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Brachiaria - grass roots answer to nitrification

Brachiaria humidicola could be a valuable tool in tackling climate change (John Miles)
Brachiaria humidicola could be a valuable tool in tackling climate change
John Miles

You don't hear much about nitrification in the news; its formidable environmental and agricultural impact is usually eclipsed by coverage of carbon dioxide (CO2) emissions. But this natural microbial process in soil causes the conversion of fertiliser nitrogen into nitrous oxide (N2O), a greenhouse gas (GHG) 300 times more potent than CO2. With the seven-fold rise in the use of nitrogen fertilisers since the 1970s directly linked to booming levels of N2O, tackling nitrification is crucial to tackling climate change.

Recent research from the International Center for Tropical Agriculture (CIAT) in Colombia shows that one promising option is contained in the roots of the tropical forage grass Brachiaria humidicola: as well as being highly nutritious and palatable to ruminants, brachiaria inhibits nitrification. Livestock have been almost universally vilified in climate change debates, but this capacity could see the grass take centre stage in the push to significantly reduce the GHG footprint not just of livestock production, but arable farming too.

Compound interest

CIAT scientists had known for more than 30 years that brachiaria grass could suppress soil nitrification, but they only recently found out how its biological nitrification inhibition (BNI) capacity works. In October 2009, in collaboration with scientists from the Japan International Research Center for Agricultural Sciences (JIRCAS), and Japan's National Food Research Institute (NFRI), they discovered and characterised brachialactone, a chemical compound in the plant's roots which is released into the soil and acts as a biological nitrification inhibitor, in turn reducing GHG emissions from brachiaria-based livestock systems.

With around 80 million hectares of brachiaria currently growing in Latin America alone, the discovery of brachialactone confirmed that this humble forage grass was actually an unsung hero of climate change mitigation, quietly working its benefit, while world attention has focused on methane emissions.

Brachiaria trials at CIAT's headquarters in Colombia (Neil Palmer (CIAT))
Brachiaria trials at CIAT's headquarters in Colombia
Neil Palmer (CIAT)

Scientists in CIAT 's Tropical Forages program are now looking into whether the widespread use of brachiaria hybrids could herald a new dawn of low-nitrifying crop-livestock systems. Since the availability of ammonium in the soil triggers and sustains the release of brachialactone, they are investigating the benefits of a fundamental shift towards ammonium-dominated agricultural systems that include crops and forages with moderate-to-high BNI capacity.

At a time when at least 11 million hectares of grassland in the Cerrados of Brazil have been converted to soybean and maize production, and a further 35-40 million hectares are available for conversion in the near future, integrating brachiaria grasses into these crop-livestock systems promises significant environmental benefits.

"The discovery of brachialactone is a major breakthrough," says CIAT plant nutritionist Idupulapati Rao. "If used in the right way, it's a win-win technology that will help to minimise nitrogen losses from crop-livestock systems through greater recovery of applied nitrogen fertiliser. This must be taken into account when calculating the ecological footprint of livestock production and the reduced production of N2O," he continues. "As a result it's clear that we need to re-evaluate the relationship between livestock production and climate change. Brachiaria could become the keystone of sustainable crop-livestock systems that have a minimal ecological impact."

New dawn and new horizons

CIAT is now leading a major thrust to find the genes responsible for the production of the brachialactone, and the institution hopes to establish whether the BNI capacity of major food crops can be improved as well: wheat and maize, for example, currently waste nearly 60 per cent of nitrogen applied as fertiliser. But inhibiting the conversion to nitrous oxide leaves more fertiliser available to the crop. "At current levels of global nitrogen fertiliser application, this could equate to feeding an extra 1 billion people worldwide, while reducing GHG emissions at the same time," says Rao.

CIAT scientists are leading a major thrust to find the genes responsible for the production of the brachialactone (Neil Palmer (CIAT))
CIAT scientists are leading a major thrust to find the genes responsible for the production of the brachialactone
Neil Palmer (CIAT)

And the good news doesn't stop there for brachiaria, which has also been shown to be a valuable forage crop for smallholder livestock producers. Studies involving thousands of livestock keepers from Southeast Asia and Central America have demonstrated that incorporating new forage options such as brachiaria into their feeding systems can help lift farmers out of poverty in one to two years. More recently, smallholder farmers in Rwanda have found that brachiaria's BNI capacity and its deep, abundant root systems not only improve soil fertility, but improve human nutrition too, through enhanced milk production in cattle - even in drought conditions and on acid soils.

As discussions about livestock and climate change continue, the case of brachiaria offers hope that livestock production could contain the seeds of its own salvation.

Written by: Neil Palmer

Date published: July 2010


Have your say

Floyd: Our advice would be to contact CIAT who implemented t... (posted by: New Agriculturist)

Has any work with Brachiaria been done in Tanzania East Afri... (posted by: Floyd Hammer)

Its great news, do the other bracharias grass such as MG-5, ... (posted by: Carlos Sosa)


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