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[NEW DELHI] Stagnating yields and rising temperatures have been a concern for wheat growers in India — the world’s second largest producer of the staple after China. However, farmers in the country’s eastern states can improve production by sowing early, says a satellite-based imaging study.  

Using a new prediction method that estimates yields in fine resolution, the study attributes low wheat yields in India to late sowing and warmer temperatures. The study was published in September in Environmental Research Letters.

“Farmers may be able to increase wheat yields by sowing earlier”

Meha Jain, University of Michigan

“Farmers may be able to increase wheat yields by sowing earlier,” Meha Jain, assistant professor at the University of Michigan, and lead author of the study, tells SciDev.Net. “However, there likely are constraints in some regions which make it challenging for farmers to sow wheat earlier,” she says.

Jain and her team applied an algorithm that uses crop models to simulate ground data by translating satellite-derived vegetation greenness to estimate wheat yields or the difference between the realistic maximum potential yields that can be achieved versus actual mean yields.

Using this novel method, Jain’s team had mapped smallholder farms in the north-western Indo-Gangetic Plains during the period 2001 – 2015 at a resolution of 30 metres to estimate wheat yields.

In the north-western states of Haryana and Punjab, known as India’s wheat belt, yields were higher with low yield-gaps. But in the eastern states of Uttar Pradesh and Bihar, yields were lower along with higher yield-gaps caused by heat stress towards the end of the growing season. Yield gap is calculated as a percentage of average farm yield in a given area.  

In the warmer eastern states, earlier sowing will ensure that wheat matures before the onset of heat and by implementing the best management practices from the region, yields can increase by 32 per cent. This strategy, if combined with the planting of heat-tolerant varieties, can further enhance yields in the long term. Deepak Ray, senior scientist at the Institute on the Environment, University of Minnesota, says that the authors are pioneers of this method.

This is an “interesting method to completely bypass the requirement to collect field-scale yield but its applicability would be more accurate in mono-culture settings,” Ray says. In India, he explains, there can be contamination from fields growing barley, rapeseed, rice or maize.  

“We all understand that wheat needs to be planted in time and late planting is always exposed to heat stress,” says Pramod Aggarwal, leader of the South Asia Regional Programme for the CGIAR Research Programme on Climate Change, Agriculture and Food Security.  

“The problem is that this is theoretical and implementation is a real challenge,” Aggarwal says. “If it is Bihar that we are talking about, a lot of the area is prone to floods and rainfall may continue late — there are many issues that one has to take into consideration.”
This piece was produced by SciDev.Net’s Asia & Pacific desk.