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Nitrogen-efficient crops on the horizon?
In a new report, an international team of crop scientists under the lead of the International Maize and Wheat Improvement Center (CIMMYT) offer a method to breed wheat and feed crop varieties that will possess a trait known as biological nitrification inhibition (BNI). Plants that carry the BNI trait can suppress the loss of nitrogen (N) from the soil and improve the efficiency of its uptake and use by themselves and other plants.
The authors, who form part of a new BNI research consortium, propose transferring the BNI trait from those plants to important food and feed crops, such as wheat, sorghum and Brachiaria range grasses.
“Nearly a fifth of the world’s fertiliser, for example, is deployed each year to grow wheat, and the crop only uses about 30 per cent of the nitrogen applied,” says Guntur Subbarao, a researcher with Japan’s International Research Center for Agricultural Sciences (JIRCAS), and lead author of the study.
“If BNI research is successful, it could turn wheat, the world’s most widely-grown food crop, into a super nitrogen-efficient crop,” he explains. “Farmers would spend far less on fertiliser, and nitrous oxide emissions from wheat farming could be reduced by as much as 30 per cent.”
Nitrogen (N) fertilisers are a major source of agricultural emissions. About 70 per cent of N applied to crops in fertilisers is either washed away or flushed into the air as nitrous oxide (N2O), a greenhouse gas 300 times more potent than CO2.
“The most widely grown crop on the planet, wheat, is a major nitrogen user and N2O emitter,” says Hans Braun, director of CIMMYT’s global wheat programme. “BNI technology is one of several options we’re pursuing to reduce nitrogen losses from wheat farming, but more funding is needed.”
The study, which was recently published in Plant Science, also mentions high-BNI forage crops, such as certain tropical Brachiaria grasses that produce brachialactone, a powerful BNI chemical.
The grasses can be eaten by cattle, while reducing N20 emissions and improving soil fertility for other crops grown in rotation on the same land, according to Michael Peters, leader of the tropical forages programme at the International Center for Tropical Agriculture (CIAT).
“It may be counter-intuitive to many, but growing BNI Brachiaria to feed cattle can actually help reduce greenhouse gas emissions from livestock production,” says Peters, adding that unlocking BNI capacity in other crops would help reduce nitrogen fertiliser use across the board, benefitting farmers and the environment at large.
According to the study, work on BNI-enabled sorghum is also under way at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT).
Major research investments are needed for the gene transfer
But scientists at CIMMYT and ICRISAT say that BNI-enabled food crops will be a few years in coming, because it is difficult and costly to transfer the genetically-complex BNI trait into elite crop varieties while preserving high-yield potential and other desirable qualities.
Subbarao and others are calling for major research investments to have high BNI food and forage crops grown widely across the globe by 2050 and thus help to meet the goal of limiting global temperature increases to two degrees Celsius above pre-industrial levels.
According to Masa Iwanaga, the president of JIRCAS, BNI technology typifies the transformation needed in the current agricultural model and practices to meet 21st century food production challenges.
“Feeding a global population projected to exceed nine billion by 2050 will place a tremendous strain on agri-food systems and the environment,” Iwanaga says. “At the same time, agriculture is not merely a commodity-producing industry, but part of a larger ecosystem that offers life support and services to human society.”
(Mike Listman, cimmyt/wi)