Stubble Burning Solution? Farmers in China, Uganda Adopt High-Yielding Rice That Needs to be Sown Once Every Two Years

Long-lived perennial rice is essentially a variety of paddy that lets farmers sow just once while allowing up to eight harvests without sacrificing yield — that's about two years of not having to worry about planting crops.

Researchers developed this perennial rice by hybridising an Asian domesticated annual rice with wild perennial rice from Africa. Taking advantage of modern genetic tools to fast-track the process, the team identified a promising hybrid in 2007, planted large-scale field experiments in 2016, and released the first commercial perennial rice variety, PR23, in 2018.

And after spending five years studying perennial rice performance alongside annual rice on farms throughout China's Yunnan Province, researchers found that their yields were the same for the first four years. However, yields began to drop in the fifth year due to various reasons, leading scientists to recommend re-sowing perennial rice after a four-year gap.

Despite this, perennial rice had several advantages over regular rice. For instance, since they didn't have to plant every season, farmers growing perennial rice required nearly 60% less labour, and it halved their expenses on seed, fertiliser, and other inputs.

Further, the economic benefits of perennial rice differed across study locations, but profits ranged from 17% to 161% above annual rice. Even in periods when perennial rice suffered temporary yield dips due to pests, farmers still achieved a greater economic return than by growing the annual crop!

And if these traits were not enough to impress you, scientists plan to use modern genetic tools to introduce other desirable characteristics such as aroma, disease resistance, and drought tolerance into new crops, potentially expanding their reach across the globe.

A potential solution to North India’s stubble burning crisis?

Apart from the obvious benefits of introducing this variety in India, long-lived perennial rice could indirectly play a role in minimising the air pollution levels across India, particularly in the northern half of the country.

Once the crops have been harvested after the Kharif season (around September and October), a 'stubble' of the crops still remains on the fields. And since this leftover takes over a month to decompose on its own, farmers who need to sow the next crop as soon as possible are driven to burn the stubble to speed up the process. However, the winds sometimes end up transporting this stubble smoke eastwards, towards Delhi-NCR, causing the landlocked capital's AQI to plummet.

States like Punjab — known for the varieties of rice they produce and the agricultural technology they deploy — are especially held back by stubble burning due to its harmful impact on air quality, human health and the environment as a whole.

However, in the hypothetical scenario wherein this high-yielding long-lived perennial paddy can replace the existing varieties with some minor modifications, farmers would then be able to obtain multiple yields from the crop, and their need to burn the stubble after harvest will be eliminated.

Of course, there are a host of other factors that will have to be considered before realistically implementing such a drastic change, but its potential benefits make it worth looking into.

"I think now, with perennial rice in farmers' fields, we have turned a corner. We have been feeding humanity by growing these grains as annuals since the dawn of agriculture, but it wasn't necessarily the better way. Now we can consciously choose to make a better crop and a better, more sustainable agriculture. We can fix the errors of history," says Erik Sacks, professor in the Department of Crop Sciences at the University of Illinois and co-author of the report on long-lived perennial paddy.

T​he findings of this study are highlighted in Nature Sustainability and can be accessed here.

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