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Farmers can grow rice and wheat with 40 percent less water and overcome the threat of future shortages, says new study
To grow more food for more people under a changing climate, radical changes are needed to how we use water and other precious resources. Nowhere is this more obvious than India, where a growing demand for food combined with climate change is putting serious pressure on groundwater resources, especially in the populous Indo-Gangetic Plains. This area in the country’s northwest is the most important production area for India’s two staple cereals: rice and wheat. Science is confronting this challenge: a pioneering study demonstrates how rice and wheat can be grown using 40 percent less water, through an innovative combination of existing irrigation and cropping techniques. The study’s authors, from the International Maize and Wheat Improvement Center (CIMMYT), the Borlaug Institute for South Asia (BISA), Punjab Agricultural University and Thapar University, claim farmers can grow similar or better yields than conventional growing methods, and still make a profit.
The role and impact of rice and wheat
Rice-wheat farming systems dominate India’s agriculture, providing 75 percent of national food grain production, which translates to essential food, nutrition and income for hundreds of millions of people. Traditionally, farmers grow rice and wheat in rotation, planting a wheat crop following the rice harvest and so forth. This system has long benefited farmers with steady food and income, and provided insurance against failed crops, while rebalancing soil health and moisture.
But traditional management of these two crops is no longer sustainable. Conventional flood irrigation consumes vast quantities of water and energy, is labor-intensive, and can deteriorate soil health. Overuse of nitrogen-based fertilizers can pollute waterways and emit harmful greenhouse gases that cause climate change. To prepare their fields, farmers typically remove and burn residual stalks and stems, an inexpensive approach that generates dangerous pollution. Residue burning also wastes a precious resource: there is a large body of evidence on the benefits of recycling residues back into the soil, including regulating soil temperature and moisture, improving soil health, and increasing yields.
Faced with these problems, scientists and the government have been looking for ways to grow more wheat and rice with less water, and environmental damage.
The search for solutions
Until now, there has been little evidence about which combination of water saving techniques will maintain yields while remaining sustainable and affordable. Existing options include drip-irrigation, which offers an efficient alternative to traditional flood irrigation. Farmers use a network of aboveground pipes to deliver precise quantities of water into the soil around each plant. Pipes laid belowground, known as subsurface drip irrigation, target the plant’s root zone and eliminate evaporation from the soil. Drip irrigation systems can also deliver a dose of fertilizer directly to the plants, a practice known as “fertigation.” Despite these possibilities, there is little understanding of the best way to design an irrigation network that can work for both rice and wheat crops with no modifications between rotations.
The researchers tested eight combinations of promising techniques over a two-year period to understand which methods could help farmers save water and money. For each mix of approaches, they measured the ratio of grain yield to the amount of water and fertilizer applied, as well as costs — such as equipment and labor — and additional revenue that farmers would earn from using the techniques.
An optimal system for rice and wheat
The study found that rice and wheat grown using a sub-surface drip fertigation system, and combined with conservation agriculture approaches — zero till, retaining residues on soil surface and dry seeding — used at least 40 percent less water than flood irrigation for the same amount of yields, and would still be cost-effective for farmers. As well, the study found that both rice and wheat needed 20 percent less nitrogen-based fertilizer (urea) under a sub-surface drip fertigation system to obtain grain yields similar to that under flood-irrigated crops, which could improve ecosystem health and cut greenhouse gas emissions. The study outlines the optimal design of a subsurface drip irrigation system for conservation agriculture-based rice-wheat systems, offering valuable guidance for farmers and policy makers.
“We urgently need rice and wheat farming to become more water efficient,” said Balwinder Singh Sidhu, Agriculture Commissioner at the Government of Punjab. “These findings offer unique and practical solutions for India’s farmers in general and Punjab in particular, and also offer hope for a sustainable and food-secure future,” he said.
Putting the findings into action
This research shows that it is possible to dramatically reduce the amount of groundwater needed for irrigation while improving rice and wheat productivity in northwest India, as well other areas facing shortages. The study demonstrates this can be accomplished with significant benefits to farmers, saving them input costs and labor. But this transformation will not happen overnight.
Although farmers in this region are known for their willingness to adopt new technologies and practices, there is still a long way to go before sub-surface drip fertigation systems become mainstream. In India, government subsidies are important drivers for agricultural technology adoption, but the current policy landscape still rewards inefficient resource use, says ML Jat, a CIMMYT Principal Scientist who co-led the study:
“At present, the government provides farmers with subsidies for water, electricity, machinery and fertilizer, irrespective of efficiency,” he said. “But we cannot afford to have free water and electricity and still ensure agricultural sustainability in the region. The government can support farmers to adopt more efficient practices, by incentivizing only those systems that use resources sustainably,” he explained.
Further efforts are also needed to promote conservation agriculture, even though India’s rice-wheat farmers have made great strides in implementing these practices over the past two decades.
The authors point to signs of progress. For example, the Government of Punjab is testing alternatives to a blanket electrical subsidy for pumping water for irrigation, by piloting a direct benefit transfer on electricity to farmers. This would encourage farmers to be frugal about the electricity they use for pumping water, and drive them to adopt more approaches that economize water use in intensive rice-wheat systems.
“Governments in the region recognize the magnitude and complexity of the water, soil and air pollution problem,” said ML Jat. “Leaders are looking towards doubling farmers’ productivity while protecting natural resources,” he stated. “The future of farming depends on strong policies that prioritize investments in these promising approaches.”
Sidhu HS, Jat ML, Singh Y, Sidhu RK, Gupta N, Singh P, Singh P, Jat HS, Gerard B. 2019. Sub-surface drip fertigation with conservation agriculture in a rice-wheat system: A breakthrough for addressing water and nitrogen use efficiency. Agricultural Water Management. 216:1 (273-283). https://doi.org/10.1016/j.agwat.2019.02.019
The study received funding from the CGIAR Research Program on Wheat (WHEAT), the Indian Council of Agricultural Research (ICAR) and the Government of Punjab. The authors acknowledge the contributions of the field staff at BISA and CIMMYT based at Ludhiana, Punjab state.