Tag Archives: soils

Biochar can help us keep climate change at bay and more food on the table, according to a new meta-study

Biochar — organic material baked in oxygen-starved environments — can help power up the agriculture industry while also fighting against climate change, according to a new paper.

Image via Wikipedia.

Coal is naturally produced underground, over millions of years, from ancient biomass. This organic matter that got buried in some way or another was then compressed and heated up through geological processes, which broke down its original structure and increased its carbon content. Biochar is produced in a very similar way, but instead of letting natural (and slow) geological processes cook it up, we make it ourselves.

This material can help fertilize soils and, thus, increase crop yields. At the same time, by preventing the carbon within it from being released back into the atmosphere, the use of biochar in agriculture can help fight climate change.

Very, very, very well done

“Biochar can draw down carbon from the atmosphere into the soil and store it for hundreds to thousands of years,” says Stephen Joseph, lead author of the paper, and a Visiting Professor in the School of Materials Science and Engineering at the University of New South Wales Science. “This study also found that biochar helps build organic carbon in soil by up to 20 percent (average 3.8 percent) and can reduce nitrous oxide emissions from the soil by 12 to 50 percent, which increases the climate change mitigation benefits of biochar.”

Biochar is a product usually made from aggregated organic waste — a mixture of waste biomass from agriculture, forestry, and household sources. For such an unassuming substance, it could lend a sizable hand towards fighting climate change and us having more food, according to a new paper. The findings are supported by the Intergovernmental Panel on Climate Change’s recent Special Report on Climate Change and Land, which estimated there was important climate change mitigation potential available through biochar. This report estimated that biochar use “could mitigate between 300 million and 660 million tons of carbon dioxide [globally] per year by 2050,” Prof. Joseph explains.

“Compare that to Australia’s emissions last year—an estimated 499 million tons of carbon dioxide—and you can see that biochar can absorb a lot of emissions. We just need a will to develop and use it.”

The meta-study reviewed 300 papers on the topic, including 33 meta-analyses that together reviewed around 14,000 biochar studies that have been published over the last 20 years. According to its result, the use of biochar, when mixed-in with crop soils, can boost yields by 10% to 42%, reduce the levels of heavy metals in plant tissues by between 17% and 39%, and increases the bioavailability of phosphorus, a critical nutrient that often acts as a bottleneck for the development of plants.

All in all, its use helps plants grow faster and larger, while also helping them better resist environmental stresses such as toxic metals, diseases, organic stressors such as herbicides and pesticides, and water stress.

The paper also explains how biochar acts on the roots of plants, boosting them. In the first three weeks of a plant’s life, it explains, biochar particles react with soils and stimulate germination (i.e. it helps seeds ‘catch’) and the development of the fledgling plant. Over the next six months or so, biochar particles in the soil form reactive surfaces which help draw nutrients towards the roots. As these particles start to age, something that happens around three to six weeks after being mixed into the soil (depending on environmental conditions), they break down and form microaggregates with other chemicals. This, in turn, helps protect roots and prevents the decomposition of organic matter.

Biochar yielded the best effects when used in acidic or sandy soils together with fertilizers, the authors explain.

“We found the positive effects of biochar were dose-dependent and also dependent on matching the properties of the biochar to soil constraints and plant nutrient requirements,” Prof. Joseph says.”Plants, particularly in low-nutrient, acidic soils common in the tropics and humid subtropics, such as the north coast of NSW and Queensland, could significantly benefit from biochar.”

“Sandy soils in Western Australia, Victoria and South Australia, particularly in dryland regions increasingly affected by drought under climate change, would also greatly benefit.”

Prof. Joseph has been studying the use of biochar ever since he was introduced to the practice by Indigenous Australians in the seventies. He explains that these people, alongside indigenous groups in Australia, Latin America (especially in the Amazon basin), and Africa, have been using biochar to maintain soil health and improve crops for centuries. Despite this, it hasn’t really been adopted as a commercial product, and most countries only produce a small amount of biochar every year.

To really make an impact, he explains, biochar needs to be integrated with farming operations on a wide scale. The first step towards that, he feels, is to tell farmers that biochar is an alternative they can opt for, and establish demonstrations so farmers can see that the benefits are real, not just words.

“This is in part due to the small number of large-scale demonstration programs that have been funded, as well as farmers’ and government advisors’ lack of knowledge about biochar, regulatory hurdles, and lack of venture capital and young entrepreneurs to fund and build biochar businesses,” he explains. “We’ve done the science, what we don’t have is enough resources to educate and train people, to establish demonstrations so farmers can see the benefits of using biochar, to develop this new industry”.

The paper “How biochar works, and when it doesn’t: A review of mechanisms controlling soil and plant responses to biochar” has been published in the journal GCB Bioenergy.

Human-induced erosion could make some soils around the world unfarmable by the end of the century

Human-induced soil erosion is a serious threat to global sustainability, endangering global food security, driving desertification and biodiversity loss, and degrading other vital ecosystem services, researchers say. According to a new study, erosion is affecting the longevity of the soils across the world.

Credit Flickr Fabian Schmidt

Soils have underpinned the health and longevity of every society. They are a critical global resource, providing the basis of food production and storing and filtering our water resources. Soils also represent the largest organic carbon store and a platform for economic development. But pressures on the soil resource grow as food demands rise and land degradation increases.

To date, 36% of the world’s cultivable land has been farmed and in many areas of the world, conventional plow-based agriculture is accelerating local soil degradation. The UN estimates that 66% of the world’s soils suffer from some form of degradation. Human-induced erosion is estimated to outpace soil formation, which means we now have thinner soils.

“Our soils are critically important and we rely on them in many ways, not least to grow our food”, said lead author Dan Evans in a statement. “There have been many headlines in recent years suggesting that the world’s topsoil could be gone in 60 years, but these claims have not been supported with evidence. This study provides the first evidence-backed, globally relevant estimates of soil lifespans.”

A study by Lancaster University in collaboration with researchers from Chang’an University in China, and KU Leuven in Belgium, looked at soil erosion data from around the globe, spanning 255 locations across 38 countries on six continents. They calculated the time it would take for the top 30 cm of soil to erode at each location—the soil lifespan.

They focused on that top layer of the soil as it’s usually rich in nutrients and organic matter, making it important for growing fibers, food, feedstock, and fuel. In their study, they included soils that are conventionally farmed as well as those managed with soil conservation techniques. That way they can see how changes to land-use practices can alter the lifespan of soil

The findings showed that 90% of the soils conventionally farmed around the world were thinning, with 16% having a lifespan of less than a century. At these sites, soil erosion is a significant threat to the soil’s capacity to grow food, support ecosystems, store and regulate water, cycle carbon and nutrients, and thus to the overall functioning of the soil system.

But there were reasons to be optimistic. The study showed soils managed with conservation strategies had a longer lifespan, promoting soil thickening. Only 7% of the conservation plot dataset had lifespans of less than 100 years, with nearly half exceeding 5,000 years and 39% exceeding 10,000 years

“Soil is a precious resource and we can’t afford to lose that much over a human lifetime,” said co-author Jess Davies in a statement. “We have the tools and practices to make a difference—employing the appropriate conservation methods in the right place can really help protect and enhance our soil resource and the future of food and farming.”

The researchers suggested using a set of strategies to extend soil lifespans and promoting annual soil gain, such as conservation and zero till practices, contour cultivation and terracing. These extend soil lifespans and may promote soil thickening, increasing the potential for water, carbon and nutrient storage, and thereby soil conditions.

The study was published in the journal Environmental Research Letters.

Warmer temperatures release carbon dioxide from tropical soils

If current trends continue, global warming will cause a massive release of carbon from soils in tropical forests — soils that contain one-third of the carbon stored in soils globally.

Credit Flickr Darren and Brad (CC BY-NC 2.0)

The input and outflow of CO2 into the soil used to be mostly in balance before humanity started ramping up emissions. The gases released by deadwood and decaying leaves were balanced by the microorganisms that fed on that matter.

But climate change is now altering such balance, researchers are warning.

“Carbon held in tropical soils is more sensitive to warming than previously recognized,” lead author Andrew Nottingham, a researcher at the University of Edinburgh, told AFP. “Even a small increase in respiration from tropical forest soils could have a large effect on atmospheric CO2 concentrations, with consequences for global climate.”

Previous research showed that rising temperatures could release carbon locked away in cooler or frozen soils such as in the Arctic tundra. A study from 2016, estimated that by 2050, soils could release as much CO2 as the US — but that study didn’t even consider tropical soils.

Carbon in tropical soils was thought to be less vulnerable to loss under climate change than is soil carbon at higher latitudes, but experimental evidence for this was lacking. In the new study, Nottingham and his team published evidence showing that tropical-forest soils might be more vulnerable to warming than was initially thought, especially if temperatures continue to rise.

The authors placed warming rods around the perimeter of undisturbed soil plots in a tropical forest on Barro Colorado Island, Panama, increasing the temperature of the soil profile by 4ºC for two years. They periodically measured the efflux of CO2 with a set of chambers placed over the soil. Their results showed observed an unexpectedly large increase of 55% in soil CO2 emissions. Trying to understand the growth, they excluded the roots from the soil under the chambers and realized that most of the extra CO2 was because of a greater-than-expected increase in the respiration of soil microbes.

Extrapolating from the findings, the researchers estimated that if all the world’s tropical soils warmed by 4ºC for a two-year period sometime before 2100, it would release 65 billion tons of carbon, equivalent to about 240 billion tons of CO2, into the atmosphere.

“That is more than six times the current annual emissions from human-related sources. This could be an underestimation, because we might see large continued loss beyond the two years in our experiment,” Nottingham said, also adding that deeper stores of carbon below two meters weren’t taken into account in the study.

The surface temperature of the planet has grown just over one degree Celsius above preindustrial levels. This has been enough to boost the severity of droughts, heatwaves and superstorms, among other climate events. On land alone, the temperature rose 2ºC, doubling the global average.

The study was published in the journal Nature.