May 11, 2013

Choking the Gulf: A Story of Industrial Agriculture - Record nitrate levels in Raccoon, Des Moines threaten Des Moines-area tap water " voluntary conservation efforts on farms aren’t working" | Des Moines Register Staff Blogs

Full Article: Choking the Gulf: A Story of Industrial Agriculture

Written by Jesse Richardson

Photo Courtesy of Rabalais, Louisiana Universities Marine Consortium

At the crack of dawn, the farmer of the 21st century wakes up and prepares for the work ahead of him. Today, unlike other days, is especially important: perhaps it’s time for another periodic spraying of pesticides or laying of fertilizer. Maybe it’s time to check the irrigation pipes to the lagoon.

Whatever it may be, all three tasks have something in common: they lead to chemicals and toxins leaching into the water supply, which is then taken down river to the Gulf of Mexico. Slowly, they exacerbate an already terrible environmental situation: increased water pollution and hypoxia, or oxygen starved waters.
A Deadly Trifecta

Pesticides: Pesticides must be sprayed multiple times a year in order to chemically manage whatever may be determined a “pest” – perhaps a certain weed, insect, or fungus. Literally, millions of tons are sprayed over our crops a year, much of it hitting everythingbut the plants targeted due to the surface area of plants, wind, and poorly calibrated machinery.

Fertilizers: Fertilizers are the next challenge that face the Gulf, its ecosystems, and the life within. With more corn than even being grown for ethanol fuel, millions of pounds of nitrogen-based fertilizer is seeping into ground water and soil, and eventually running off to the Mississippi River. As we’ll see later, nitrogen is key to the problem (and that addressing nitrogen as the issue is key to the solution).

Animal Waste: Finally, animal waste is also a major problem. With “lagoons,” a term used for the cesspools of animal waste at farms for such animals as the pig, there is a constant threat of leaking or spreading of waste by storms. Although the nitrates in animal wasteaccount for roughly 15 percent of the nitrogen influx at the gulf, they still spread chemicals, toxins, and throughout the waterways and can contaminate fresh water supplies.

Over the year, each of the above – the pesticides, fertilizers, and leeching waste – slowly make their way to the Mississippi River, or other rivers that flow into the Mississippi, from their respective sources. The massive fields, the empires of dairy and animal farming, the systematic spraying and enhancing of all things contribute to a trail of toxic soup. Along the way, they degrade soil, ravish ecosystems, and threaten human health and safety.

However, the worse place is the final destination: the Gulf of Mexico.
Choking the Gulf

All the chemicals, nitrates, and waste ends up in one place: the Gulf of Mexico. Every years, millions of tons of contaminated water rush into the Gulf and the natural ecosystems that exist there. From aerial views, one can literally see the stark contrast of color: sediment (and nitrate) laden water coming into the blue of the ocean. The picture above shows the two forces clash.

And despite natural runoff being beneficial to the Gulf, the runoff industrial agriculture produces is something different. Nitrates that accumulate from across the Midwest (picture left) have an extremely adverse effect in the Gulf: hypoxia, or the starving of oxygen.

Nitrates feed life in the water just as they do on land. Each year, huge blooms of algae are spawned. As these grow, they suffocate the waters – literally depleting the water of oxygen. Soon, oxygen dependent ocean-life die off, including fish, crabs, and plankton. Crops contribute the most, especially corn and soybean, but animals waste contributes as well. Pesticides “toxify” the environment along the way, as well as the Gulf itself.
Looking for a Solution

Currently, the EPA has yet to mandate any formal regulation, and while some states have taken initiative, there is little serious focus on runoff and the Gulf specifically.

Three areas must be addressed: 1) the release of these nitrates and toxins, 2) the persistence of runoff, and 3) the effect it has on the environment. First, farms must begin to use less and less pesticides and artificial fertilizers. Not only does organic farming (done with intensive organic methods) yield equal or greater crops, but it does so without the use of synthetic chemicals.

Second, the farms that remain on the current system must work are irrigating and recapturing their waste. Just as a driver cannot throw his trash our the window, a farmer must not be able to pump their waste downstream.

Finally, work must be done to rehabilitate and protect the Gulf. The dead zone, which is now the size of New Jersey and looking to grow with this last season of intense storms, must be minimized and addressed. Not only does the life of the Gulf depend on it, but thelives of coastal resident do as well.


Record nitrate levels in Raccoon, Des Moines threaten Des Moines-area tap water - "voluntary conservation efforts on farms aren’t working"

FULL ARTICLE:  Record nitrate levels in Raccoon, Des Moines threaten Des Moines-area tap water | Des Moines Register Staff Blogs

Des Moines Water Works turned on the world’s largest nitrate-removal facility Friday morning for the first time since 2007 after levels of health-threatening nitrates hit records in both the Des Moines and Raccoon rivers, two of the main drinking-water sources.

The predicament shows that voluntary conservation efforts on farms aren’t working and do not bode well for the future of the area’s water supply, said Water Works General Manager Bill Stowe. He added that the nitrates primarily come from crop fertilizers, and that better field drainage systems have worsened the situation.

“We are off our playing field. We haven’t seen this before,” Stowe said.

“The issue is the quality of the water in the Raccoon and the Des Moines. This trend is absolutely off the scale,” Stowe said. “It’s like having serial tornadoes. You can deal with one, you can deal with two, but you can’t deal with them every day.”

“The state’s Nutrient Reduction Strategy, with it’s emphasis on the voluntary measure, clearly isn’t working,” Stowe said. “And our ratepayers are paying significantly to remove nitrates.”

The strategy for cutting runoff from farms, developed largely by the Iowa Department of Agriculture and Land Stewardship, was designed to address concerns about the so-called dead zone in the Gulf of Mexico. Midwest fertilizers feed algae blooms that eventually suck oxygen from a large part of the Gulf in summer.

Agriculture Secretary Bill Northey has said the voluntary measures are the best bet for action, because they avoid court challenges that regulations bring and avoid “one size fits all” solutions.

Nitrates have been linked to blue-baby syndrome, in which infants suffocate, as well as to various cancers and miscarriages. The federal limit is 10 milligrams per liter nitrate in drinking water; both rivers have posted readings in the range of 20.

The Raccoon River hit 24 this week; the previous record was 22. The Des Moines was just under 18; the record was 14.2.

Stowe said tap water will remain safe, even with the unusual difficulty in finding water with lower nitrate levels to blend with the supplies running high. The $4 million nitrate-removal plant, installed in 1992 costs about $7,000 a day to run. So far, the utility is using four of the eight treatment cells where nitrates are stripped from the water. EPA had ordered Des Moines to act to remove nitrates after the contaminant exceeded the federal limit.

Even the water in the so-called gallery — the shallow wells at the Fleur Drive plant — are running close to the nitrate limit for tap water, further limiting the options for combining water supplies. Water Works has turned on its backup plants at Maffitt Reservoir, Crystal Lake and the Saylor Township plant opened several years ago.

Stowe said the nitrates then are dumped back in the river, an EPA-approved arrangement he hopes to avoid in the future. He is researching better ways to dispose of the slurry.

Some upstream levels were more than twice the U.S. Environmental Protection Agency limit for drinking water.

Tags: D+, dead zone, Des Moines Water Works, nitrate removal, nitrates, Nutrient Reduction Strategy, water pollution

May 10, 2013

The most controversial chart in history, hockey stick graph explained | Climate Scientist Michael Mann | Grist

James West/Climate Desk
Climate Scientist Michael Mann
By Chris Mooney

Back in 1998, a little-known climate scientist named Michael Mann and two colleagues published a paper [PDF] that sought to reconstruct the planet’s past temperatures going back half a millennium before the era of thermometers — thereby showing just how out of whack recent warming has been. The finding: Recent Northern Hemisphere temperatures had been “warmer than any other year since (at least) AD 1400.” The graph depicting this result looked rather like a hockey stick: After a long period of relatively minor temperature variations (the “shaft”), it showed a sharp mercury upswing during the last century or so (“the blade”).

The report moved quickly through climate science circles. Mann and a colleague soon lengthened the shaft [PDF] of the hockey stick back to the year 1000 AD — and then, in 2001, the U.N.’s Intergovernmental Panel on Climate Change prominently featured the hockey stick in its Third Assessment Report. Based on this evidence, the IPCC proclaimed that “the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1,000 years.”

And then all hell broke loose.
IPCC Third Assessment Report / Wikipedia
Click to embiggen.

Mann tells the full story of the hockey stick — and the myriad unsuccessful attacks on it — in his 2012 book The Hockey Stick and the Climate Wars: Dispatches From the Front Lines; Mann will appear at a Climate Desk Live event on May 15 to discuss this saga. But to summarize a very complex history of scientific and political skirmishes in a few paragraphs:

The hockey stick was repeatedly attacked, and so was Mann himself. Congress got involved, with demands for Mann’s data and other information, including a computer code used in his research. Then the National Academy of Sciences weighed in in 2006, vindicating the hockey stick as good science and noting:

The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on ice caps and the retreat of glaciers around the world.

It didn’t change the minds of the deniers, though — and soon Mann and his colleagues were drawn into the 2009 “Climategate” pseudo-scandal, which purported to reveal internal emails that (among other things) seemingly undermined the hockey stick. Only, they didn’t.

In the meantime, those wacky scientists kept doing what they do best — finding out what’s true. As Mann relates, over the years other researchers were able to test his work using “more extensive data sets, and more sophisticated methods. And the bottom line conclusion doesn’t change.” Thus the single hockey stick gradually became what Mann calls a “hockey team.” “If you look at all the different groups, there are literally about two dozen” hockey sticks now, he says.

Mother Jones’ Jaeah Lee traced the strange evolution of the hockey stick story in this video:

Indeed, two just-published studies support the hockey stick more powerfully than ever. One, just out in Nature Geoscience, featuring more than 80 authors, showed with extensive global data on past temperatures that the hockey stick’s shaft seems to extend back reliably for at least 1,400 years. Recently in Science, meanwhile, Shaun Marcott of Oregon State University and his colleagues extended the original hockey stick shaft back 11,000 years. “There’s now at least tentative evidence that the warming is unprecedented over the entire period of the Holocene, the entire period since the last ice age,” says Mann.

So what does it all mean? Well, here’s the millennial-scale irony: Climate deniers threw everything they had at the hockey stick. They focused immense resources on what they thought was the Achilles’ heel of global warming research — and even then, they couldn’t hobble it. (Though they certainly sowed plenty of doubt in the mind of the public.)

What’s more, even if they’d succeeded, in a scientific sense it wouldn’t have even mattered.

“Climate deniers like to make it seem like the entire weight of evidence for climate change rests on the hockey stick,” explains Mann. “And that’s not the case. We could get rid of all these reconstructions, and we could still know that climate change is a threat, and that we’re causing it.” The basic case for global warming caused by humans rests on basic physics — and basic thermometer readings from around the globe. The hockey stick, in contrast, is the result of a field of research called paleoclimatology (the study of past climates) that, while fascinating, only provides one thread of evidence among many for what we're doing to the planet.
Center for American Progress
Click to embiggen.

Meanwhile, the hockey stick’s blade doesn’t just stop rising of its own accord. It’s just going to go up, and up, and up, as the image above, combining the Marcott hockey stick with projections of where temperatures are headed by 2100, plainly shows.

When he shows that graph to audiences, says Mann, “I often hear an audible gasp.” In this sense, the hockey stick does indeed matter — for it dramatizes just how much human irresponsibility, in a relatively short period of time, can devastate the only home we have.

This story was produced as part of the Climate Deskcollaboration.
Chris Mooney is host of the Point of Inquiry podcast and the author of four books, including The Republican War on Science and The Republican Brain: The Science of Why They Deny Science and Reality.
FULL ARTICLE: The most controversial chart in history, explained | Grist

In Our Backyard (A Monsanto Introspective) (2009) | Watch Documentary Free Online

The focus of the piece is on a small village just east of St. Louis known as Sauget. Years ago this tiny area was incorporated as Monsanto.

For those who remain unaware Monsanto Company was one of the leading chemical producers of the twentieth century and has been responsible for producing chemicals like DDT, an insecticide known to be carcinogenic. Agent Orange, a dioxin riddled chemical used as a defoliant in the Vietnam war. Still to this day in Vietnam we can see horrible genetic mutations, horrid skin conditions, and cancers attributed to the effects of Agent Orange. Also, Bovine Growth Hormones, which Monsanto continuously tries to keep under wraps, due to the fact it makes cows sick, thus their bacteria and the antibiotics they are pumped full of go right back into American milk. As a result BGH has been banned in Europe and Canada.

Today Monsanto is an agricultural biotechnology company that is known for their genetically altering and patenting of various seed varieties, which are injected with a protein in order make the plants resistant to Roundup Weed Killer, one of Monsanto's best selling products.

Solutia is currently Monsanto's chemical division, a subsidiary made years ago when the Monsanto name became tainted. Monsanto and Solutia have received an array of negative publicity, and we must question why. We also must question what good has Monsanto Company done for this world?

There are two toxic dumping sites in Sauget known as superfund sites, in which Monsanto and Solutia have been found directly attributed to.

While filming Solutia company my crew and I nearly got arrested while on public property, and were coerced into surrendering our ID's only to be placed on a FBI domestic terrorist watch list.

It's important to question what exactly Monsanto and Solutia are afraid of. This film is only a brief introduction into the atrocities occurring at the hands of Monsanto in the areas surrounding St. Louis, and the world.

Support the film-makers. Buy the DVD. Host a film screening.

Truth and facts help a democracy work better...  Monsanto Company - EXAMPLE OF A COMPANY OUT CONTROL WITHOUT PERSONNEL ETHICS AND INTEGRITY ... 
Monte Hines

In Our Backyard (A Monsanto Introspective) (2009) | Watch Documentary Free Online

May 9, 2013

Determining How Much Nitrogen Is Present

MAY 9, 2013
By: University News Release

By Fabián Fernández, University of Illinois

Fall Nitrogen

With a still fresh memory of the drought conditions during last year, recent rains have reduced concerns over water availability for the start of the 2013 growing season, but at the same time, concerns over nitrogen (N) loss have increased. Nitrogen loss is difficult to predict because it depends in many factors such as time of N application, type of N source, soil type and temperature, and the amount of precipitation received. While it is difficult to know how much N is lost without a direct analysis of soil N, I would like to provide some information that can help you determine what to do about N applications this growing season.

Most of the fall-applied N is either ammonium (NH4+) or a form that transforms rapidly into ammonium. Nitrification, or the conversion of ammonium to nitrate (NO3-), is a bacteria-mediated transformation. The bacterium Nitrosomonas converts NH4+ into nitrite (NO2-) while the bacterium Nitrobacter converts NO2- to NO3-. The activity of these bacteria is minimal at temperatures below 50ºF. These bacteria also need aerobic conditions (unsaturated soil-water conditions) to nitrify ammonium. Thus, the amount of nitrification that occurs in the soil is largely dependent on soil temperature and the time elapsed from application until the soil becomes saturated with water. Further, the nitrification process can be reduced with the use of nitrification inhibitors that reduces the activity of Nitrosomonas and allow N to stay in the ammonium form for a longer period of time.

When soils become saturated, the potential for N losses is directly related to the amount of N present in the nitrate (NO3-) form. While wet soil conditions this spring may be a reason for concern that some of the N applied last fall may be lost, the cold temperatures we had until recently likely substantially reduced nitrification. From now on, as temperatures increase, nitrification will also increase. When nitrate is present and soils warm up, N loss will start under saturated water conditions mostly through denitrification in fine-textured soils and through leaching in coarse-textured soils or intensively drained soils.

An important point to keep in mind is that the portion of the applied N that is in nitrate form is only subject to denitrification or leaching. However, the fact that N is in the nitrate form does not mean that N is lost; it simply means that it is susceptible to loss. Data from a study conducted a number of years ago (Table 1) provides a measure of the percent of ammonium that was transformed to nitrate by the end of May from three locations in Illinois depending on whether a nitrification inhibitor was used and when the application was done.

After determining how much of the N is in the nitrate form, it is possible to estimate how much N is potentially lost through denitrification based on soil temperature and the number of days the soil has been saturated.

Current 4-inch depth soil temperatures can be accessed at

In Illinois we have seen that for each day the soil is saturated with water, 1 to 2 % of the N in the nitrate form is lost via denitrification when temperatures are below 55°F. When temperatures are between 55 and 65°F the loss is 2 to 3%, and when temperatures are above 65 to 70°F losses are about 4 to 5%. Again, these losses are not for the total nitrogen applied, but rather for the portion that is in the nitrate form. Loss will vary depending on different factors, but these values are intended to provide an estimate.

The following calculation is a hypothetical situation given as an example using the data in Table 1 and current soil temperatures below 65°F:

Let’s assume that 180 lb N/acre were applied in early November with a nitrification inhibitor in a silty clay loam soil in DeKalb and soils were saturated for 5 days in late April.

First calculate N present as nitrate
N applied x % in nitrate form
180 lb N/acre x 0.55 = 99 lb N/acre

Second calculate N denitrified
N in nitrate form x % denitrified
99 x 0.15 (5 days x 3%/day)
15 lb N/acre lost

If leaching is a greater concern than denitrification, for each inch of precipitation, nitrate moves approximately 5 to 6 inches in silt loam and clay loam soils and approximately 12 inches in coarser textured-soils.

The above discussion was for fall N applications. However, this year an important concern is the potential for loss of the carryover N for fields going back to corn this year. As we indicated in earlier bulletin articles some fields had substantial amounts of N after last growing season. Most of this N was in the nitrate form, thus the potential for loss by leaching since last fall was not related to temperature, but by the amount of excess precipitation. The fall and winter were relatively dry and most of the precipitation was used to replenish water in the soil profile. Unfortunately, excess precipitation in April has made it so that some of that carryover N is no longer available.

What To Do Now

Regardless of how much nitrogen may or may not be present, if you have not planted your field yet, it will be more important to plant now and apply additional N later so planting is not delayed further. One way to determine the need for additional N in fields where substantial carryover N is suspected or where the soil has high potential for mineralization (for example fields where manure was applied within the last 2-3 years) is to use the pre-sidedress nitrate test (PSNT) during late May to early June. This timing should work well to allow results to comeback from the testing lab with ample time for a sidedress application. An additional advantage to collecting soil samples starting in late May is that the test provides a good reliable measure of N because 1) the potential for N loss of all the N present in the soil is low by the end of May and 2) since soil temperatures are warm by then the test will measure mineralized N from the soil organic pool in addition to other sources such as carryover N. The sample needs to be collected from the top 12-inches of the soil. lf the field had a history of broadcast applications, randomly collect 20 to 25 samples from an area no greater than 10 acres. If band applications of fertilizer or manure were used to fertilize the previous crops, make a sample by collecting at least 10 sets of three cores each between two corn rows. The first core is collected 3 inches to the right of the corn row, the second core in the middle of the two rows, and the third core 3 inches to the left of the next corn row. Collecting a sample less than the full 12 inches or not collecting all the cores will produce unreli­able results. If the samples cannot be delivered to the labo­ratory the same day, either freeze or quickly air-dry the sample. Make sure to tell the labora­tory that you want to measure NO3– nitrogen. If the test results comeback above 25 parts per million (ppm) no additional nitrogen will be necessary. If results are less than 10 ppm a full rate will be needed (as long as no yield potential has been lost). If test levels are between 25 and 10 ppm, the N rate should be adjusted proportionally.

Another way to determine if additional N will be needed is to establish a couple strips with 10 to 25% more N than the full application amount planned, and then compare the color of the crop as the season progresses. If the strips are substantially greener than the rest of the field any time before tasseling, that would be an indication that additional N is needed. Some of the potential drawbacks to be aware of when using this approach are that color differences could develop too late for a timely application, or that there might not be sufficient rain to move the late-applied N into the root zone.

Larger Image

RELATED TOPICS: Inputs, Fertilzer, Spring Planting 2013

Denialism of Climate Change and Evolution - YouTube

Published on May 7, 2013
Far more people are climate change deniers than evolution deniers, but both camps use similar strategies to promote their views. Genie Scott explores the connections, the similarities, and the divergent ideologies. Where: New York. When: 10/23/2011. Hosted by the New York City Skeptics.
Denialism of Climate Change and Evolution - YouTube

Sustainable Ag Expert: New ‘Land Ethic’ Needed - Yankton Press & Dakotan: Community

Sustainable Ag Expert: New ‘Land Ethic’ Needed

Dr. Frederick Kirschenmann of the Leopold Center for Sustainable Agriculture was the featured speaker at MMC’s annual Benedictine Lecture, Thursday. (Kelly Hertz/P&D)

By Lisa Hare

Ask any farmer today for a job description of their vocation, and you’re likely to get a wide variety of answers, from raising crops and tending livestock, marketing and selling commodities, to feeding the world and fueling the future.

But not too many would probably call their relationship to their work a spiritual journey. And that, says sustainable agriculture expert Dr. Frederick Kirschenmann, is one of our biggest problems.

Thursday evening, at the annual Benedictine lecture held at Marian Auditorium at Mount Marty College, Kirschenmann urged the faith community to get involved in the development of a new “ecological conscience” to save natural resources and alter industrial ag production to more sustainable practices.

The ideas presented in his lecture were from years of extensive study in sustainable ag practices which led him to write his most recent book, “Cultivating An Ecological Conscience.”

“There are currently two schools of thought in this issue,” Kirschenmann said. “We can do more of the same and try to keep increasing production in the face of rapidly depleting resources, or we can change our systems to ways that are more sustainable.”

Kirschenmann, who holds a doctorate in philosophy and has written extensively about ethics and agriculture, is a Distinguished Fellow for the Leopold Center for Sustainable Agriculture at Iowa State University. A longtime national and international leader in sustainable ag, he also serves as president of Stone Barns Center for Food and Agriculture in Pocantico Hills, N.Y., oversees management of the family’s 3,5000-acre organic farm in south central North Dakota, and is a professor of religion and philosophy at ISU.

But before all that, Kirschenmann began his studies as a student at Yankton College in the 1950s. He later returned to become a faculty member there.

“It feels a bit like coming home to be here,” he said.

A self-proclaimed “big-picture thinker,” Kirschenmann said in the context of history, we are nearing the end of our current food production practices — that very soon, we won’t have a choice.

“We’ve lost half of our top soil, depleted and poisoned our fresh water sources; we’re using up phosphorus and potash stores at unprecedented rates, as well as losing the biodiversity in our ecosystems,” he said.

He added that of these losses, and climate change issues aside, the loss of soil is the most critical.

“It’s the foundation of all else,” he said. Soil fertility and water retention is largely determined by the level of organic matter in the soil, he added.

“With just 1 percent organic matter, the soil can hold only 33 pounds of water per cubic meter. But if you increased that organic matter to just 5 percent, the water level held goes up to 195 pounds.”

That’s a significant factor when you consider that worldwide, 70 percent of all our fresh water is used in agriculture irrigation.

Another pressing issue, Kirschenmann said, is the declining farming population.

“In the U.S., 75 percent of all production is accomplished by 194,000 farms,” he said, adding that the vast majority of those are farmers over age 60.

“We need research to explore ecological answers, and programs to encourage young people to get involved so we can increase our farming population,” he said.

Though some emphasis was given to the importance of programs and regulatory support, Kirshenmann’s message focused more on individual responsibility and spiritual development of a new “ecological conscience.”

“Aldo Leopold said an ecological conscience cannot come from regulation or the free market system,” Kirschenmann said. “We need a new ‘land ethic.’”

He added that the right land ethic would preserve the integrity, resilience and beauty of the earth.

“To tend to anything else is wrong,” he said, adding that the health of the people is in direct relationship to the health of the land.

“Fifteen million children die every year from hunger and hunger-related illnesses,” he said. However, only 1 percent of U.S.-produced corn, and less than one percent of our soybeans actually goes to the world’s 5 hungriest nations, he said.

“Health of the land is found in its capacity for renewal,” Kirschenmann added.

“All over the world, and even here in the U.S., models exist that are not dependent on our limited resources for energy — that use biological organisms for sustainability,” Kirschenmann said. “Our current structure isn’t working.”

He added that here in the Midwest and in the South where there is the heaviest concentration of commodity farming, there are many people committed to furthering the existing systems.

But Kirschenmann is hopeful that a new generation of ecologically-conscious farmers will find better ways of feeding the world.

“It’s about our relationships to the land and to each other,” he said. “And the faith community has a very important role to play in this journey.”

Full Article: Sustainable Ag Expert: New ‘Land Ethic’ Needed - Yankton Press & Dakotan: Community

May 7, 2013

GM Crops and Water - A Recipe for Disaster

GMOs, Health & Disease, Soil Erosion & Contamination, Water Contaminaton & Loss — by I-SIS May 7, 2013

A fully referenced and illustrated version of this article is posted on ISIS members website and is otherwise available for download here.

Genetically modified foods are a threat to our dwindling water supplies; they are less water-efficient and contaminate fresh water

by Dr Eva Sirinathsinghji

Genetically Modified (GM) crops are widely recognized for their potential to damage both human health and the environment. Evidence is now accumulating of the contamination of streams, rivers, rain, as well as groundwater with GM-associated chemicals including Monsanto’s glyphosate-based herbicide, while genetic elements such as antibiotic resistant genes are emerging in water-borne microbes. Further, GM crops have been shown to be less water efficient, corroborating farmer’s reports of failing GM crops during droughts. Industrial farming in general has been shown to be ill-adapted to extreme weather events such as hurricanes as well as droughts; and GM crops are not expected to do any better.

Cultivation of GM crops is a serious threat to food security particularly as global water supply is depleting (see [1] World Water Supply in Jeopardy, SiS 56) and already heavily polluted; with elicit and licit drugs (see [2] Pharmaceutical Cocktails Anyone?, SiS 56, [3] Illicit Drugs in Drinking Water), in addition to pathogens, arsenic, fluoride, chemical fertilizers, pesticides, industrial waste products, landfill leaks, and gasoline etc. [4] Water Not Fit to Drink, SiS 57).

Glyphosate in groundwater, surface water and rainfall

Glyphosate, the active ingredient of Monsanto’s Roundup herbicide, is one of the most commonly used herbicides in the world, owing to the widespread planting of glyphosate-tolerant (GT) crops. It has been associated with a host of human and livestock health issues including birth defects, reproductive problems, carcinogenicity, endocrine disruption, neurotoxicity and internal organ toxicity, as well as lethality to frogs and harm to soil and aquatic ecosystems (see [5] Why Glyphosate Should be Banned, SiS 56). With all this in mind, the contamination of water supplies with glyphosate, a highly water soluble herbicide, has wide-ranging implications. Read more at full article post: GM Crops and Water - A Recipe for Disaster

May 6, 2013

Source of Greenhouse Gas Emissions from Agricultural Soil Underestimated---Chinese Academy Of Sciences


Changes in agricultural practices could reduce soil emissions of nitrous oxide (N2O) and nitric oxide (NO), according to a new study by scientists at Chengdu Institute of Biology, Chinese Academy of Sciences and the University of California, Davis.

Nitrous oxide is a greenhouse gas and destroys the ozone layer that shields Earth from ultraviolet light high in the atmosphere. Nitric oxide is key to atmospheric photochemistry and air quality. Agriculture and the use of nitrogen-based fertilizer are a major source of atmospheric N2O and NO, which are produced through microbial and abiotic chemical reactions.

Prof. WU Ning and Dr. ZHU Xia from Chengdu Institute of Biology studied N2O and NO production from three different soil types fertilized with urea or ammonium sulfate under different oxygen concentrations. By labeling 15N in ammonium (NH4+) and nitrate (NO3-), 18O in H2O and NO3-, they distinguished N2O produced from different pathways, and found that low oxygen concentrations yielded more N2O and NO from ammonia oxidation pathways.

In this process, the opposite of what researchers previously believed based on indirect measures of oxygen was proved availability. Urea fertilizer also produced more N2O and NO. The results indicate that fertilizer choice and agricultural practices to promote soil aeration can reduce emissions.

The study’s other co-authors include UC Davis Department of Land, Air and Water Resources Professor William R Horwath, researchers Martin Burger and Timothy Doane. Funding for the study was provided through the J.G. Boswell Endowed Chair in Soil Science at UC Davis.

This paper entitled “Ammonia oxidation pathways and nitrifier denitrification are significant sources of N2O and NO under low oxygen availability” was published online in Proc. Nat. Acad. Sci. USA, DOI: 10.1073/pnas.1219993110. 

Full Text Link: Source of Greenhouse Gas Emissions from Agricultural Soil Underestimated---Chinese Academy Of Sciences

Smoke signals: How burning plants tell seeds to rise from the ashes - Salk Institute - News Release

April 29, 2013

LA JOLLA, CA—In the spring following a forest fire, trees that survived the blaze explode in new growth and plants sprout in abundance from the scorched earth. For centuries, it was a mystery how seeds, some long dormant in the soil, knew to push through the ashes to regenerate the burned forest.

In the April 23, 2013 early online edition of the Proceedings of the National Academy of Sciences(PNAS), scientists at the Salk Institute and the University of California, San Diego, report the results of a study that answers this fundamental "circle of life" question in plant ecology. In addition to explaining how fires lead to regeneration of forests and grasslands, their findings may aid in the development of plant varieties that help maintain and restore ecosystems that support all human societies.

"This is a very important and fundamental process of ecosystem renewal around the planet that we really didn't understand," says co-senior investigator Joseph P. Noel, professor and director of Salk's Jack H. Skirball Center for Chemical Biology and Proteomics. "Now we know the molecular triggers for how it occurs."

Noel's co-senior investigator on the project, Joanne Chory, professor and director of Salk's Plant Molecular and Cellular Biology Laboratory, says the team found the molecular "wake-up call" for burned forests. "What we discovered," she says, "is how a dying plant generates a chemical message for the next generation, telling dormant seeds it's time to sprout."

From left: Joanne Chory, Yongxia Guo, Joseph Noel, Zuyu Zheng and James J. La Clair
Image: Courtesy of the Salk Institute for Biological Studies

While controlled burns are common today, they weren't 50 years ago. The U.S. park service actively suppressed forest fires until they realized that the practice left the soil of mature forests lacking important minerals and chemicals. This created an intensely competitive environment that was ultimately detrimental to the entire forest ecosystem.

"When Yellowstone National Park was allowed to burn in 1988, many people felt that it would never be restored to its former beauty," says James J. La Clair, a researcher from the Department of Chemistry and Biochemistry at the University of California who worked on the project. "But by the following spring, when the rains arrived, there was a burst of flowering plants amid the nutrient-rich ash and charred ground."

In previous studies, scientists had discovered that special chemicals known as karrikins are created as trees and shrubs burn during a forest fire and remain in the soil after the fire, ensuring the forest will regenerate.

The Salk scientists' new study sought to uncover exactly how karrikins stimulate new plant growth. First, the researchers determined the structure of a plant protein know as KAI2, which binds to karrikin in dormant seeds. Then, comparing the karrikin-bound KAI2 protein to the structure of an unbound KAI2 protein allowed the researchers to speculate how KAI2 allows a seed to perceive karrikin in its environment.

The chemical structures the team solved revealed all the molecular contacts between karrikin and KAI2, according to Salk research associate Yongxia Guo, a structural enzymologist and one of the study's lead investigators. "But, more than that," Gou says, "we also now know that when karrikin binds to the KAI2 protein it causes a change in its shape."

The studies' other lead investigator, Salk research associate and plant geneticist Zuyu Zheng, says this karrikin-induced shape change may send a new signal to other proteins in the seeds. "These other protein players," he says, "together with karrikin and KAI2, generate the signal causing seed germination at the right place and time after a wildfire."

Guo and Zheng, a married couple working as postdoctoral researchers in the Noel and Chory labs, respectively, came up with the idea for the study while talking over dinner. La Clair then joined the study, contributing his chemistry expertise. While the new findings were made in Arabidopsis, a model organism that many plant researchers study, the scientists say the same karrikin-KAI2 regeneration strategy is undoubtedly found in many plant species.

"In plants, one member of this family of enzymes has been recruited somehow through natural selection to bind to this molecule in smoke and ash and generate this signal," says Noel, holder of Salk's Arthur and Julie Woodrow Chair and a Howard Hughes Medical Institute investigator. "KAI2 likely evolved when plant ecosystems started to flourish on the terrestrial earth and fire became a very important part of ecosystems to free up nutrients locked up in dying and dead plants."

More research is needed to understand exactly how the change in shape of the KAI2 protein activates a genetic pathway that regulates germination, says Chory, the Howard H. and Maryam R. Newman Chair in Plant Biology and a Howard Hughes Medical Institute investigator. "But this finding is an absolutely critical step in understanding this genetic program and how plant ecosystems, forests and grasslands renew themselves."

The work was supported by the National Institutes of Health grants 5R01GM52413 and GM094428,National Science Foundation awards EEC-0813570 and MCB-0645794 and the Howard Hughes Medical Institute.

About the Salk Institute for Biological Studies:
The Salk Institute for Biological Studies is one of the world's preeminent basic research institutions, where internationally renowned faculty probe fundamental life science questions in a unique, collaborative, and creative environment. Focused both on discovery and on mentoring future generations of researchers, Salk scientists make groundbreaking contributions to our understanding of cancer, aging, Alzheimer's, diabetes and infectious diseases by studying neuroscience, genetics, cell and plant biology, and related disciplines.

Faculty achievements have been recognized with numerous honors, including Nobel Prizes and memberships in the National Academy of Sciences. Founded in 1960 by polio vaccine pioneer Jonas Salk, M.D., the Institute is an independent nonprofit organization and architectural landmark.

Full Article: Smoke signals: How burning plants tell seeds to rise from the ashes - Salk Institute - News Release

Biochar and denitrification in soils: when, how much and why does biochar reduce N2O emissions? : Scientific Reports : Nature Publishing Group

Maria Luz Cayuela,
Miguel Angel Sánchez-Monedero,
Asunción Roig,
Kelly Hanley,
Akio Enders
& Johannes Lehmann
Corresponding author
Scientific Reports 3, 
Article number: 1732 doi:10.1038/srep01732
Received 09 January 2013 
Accepted 04 April 2013 
Published 25 April 2013

Agricultural soils represent the main source of anthropogenic N2O emissions. Recently, interactions of black carbon with the nitrogen cycle have been recognized and the use of biochar is being investigated as a means to reduce N2O emissions. However, the mechanisms of reduction remain unclear. Here we demonstrate the significant impact of biochar on denitrification, with a consistent decrease in N2O emissions by 10–90% in 14 different agricultural soils. Using the 15N gas-flux method we observed a consistent reduction of the N2O/(N2 + N2O) ratio, which demonstrates that biochar facilitates the last step of denitrification. Biochar acid buffer capacity was identified as an important aspect for mitigation that was not primarily caused by a pH shift in soil. We propose the function of biochar as an “electron shuttle” that facilitates the transfer of electrons to soil denitrifying microorganisms, which together with its liming effect would promote the reduction of N2O to N2.

Subject terms:
Environmental biotechnology
Climate-change mitigation

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In spite of numerous studies on biochar as a strategy to mitigate N2O emissions from soil1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14, 15, the factors and mechanisms involved remain elusive. This is the case in part because N2O can be formed through several distinct but often connected processes in soil16, which poses challenges to its quantification due to high spatial and temporal variability17, 18.

Although abiotic denitrification has been reported19, research has shown that most N2O emitted from soil is produced by three main biotic processes: denitrification17, nitrification20 and nitrifier denitrification21. These mechanisms may occur simultaneously at different micro-sites of the same soil, but it is generally assumed that most N2O emitted from agricultural lands is produced through denitrification16, 17, 22, 23.

Two principally different pathways can lead to lower denitrification N2O in soil16: (i) a decline in the total N denitrified (with less N2O emitted from soil in the intermediate reaction) or (ii) an enhancement of its further reduction to N2. The second pathway does not minimize total N losses (N2 + N2O), but the ratio N2O/(N2 + N2O) decreases and the environmental consequences of N2O emissions decrease. There are many mechanisms by which biochar might affect these two pathways. Biochar can modify the microbial activity in soil24, the concentration of available NO3−and organic C25, 26, pH11, 27 and soil aeration28, which are all important factors known to change both the N2O/(N2 + N2O) ratio and the total N denitrified29. At present there is no consensus about what makes a biochar able to mitigate N2O emissions. Most studies found that, in general, slow pyrolysis high-temperature biochars lead to the greatest N2O reductions8, 9, 10, 11, 12, 13, 14. However, there are no studies distinguishing between different N2O production mechanisms or quantifying total denitrification, which makes interpretation and generalization difficult. Therefore, we investigated the causes and the magnitude of denitrification with particular attention to the climate-relevant N2O after biochar addition to agricultural soils.


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Supplementary information
Does biochar promote or inhibit abiotic denitrification?

We found no N2O emitted from soil under abiotic conditions both in the presence and absence of biochar (Experiment 1; Table S1).
Does biochar reduce N2O emissions during denitrification and by which pathway?

In an incubation study (Experiment 2) with brush biochar and 15 agricultural soils (Tables S2, S3) we found significantly (P < 0.001) lower N2O emissions when biochar had been added (Fig. S1,Table 1). The intensity of mitigation ranged from 10 to 90%. In 10 out of the 15 measured soils, biochar did not only decrease the ratio N2O/(N2 + N2O) but also the total N denitrified. However, this result was less consistent, with five soils increasing the total N denitrified between 4 and 232%.
Table 1: Total N2O emissions from 15 agricultural soils un-amended (control) or mixed with 2% biochar (dry weight basis) under denitrification conditions (90% WFPS and 30°C). Soils were spiked with KNO3 (15N 99% enrichment), which allowed the determination of the total N denitrified (N2 + N2O) and the ratio N2O/(N2 + N2O) by the 15N gas-flux method
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In order to discern which soil characteristics influenced the ability of biochar additions to decrease N2O emissions, we performed a multivariate correlation (redundancy analysis) with the soil characteristics (Table S3) as predictor variables and the changes induced by biochar as response variables (Fig. 1). The first two ordination axes explained 49% of the variance. The first axis alone explained a significant part of the variation of the response variables (F = 21.9; P ≤ 0.002). High predictor-response correlations (first canonical axis: 0.915; second canonical axis: 0.654) revealed a strong relationship between soil characteristics and biochar effectiveness to reduce N2O emission. Biochar decreased the ratio of N2O/(N2 + N2O) predominantly in fine-textured soils. However, the ability of biochar to decrease total N2O emissions was independent of soil texture but highly correlated with initial soil NO3− concentrations and dissolved organic C.
Figure 1: Correlation triplot based on a redundancy analysis (RDA) depicting the relationship between the main physico-chemical characteristics of the soils (predictor variables) and the differences induced by biochar applications (response in soil) (according to Lepš and Šmilauer49).

Blue arrows point to maximum shifts produced by the biochar amendment, i.e. a decrease in the total cumulative N2O, the N2O/(N2 + N2O) ratio, and the flux of total N denitrified (N2 + N2O). Eigenvalues of the first two axes are 0.343 and 0.161, the sum of all canonical axes is 0.555. “Cumulative N2O” represents the difference (control-biochar) in total N2O emitted during the entire incubation period; “ratio” and “Total N denitrified” represent the differences (control-biochar) at the day selected for isotopic gas analysis (see Fig. S1). Tsilt, Tclay and Tsand represent the percentages of soil silt, clay and sand. DOC: dissolved organic C in soil.
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Why does biochar reduce N2O emissions?

In Experiment 3 we measured N2O emitted after soil amendment using nine biochars with different C/N ratios (Table S2; Fig. S2) after their pH had been adjusted to the same pH as the soil (pH: 5.6) (Fig. 2.A). Then, we repeated the incubation with the same biochars added without adjusting the pH (Fig. 2.B). The difference between Fig. 2.A and Fig. 2.B corresponds to the effect of biochar pH on total emissions. We found that this difference strongly correlates (r2 = 0.809; P < 0.01) with biochar buffer capacity (i.e. mmol H3O+ per gram of biochar necessary to adjust its pH to the same pH of the soil), but not with pH alone (r2 = 0.615; P > 0.05).
Figure 2: Total N2O emissions after 30 days of incubation of a muck soil (Elba) amended with different biochars (2% weight) under denitrification conditions (90% WFPS, 30°C).

The dashed line represents emissions from the control soil (unamended). Fig. 2A shows N2O emissions from soil amended with biochars for which the pH had been adjusted to the pH of the soil (5.6). Fig. 2.B shows N2O emissions from soil amended with biochars at their actual pH. Biochars are arranged from high to low C/N ratios. Error bars represent standard errors of the mean (n = 4).
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Given the known effect of pH on N2O production, we performed a parallel incubation (Experiment 4) to monitor the shift in soil pH induced by the different biochar additions. However, only dairy manure biochar led to a statistically significant yet low increase of 0.1 pH units (Table S4). We then analyzed N2O emissions from the same soil where the pH had been experimentally increased using additions of CaCO3 (Fig. S3) and observed no N2O mitigation (total N2O emissions after 13 days: 38.7 ± 4.4 for control (pH 5.60), 44.5 ± 3.9 for pH 5.79 and 45.5 ± 5.5 for pH 6.10, respectively).
Is it a short-term effect?

After 30 days of incubation (Experiment 3), N2O fluxes had leveled off in all treatments (Fig. S2) pointing to a depletion of NO3− or available organic C in soil. At day 34 we added 100 mg of NO3−-N and 1.0 g of glucose-C per kg of soil and production of N2O increased immediately (Experiment 5;Fig. S4). When pH was adjusted, only two of the biochars (pine and oak) significantly reduced N2O emissions (Fig. 3A). When pH was not adjusted, however, most biochars decrease the total amount of N2O emitted (between 41 and 72%), although only additions of biochars made from bamboo and oak had significantly lower emissions compared to the control at P < 0.05 (Fig. 3B). It is important to note that the different treatments had undergone 30 days under denitrification conditions, and their initial NO3− concentration (before spiking them with NO3− and glucose) might significantly differ.
Figure 3: Total cumulative N2O emissions produced after 7 days of incubation of a muck soil (Elba) spiked with 100 mg NO3− -N and 1 g of glucose-C per kg of soil.

The soil had been incubated with different biochars (2% weight) under denitrification conditions (90% WFPS, 30°C) during 1 month prior to N and C addition. The dashed line represents emissions from the control soil (without biochar). Fig. 1A shows N2O emissions from soil amended with biochars for which the pH had been previously adjusted to the pH of the soil (5.6). Fig. 1.B shows N2O emissions from soil amended with biochars at their actual pH. Biochars are arranged from high to low C/N ratios. Error bars represent standard errors of the mean (n = 4).
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In order to more closely investigate the mechanism of the observed medium-term mitigation we performed a second experiment where three soils (Secanos, Tioga and Elba) were pre-incubated (with and without biochar) for 14 days under denitrification conditions (Experiment 6) and subsequently spiked with a solution of K15NO3. After the pre-incubation period, the soils with added biochar showed far more NO3− compared to the soils without added biochar (Table 2). Even after the 15NO3− addition, the alkaline soil (Secanos) hardly showed any denitrification. The reason may be a lack of available C after the pre-incubation period, since this soil had a markedly lower total organic carbon concentration (8 g C kg−1 soil) compared to Tioga (29 g C kg−1 soil) or Elba soils (495 g C kg−1 soil). Both Tioga and Elba soils emitted N2O, but without any detectable N2. Recognizing the different initial NO3− concentrations of soils with and without biochar additions, we calculated the N2O emitted (as a result of the 15NO3− spike) per unit of NO3− in soil and observed a comparable mitigation effect for the Tioga soil and an even larger one for the Elba soil (Table 2) compared to Experiment 2 (Table 1), where soils were not pre-incubated.
Table 2: Influence of biochar (made from brush at 500°C) on N2O emissions from three different soils after a preincubation period (2 weeks)
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Supplementary information

Although biological processes dominate N2O production in most environments, chemodenitrification, an abiotic process wherein inorganic N species are reduced to gaseous species has been reported in soils with high concentrations of Fe (II) or humic acid extracts19. We did not find N2O emitted under abiotic conditions in the two soils most susceptible to chemodenitrification used in this study (Elba and Guarapuava), which implies that the N2O emitted from the soils was entirely produced through biotically mediated mechanisms. It also shows that biochar did in our study not abiotically induce N2O formation in soil through previously proposed catalytic reactions with hydroquinones30,31, metal ions or radicals19, 32, which are abundant in biochars31, 33.

Previous studies on N2O emissions and biochar are limited to one or two soil types3, 4, 7, 9, 10, 12, 13,34, 35. Given that these experiments have been conducted under varying environmental conditions and with different biochars, comparison between soil properties is difficult, which enormously limits generalization. Our study revealed that soil texture was closely related to the ability of biochar to decrease the ratio of N2O/(N2 + N2O) at the time of maximum N2O emissions (Fig. 1). The fact that biochar promoted the last step of denitrification predominantly in fine-textured soils (e.g. Lentiscosa, Madalin, Costa) indicates that the mechanism of reduction is not linked to an increase in soil aeration (if that were the case, biochar would decrease total denitrified N in these soils, instead of promoting the last step of denitrification to N2). This confirms recent findings6, which noticed soil aeration to be a negligible factor for N2O mitigation in soils containing biochar.

The strong correlation between NO3− concentration in the soil and total N2O mitigation by biochar additions (Fig. 1) suggested that biochar might reduce NO3− availability. A reduction in NO3−availability would indeed decrease the total N denitrified and it would favor the last step of denitrification (decreasing the ratio N2O/(N2 + N2O))36. On the other hand, N2O mitigation was also highly correlated with soil DOC, and less strongly with soil pH, which are known to control the denitrification capacity in soil37.

In Experiments 3 and 4 we further investigated these possible reasons for the observed reductions in N2O emissions. We postulated that by using a soil where the addition of biochar does not significantly influence its water filled pore space, the effect of biochar on denitrification N2O would mostly depend on biochar pH and its C/N ratio. Most biochars used in this study may immobilize NO3−, since their C/N ratios are greater than that of the soil (C/N = 18.7). Nitrogen immobilization in soil has often been found to decrease denitrification N2O38. Despite their high C/N ratios, we did not find a correlation between N2O mitigation and biochar C/N (range of C/N ratios: 11–859) irrespective of whether or not the pH of the biochars was adjusted. The high recalcitrance of high-temperature biochars to microbial degradation1, 8, 27 and the lack of correlation between biochar C/N and N2O mitigation found in our experiment do not suggest microbial immobilization of NO3− as the driving mechanism for the observed N2O reductions.

When the pH was adjusted, additions of high-N biochars led to more emitted N2O (Fig. 2B), which is probably due to an increase of NO3− concentrations in the soil. Although some N from the biochar may be mineralized, this does normally not exceed 10–20% of its total N content15. A salting-out effect through an increase of the ionic strength in the soil solution, which has shown to reduce the solubility of N2O (Setchenow effect) favoring its emission22, might have played a role for the differences among biochars. The correlation between ash content and N2O emissions was highly significant (r2 = 0.809; P = 0.002). However, the persistence of the reduction in denitrification found in Experiment 6 sheds doubts on this explanation.

A mere shift in soil pH was not the reason for the mitigation of N2O emissions as demonstrated in Experiment 4 (Fig. S3). Our finding is in agreement with those by Yanai et al.2, who after increasing the soil pH with ash applications (instead of biochar) did not observe any reductions in N2O emissions. This suggests that the change in soil pH does not by itself induce the N2O reductions, but rather other properties of biochar intrinsically connected to pH.

Despite its refractory nature, biochar contains abundant redox-reactive organic and inorganic compounds31. For example, quinone groups may be reduced during suboxic conditions to hydroquinone or phenols that can subsequently act as electron donors. Such redox systems readily changing from one steady-state to another31 have been described for other forms of organic matter in soil, such as humic substances extracts39 or plant and microbial exudates40, and are known as “electron shuttles”. The presence of free radicals in some biochars may even increase their reactivity31.

Under suboxic conditions, facultative anaerobic microorganisms can utilize NO3−, Mn (IV) and Fe (III) compounds substituting O2 as electron acceptor41. Biochar contains both Mn and Fe at varying concentrations depending on the feedstock and pyrolysis temperature27. For example Enders et al.27 reported Mn and Fe concentrations of up to 9% (d.w.) in biochars produced at 500°C. Mn (IV) and Fe (III) are known to readily function as electron acceptors at circumneutral pH42. Biochar might act as a reducing agent itself and additionally as an electron shuttle, facilitating the electron transfer to microorganisms by acting as an electrical conduit. Thus, biochar might compete with NO3− as an electron sink, which could explain the lower total N denitrified in many soils. On the other hand, its function as an electron shuttle connected to its liming effect might facilitate the activity of N2O reductase and therefore promote the last step of denitrification29, both hypotheses that need further testing.

Another controversial aspect of N2O mitigation with biochar is the debate about its transitory effect. In a recent study Spokas43 found that three years ageing negated the N2O mitigation that was originally observed from the fresh biochar in laboratory incubations. Ageing is known to substantially alter biochar surface chemistry and reactivity31, which may impact the ability of biochars to function as an electron acceptor or shuttle. Experiment 5 showed that N2O mitigation is effective one month after biochar application and it is still strongly related to pH, albeit not a result of pH changes as indicated above. One of the hypotheses proposed for temporary N2O mitigation is that, immediately after application, biochar might have a short-term inhibitory effect, decreasing the microbial activity in soil. For example, Spokas et al.35 found a correlation between ethylene concentration and N2O production in soil amended with biochar and proposed the inhibitory impact of ethylene on microbial biomass as a mechanism that could significantly contribute to N2O mitigation. This mechanism may be significant for biochars produced at low temperatures, with a high concentration of tars, which might temporarily reduce the activity of denitrifier communities in soil. Nonetheless, for biochars produced at 500°C, the contribution of this mechanism appears to be minor. Looking more closely at the mechanism of medium-term mitigation in Experiment 6, the soils pre-incubated with biochar showed far more NO3− compared to the control soils (Table 2). These results stand in stark contrast to the hypothesis that decreasing N2O emissions were caused by the ability of biochar to adsorb NO3− in soil6, 13. Even though we investigated medium-term effects after several weeks separately from effects observed immediately after addition of fresh biochars to soil, aging of biochars over periods of months and years may affect the results43. Additional long-term studies on N2O mitigation with biochar are required to quantify the duration of this effect31, 43.

In summary, under optimum denitrification conditions, biochar consistently reduced N2O emissions in the investigated agricultural soils. It decreased the ratio of N2O/(N2 + N2O) and in most cases also the total N denitrified. Biochars obtained at 500°C by slow pyrolysis, independently of their original feedstock, were able to decrease N2O fluxes produced by denitrification. In light of our results, we discard biochar toxicity, NO3− immobilization or NO3− sorption as relevant mechanisms for N2O mitigation with high-temperature slow-pyrolysis biochar. The complexity of biotic and abiotic biochar-soil interactions points at several mitigation mechanisms occurring simultaneously. Biochar buffer capacity appears to be fundamental to decreasing N2O emissions during denitrification, not because of a change of soil pH in itself, but because the mechanism of mitigation is intrinsically connected to pH. We have demonstrated that biochars promote the last step of denitrification, and in two out of three cases it also decreased total N denitrified. We propose as a plausible explanation that biochar is able to facilitate the transfer of electrons to denitrifying microorganisms in soil, thus acting as an electron shuttle. This together with its liming effect and high surface area would promote the reduction of N2O to N2. Our results are based on short-term laboratory assays that did not take into account other important aspects occurring under field conditions, including biochar ageing or soil-plant-microbe interactions. The results of our study allowed us to formulate a new hypothesis that had not been considered before and that might play an important role explaining reductions in N2O formation when denitrification is the dominant pathway. This hypothesis requires further experimentation to prove its magnitude and eventually its practical significance.


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Supplementary information

Nine biochars produced at 500°C by slow pyrolysis as described in Enders et al.27 were selected with the aim of obtaining a wide range of C/N ratios from 11 to 859 and pH values between 6.4 and 10.7 (Table S2). Biochars were ground and sieved to a particle size between 200–500 μm before soil application. Brush biochar was used in all experiments and selected for those involving different soils (Experiments 1, 2 and 6) because of its neutral pH and also because it can be considered as representative of a generic biochar widely utilized and available worldwide.

Fifteen agricultural soils from 3 different geographical areas (USA, Spain and Brazil) were selected comprising a wide range of textures and pH values (Table S3). The soils were sampled from a depth of 0–0.25 m of agricultural fields, air-dried and sieved (<2 mm). Agricultural organic soils have been reported to emit high fluxes of N2O44. In experiments involving different biochars (Experiments 3 and 5) we therefore selected a muck soil (drained cultivated Histosol) in order to obtain high N2O emissions that allowed us to detect the effects of different biochars more sensitively. If an effect (positive or negative) was not observed at high emissions, biochar would not play a role. In addition, this organic soil has a high porosity, which allowed us to assume that biochar additions would not modify its water filled pore space. For practical reasons the collected muck soil was maintained in its field moist condition, sieved (<2 mm) and stored at 4°C until the beginning of the experiment.
Chemical-physical analyses of biochars and soils

Biochars: Proximate analysis was conducted using ASTM D1762-84 Chemical Analysis of Wood Charcoal. Total C and N were determined by Dumas combustion using a PDZ Europa ANCA-GSL elemental analyzer connected to a PDZ Europa 20–20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK). pH and electrical conductivity (EC) were determined in 1:10 (w:v) water-soluble extracts. NH4+ and NO3− were extracted with 2.0 M KCl at 1:10 (w:v) and quantified colorimetrically using a continuous flow analyzer (Bran and Luebbe Autoanalyzer, SPX, Charlotte, NC). Soils: Soil texture was determined using the pipette method according to Kettler et al.45. pH was determined in 1:10 (w:v) water extracts. Dissolved organic C (DOC) and total dissolved N (TDN) were determined in 1:10 (w:v) water extracts (shaken for 2 h, centrifuged for 10 min at 1500×g and filtered (GF/F Whatman glass filters) with a TOC analyzer (Shimadzu Total Organic Carbon-Visionary Series; TOC-VCSH).
Incubation studies

The incubation experiments were performed with units consisting of 100 g dry soil (control) or 98 g dry soil and 2 g biochar (treatments) in 250 ml (or 500 ml in the case of the muck soil) glass jars at optimum conditions for denitrification: 30°C and a moisture of 90% of the water filled pore space (WFPS). The biochars were thoroughly mixed with the dry soil to obtain a completely homogeneous mixture. Subsequently, water (or a solution containing the appropriate concentration of NO3−) was added to attain the required moisture. The jars were covered with a polyethylene sheet that allows gas exchange but minimizes evaporation. Moisture was kept constant by adjusting the water content every other day. The experiments were laid out as a randomized block design with four replicates.
Experiment 1

This experiment was aimed at quantifying any abiotic contribution to N2O formation (chemodenitrification) from the two soils most susceptible to chemodenitrification in this study (Elba and Guarapuava; total organic C: 495 and 43.5 g kg−1, respectively). 50 g of Elba or 100 g Gurapuava soils were either untreated (controls) or treated with 2% biochar (made from brush), subsequently placed in 250-ml jars at 90% WFPS and doubly autoclaved for sterilisation (103.4 kPa and 121°C for 1 h, incubated 24 h, and autoclaved for an additional 1 h). The samples were cooled down to 30°C overnight and N2O concentrations were measured by means of gas chromatography equipped with an electron capture detector (ECD) 12 h after sterilization. Since no N2O was emitted from any of the samples, a sterile solution of KNO3 was added (100 mg N kg−1 soil) and the N2O accumulated in the headspace during 40 min was immediately measured (Table S1).
Experiment 2

This study was designed to determine the magnitude of N2O mitigation by biochar in different soils as well as investigating the mechanism involved. Brush biochar was applied at an equal rate (2% dry weight) to 15 different agricultural soils. Moisture was adjusted to 90% WFPS in each jar by adding the required volume of a solution containing KNO3 (>99% 15N enrichment) at the appropriate concentration to obtain 90% WFPS and exactly 5 mg of NO3−-15N-per jar (50 mg of NO3−-15N kg−1 soil). Rewetting the soils in this fashion guaranteed a homogenous 15N-NO3− pool, which is essential to correctly apply the equations derived by Mulvaney and Boast46 to calculate total N denitrified. We measured N2O fluxes from the 15 unamended soils compared to those amended with 2% biochar (Fig. S1).
Experiment 3

The organic soil (Elba) was sampled from a depth of 0–0.25 m of a horticultural field in Genesse County, NY. We assumed that the addition of biochar (at 2%, w:w) to this soil would not modify its aeration at 90% WFPS. With the aim of verifying this assumption we tested its water retention curves (Fig. S6) and observed no significant differences among treatments.

To differentiate the effects of pH values from C/N ratios we carried out two incubations. In the first one the pH of the biochars was adjusted to the same pH of the soil (5.6) prior to application. The pH adjustment was done by shaking each biochar with water (1:20, w:v) for 12 hours; pH was measured and adjusted to 5.6 first with a 2 M HCl solution and later with a 0.1 M HCl solution (close to the end point). The volume of HCl solution necessary to adjust the pH was registered in order to calculate the biochars' buffer capacity (i.e. mmol H3O+ per gram of biochar necessary to adjust its pH to 5.6). Once the pH had been adjusted, the biochars were shaken for 12 hours and the pH was tested again. Biochars were then dried for 2 days at 80°C and homogenized before their addition to soil. We also checked that the pH adjustment did not modify the amount of water-extractable NO3− in biochars. In the second incubation the biochars were applied without any pre-treatment. In both cases biochars were applied at 2% (w:w) and thoroughly mixed with the soil, which was re-packed to the average field bulk density (0.65 g l−1) inside the jars. De-ionized water was added to adjust the moisture to 90% WFPS, equivalent to 2.07 g water per g dry soil. N2O fluxes were analyzed during one month of incubation (Fig. S2).
Experiment 4

In this experiment we investigated how the manipulation of soil pH influences N2O emissions. First we evaluated the magnitude of pH changes induced by the biochars in Experiment 2. We carried out a parallel incubation (2 replicates per treatment) under identical environmental conditions where we monitored the pH after 1, 3 and 14 days of incubation (Table S4). Second, we performed an incubation study with the same soil where we modified its pH in the same order of magnitude as was induced by biochars measured in the preceding experiment. We included a control (Elba soil at its natural pH of 5.6) and two treatments where we increased the pH of the soil to 5.79 and 6.10 by adjusting to 90% WFPS with water solutions containing 0.010 and 0.020 g of CaCO3 per 100 g of dry soil, respectively. We compared the N2O emissions over two weeks (Fig. S3).
Experiment 5

This experiment was an extension of Experiment 3 aimed at studying the temporal dynamics of biochar effects. After 1 month of incubation N2O fluxes were low in all samples (Fig. S2). At day 34 we applied 5 ml of a solution containing KNO3 (2 g N L−1) and glucose (20 g C L−1), which is equivalent to 100 mg N and 1 g C kg−1 soil and measured the N2O fluxes resulting from this addition (Fig. S4).
Experiment 6

Two mineral soils with a loamy texture and contrasting pH (Secanos, Tioga) and the organic soil (Elba) were selected for this experiment. Each control soil and its corresponding biochar treatment (2%, w:w) was pre-incubated for 14 days under denitrification conditions (90% WFPS, 30°C). From day 13 to day 16 the samples were left to dry to ca. 50% WFPS, which was verified gravimetrically. At day 16, moisture was re-adjusted to 90% WFPS in each jar by adding the required volume of a solution containing KNO3 (>99%15N enrichment) at the necessary concentration to obtain 5 mg of NO3−-15N per jar (similarly to Experiment 2) (Fig. S5).
N2O sampling and measurements

Gas sampling was conducted by sealing each unit with screw caps for 40 min. 10 ml of the headspace gas was sampled with 25 ml gastight polypropylene syringes and measured within 12 hours by gas chromatography (Shimadzu GC-14A GC equipped with ECD (Ni63) detector (Kyoto, Japan)). Measurements were done daily during the first three days; decreasing subsequently to every other day, three times per week, etc. (see Fig. S1, Fig. S2, Fig. S3 etc. in the supporting information section).

N2O fluxes were calculated assuming a linear increase during the accumulation (closing) period, a fact that was checked prior to the experiments (every 15 minutes for 1 hour). Cumulative N2O was calculated assuming linear changes in fluxes between the two closest measurement points.

In experiments with 15NO3− (Experiments 2 and 6) the 15N gas-flux method46, 47, 48 was used to quantify N2O and N2 emissions. The gas sampling for isotopic analysis was made each day preceding the gas sampling for GC-ECD analysis and within an independent accumulation period. Two gas samples were collected using a 12-ml syringe and needle: one immediately after the lid was fitted to the jar (t = 0) and the second after 40 min (t = 40). The gas samples were transferred to 12-ml vials (Labco) previously purged with He and evacuated. A posteriori, gas samples were selected at time points where the difference in N2O fluxes (measured by GC-ECD) between biochar and control soils were the greatest, which normally corresponded with the peak in N2O emissions. Selected samples (a total of 320) were analyzed for their isotope ratios of N2 (29/28 (29R) and 30/28 (30R)) and N2O (45/44 (45R) and 46/44 (46R)) by automated isotope ratio mass spectroscopy (ThermoFinnigan GasBench & PreCon trace gas concentration system interfaced to a ThermoScientific Delta V Plus isotope-ratio mass spectrometer (Bremen, Germany)).
Data calculations and statistics

The molar fraction of 15N-NO3− (15XN) in the soil pool was calculated from the Δ45R and Δ46R according to Stevens and Laughlin48. The flux of N2 and N2O was then calculated by the equations given by Mulvaney and Boast46.

Since data were not normally distributed, they were ln-transformed prior to univariate analysis of variance with SPSS 19.0. The correlation between soil properties and biochar effectiveness in reducing emissions was determined by redundancy analysis (RDA) using CANOCO 4.5 for Windows. The characteristics of the soil (silt, clay, sand, pH, DOC, NO3−, NH4+) were included as predictor variables and the (i) total N2O emissions, (ii) flux of total N denitrified, and (iii) N2O/(N2 + N2O) ratios between controls and biochar treatments as the dependent variables. Data were centered and standardized. Significance of the ordination axes was calculated by the Monte-Carlo permutation test; n = 499.

Full Article:
Biochar and denitrification in soils: when, how much and why does biochar reduce N2O emissions? : Scientific Reports : Nature Publishing Group