Shifting to millets increases groundwater recharge more than drip irrigation in India’s northern plains: Study

Switching from rice to millets such as pearl millet & sorghum during the Kharif season and shifting from wheat to sorghum in the Rabi season could lower water consumption by 32%

By Shagun
Published: Thursday 12 October 2023
Representative photo: iStock_

Switching from rice to pearl millet (bajra) and sorghum during the Kharif season and shifting from wheat to sorghum (jowar) in the Rabi season could lower water consumption in the Indo-Gangetic Plains (IGP) by 32 per cent and boost farmers’ profits by 140 per cent, according to a new study.

The Ganga basin has seen a significant groundwater depletion in recent years, raising questions about the sustainability of present agricultural practices. Among the solutions proposed to address this unsustainable water consumption, crop switching has received growing attention.

However, its potential to produce co-benefits or trade-offs for other dimensions of sustainability — food supply and farmers’ profits — remains largely unquantified.

Six researchers from the Indian Institute of Technology Bombay, University of Delaware, Columbia University and Yale School of the Environment analysed crop shifting’s prospect in 124 districts of three states: Uttar Pradesh, Bihar and West Bengal — covering the upper, middle and lower Ganga basin in the agricultural belt of India.

Of the country’s total food production, 30 per cent comes from these three states, which are a part of one of the world’s most important and complex groundwater-dominated food systems — cereal production in the IGP.

Stretching from Punjab in the west to West Bengal in the east, IGP is the most populated region in the country, with a population of 400 million people, according to several studies.

Along with benefits in water consumption and farmers’ incomes, the study, published in the journal Nature Water on October 9, 2023 also found an improvement in calorie production by 39 per cent.

The authors focussed on cereal crops (rice, wheat, maize, bajra, sorghum and barley), which cover 52 per cent of the total crop area. These crops account for 50 per cent of the total water consumption in the three states of the IGP region and contribute a significant fraction of calories for the Indian population.

With the optimised crop replacement scenario, there could be 55 per cent and 9 per cent water savings in the Kharif and Rabi seasons, respectively, compared with present practices. The increases in profit from the proposed alternatives are 139 per cent and 152 per cent for the Kharif and Rabi seasons, respectively.

The authors developed a multi-objective optimisation model that reallocates cropped areas between cereals to maximise calorie production and farmers’ profits while minimising water consumption (and subsequent energy use) at the district level.

The intensively cultivated rice–wheat system results in a high agricultural water demand for cereals and is primarily met by irrigation — 40 per cent of which comes from groundwater sources. However, rice and wheat are the major staple cereals produced on a large scale in the IGP and meet 63 per cent of the calorie demand of the country.

The authors compared the benefits of crop switching vis-a-vis improving irrigation efficiency — from flood to drip irrigation — and found that there is a larger reduction in groundwater depletion and energy savings with the first method.

Continuing with the same crop with drip irrigation improves net groundwater recharge by 34 per cent, whereas changing crop practices improves net recharge by 41 per cent. However, the drip irrigation method does not improve calorie production or farmers’ profits.

However, a third scenario — a combination of crop switching and drip irrigation — showed the greatest improvements in net recharge at a district level and reduced groundwater depletion by 78 per cent.

The team of researchers — Ruparati Chakraborti, Kyle Frankel Davis, Ruth DeFries, Narasimha D Rao, Jisha Joseph and Subimal Ghosh — highlighted how a multi-objective approach of reducing water consumption and increasing calorie production and farmers’ incomes will benefit more than a single objective.

If crop switching is carried out on the basis of only one objective of water consumption minimisation, water savings can be increased by 4 per cent. At the same time, there will be a reduction in the improvements in calorie production and profit by 23 per cent and 126 per cent, respectively, compared with the proposed solutions.

Similarly, when the maximisation of profit was considered as the only objective, the entire cropped area will be replaced by the highest profit-making crop — sorghum, as it has the highest minimum support price and lowest cost of cultivation.

“This scenario will increase profits by 58 per cent compared with the proposed solution from the multi-objective framework but, simultaneously, reduce calorie production by 18.5 per cent with a marginal increase in water savings of 2 per cent,” the study read.

Further, shifting from the rice–wheat system to nutri cereals also provides more micronutrients and proteins than rice and wheat.

The findings showed sorghum and bajra are the dominant crops to replace rice and wheat, the study said.

“We conclude that there would be a greater production of protein and other micronutrients (iron and zinc) in the replacement scenario, with 46 per cent increased production of protein and 353 per cent and 82 per cent increased production of iron and zinc, respectively. This is another benefit of shifting from rice to nutri cereals from the consumer perspective,” it added.

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