Alternative grains like millets and sorghum could help India cope better with the impact of global heating on agriculture and variations in supply than continuing to rely on rice and wheat alone. This is the heartening conclusion of a new study, but it also cautions that the cultivation area should be selected with care to avoid any production shortfalls.
An international team of scientists modelled crop cultivation and growth and found that, compared to finger millet, pearl millet and sorghum, “rice yields are significantly more sensitive to inter-annual fluctuations in monsoon rainfall on both irrigated and rain-fed croplands.” The team included scientists from universities in the US – University of Delaware, Columbia University, Yale University and Washington State University – and from the International Institute for Applied Systems Analysis, Laxenburg, Austria; and the Indian School of Business, Hyderabad.
Their study shows that allocating more cropland to alternative grains can help stabilise grain production in a variety of climatic conditions. It “adds to the empirical information needed for comprehensively assessing the potential co-benefits and tradeoffs associated with increased alternative grain production,” their paper, published on June 13 this year, says.
Kyle Frankel Davis, of the Data Science Institute at Columbia University and one of the authors of the paper, told The Wire that the study “shows for the first time that the yields from grains such as millet, sorghum, and maize are more resilient to extreme events like droughts.” On the other hand, the yield of rice – India’s main crop – declines to a greater extent during extreme weather conditions. So “by relying more and more on a single crop – rice – India’s food supply is potentially vulnerable to the effects of varying climate,” Davis cautioned.
He and his colleagues began by examining the historical links between inter-annual variations in temperature and rainfall and rain-fed yield variability for five monsoon crops – rice, finger millet, maize, pearl millet and sorghum – between 1966 and 2011. They focused on yields under rain-fed conditions since most of the rice, maize and millets grown in India are done so in rain-fed conditions.
Then, they combined district-level crop production data with average temperature and rainfall numbers for June, July and August, from 1966 to 2011. They used computer models to estimate the grain yield responses to changes in rainfall and temperature.
Most previous studies on links between climate variability and crop yields in India have focused on rice and wheat but haven’t compared them in turn to alternate grains. At present, rice accounts for 44% of India annual grain production and as much as 73% during the kharif season. Maize accounts for 15%, pearl millet 8%, sorghum 2.5% and finger millet (1.5%) during kharif.
The scientists found that, compared to rice, the alternative grains experienced smaller declines in yield under climate extremes. However, there was a catch: while the alternatives were more resilient, they didn’t scale as well as rice did, and rice plants are known for their high yield. For example, increasing the amount of cropland allocated just to the coarse grains reduced their yield by 17% under drought conditions and by 18% in non-drought years. In contrast, allocating more land to all alternative grains, including maize, appeared to enhance production by 39.6% under drought conditions and by 37% during non-drought years.
According to V. Geethalakshmi, the study is important because it employs a technique called model inter-comparison, an increasingly useful part of agri research around the world in the last half decade, to make more accurate predictions and reach conclusions closer to reality. Geethalakshmi is a professor at the agro-climate research centre at the Tamil Nadu Agricultural University, Coimbatore. Her team has been working with Columbia University on the Agricultural Model Intercomparison and Improvement Project involving 30 countries.
She added that, from a practical point of view, such model predictions based on future changes in temperatures and rainfall, attributed in turn to climate change, can help policymakers designate alternate crops to offset declining farm yields.
India’s climate variability has increased both in area and over time over the past half century. The total monsoon rainfall in some regions has fallen, extreme rainfall events have become more frequent and rainfall distribution has been becoming more uneven.
Consequently, the ministry of agriculture has recognised the effects of climate change on agricultural crops. In a written reply to a parliamentary committee, the agriculture ministry acknowledged in January this year that rice, wheat, maize, sorghum, mustard, potato, cotton and coconut crops are likely to be adversely affected by climate change. The ministry also said that the production of rice could fall by 4-6% by 2020, of wheat by 6-23% by 2050 and of maize by 18% by 2050, all thanks to climate change. Then again, it also pointed out that, production of rice could be increased by 17-20% through proper and timely interventions.
Recent research from 10 countries that consume the most rice has shown that the quality of grains could suffer as well. For example, rice could produce fewer proteins, vitamins and minerals essential for humans in response to rising carbon dioxide concentrations that are implicated in global heating. They confirm previously reported declines in protein, iron and zinc levels, offer additional information on consistent declines in vitamins B1, B2,B5, and B9 and – conversely – an increase in vitamin E in rice produced under higher carbon dioxide conditions.
However, not all scientists agree with the international study’s approach. For one, in the case of rain-fed systems in India, it is “intra-district variability that is crucial. So district-wise data tells us very little,” Rajeswari Raina, a professor at the School of Humanities and Social Sciences, Shiv Nadar University, Gurgaon, said.
So scientists need to go beyond “banal” yield responses and understand the social-ecological systems, including how human and/or social responses change according to changes in temperature and precipitation, she added.
Intra-district variation in production and technological capacities have not received much attention in India. Even the detailed block-wise soil maps contain little information on the nature of habitation and land-use patterns, physical infrastructure and production capacities or calorie demands.
“Unfortunately, little has been done thus far to analyse or relate the available information within agricultural research organisations with the socio-economic changes in rain-fed agriculture,” Raina said.
T.V. Padma is a freelance science journalist.