of the total. Therefore, it is important to analyse the emission mitigation potential of the alternate cultivation strategy described in the previous section.

Table 3 showcases the emission reduction potential of top rice-producing states using alternate cultivation methods. Based on the literature review, two to three strategies have been mentioned against a state, representing the mitigation potential against each method. DI, SI, DSR, and AWD can be applied to irrigated areas, while SDC can be used in rainfed regions, as it is difficult to control irrigation water in flood-prone and deep water regions.

Table 3. State-wise methane emission reduction potential for alternative rice cultivation techniques

Source : Author’s analysis
Note: Note: 1)The table represents only the studies from the top 12 rice-producing states of India (except MP and CG).
2) For future emissions projections of rice, we obtain historical trends of absolute increase/decrease of area under rice cultivation between 2018 and 2024, and then project the same trend into the future to 2030. For Telangana alone, where the area under rice cultivation has seen a sharp rise, we limit area under rice cultivation to 24 per cent, which is highest among states. We also assume future shares of cultivation practices to remain same as 2009, received from Pathak et al. 2010.
3) We make a simple assumption that 100 per cent of area will shift to this option to estimate the emissions reduction potential. In reality, the potential will be lower if only a fraction of this area actually shifts to the given option.
4) AWD = alternate wetting and drying; DSR = direct-seeded rice; SRI = system of rice intensification; DI = drip irrigation.

We have made the following observations based on available technologies for rice cultivation as noted in Table 3.

• Drip irrigation has shown the most optimistic results in reducing emissions, but there have been just a handful of studies backing up this claim, specifically in the Indo-Gangetic plains. Research shows that drip irrigation helps in increasing the yield and net income gain. Also, the initial cost of installing the system is high, hence the intervention can be promoted on high priority in states with water scarcity, such as Punjab, Haryana and Uttar Pradesh, by incentivising the machinery for the farmers.
• System of rice intensification has shown significant emissions reduction, especially in the southern states, along with a higher yield without raising the cost of cultivation, providing net profit that can withstand adverse weather conditions such as strong winds and cyclones. The technique can be promoted on high priority in coastal states that experience frequent cyclones.
• Techniques like DSR and AWD have also shown emission reduction potential as well as great water savings, but have thrown up fluctuating results regarding yield benefits and economic return. Hence, these will require more regionspecific research to scale up the benefits. They can be promoted in states which require lowinvestment techniques.
• Short-duration cultivars (SDCs) are the bestsuited strategy for the rainfed ecosystem (deepwater and flood-prone regimes), as managing water resources is scarcely a practical mitigation method. However, development of rice cultivars that have low emission potential and high yield return can be a possible strategy to reduce emission in states that receive higher rainfall, such as Assam.
• Adding alternate chemical substrate to the farm, such as ammonium sulphate, has also shown emission mitigation potential and higher yield in limited laboratory experimental studies, but its impact on farmers’ net income and health implications or the nutritional quality of the rice produced are not yet known. Hence, more field research may be required before scaling up the intervention.

State-wise emission-income correlation

In developing nations like India, agriculture is one of the most price- and income-sensitive sectors. The contributing factors are the current lower income of the farmers, high investment requirements and lack of skills for modern techniques, and higher dependencies on natural factors. In this section, we highlight the correlation between income and emissions from rice cultivation across states (refer to Figure ES1). The schematic describes minimum rice-linked income per hectare of rice cultivation land on the x-axis, and the emissions per hectare of rice cultivation land on the y-axis .The x-axis variable represents the ratio of minimum rice income (which is calculated based on the reported production of rice and the minimum support price declared by the government) and the rice cultivation area, whereas the y-axis variable is the ratio of the emissions from rice within a state and land under rice cultivation.

From Figure ES1, we can observe that the first quadrant has mainly southern states (plus West Bengal) that have high income and high emissions per hectare. The second quadrant has eastern states with low income and high emissions. In the third quadrant are central states with low income and low emissions, while in the fourth quadrant are northern states with low emissions and high income. The target is to therefore move most states towards the green zone (fourth quadrant), where they may emit less, but ensure that farmer incomes are not hit.

Sustainable rice production must involve cultivation of rice that ensures lower emissions as well as higher resilience to the impacts of climate change. Some of our recommendations to support sustainable rice cultivation are as follows.

Continued research on new cultivation methods that increase reliance of rice and lower emissions: There is a noticeable deficiency of regional/statespecific literature regarding the methane emission reduction potential of DSR, AWD, SRI, DI and SDC. Although a slim body of literature exists on the benefits of alternative rice cultivation techniques, more experimental plots at different agroecological zones are required for a comprehensive understanding of the benefits and challenges of these methods.

Building farmer’s capacity for sustainable practices: Awareness regarding alternative rice cultivation techniques is required, along with dedicated capacity building and demonstration programmes. These must be set up at village and block levels for better dissemination. Farmers learning the process must be made aware of success stories of the various different techniques so that they gain confidence.

Bridging the technology gap: Essential machinery for sustainable rice cultivation includes drum seeder for direct seeding, laser land-levellers for uniform field surfaces and efficient water management, mechanised equipment for post-harvest operations to reduce losses, village-level storage facilities to preserve harvested rice, and controlled irrigation systems for optimal water usage, as well as distribution of climate-resilient seed varieties. Access to these technologies is crucial for both mitigation and adaptation strategies, promoting water conservation, minimising post-harvest losses, and enhancing overall crop efficiency.

Bridging the communication gap: Timely forecast of upcoming weather patterns regarding heat waves and rainfall should be broadcasted at the regional level, along with an advisory regarding sowing and harvesting windows. This will allow the farmers to adjust their crop calendar and adapt better to climate change. Moreover, benefits or an incentive structure regarding government schemes for promotion of these alternate cultivation strategies must be communicated effectively.

Creating a market for sustainable rice: There is a need to create consumer demand for sustainable rice. It can create the push required to adopt the mitigation techniques at the farm level. One way is to label the sustainably produced rice so consumers can make informed choices and contribute towards the decarbonisation of agriculture.

As one of the major staple crops in India, rice cultivation needs to move towards building resilience against the impacts of climate change, and reducing emissions, so that the country is able to meet the food demand sustainably. Therefore, coordinated efforts from farmers, agricultural extension workers, national and state governments, as well as private sector players, are essential to ensure the adoption of sustainable and climate-smart strategies for rice cultivation.