A Greener Revolution In Rice Needed To Make It Climate Change Compatible

India has made impressive strides in raising rice production since the 1960s, but those gains will be under threat if the crop does not adapt to climate change. Though rice is a versatile crop and is grown in different agro-ecologies, it is also an environmentally vulnerable crop due to its dependence on water.

Climate change is producing erratic weather behaviour. Extreme weather events are occurring more frequently, as we have seen in north India recently. A few days of heavy downpour are followed by long dry spells. Coastal areas have to deal with seawater ingress. There are unseasonal rains as well.

Intensive cultivation has caused groundwater depletion, particularly in areas like Punjab, which produces a tenth of India’s rice production.

India’s rice production has grown nearly sixfold since the 1950s, from 21.5 million tonne to 124.5 million tonne, even as the population has increased nearly fourfold. The yearly per person rice availability has increased from 58 kg to 69 kg. With better incomes, people will consume more proteins and less carbs. But rice consumption will increase because of population growth, more poor people eating better with rising incomes, and a policy that favours the distribution of rationed rice. Many eastern states are also incentivising rice cultivation as they try to pull poor farming families out of poverty. So, even though rice consumption is linked to elevated blood sugar levels and diabetes, and the government is pushing the consumption of millets, rice consumption might decline only gradually.

But we cannot cultivate rice the way we have. Intensive cultivation is inevitable with shrinking arable land. But it has to be done sustainably. In 2021, the World Meteorological Organisation estimated that rice farming accounts for 8% of the earth-warming methane emissions caused by human activity. India has assessed its methane emissions from paddies at 4.75 million tonne in 2020, which is 20% of the world’s methane emissions from rice cultivation.

Methane is generated from the decay of organic matter in puddled fields of transplanted rice. This is how rice cultivation has evolved. A kg of puddled transplanted rice requires 3,000–4,000 litres of water. But rice does not need so much water, says AK Singh, a rice breeder who has worked on popular basmati varieties and is director of the Indian Agricultural Research Institute, Delhi—whose campus was one of the test sites for dwarf varieties of Mexican wheat that heralded the Green Revolution.

The cultivation of transplanted rice in puddled fields, where the soil is churned to a fine consistency to make it impervious, has evolved as a response to weed growth. Rice is heavily infested with weeds. Standing water in rice fields acts as a weedicide. But puddling causes huge evaporation losses; and though decaying organic matter enriches the soil, it prevents the percolation of water and the recharge of aquifers.

Scientists are recommending direct-seeded rice as an alternative. The International Rice Research Institute, Manila, which ushered in the Green Revolution in rice with the IR8 high-yielding and semi-dwarf variety in the 1960s, has formed the Direct Seeded Rice Consortium as a partnership between agritech companies, research organisations, and donor agencies to improve the environmental and socio-economic sustainability of rice production systems. The Punjab government is giving Rs 1,500 an acre to rice farmers to switch to direct seeding. In Haryana, the incentive is Rs 4,000 an acre.

In direct seeding, rice is broadcast or sown with seed drills in moist fields that have been ploughed and planked, preferably with a laser level for even distribution of water. Weed control is done with herbicides that are applied immediately after sowing and 25 days later. In puddled and transplanted fields, 30 irrigations are given for a 160-day crop. The water column is 5 cm high. In direct seeding, 22 irrigations are needed for the same duration (seed-to-grain) crop, and the water height is about half. There are water savings of up to 35%, a reduction in greenhouse gases, and a labour savings of Rs 4,000 an acre, according to Singh. Another gain is faster maturity as direct-seeded plants are spared the shock of transplanting, which requires a recovery time of about a week.

Singh recommends DSR even for regions, like eastern India, that receive heavy rainfall and are susceptible to flooding. These areas don’t have assured irrigation, like Punjab, and have to depend on rainfall. If the monsoon plays truant, transplanting is affected. Downpours result in runoffs. A better alternative is to store rainwater in ponds and use it sparingly by practising DSR.

As per IRRI, Malaysia, Vietnam, Cambodia, and Sri Lanka have high shares of DSR. But it has not caught on in India. Last year, only 70,000 ha out of 3 million ha under rice in Punjab were under DSR, hugely underperforming the target of about 2 lakh ha. This year, the target has been missed because of early rains. But farmers are also wary of DSR because of yield losses caused by weed infestations. The herbicides currently being applied are not very effective. Singh says IARI has developed rice tolerance to the herbicide Imazethapyr, which kills a variety of weeds. This has been done through conventional mutation breeding without the use of genetic engineering technology, which the country is touchy about. The traits have been transferred to two blockbuster basmati varieties, and researchers at other institutes are working on transferring them to non-basmati rice varieties. IRRI and the agrichemical company BASF have also developed rice varieties that are resistant to two of BASF’s herbicides.

Farmers also need rice varieties that are suitable for DSR. Though there are varieties like Shabhagidhan, Pyari, and CR Dhan 201 and 202 of the National Rice Research Institute, there are not enough of them.

Apart from priming rice for low water use, it will also have to adapt to other environmental stresses. Eastern India is prone to flooding. It needs rice varieties that can stay underwater for a long time. In 2009, a rice variety, Swarna, with the submergence tolerance gene Sub-1 was released. It allows the plant to remain completely submerged in muddy water for 7–10 days and in clear water for 14 days. The gene was isolated from a variety called FR 13A (FR for flood resistance) derived from an heirloom variety, Dhalputtia, of Odisha. The Sub-1 gene has been incorporated into many popular rice varieties for cultivation in areas that are prone to flash floods.

While underwater, scuba rice, as it is called, remains dormant. When the floods recede, it uses conserved carbohydrates to regenerate.  IRRI says the average yield of scuba or Sub1 rice varieties is 4.5–6.5 tonnes per hectare, and the yield advantage is 1-3 tonnes per hectare over those that don’t have the Sub1 gene. 

Since flood prone areas are also vulnerable to droughts, rice varieties stacked with both submergence and drought-tolerant traits have been developed. Easy genome editing regulations notified by the government last year have enabled the development of a rice variety popular in Telangana and Andhra Pradesh, MPU 1010, that is tolerant to drought and salinity. It is being tested in all India coordinated trials.

The research trend is towards developing shorter-duration rice varieties, say 100 to 120 days. These require less water compared to 150–160-day rice.

And while reducing water use and greenhouse gas emissions, rice varieties also have to be protected from pests and pathogens that will evolve with changing weather patterns. So scientists, agronomists, and farmers have their work cut out for them. We have had the Green Revolution. We need to make it greener.