Урожайность сахарного тростля в Индии растет, но культура становится уязвимой к климатическим изменениям

Sugarcane cultivation across parts of India’s Deccan Plateau is becoming more productive. But, it is also becoming more vulnerable to climate variability, a new long-term study finds. Sugarcane has long shaped India’s rural economy. It powers sugar mills, supports ethanol and bioenergy production, and sustains millions of farmers. But the crop is also at the centre of mounting concerns over water use, particularly in semi-arid regions facing recurrent droughts and groundwater stress. The study analysed 22 years of sugarcane production trends across five districts in Maharashtra and Karnataka to understand how cultivation, yields and production patterns have changed under varying climatic conditions. “We noticed that sugarcane cultivation in Maharashtra and Karnataka was increasingly being affected by climatic variability, even though it remains one of the most important economic activities across the Deccan Plateau,” says Krishna Kumar from the Department of Applied Science and Humanities at MIT-ADT University, Pune, and one of the study’s researchers. Across climate zones Sugarcane production trends in India have been studied extensively at national and state levels, but long-term district-level analyses incorporating weather variability remain limited. “The main concern was to pin down how climate variability impacts agricultural production in water-limited sugarcane systems,” adds Kumar. “This kind of insight matters a lot for creating climate resilient agricultural policies and planning better infrastructure.” For the study, researchers analysed sugarcane production trends between 1999 and 2021 in Ahmednagar, Solapur and Nashik in Maharashtra, and Bellary and Dharwad in Karnataka. The five districts span distinct agro-climatic zones across the Deccan Plateau. Bellary and Solapur lie in relatively dry regions, receiving less than 780 millimetres and around 500 mm of annual rainfall, respectively. Ahmednagar and Nashik fall across scarcity and plains zones that receive roughly 500 mm to 1,200 mm of rainfall annually. Dharwad lies in a transition zone with comparatively higher rainfall ranging from 620 mm to 1,300 mm annually. “Sugarcane performance in semi-arid regions is highly location-specific, says Kumar. “State averages often mask major differences between districts.” The study tracked three indicators: cultivation area, total production and yield per hectare. Researchers used crop data from the Directorate of Economics and Statistics and meteorological records from the India Meteorological Department and then applied statistical methods to identify long-term trends in sugarcane production. To understand changes over time, the researchers also divided the analysis into three phases –1999-2006, 2007-2013 and 2014-2020. Yield gains linked more to productivity Solapur emerged as the largest sugarcane-producing district among the five studied, with an average cultivation area of about 117 thousand hectares and average production of 10 million tonnes. Bellary recorded the highest average yield of sugarcane at almost 90 tonnes per hectare, while Dharwad had the lowest average yield at about 69 tonnes per hectare. Some districts showed clear signs of long-term productivity gains. Ahmednagar recorded a statistically significant annual yield increase of around 1.12 tonnes per hectare, while Nashik saw a similar annual increase of around 1.08 tonnes per hectare. “The yield gains seen in Ahmednagar and Nashik seem to be driven by a mix of factors,” says Kumar, adding that the trends may reflect improvements in irrigation, water management and farming practices over time. Across districts, average yields were generally higher during the later study periods than during 1999-2006. In Ahmednagar, average sugarcane yield increased from 69 tonnes per hectare during 1999-2006 to 87 tonnes per hectare during 2014-2020. Nashik saw an even sharper increase, rising from around 69 tonnes per hectare to 89 tonnes per hectare over the same periods. Bellary maintained consistently high yields through much of the study period, though researchers did not find a statistically significant upward trend there. Dharwad, meanwhile, showed more unstable patterns, with yields dipping during the middle phase before partially recovering later. The researchers found that yield was generally more stable than cultivation area or total production. Area under sugarcane fluctuated more sharply across several districts, which the researchers suggest may reflect changing water availability and irrigation conditions. “In several districts, production growth happened mainly because yields improved, rather than because more land was brought under cultivation,” says Kumar. The study suggests that improved crop traits, fertiliser use and field management practices may have contributed to these gains. Climate variability The study also highlighted differences in how districts performed under climate stress. “Solapur comes out as the most stable in terms of yields,” says Kumar. Bellary, meanwhile, maintained the highest mean yields despite being located in a drier zone. Extreme weather years continued to influence sugarcane production across multiple districts, with sharp swings between drought-affected and favourable years. Ahmednagar recorded its lowest yield in 2003-2004 at 47 tonnes per hectare. In contrast, its highest yield came in 2020-2021 at 108 tonnes per hectare. The researchers found that years with lower rainfall deficits and fewer heat stress days were generally associated with stronger yields, while drought conditions and prolonged high temperatures coincided with poorer crop performance. Researchers compared crop performance with weather indicators. “The drought index, moisture adequacy index, and heat stress days are strongly related to sugarcane yields in the study districts,” says Kumar. Ahmednagar recorded mean drought index values near -0.79 along with around 89 heat stress days per crop year. Solapur showed even greater heat stress exposure, with roughly 127 heat stress days annually. The researchers say the findings point to moderate to high vulnerability under future climate change, particularly in water-limited regions. “Warming temperatures are projected to push up crop water requirements and also increase the chance of yield losses under water limited conditions,” says Kumar. Priyanka Singh, an independent expert and senior scientific officer (chemistry) at the UP Council of Sugarcane Research, says the findings broadly align with trends already being observed across major sugarcane-growing regions in India. “There is increasing evidence that prolonged dry spells, erratic monsoon distribution, higher temperature episodes and water stress are affecting cane productivity.” According to Singh, the findings should not be interpreted as suggesting that sugarcane cultivation cannot continue in these regions. Instead, many areas are already shifting toward drip irrigation, fertigation, improved water scheduling and stress-tolerant crop varieties. “The broader national trend is not simply declining sugarcane productivity due to climate change, but increasing variability and increasing dependence on efficient management,” she says, adding that the study’s climate analysis should be interpreted carefully because meteorological records were limited for some districts. Bellary and Dharwad, for instance, had relatively few long-term meteorological records available for analysis. Despite these limitations, researchers say the findings can help guide water management and agricultural planning in water-scarce regions. “The evidence supports that climate-smart agriculture practices, efficient irrigation systems, and drought contingency measures will matter more and more,” says Kumar. This article was first published on Mongabay.