Pedology and CO2

In a previous post I provided an oblique link to a news release: Climate Change Alters Ocean Chemistry. It makes reference to conditions resonating with the theory of biorhexistacy:

The research team, which included Caldeira, Elizabeth M. Griffith and Adina Paytan of the University of California, Santa Cruz, plus two other colleagues, studied core samples of deep oceanic sediment recovered from the Pacific Ocean Basin. By analyzing the calcium isotopes in grains of the mineral barite in different layers, they determined that between 13 and 8 million years ago the ocean’s calcium levels shifted dramatically. The shift corresponds to the growth of the Antarctic ice sheets during the same time interval. Because of the huge volume of water that became locked up in the ice cap, sea level also dropped.

“The climate got colder, ice sheets expanded, sea level dropped, and the intensity, type, and extent of weathering on land changed,” explains Griffith.

“This caused changes in ocean circulation and in the amount and composition of what rivers delivered to the ocean,” adds Paytan. “This in turn impacted the biology and chemistry of the ocean.”

These folks are saying that momentous changes in oceanic chemistry recorded in the sediment record must have been predicated by equally momentous changes in soil chemistry, changes tied to both atmospheric carbon dioxide content and climatic conditions.

From a pedologist's view, it is clear that under the expanded humid, warm, stable conditions envisioned by H. Erhart for biostasis, we would see deeper residual soils and more rapid formation of argillic horizons. In terms of soil taxonomic orders (USDA), more intense chemical weathering would cause the expansion of inceptisols at the expense of mollisols, ultisols at the expense of alfisols, and oxisols at the expense of ultisols.

Caldeira and company tie warm climate to higher river calcium content, but strongly implicate higher atmospheric carbon dioxide as the primary driver of increased chemical weathering. Atmospheric carbon dioxide levels do not appear to be part of Erhart's construct, but could certainly enhance these pedogenetic trends.

Acid rain alarm bells are ringing faintly in the distance at this point. But it is a false alarm. Rain water pH is due mostly to equilibrium with atmospheric carbon dioxide. The carbonic acid formed buffers rain drop pH to 5.6, and higher atmospheric carbon dioxide increases the carbonic acid content, but it doesn't lower pH below 5.6. Other constituents accomplish that. Thus increased atmospheric carbon dioxide isn't being implicated in some futuristic acid rain scenario.

Oxisols, ultisols and spodosols would increase in extent with increased soil weathering. But could it also mean lower plant disease, and more nutritious crops? Increased carbonic acid would drive faster pedogenesis, as would increased the biological activity stimulated by higher carbon dioxide. For soil, that would mean a richer solute content in the soil water, more rapid formation of secondary minerals, more eluviation or translocation of minerals with percolation. To the list of pedological shifts at the soil order level, we can add the expansion of spodosols at the expense of inceptisols.

Something very positive can be expected for soil that is not captured in the shifting soil order paradigm. For plants and soil microbes, richer solute content would mean greater availability of mineral nutrients. In soil husbandry and slow food circles, higher mineral availability translates to healthier soil, lower plant disease, and more nutritious harvests. What the shifting soil order paradigm does signal is that soils will be at greater risk of losing their fertility to leaching. Having the soil chockablock full of biochar will be essential to mitigate this last effect. Let's start now.

(Recycled from nscss.org)

Biostasy

The Theory of Biorhexistasy describes climatic conditions necessary for periods of soil formation (pedogenesis) separated by periods of soil erosion. Proposed by pedologist H. Erhart in 1951, the theory defines two climatic phases: biostasy and rhexistasy.

If I recall, H. Erhart figured this out while on the Congo river contemplating a low sediment load in a high rainfall, potentially highly erosive setting. Impressive. There is a soil science truism that clean water is hungry water, and can't wash across or through the land without taking some with. From a soil scientist's perspective, water is soil in highly dilute form. (So is air.)

Reading between the lines, I don't think Erhart had a research budget much beyond travel expenses. He simply deduced from what he knew of tropical weathering that the river had to be laden with dissolved minerals, calcium especially, washed from the soil by percolating rain water. Groundbreaking as that was in its own right, he didn't stop there. Using induction, he reasoned that when similar conditions dominated it ages past, rivers would have delivered abundant calcium to ancient seas subsequently (at the close of the age, perhaps) yielding vast limestone deposits. He saw these ages as lush, moist, and warm with accelerated chemical weathering accompanied by the formation of deep soils. Biostasy. Between periods of biostasy, he envisioned conditions dominated instead by physical weathering: severe fluctuations in temperature and moisture, sparse vegetation, shallow exposed soils, rivers choked with sediments, but with low solute content. This insight informs interpreting endokarstic sediments(Yves Quinif) in Europe where stalacite formation is observed to be greatest, and with least sediment, during interglacial periods due to higher dissolved calcium content, and less soil erosion.

Simply as a mental exercise, consider a scenario where atmospheric carbon dioxide hits 1200 ppm 200 years from now. In the context of biorhexistasy, what is going to dominate? biostasy, rhexistasy or will it be something well outside H. Erhart's elegant construct? Considering that the Congo and the sediment laden Nile coexist in the same age, it is certainly conceivable that biorhexistasy will continue to play out differently based on location, with neither dominating. But the undeniable effect of higher carbon dioxide is higher chemical weathering. So maybe rhexistasy during the transition, followed by biostasy.

(Recycled from nscss.org)

Redox Cascade

This chart (click for a readable version) shows shows the cascading preference of electron acceptors needed to sustain microbial respiration. When a soil system runs out of oxygen, it relies on nitrate (denitrification) to accept the electrons freed by respiration, and so forth down the cascade. Not shown at the bottom of the cascade is the production of hydrogen from water, but then that is an extreme seldom achieved in nature. The units for Eh are millivolts, the standard measure of redox potential.

An equivalent measure of redox potential is pE. Just as pH is the negative log of the hydrion activity, pE is the negative log of electron activity (source). Soil pE and soil pH are equally important to predicting charge state of metals and nutrients. However, because measuring pH is relatively easier by far, and because knowing pH tells us volumes about expected pE, soil pE is a less discussed subject. It is important to bioremediation, industrial chemistry, and wetland science. Not a household term.

These two are more than a mirror pair, although mirroring is their most notable characteristic. When pH changes, pE must also change in response. The reverse is true also. In soil, that response departs from simple mirroring. So much so that it can seem to be two separate dances.

Soil pH and pE have different causes of change and different effective buffering agents. The term 'buffering' is replaced in a pE context - it is called poise. A stabilized soil pE system is referred to as a well poised system, differences in soil buffering versus soil poise account for the departure from 1:1 mirroring.

Now for the exciting stuff. To many of us, what makes soil different than geologic material is that it is in an excited state, excited mostly by solar energy as facilitated by living processes. Unlike soil pH, soil pE is directly influenced by these energy fluxes.

The most influential cause of changes in soil pE is metabolic respiration aka oxidation. Oxidation doesn't necessarily involve oxygen. Oxidation does necessarily involve shedding an electron. Thus, respiring living systems lower the pE of a soil system, and with pE in the dance lead, pH must follow. Wetlands are low pE systems, wetlands with hydrogen sulphide odors are very low pE systems. Common dryland agricultural crops, like wheat, cannot abide low pE systems. Rice is adapted to low pE conditions.

A well recognized soil buffering agent is lime, which buffers a soil to about pH 8.2. The major agent of soil poise is iron. By all rights, the chart should show iron as having the longest duration horizontal line: there is a vast amount of iron in soil compared to nitrate and manganese. However soil manganese, although far less abundant than iron, plays a more important, more dynamic role in most soil systems.

One soil scientist, Richmond Bartlett, was so taken with the importance of manganese in this regard that he opened his chapter on manganese in a 1995 soil chemistry text (1995, Environmental Soil Chemistry, edited by Don Sparks) with the phrase “We all should fall upon our knees and sing out praise for manganese” Richmond Bartlett goes on to describe the role of manganese in terms that nearly describe a catalyst. Mn is not consumed, and the capacity for metabolic respiration increases in its presence.

This is sheer speculation on my part: from my view through the knothole, the nearly catalytic nature of traces of Mn is a finessing touch that makes bio-char the wonderful soil reef it is. It is a fine point, and one hardly worth mentioning considering the much more important issues that need working out in our pursuit of Wim Sombroek's vision for terra preta nova.

Expanded from information originally posted on the terra preta forum.

Dilution is the solution to pollution

Land treatment of industrial waste water can save energy. Mechanical aeration for treatment demands large quantities of electrical power. In land treatment, this is replaced by passive aeration. The energy cost reduction can be well in excess of the payments needed to purchase the land. A disadvantage of land application of waste waste is that it can contribute to ground water salinity.
Crops and soil treatment do little to remove mineral salinity from applied waters. How much salinity in ground water is too much? Salinity doesn't threaten health as much as it taints taste. This creates a dilemma. Environmental regulators are challenged to defend enforcement limits based on aesthetics with the same vigor as criteria based on human health. They are particularly challenged when the industries contributing to groundwater salinity are valued employers contributing to rural economies. But defend water quality standards they must.
Salt load in land applied waste water is considered by many to be the single most important challenge facing the industries which use land application to treat waste water. Particularly sensitive to this issue are briners, cheese processors and some electronics manufacturers. Among waste water spray field management advisers the consensus is that saline waste water spray field operations should avoid sites where the discharge can't be diluted by substantial rainfall and/or groundwater flux. In short, dilution is the only practical solution when it comes to salts in waste water. If the operation is located in an area that does not enjoy the benefits of natural dilution, the brine portion of the waste water stream can be segregated and transported to an area that does. Not an easy task but not unprecedented. A municipal waste water treatment plant discharging to a substantial body of water is a logical choice for receiving the brine.
These comments are prompted by a news article today in the Sacramento Bee (free registration required): Hilmar faces more pollution rules. Cheese factory agrees to give water quality board more authority.
[follow-up comment from Chris Bowman, Sac-Bee: The brine collected from the reverse osmosis filters is hauled to an East Bay MUD treatment plant.]

Tech Tags: Environment news article government regulation permit

Dry lab fraud alleged

Have you taken soil samples and tested soils to determine the level of plant available nutrients in the soil?

Question No. 1, page 12, Self-Assessment Workbook (pdf)

Most soil lab procedures involve wet chemistry. Dry lab results, in the vernacular, are made-up results, place-holders if you will. Sometimes they serve a legitimate purpose. Dry labbing with the intent to deceive for monetary gain is fraud. This is apparently what USDA-NRCS is accusing 15 unnamed eastern Washington farmers of when they self-qualified for monetary awards under the Conservation Security Program. CSP participants in the top tier receive up to $45,000 per year for a 10 year period for the most environmentally conscious farms. Reading both the linked Seattle P-I article and the original Spokesman-Review article, (subscription required) it looks like a few farmers fabricated a history of soil sampling and lab analysis in order to qualify. The good news is that 131 farmers audited came up clean.

For other CSP news, see also:
Capital Press article (subscription required): “CSP losing momentum”
Delta Farm Press article: “USDA announces cut in CSP watersheds in 2006”

Tech Tags: farm news soil lab analysis fraud

Tetany animal health issue and soil, hay links

Tetany is a complex disease in that no specific condition triggers it in all cases. Gauge tetany risk using soil and tissue analysis when growing or feeding hay comprised solely of cool-season grasses. A grass-legume mix does not have this risk.

Tetany is a disease affecting ruminants and is associated with feeding or grazing bluegrass, bromegrass, fescue, orchardgrass, ryegrass, timothy and wheatgrass. It is caused by low blood levels of calcium and/or magnesium. Classic risk conditions occur when the forage grass is growing quickly in the spring and nitrogen levels are high. Less well known is that tetany can be a problem when hay is grown on soils with excessive soil potassium. Manure and potassium hydroxide cleansers are two potential sources. Lactating animals are more susceptible to tetany, thus dairies are particularly alert to the concern and tend to avoid growing or feeding grass hay exclusively. Forage guides may not mention it as a concern. A forage tissue ratio of K/(Ca+Mg) of more than 2.2 indicates a high risk of tetany and the need to supplement feed with magnesium (Mg) (see also). If an animal goes down and tetany is suspected, a veterinarian should be contacted for immediate treatment. Often an animal will recover if it can be given an injection of magnesium sulfate (Epsom salts) early on.

Preventative Mg feed supplement and the ready supply of alfalfa tends to keep the incidence of tetany to a minimum. My thought is that tetany is additionally controlled by the close knit nature of farm communities. Caring neighbors and long memories tend to interact sufficiently that tetany symptoms don't take more than an animal or two, usually the weakest anyway, before it is figured out. Perhaps this explains why analytical laboratories in my region are generally unaware of tetany or the role of soil and tissue nutrient levels. My opinion is that cooperative extension publications in the Pacific Northwest can do better in this area. Tips for preventing animal loss due to tetany should be included in the fertility guides published to help folk interpret forage test results.

See also:
Spring Mineral Considerations by Jeff Heldt (link added 03MAR06)
Controlling Grass Tetany in Livestock, by Cooperative Extension, New Mexico State University, available in pdf format

Tech Tags: soil science animal nutrition environment chemistry dairy manure farm waste recycling land treatment information

In 1794

On January 4th in 1794, was born Edward Ruffin the father of soil chemistry in the U.S., who showed how to restore fertility to depleted soil. Though without formal science education, Ruffin determined that the soil of southeast plantations that had been overused with single-crop production had become more acidic and unable to benefit from fertilizers. The remedy he published (1818) was the spreading of marl to neutralize the acidity. He went further by specifying effective methods of fertilizing, plowing and rotating crops to increase production of grains. He expanded his recommendations in book and journal article form, as well as lecturing up to the 1850's. He then became an outspoken secessionist, and took his own life upon the South losing in the Civil War, at least when he learned of it on June 18, 1865.

Today in Science History

Adapted from a post at XDA blog by Roger Fraley.

This would be a good addition to soil science articles in wikipedia.

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