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Insights into plant growth could curb need for fertilizers

New insights into how plants regulate their absorption of an essential nutrient could help avoid pollution caused by excess use of fertilizer.

The findings could lead to the development of crop varieties that need less of the primary nutrient — nitrogen — than conventional crops. It could also inform how much nitrogen should be added to plant feed.

This would allow optimum plant growth without producing excess nitrogen in run-off from fields, which is a major source of water pollution.

Agricultural fertilizers typically contain high levels of nitrogen that boost plant growth and yield even on poor soils. This helps plants avoid the typical characteristics of nitrogen deficiency — stunted growth and pale or yellow leaves.

The study, by researchers at the University of Edinburgh and the University of Campinas in Brazil, examined how nitrogen is absorbed and converted into cellular building blocks in plants.

They found that when nitrogen is absorbed, plant cells produce nitric oxide, which acts as a signalling molecule. This nitric oxide fine-tunes how much nitrogen is used for growth, by signalling to the plant’s cells when to limit its uptake.

The scientists say that because nitric oxide plays important roles in shaping the development of plants, and how plants respond to environmental stress, these insights highlight key considerations of how nitrogen-based fertilisers should be used in agriculture.

Their study, published in Nature Communications, was funded by the Royal Society and the Biotechnology and Biological Sciences Research Council.

Dr Steven Spoel of the University of Edinburgh’s School of Biological Sciences, who led the study, said: “Understanding nitrogen absorption better will ultimately allow us to breed crop varieties that need less fertiliser, and therefore are better for the environment.”

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The above story is based on materials provided by University of Edinburgh. Note: Materials may be edited for content and length.

Agriculture and Food News — ScienceDaily

Efforts to curb climate change require greater emphasis on livestock

Dec. 20, 2013 — While climate change negotiators struggle to agree on ways to reduce carbon dioxide (CO2) emissions, they have paid inadequate attention to other greenhouse gases associated with livestock, according to an analysis by an international research team.

A reduction in non-CO2 greenhouse gases will be required to abate climate change, the researchers said. Cutting releases of methane and nitrous oxide, two gases that pound-for-pound trap more heat than does CO2, should be considered alongside the challenge of reducing fossil fuel use.

The researchers’ analysis, “Ruminants, Climate Change, and Climate Policy,” is being published today as an opinion commentary in Nature Climate Change, a professional journal.

William Ripple, a professor in the College of Forestry at Oregon State University, and co-authors from Scotland, Austria, Australia and the United States, reached their conclusions on the basis of a synthesis of scientific knowledge on greenhouse gases, climate change and food and environmental issues. They drew from a variety of sources including the Food and Agricultural Organization, the United Nations Framework Convention on Climate Change (UNFCCC) and recent peer-reviewed publications.

“Because the Earth’s climate may be near a tipping point to major climate change, multiple approaches are needed for mitigation,” said Ripple. “We clearly need to reduce the burning of fossil fuels to cut CO2 emissions. But that addresses only part of the problem. We also need to reduce non-CO2 greenhouse gases to lessen the likelihood of us crossing this climatic threshold.”

Methane is the second most abundant greenhouse gas, and a recent report estimated that in the United States methane releases from all sources could be much higher than previously thought. Among the largest human-related sources of methane are ruminant animals (cattle, sheep, goats, and buffalo) and fossil fuel extraction and combustion.

One of the most effective ways to cut methane, the researchers wrote, is to reduce global populations of ruminant livestock, especially cattle. Ruminants are estimated to comprise the largest single human-related source of methane. By reflecting the latest estimates of greenhouse gas emissions on the basis of a life-cycle or a “farm to fork” analysis, the researchers observed that greenhouse gas emissions from cattle and sheep production are 19 to 48 times higher (on the basis of pounds of food produced) than they are from producing protein-rich plant foods such as beans, grains, or soy products.

Unlike non-ruminant animals such as pigs and poultry, ruminants produce copious amounts of methane in their digestive systems. Although CO2 is the most abundant greenhouse gas, the international community could achieve a more rapid reduction in the causes of global warming by lowering methane emissions through a reduction in the number of ruminants, the authors said, than by cutting CO2 alone.

The authors also observed that, on a global basis, ruminant livestock production is having a growing impact on the environment:

  • Globally, the number of ruminant livestock has increased by 50 percent in the last 50 years, and there are now about 3.6 billion ruminant livestock on the planet.
  • About a quarter of the Earth’s land area is dedicated to grazing, mostly for cattle, sheep and goats.
  • A third of all arable land is used to grow feed crops for livestock.

In addition to reducing direct methane emissions from ruminants, cutting ruminant numbers would deliver a significant reduction in the greenhouse gas emissions associated with the production of feed crops for livestock, they added.

“Reducing demand for ruminant products could help to achieve substantial greenhouse gas reductions in the near-term,” said co-author Helmut Haberl of the Institute of Social Ecology in Austria, “but implementation of demand changes represent a considerable political challenge.”

Among agricultural approaches to climate change, reducing demand for meat from ruminants offers greater greenhouse gas reduction potential than do other steps such as increasing livestock feeding efficiency or crop yields per acre. Nevertheless, they wrote, policies to achieve both types of reductions “have the best chance of providing rapid and lasting climate benefits.”

Such steps could have other benefits as well, said co-author Pete Smith of the University of Aberdeen in Scotland. “Cutting the number of ruminant livestock could have additional benefits for food security, human health and environmental conservation involving water quality, wildlife habitat and biodiversity,” he explained. 

Agricultural researchers are also studying methane reduction through improved animal genetics and methods to inhibit production of the gas during digestion.

International climate negotiations such as the UNFCCC have not given “adequate attention” to greenhouse gas reductions from ruminants, they added. The Kyoto Protocol, for example, does not target ruminant emissions from developing countries, which are among the fastest-growing ruminant producers.

ScienceDaily: Agriculture and Food News

‘Grassroots action’ in livestock feeding to help curb global climate change

Sep. 13, 2013 — In a series of papers to be presented next week, scientists offer new evidence that a potent chemical mechanism operating in the roots of a tropical grass used for livestock feed has enormous potential to reduce greenhouse gas emissions.

Referred to as “biological nitrification inhibition” or BNI, the mechanism markedly reduces the conversion of nitrogen applied to soil as fertilizer into nitrous oxide, according to papers prepared for the 22nd International Grasslands Congress. Nitrous oxide is the most powerful and aggressive greenhouse gas, with a global warming potential 300 times that of carbon dioxide.

“Nitrous oxide makes up about 38 percent of all greenhouse gas emissions in agriculture, which accounts for almost a third of total emissions worldwide,” said Michael Peters, who leads research on forages at the Colombia-based International Center for Tropical Agriculture (CIAT), a member of the CGIAR Consortium. “BNI offers what could be agriculture’s best bet for keeping global climate change within manageable limits.”

Scientists at CIAT and the Japan International Research Center for Agricultural Sciences (JIRCAS) have researched BNI collaboratively for the last 15 years.

“This approach offers tremendous possibilities to reduce nitrous oxide emissions and the leaching of polluting nitrates into water supplies, while also raising crop yields through more efficient use of nitrogen fertilizer,” said G.V. Subbarao, a senior scientist at JIRCAS.

As a result of recent advances, scientists have developed the means to exploit the BNI phenomenon on a large scale:

  • CIAT researchers have found ways to increase BNI through plant breeding in different species of Brachiaria grasses. The new techniques include methods for rapidly quantifying BNI in Brachiaria together with molecular markers, which reduce the time needed for field testing.
  • Center scientists have also just gathered evidence that a maize crop grown after Brachiaria humidicola pastures gave acceptable yields with only half the amount of nitrogen fertilizer normally used, because more nitrogen was retained in the soil, thus reducing nitrous oxide emissions and nitrate leaching. The researchers determined that BNI had boosted nitrogen-use efficiency by a factor of 3.8.
  • In addition, scientists have developed hybrids of Brachiaria humidicola and delivered these, with support from the German government, to farmers in Colombia and Nicaragua for productivity and quality testing. Previous grass hybrids have increased milk and meat production by several orders of magnitude, compared to native savanna grasses, and by at least 30 percent, compared to commercial grass cultivars. Based on evaluation of the new hybrids and with the aid of simulation models, researchers are studying where else the hybrids can be introduced and on how large a scale.

“Livestock production provides livelihoods for a billion people, but it also contributes about half of agriculture’s greenhouse gas emissions,” Peters explained. “BNI is a rare triple-win technology that’s good for rural livelihoods as well as the global environment and climate. It defies the widespread notion that livestock are necessarily in the minus column of any food security and environmental calculation.”

“The problem is that today’s crop and livestock systems are very ‘leaky,’” said Subbarao. “About 70 percent of the 150 million tons of nitrogen fertilizer applied globally is lost through nitrate leaching and nitrous oxide emissions; the lost fertilizer has an annual estimated value of US$ 90 billion.”

“BNI has huge possibilities for reducing nitrogen leakage,” said CIAT scientist Idupulapati Rao. “Grassland pastures are the single biggest use of agricultural land — covering 3.2 billion hectares out of a global total of 4.9 billion. In Brazil alone, 11 million hectares of grassland have been converted to maize and soybean production, and another 35-40 million could be shifted to crop production in the near future. Instead of more monocropping, developing countries need to integrate Brachiaria grasses into mixed crop-livestock systems on a massive scale to make them more sustainable.”

Originally from sub-Saharan Africa, Brachiaria grasses found their way to South America centuries ago — possibly as bedding on slave ships. Improved varieties of the grass are widely grown on pasturelands in Brazil, Colombia, and other countries, and they have recently been taken back to Africa to help ease severe shortages of livestock feed.

In a major breakthrough, JIRCAS scientists discovered several years ago the chemical substance responsible for BNI and developed a reliable method for detecting the nitrification inhibitor coming from plant roots. Scientists at CIAT then validated the BNI concept in the field, demonstrating that Brachiaria grass suppresses nitrification and nitrous oxide emissions, compared with soybean, which lacks this ability.

Other research has shown that deep-rooted, productive Brachiaria grasses capture large amounts of atmospheric carbon — on a scale similar to that of tropical forests — a further plus for climate change mitigation.

“Our work on BNI started with a field observation made by one of our scientists in the 1980s — back then it was nothing more than a dream,” said Peters. “But now it’s a dream with an action plan and solid scientific achievements behind it.”

BNI research forms part of a larger initiative referred to as LivestockPlus, which proposes to deliver major benefits for the poor and the environment through innovative research on tropical forage grasses and legumes.

The LivestockPlus initiative takes place within the global framework of the CGIAR Research Program on Livestock and Fish, led by the Kenya-based International Livestock Research Institute (ILRI). The program aims to increase the availability and affordability of meat, milk and fish for poor consumers and raise the incomes of smallholders producing these commodities.

ScienceDaily: Agriculture and Food News