Soil Horizons

Up and down. Up and down. Earthworms slowly wriggle their way through the soil, eating leaves, burrowing holes, leaving behind nutrients … and completely altering the forest floor. While people usually perceive earthworms as good for the soil, forest soils invaded by earthworms are a different story. "The forest floor is an organic-rich soil layer, and it's just candy for the exotic earthworms that are invading forests in the non-glaciated regions of North America," says Peter Groffman of the Cary Institute of Ecosystem Studies who has been researching these invasions with funding from the National Science Foundation. "They burrow through [that layer], mix it with the [underlying] soil, and stimulate microbial growth. It's a physical, chemical, and biological transformation of that forest floor into something else, and it has huge implications for the health of the forest." The forest floor is the top layer of forest soil, and it is made up of fallen leaves, roots, stems, branches, and bark, all at varying stages of decomposition. Groffman is working to learn how exotic earthworms invade and affect northern temperate forests and their soils in North America. Natural history tells us that glaciers eliminated native earthworms from these forests 15,000 years ago, and they have been without them ever since. But Groffman says that about 30 years ago, people began to notice that earthworms from Europe and Asia were colonizing some forests in northeastern North America. Now, up to 16 different species of earthworms can be found in these soils. The European worms in question are mainly from the Lumbricidae family and include the surface dweller Lumbricus rubellus and the deep-burrowing common night crawler Lumbricus terrestris. Groffman says these were introduced to the United States during colonial times. The more recent Asian species are from the genus Amynthas. Invasive species are a problem in many areas of the United States. They are insects, animals, or plants—both terrestrial and aquatic—that become established in ecosystems where they traditionally weren't present. In many of these ecosystems, native organisms and environments have evolved in tandem for millennia. Throwing off this balance and forcing an ecosystem to take on a new species can cause a lot of strain. Establishment of invasive species is aided when they don't have any natural predators in the area. This allows their population numbers to rise unchecked and overwhelm native species, which have no natural defenses against the invasion. The most obvious effect of an exotic earthworm invasion in northern forests is that the forest floor would disappear within just two to five years. This drew the attention of researchers because that layer is considered very important. The top layer of forest soils in North American forests, the forest floor, is being transformed by exotic earthworms. Photo by Samantha Cillo. When the forest floor disappears, so do the organisms that live there. These invasions harm the biodiversity of the soil, which serves as habitat for a large number of organisms—from salamanders, small mammals, and ground-nesting birds to beetles and plants. "Many of the organisms that used to live in the forest floor can't live there anymore because it's gone," Groffman says. "It's a classic case of habitat loss reducing biodiversity." Along with decreasing biodiversity, the disappearance of the forest floor can increase the susceptibility of the soil to erosion and drought, alter its ability to store, or "sequester," carbon long term, and modify the cycling of carbon, nitrogen, and phosphorus. "We would like to think that our forests are sequestering carbon from the atmosphere," Groffman says. "These ecosystems are large natural reservoirs of carbon and play a role in curbing climate change. However, when earthworms invade, they transfer much of the carbon from the forest floor back into the atmosphere. In addition to directly eating and respiring some of the forest floor organic matter, they also mix organic matter into the soil, stimulating microorganisms that also eat carbon and send it back into the atmosphere." Surprisingly, the nitrogen content of some of the soils Groffman studied did not decline along with carbon. This caused the carbon-to-nitrogen ratio to decrease, which can reduce the forest soils' ability to hold on to the nitrogen from the atmosphere or from runoff from adjacent agricultural lands or urban areas. When it comes to phosphorus, earthworms may be causing two effects. At the surface, earthworms appear to cause losses of the phosphorus that plants need, but at the same time, some earthworms seem to be bringing up phosphorus from deep down in the soil, which is not in a form that plants can use. It really depends on the species of earthworm in a particular soil because some burrow deep, and others stay closer to the surface. The loss of phosphorus from the surface soil is a concern because this nutrient can pollute downstream lakes and rivers. The loss of the forest floor can also make a forest more susceptible to drought. The forest floor can act like mulch to keep the soil moist. Moreover, earthworms disrupt the interactions that trees have with mycorrhizal fungi, which help roots to take up nutrients. Together, these effects could reduce tree health. The reasons for the invasion are complex and likely due to multiple factors. Groffman says that there is a strong possibility the invasion is human-driven and that habitat fragmentation is to blame. "If you have long tracks of forest where there's very little human activity, you're much less likely to have invasive species introduced there," he explains. "But as we cut the forest into smaller and smaller pieces and have more human interaction with the forest, you're much more likely to get invasions." Additionally, there's a hypothesis about people's fishing habits causing invasions. Exotic earthworms may be found around lakes simply because it's good habitat for them. But Groffman says that anglers may also be inadvertently introducing them by discarding earthworms they use as bait at their fishing site instead of taking the leftover worms with them. Climate change may also be facilitating earthworm invasions. As certain areas experience warmer temperatures, earthworms that usually wouldn't be able to persist over winter are able to move in and establish themselves. Forest fragmentation (top) and people's fishing habits (bottom) could be two reasons for the earthworm invasion. Top photo courtesy of Wikimedia Commons/ Larrousiney. Bottom image courtesy of Flickr/Sarah and Jason. "For a lot of species, there are reported temperature tolerances, so, for instance, we weren't supposed to see some of these species in areas of New York where we have been working," Groffman says. "Now, it's possible we had incomplete data on their tolerance, but it's also possible that the earthworms are now able to persist in these areas because the climate is warming." While the invasion may be human-driven, the solutions can be as well. The problem is multifaceted. Scientists must first work to change the perceptions of these earthworms so people become aware that they aren't good for some soils. Then researchers need to attempt to change people's behavior so that they stop accidentally introducing them into forest soils. One of the few solutions to eradicate a current invasion is to use pesticides, but "we don't necessarily want to be spraying pesticides all over our forests," Groffman notes. Another idea is to use chemicals to make the soil more acidic so that earthworms can't live there. But, this practice can cause harmful side effects, similar to when a forest falls victim to acid rain. Instead, scientists use their resources to prevent the spread of invasive species because they are so hard to get rid of once established. "Some researchers, such as those at the Great Lakes Worm Watch have done really great work with education and outreach programs to teach people to be more careful with worms when they fish or use worms for composting," Groffman says. "It's hard to convince people that something they've known to be beneficial all their lives is actually harmful and a problem." He adds that researchers have had luck explaining that earthworms are harmful by using examples of some of the more recent invasive species in their outreach and citizen-science education programs. The demonstrations help change public perceptions because some invasive species look and behave differently than the earthworms people have experienced for decades in their gardens. This helps people realize they are dealing with an invader and are more likely to work to prevent their spread. That said, earthworms are not all bad. They are useful for loosening up compacted soils, and they are fantastic in compost piles, greatly speeding up the conversion of organic materials into compost. But these are not desirable functions in forest soils, Groffman explains. Most forest soils are not compacted, and speeding up decomposition and nutrient cycling can increase nutrient losses to surrounding environments. Some researchers have had luck explaining that earthworms are harmful by using examples of some of the more recent invasive species in their outreach and citizen-science education programs. Photo courtesy of Great Lakes Worm Watch. Of course, forests in other parts of the world do naturally have earthworms, he adds. But those forests function differently than forests in northern North America. "The forests we are studying are changing from a state where they didn't have earthworms to a condition where they do," he says. "So there is going to be a transition phase, with rapid loss of the forest floor and then a more stable phase once the earthworms become established. These new forests have thinner forest floors, less carbon storage, and less biodiversity." Groffman admits it can be an uphill battle to draw attention to these invasions because they occur under everyone's feet, but he hopes research can help make scientists and citizens both more aware of the issue. While there is a lot of interest in invasive species such feral pigs and zebra mussels in the Great Lakes, soils receive little attention. "Often times, soils are overlooked in general, and then when it comes to invasive species in the soil, they are further ignored," he says. "People overlook invasive species in the soil just because they're not that obvious. But their detrimental effects in the future will likely be very obvious."

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. T year 2015 is special on two fronts: 1) It is the International Year of Soils, which will raise awareness about the fundamental roles of soils for human life (Fig. 1); and 2) It is also the decisive year for setting sustainable development goals (SDGs) for the global community, in which soils are an integral part of the United Nations’ SDGs initiative and post-2015 agenda. An integrated strategy addressing both these fronts, as illustrated in Fig. 2, can help increase the public’s understanding and appreciation for soils. Understanding is the first step towards meaningful action and long-term improvement. At the core of this strategy is a fundamental shift in our perception of soils and an ethic for caring about soils.

The National Soil Project (NSP) at Northeastern University has been measuring the total and sequestered soil organic matter (SOM) contents of more than 2000 soil horizons from all 50 US states since 2008. The sequestration data establish a baseline SOM content of a soil and are a measure of its quality and health. In this paper, on behalf of the National Ecological Observatory Network (NEON)–NSP collaboration we report the total and sequestered SOM contents of 11 grassland and forest profiles in eight US states at elevations of 25 to 1548 m and 7 soil orders to depths of 200 cm. Such soils serve (i) as standards with which other soils can be compared and (ii) as benchmarks for NEON measurements. Total SOM was measured by optimized loss-on-ignition (LOI) of dried soil samples at 650°C for 12 h. Sequestered SOM is represented by long-lived humic substances (HS) in the form of humic acids (HA), fulvic acids (FA), and sequestered dissolved organic carbon (DOC). Humic acids were measured gravimetrically; FA and sequestered DOC were measured by visible and UV spectrophotometry, respectively. Major findings are: (i) the data are mostly reproducible; (ii) carbon sequestration drops sharply below the A horizons; (iii) there are three profile types (in six Type A profiles the percentage HA exhibits a minimum with increasing depth, whereas no minimum is evident in the four Type B profiles investigated, and the Jornada profile labeled C features increasing percentage HA with increasing depth due to a carbonate barrier at 78 cm depth); (iv) decreasing FA/HA ratios with increasing percentage humification indicates FA as precursors of HA; (v) regression of FA against HA for all Type B profiles has a slope of 0.38 (cf. 0.29 for Maine profiles) and is a measure of the sequestration status of those soils; and (vi) HA in four of the profiles retain about three times more water than their total SOM, as observed previously for soil profiles in northern Maine. Peer Reviewed Papers

Previous studies have suggested researchers should use Soil Survey maps to create surficial geology maps where more spatial detail about surficial geology is needed than is available from maps already produced by geologists. Despite the widespread availability of relatively detailed soil maps in the United States, few areas have a surficial geology map published at similar map scales. This apparent gap between disciplines calls to question the accuracy of soil maps to represent the spatial distribution of surficial geologic materials. Therefore, the purpose of this research is to test the agreement between maps from these two sources. To accomplish this, published surficial geology maps are compared to those derived from Soil Survey maps in an area where geologists have a close relationship with soil scientists, but the coverage of detailed surficial geology maps is limited. This study compares seventeen 1:100,000 and ten 1:24,000 surficial geology maps recently produced by the Iowa Geologic Survey with Soil Survey maps that have been categorized to represent the surficial geology of the same areas. Depending on the state of understanding the geologic history for an area when the map was produced and the acceptance of differences due to cartographic scale, most of the maps were in agreement at 67 to 99% of the examined sites. Lower agreement percentages were in areas with more complicated geologic histories, such as areas described as loamy sediments or where a thin loess cover could be obscured bioturbation.

Ed Landa has been captivated by soils since his undergrad days, but they've hardly been his sole fascination. His love of art, history, and storytelling led him to co-edit a book, Soil and Culture, exploring the perception of soil in ancient to modern societies. His professional interests have encompassed mineralogy, toxic waste materials, and the impact of rubber tire-wear particles on soil and water. Now “retired,” he's still writing and studying; one of his latest works appeared in the last issue of Soil Horizons, in fact. The article's title begins with “Hooked!” and that pretty much sums up Landa's career. But he also recently shared some of the details. Soil Horizons: You started out studying geology and then switched to soil science. What was it about soil science that piqued your interest? Landa: I was particularly interested in mineralogy. At some point in my junior year at the City College of New York, as part of a class assignment, I came across a 1968 paper in Science magazine on electron microscope studies of the weathering of mica minerals in soils. The work was by Charles Rich at Virginia Tech. Soil—this highly dynamic, low-temperature environment—was new and exciting terrain for me. Ed Landa (center) with soil science colleagues from Japan. That summer, I was able to secure a job on a forest soils research project at the New York State College of Forestry's Charles Lathrop Pack Forest in the southern Adirondacks. That was the summer of 1969, and besides climbing trees, unplugging irrigation hoses, and learning about nutrient deficiencies in red pine, another vivid memory was watching the Apollo 11 moon landing. Soil Horizons: What happened next? Landa: I came back for my senior year, took microbiology and ecology in addition to my geology courses, and applied to grad school in soil science. I had the great privilege to work with clay mineralogist Bob Gast in the soils department of the University of Minnesota. I worked on the mineralogy of iron oxides for my master's degree, and on a problem related to radioactive waste disposal for my Ph.D. I then did a postdoc in the soils department at Oregon State University, looking at the fate in soils of mercury released from coal combustion. Soil Horizons: You worked most of your career at the U.S. Geological Survey (USGS) in the Washington, DC area, correct? What kind of work did you do there? Landa: Yes, I joined the geochemistry research group within the Water Resources Division of USGS in 1978. “The Survey,” as we call it, was home for more than 35 years. My initial assignment was to look at uranium mill tailings, the crushed rock residues left after uranium is removed from ores by chemical treatment—typically hot sulfuric acid. To me, these “soil-like materials,” deposited in ponds that later drained, were soils in the making, subject to the same biological and non-biological processes that form natural soils from parent material. So I looked at processes such as microbial iron reduction and sulfate reduction that are part-and-parcel of how we think about soil formation. The goal of this mission-oriented research was to assess environmental conditions that could impact the movement of toxic substances from these waste materials and to identify disposal sites that might be problematic. Soil Horizons: What else did you study? Landa: In my later years at USGS, my research in collaboration with university colleagues focused on the environmental fate of zinc associated with tire rubber. We looked at multiple environmental pathways: as tire-wear particles (deposited in roadside soils and storm water ponds) and as combustion by-products (such as stack emissions from industrial operations where scrap tires are used as a fuel). I'm continuing this tire work with colleagues here at the University of Maryland. Soil Horizons: What is the coolest thing you've learned about soils? Landa: I can honestly say that cool things are the “gifts that keep on giving” in soil science. So the list is more than one. This past month's cool thing was learning about the staining of gastropod shells in soils from Maryland. Here, the shell color is diagnostic of the biogeochemical conditions that controlled iron deposition in the soils. One from my first year of grad school was seeing “slickensides” in a high clay-content soil. These are polished surfaces that occur along shear planes within shrink-swell soils. I had seen slickensides in rocks within faults—but in soils?—who knew! Although I've never worked directly with soil fungi, they remain a source of continuing fascination for me. Their degradation of plant material in soils can be studied by experiments using buried tea bags—Dietrich Epp Schmidt and Stephanie Yarwood in our department are currently collaborating on such a project. Fungal hyphae can act as networks that lead to the rapid lateral movement of ions within soils. They can also drill nearly circular tunnels in soil minerals. Now, who can say that's not cool? Slickensides form in soils with significant amounts of shrink-swell clays. As the clays expand and contract along cracks, the sides of the fracture are “rubbed” smooth. Photo by J. Kelley and courtesy of Flickr/soil science@ nc state. Soil Horizons: Speaking of cool, tell our readers about your book, Soil and Culture. How did it come about? Soil fungal hyphae. Photo courtesy of Wikimedia Commons. Landa: The idea for the book was born in the lobby of the Philadelphia Convention Center at the World Congress of Soil Science in the summer of 2006. At the start of that week, Christian Feller from France was known to me by name only—we were the incoming chair and vice chair of the International Union of Soil Sciences’ Commission on the History, Philosophy, and Sociology of Soil Science. Christian is a student of fine art, fine wine, and history, and a collector of antique books. I enjoy contemporary art and movies. In the coming months, we recruited a cadre of contributors from within and outside soil science, the latter including textile artists, sculptors, poets, geographers, geologists, anthropologists, archaeologists, and wine specialists. What emerged in 2010, in time for the World Congress in Brisbane, was our book, Soil and Culture, and an enduring friendship. I have cooked in Christian's wonderful kitchen, learning to make a pureed leek soup—an unexpected but truly memorable part of our collaboration. Soil Horizons: What are you doing in your “retirement”? Landa: I am an adjunct faculty member in the Department of Environmental Science and Technology at the University of Maryland. I am a firm believer in the power of “place,” and this is a physically and intellectually immersive place for thinking about soils, with monoliths lining the hallways on the way to my office. I am very grateful for the great colleagues and students here. This semester, I am co-teaching a course on the environmental history of Maryland. I continue to do research and have ramped up work on the history of science and technology. Soil Horizons: You've been a member of SSSA for nearly 50 years! Do you have any key pieces of advice for the new generations of soil scientists coming after you? Landa: I can think of no better field to be in! There is a niche for every interest and an umbrella that is expansive in its breadth. We are members of a profession that was doing environmental science and biogeochemistry research long before these disciplines were part of the mainstream. The size of the soil science community is not like that of the big sciences—it has a human scale, and friends you went to grad school with will be among the folks you'll see and interact with throughout your career. That's unique. I went to my first SSSA meeting in Tucson within a few months of entering the field and am looking forward to the Minneapolis meeting this year.

As an art major at the University of California–Davis, consulting soil scientist Phil Small says he always dug clay much more than the ceramics made with it. But it was a summer job on a farm that really sparked his interest in soil. After graduating with a B.S. in soil and water science in 1977, Small worked as a soil scientist for many West Coast companies and organizations, including the Yakama Indian Nation and Agrimanagement, Inc., before founding his own company, Land Profile, in 1992. Now based in Spokane, WA, Small recently spoke with Soil Horizons about what he's learned during his long career, as well as his latest fascination: biochar. Soil Horizons: First of all, tell our readers a bit more about your background: Where did you grow up and how did you get turned on to soil science? Small: I grew up in Santa Rosa, CA and went to college at UC-Davis, near Sacramento. I started out as an art student under a great ceramicist, Bob Arneson. But I found myself geeking out more on the clay material than the art. Bob found me uninspired. I found art as a livelihood terrifying. Then, I got a summer job driving tractor at Sagemore Farms in Pasco, WA, with two other UC-Davis students, the Worsham brothers, Ron and Keith. Ron had taken soils classes, and our employer pointedly asked for his counsel alone on the farm. That really made an impression on me. That was two years into my college career: plenty of time to convert from a four-year B.A. track to a 4.7-year B.S. track. Soil Horizons: Since graduating, you've worked for many different agencies and companies. Any big take-home lessons you'd like to share from these diverse work experiences? Small: The common thread in my diverse soil science engagements has been a professional requirement to embrace soil complexity but to communicate simply, providing a tightly focused, actionable rendering of that complexity. Having a purpose-driven investigatory methodology and a tight technical report format also helps pare away the complexity and clarify the message. I have Don Jameson, owner at Agrimanagement, to thank for that lesson. (See sidebar for Small's other big take-home lessons.) Soil Horizons: Why did you ultimately decide to go out on your own and found Land Profile? Small: I struck out on my own in the early 1990s because of the very positive feedback I was getting from the environmental soil science clients I had attracted while at Agrimanagement. Being one of many agricultural soil scientists in the county versus being the only ag-aware environmental soil scientist within 200 miles was a major kick. I found that I love to seek out the less populated professional soil science niches. Like biochar. Phil Small, owner/soil scientist at Land Profile, Inc. The first time I went out on my own, though, was in 1978, about a year after graduation. In transition between jobs, I interviewed for a lab tech position with the Natural Resources Conservation Service (NRCS). My interviewer, a district conservationist, urged me to go into business for myself doing septic system site assessments. Permit support work. It was a better use for my soil classification skills than being a lab tech. The business succeeded, and I caught the bug to be on my own. iStock/BartCo Soil Horizons: What kind of work have you specialized in at Land Profile? Small: We've developed a diverse palette of client project services, but the core services have always centered on reclaiming the nutritive value in treated municipal waste or food processing waste to grow forage, food, and forests. Groundwater quality concerns drive this work more than surface water quality. For example, a fair amount of what drives my business is preventing waste-induced anaerobic soil failure points and the anaerobic groundwater plumes these generate. Then, the rest of our business is quite diverse. There are hundreds of reasons why people call a soil scientist: crop- and plant-related soil problems, environmental property audits, stormwater, septic systems, post mortems on various types of soil failures, expert witness testimony, prime farmland determination, wetland delineation, seep-induced structural failure, land use conundrums… Soil Horizons: From your LinkedIn profile, I see that you've gotten intrigued by biochar. Why is this? How have you been working with it? Small: I teach folks how to make and use biochar. I also teach some approachable methods anyone can use to characterize biochar so as to avoid the classic mismatches that can occur between it and soils (see “Campfire Lessons” article). I was attracted to understanding soil charcoal, or biochar, upon reading the book 1491 by Charles Mann. His story of Terra Preta is amazing—every soil scientist should read it. At the time, I was particularly depressed about the inexorable progression of erosion and chemical degradation of our soil resource. Biochar gives me hope. We understand so little about charcoal in soils, though, that I feel it will take us generations to learn how to effectively revitalize our soil resource using biochar. Working toward that end lifts my spirits, but beyond that, I am deeply intrigued intellectually. It dawned on me that my soils education—both formal and continuing education—hadn't included anything about the role of naturally occurring charcoal in soil. This made me want to learn more. Since then, I've found that biochar has everything that made me fall in love with soils in the first place: Long, slow changes over time; a diversity of material characteristic; functional complexity beyond what any one individual can grasp; applicability across every continent, yet with dramatic regional differences; and ubiquity, requiring an integrated understanding of all the natural sciences. I am hooked. Biochar. Photo courtesy of Flickr/Simon Dooley. Soil Horizons: On top of your consulting work, you were secretary of the National Society of Consulting Soil Scientists (NSCSS) for more than 24 years! Why has giving back to the profession been so important to you? Small: I got more out of it than I gave. Learning from other soil scientists about how they make a living informed my choices of services to develop and other business decisions. What I learned from my peers kept me in soil science, for which I am forever grateful. I reciprocated as best I could. There was also a time when the identity of soil science was more in jeopardy than it is today, and much of my motivation was to increase awareness of our profession, and how it fits in with other professions. Mike Singer [a UC-Davis professor and former SSSA president] talked to our consultants one year, and it was a pivotal moment when he pointed out that our International Union of Soil Sciences (IUSS) was established in 1924 as a formal union under the International Council for Science (ICSU), not as a division of the International Unions of Biological Sciences or Geological Sciences. The point was that soil science stands as an equal among the formal sciences, and no reorganization of university soil science departments is ever going to change that. This was deeply empowering for us. Besides motivating me to recommit to the profession in my leadership position with NSCSS, I was energized to lead a small group of soil scientists in restructuring the soil science content in Wikipedia. This involved removing soils content from the engineering, geology, biology, agronomic, and geography directory structures, and making a distinction between soil as a material and soil as a resource. We also reanimated the concept of edaphology [the influence of soils on living things] as distinct from pedology [the study of soil as a natural resource]. There was definitely some resistance to our efforts. But I consider the Wikipedia campaign to be one of the most effective actions I ever took on behalf of the profession to define soil science in the minds of the general public. Soil Horizons: What's the coolest thing you've learned during your career? Small: It's hard to top biochar. But a close second has to be the degree to which plants feed energy into the soil rhizosphere through root exudates. I knew it was a process, but the sheer mass of carbon delivered is pretty astonishing. Also the soil energy cycle, how that symphony plays out between sunlight and soil vitality, is intensely cool. Soil Horizons: Any final advice for students who want to follow in your footsteps? The rhizosphere represents a critical zone where plant roots, microbes, and minerals interface, and where biogeochemical weathering provides nutrients to plants. Shown above the spores of an opportunistic soil fungus Penicillium sp. that associates with the plant roots, microbial biofilms, and soil minerals. Photo courtesy of Pacific Northwest National Laboratory. Small: Take a technical writing class. Take a bookkeeping and financials class. Take an art class. Get on the soil science certified professional track, and become qualified through coursework to work as a soil scientist. Cultivate your contact network, especially with other qualified soil scientists. For early career soil scientists, check out our code of professional conduct. It is an amazing document, a solid guide for those who make a living providing objective science as a service. I'd also say that business is more about people, and the opportunities in soil science are most dynamic at the urban/soil-resource interface. Early career soil scientists, faced with multiple career choices, should look to geographic interfaces, as well as the interfaces between disparate scientific and technical disciplines, for opportunities to apply soil science in developing high-value solutions.

ity. On-site treatment systems are now an integral part of our wastewater infrastructure and are collectively referred to as decentralized wastewater systems. Decentralized wastewater technology and management refers to wastewater treatment and dispersal systems from the individual on-site treatment system (septic systems) to small community collection and treatment systems (cluster systems) and includes the process involved in siting, installing, operating and maintaining the systems. These systems rely upon land application by surface or subsurface dispersal and proper treatment of the wastewater. They allow the treated wastewater to re-enter the hydrologic cycle close to where the potable water was removed. Often, as in the case of an individual system, this is less than a few hundred feet. They are considered to be non-point source discharges by federal and state standards. Often septic systems are portrayed in a negative light but they are now an integral part of our wastewater infrastructure. Photo by David Lindbo and courtesy of Soil Science @ NC State's Flickr photostream.

Soil HorizonsVolume 56, Issue 4 sh2015-56-4-gc p. 1-3 Guest ColumnOpen Access Soils and Health: Closing the Soil Knowledge Gap Howard W. Mielke Ph.D., Howard W. Mielke Ph.D. Department of Pharmacology, Tulane University School of Medicine, New Orleans, LASearch for more papers by this author Howard W. Mielke Ph.D., Howard W. Mielke Ph.D. Department of Pharmacology, Tulane University School of Medicine, New Orleans, LASearch for more papers by this author First published: 17 July 2015 https://doi.org/10.2136/sh2015-56-4-gcCitations: 4 All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat The U.S. has a Clean Air Act and Clean Water Act. The missing environmental component, soil, results in a knowledge gap that has a profound influence on the lives of children. The national issue of children's lead exposure illustrates the effect of the soil knowledge gap. Clinicians have evaluated low lead exposure impacts on children and throughout one's lifespan. The medical impacts range from learning and behavioral problems to some of the most difficult and expensive chronic health conditions known to medicine, including kidney failure requiring dialysis, hypertension and heart disease, diabetes, and many nervous system dysfunctions including Alzheimer's disease. In response to clinical findings, the Centers for Disease Control and Prevention recognize that there is no known safe level of lead exposure for humans (USCDC, 11). To complicate the problem, the ordinary medical method for intervention, which focuses on lead-based paint, is deemed ineffective. Moving forward with primary prevention of children's exposure to lead requires essential knowledge about human biology, urban contamination, and soil. Hand-to-Mouth Behavior Is an Innate Human Trait Children's behavior is controlled by a specific DNA-directed hand-to-mouth behavior (Fig. 1). The behavior begins in the womb during early gestation and continues after birth (Desmurget et al., 2). Simply stated, hand-to-mouth behavior is hard-wired into the human brain, and the exposure vulnerability to lead dust of infants, toddlers, and young children is tied to that fact. "The motor repertoire of infants is narrow. Yet newborns can accurately bring their hands toward their mouth for self-feeding, thumb-sucking, or perioral exploration, thus showing fine coordinated movement synergies between the hand and mouth….these gestures of high ethological value are selectively encoded in the human brain and represented as integrated primitives within the precentral gyrus, a key region for sensorimotor processing" (Desmurget et al., 2). An essential requirement for preventing children's exposure to lead is the need for clean air, water, and soil. Figure 1Open in figure viewer Children's behavior is controlled by a specific DNA-directed hand-to-mouth behavior. Ordinary Medical Intervention Is Ineffective The usual medical strategy for intervention focuses on education and household dust cleanup. Cochrane Collaboration provides critical reviews for evaluating the effectiveness of medical interventions. A recent Cochrane evaluation was performed on education and household interventions for preventing children's lead exposure. The Cochrane report unequivocally states that the existing intervention method is ineffective at reducing children's blood lead levels (Yeoh et al., 15). The corollary is that there is no known intervention for primary prevention of lead dust. The lack of effective intervention means that even when diagnosed, children endure continuing lead poisoning. The lifelong medical and societal consequences are enormous (Bellinger, 1). An essential requirement for preventing children's exposure to lead is the need for clean air, water, and soil. Photo courtesy of Flickr/Susy Morris. The situation is even more alarming because lead intervention is triggered by blood lead findings, and children are being used for testing lead residues in the environment. This violates national and international standards for the treatment of human subjects. According to World Medical Association (14) criteria, if a method is shown to be ineffective, then the medical community must revise the intervention to prevent harm. The U.S. treatment protocols are thus doubly culpable because not only do they employ children's blood lead as an indicator of lead contamination, but they also use an ineffective intervention method to prevent children from further harm. Soil Is a Potent Reservoir of Lead Dust While lead-based paint is believed to be the major source of interior dust, seasonal changes in children's blood lead do not support that perception. In Detroit and other cities, blood lead is lowest toward the end of winter after children have been cooped up inside (and presumably exposed to household paint) and highest during the late summer and early fall when the children are outside and in contact with soil (Zahran et al. 16). Urban soil has become severely lead contaminated, especially in inner cities (Filippelli and Laidlaw 3; Mielke et al. 9). Soil ingestion is recognized as common among humans (Starks and Slabach, 10). When ingestion is involved, a factor of 10 is normally used for a margin of safety (USEPA, 13; USDHHS, 12). Assuming ingestion and adding the margin of safety, the USEPA soil lead standard should be reduced from 400 mg/kg to 40 mg/kg. Some states and many nations have promulgated soil lead standards at or below 100 mg/kg (Jennings, 4). Accumulated lead residues in soil are a source of lead aerosols. During seasonally drier periods such as late summer and fall, lead dust resuspension from contaminated soil is directly associated with fluctuations in blood Pb (Laidlaw et al., 5, 6). Empirical research shows that if the goal is to prevent Pb exposure ≥10 µg/dL for children living in a community, then the median soil lead must be <80 mg/kg (Mielke et al., 8). Given the current CDC 5 µg/dL blood lead reference value, the soil Pb standard must be revised sufficiently downward to ensure a margin of safety that protects most children from the risks of inadvertent exposure to soil reservoirs of lead dust. One major issue is that outdoor lead is being measured in units of lead content per weight of soil whereas interior dust is measured in units of lead per surface area. The interior standard is 40 micrograms per square foot. When measured outdoors in units of lead per surface area it is daunting to discover that the U.S. soil standard of 400 mg/kg (ppm) is equivalent to surface loading of about 1,500 µg/ft2 (Mielke et al., 7). The standard measurement used to describe outdoor soil is ineffective as a guideline for safety because it fails to clearly communicate how much lead children can obtain on their hands from the soil surface (see Fig. 2). Figure 2Open in figure viewer Three-dimensional map of New Orleans showing both soil lead in µg/g and µg/ft2. Note the large difference between the usual soil measurement and the lead loading in µg/ft2 of the soil surface. The U.S. lead loading standard of the interior floor is 40 µg/ft2, and this compares with the lead loading of 1,500 µg/ft2 when the soil lead meets the U.S. soil standard of 400 µg/g or ppm (Mielke et al., 7). Conclusions The soil knowledge gap among health practitioners is related to the failure to understand essential characteristics about human biology in the context of the air–water–soil nexus of children's environmental health. In the case of the lead exposure issue, closing the soil knowledge gap at least requires: Acknowledging the innate vulnerability of less than three-year-old children to lead residues in their environment including, air, water, and soil; conceding the failure of current lead-based paint intensive interventions for preventing exposure of children; underscoring soil loading vs. lead content as part of risk analysis; upgrading standards to use at least a factor of 10 to protect children; exploiting federal resources such as the USDA and the U.S. Geological Survey to map urban soils; recognizing the value of low lead soils that exist outside of every city as an essential resource for revitalizing urban lands to create safe areas for the youngest citizens; and accepting clean soil along with air and water as critical components of the long-term goal of resolving national health issues. References 1Bellinger, D. 2011. The protean toxicities of lead: new chapter in a familiar story. Int. J. Environ. Res. Public Health 8(7): 2593– 2628. https://doi.org/10.3390/ijerph8072593 2Desmurget, M., Richard, N., Harquel, S., Baraduc, P., Szathmari, A., Mottolese, C., and Sirigu, A.. 2014. Neural representations of ethologically relevant hand/mouth synergies in the human precentral gyrus. PNAS 111: 5718– 5722. https://doi.org/10.1073/pnas.1321909111 3Filippelli, G.M., and Laidlaw, M.A.S.. 2009. The elephant in the playground: confronting lead-contaminated soils as an important source of lead burdens to urban populations. Perspect. Biol. Med. 53(1): 31– 45. doi: 10.1353/pbm.0.0136 4Jennings, A.A. 2013. Analysis of worldwide regulatory guidance values for the most commonly regulated elemental surface soil contamination. J. Environ. Manage. 118: 72– 95.https://doi.org/10.1016/j.jenvman.2012.12.032 5Laidlaw, M.A.S., Mielke, H.W., Filippelli, G.M., Johnson, D.L., and Gonzales, C.R.. 2005. Seasonality and children's blood lead levels: Developing a predictive model using climatic variables and blood lead data from Indianapolis, Indiana, Syracuse, New York and New Orleans, Louisiana (USA). Environ. Health Perspect. 113(6): 793– 800.https://doi.org/10.1289/ehp.7759 6Laidlaw, M.A.S., Zahran, S., Mielke, H.W., Taylor, M.P, and Filippelli, G.M.. 2012. Re-suspension of lead contaminated urban soil as a dominant source of atmospheric lead in Birmingham, Chicago, Detroit and Pittsburgh, USA. Atmospheric Environ. 49: 302– 310.https://doi.org/10.1016/j.atmosenv.2011.11.030 7Mielke, H.W., Powell, E.T., Gonzales, C.R., and Mielke, P.W.. 2007. Potential lead on play surfaces: Evaluation of the PLOPS sampler as a new tool for primary lead prevention. Environ. Res. 103: 154– 159.https://doi.org/10.1016/j.envres.2006.08.007 8Mielke, H.W., Smith, M.K., Gonzales, C.R., and Mielke, P.W.. 1999. The urban environment and children's health: Soils as an integrator of lead, zinc and cadmium in New Orleans, Louisiana, USA. Environ. Res. 80(2): 117– 129. 9Mielke, H.W., Gonzales, C.R., Powell, E.T., and Mielke, P.W.. 2013. Environmental and health disparities in residential communities of New Orleans: The need for soil lead intervention to advance primary prevention. Environ. Int. 51: 73– 81.https://doi.org/10.1016/j.envint.2012.10.013 10Starks, P.T.B., and Slabach, B.L.. 2012. The scoop on eating dirt. Sci. Am. 306: 30– 32. https://doi.org/10.1038/scientificamerican0412-30 11 USCDC. 2012. Response to Advisory Committee on Childhood Lead Poisoning Prevention recommendations in low level lead exposure harms children: A renewed call for primary prevention. http://www.cdc.gov/nceh/lead/acclpp/cdc_response_lead_exposure_recs.pdf. U.S. Centers for Disease Control and Prevention, Atlanta, GA. 12 USDHHS. 2005. Guidance for industry estimating the maximum safe starting dose in initial clinical trials for therapeutics in adult healthy volunteers. http://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/ucm078932.pdf2005. U.S. Department of Health and Human Services, Pharmacology and Toxicology. 13 USEPA. 2002. Determination of the appropriate Food Quality Protection Act (FQPA) safety factor(s) in tolerance assessment. http://www.epa.gov/oppfead1/trac/science/determ.pdf 14 World Medical Association. 2013. Declaration of Helsinki—Ethical principles for medical research involving human subjects. http://www.wma.net/en/30publications/10policies/b3/ 15Yeoh, B., Woolfenden, S., Lanphear, B., Ridley, G.F., and Livingstone, N.. 2012. Household interventions for preventing domestic lead exposure in children. Cochrane Database Syst. Rev. 2012 Apr 18; 4:CD006047. doi: 10.1002/14651858.CD006047.pub3 16Zahran, S., Laidlaw, M.A.S., McElmurry, S.P., Filippelli, G.M., and Taylor, M.. 2013. Linking source and effect: Resuspended soil lead, air lead, and children's blood lead levels in Detroit, Michigan. Environ. Sci. Technol. 47(6): 2839– 2845.https://doi.org/10.1021/es303854c Citing Literature Volume56, Issue4July‐August 2015Pages 1-3 FiguresReferencesRelatedInformation

Soil profile descriptions have largely relied on morphometrics by which soil profile properties are mechanically measured and visually observed. These observations are then combined with chemical, physical, and mineralogical data or thin sections from soil horizons. Official guidelines and handbook for describing soils include the Soil Survey Manual (Soil Survey Division Staff, 5) and the Field Book for Describing and Sampling Soils (Schoeneberger et al., 4). Detailed soil observations are made for a whole range of purposes (e.g., mapping, classification, land evaluation, and pedological investigation). Commonly, a soil pit is dug, but observations are also made using augers, samplers, push probes, slice shovels, trenches, road cuts, or in quarries. The overall purpose of describing a soil profile is to preserve the image of the soil, and a full soil profile description consists of reference and geographic location, profile environment (climate and geology), site and area description, and a description of the soil horizons and its attributes and properties. The traditional field toolbox for soil profile descriptions includes augers, pickaxe, spade, knife, spatula, rock hammer, Munsell charts, maps, notebook, water bottle, HCl, sample bags, tape measure, clinometer, compass, altimeter or GPS, and camera (Fig. 1). These are used to measure and observe soil properties and horizons. Traditional toolkit for sampling and describing soil profiles. The designation of horizons consists of interpretative symbols (e.g. Ah, Bt, etc.) that are based on morphology and soil genesis, and they are generally distinguished based on properties relative to those of an estimated parent material. Assessment in the field is based on differences in soil texture, color, coarse fragments, clay bridges, structural change, organic matter, mineralogy, concretions and accumulations, HCl effervescence, or the effect of frosts. The range of properties and features to distinguish horizons and horizon topographies (smooth or broken), distinctness (abrupt or gradual), and spatial variation requires pedological experience. Many soil profiles have complex horizons that can be turned into pixels or polygons. Figure 2 shows an example of a sandy overblown Spodosol—the polygon version of the soil profile (third from left) shows similarity to a polygon soil map (see example of soil map of parts of Oregon State). In a sense, soil profiles and horizons can be seen as polygon soil map. Just like we have put our soil maps in a geographic information system, we need to put our soil profile descriptions in a system. Overblown Spodosol (left) and pixelized and polygon version of the same soil profile—compared with a polygon soil map on the right (1:24,000). Currently a range of sensors is being used in agricultural and environmental soil studies. These sensors and tools have been valuable for measuring and predicting soil properties, processes, and behavior in a horizontal sense, that is, across the landscape. They have been less applied for studying soils in the vertical sense, and observations of soil profiles rely on a toolbox that has not changed in the past decades. There are new tools available that can be used to investigate a soil profile—which I term here as digital morphometrics, or the application of tools and techniques for measuring and mapping soil profile properties and deriving continuous depth functions (Hartemink and Minasny, 1). Digital morphometric techniques have been used for all soil properties both in a soil pit and on monoliths in the laboratory (Fig. 3). Handheld XRF of an Arenic Hapludalfs and a map of the Fe content of the same profile. Jenny (2) emphasized that every soil property has its own vertical distribution pattern and depth function. Several depth functions are available that approximate the anisotropic character of soil properties, and these functions use a limited number of data points (usually from soil horizon data) and interpolate soil property values. Values for every possible soil depth increment are given, creating a continuous function of which the uncertainty can be quantified (Malone et al., 3). In some cases, measurements can be made in a soil pit at very small depth intervals, and in other cases, the measurement is conducted in the lab and gives intervals in the micron or centimeter range and the increment is much smaller than the depth of soil horizons. It has the potential to create continuous depth functions of soil properties based on measurements rather than interpolations. It also has the potential to more precisely investigate horizon boundaries. Pedology advances when increased data availability is combined with sound theoretical soil models and thinking that is tested across a wide range of conditions. Digital morphometrics follow the advances in proximal soil sensing devices. Attempts have been made to measure soil properties and attributes of soil profiles, and here I call for the use and integration of the proximal soil sensing technology and digital morphometrics in the analysis and mapping of soil profiles. Sampling protocols need to be developed to deal with the two- and three-dimensional variability in the soil pit. Core sampling (few centimeters in diameter) ignores much of the horizontal variation in soil horizons, just like the soil profile (relative narrow vertical cross-sections) ignores the three-dimensional body of the soil. Considerable progress has been made in digital soil mapping and the timely collection of new soil data and information. There is an increased demand for soil information by a range of users that drives many of the new soil projects. That drive is related to issues around food, water, climate change, energy, ecosystems, or biodiversity. The wide array and use of proximal soil sensors contributes to increased data availability and soil information, and there is potential for using digital morphometrics for in situ soil characterization and the production of continuous soil depth functions. The combination of digital soil morphometrics and continuous soil depth functions has the potential to frame our understanding of soils and be valuable in the resurrection of pedology programs across the world.

Science literacy requires the target audience to engage with science concepts presented in written, oral, or visual formats. Anecdotes that elicit the personal interest of the audience can be “seductive details” (van den Broek, 37) that increase motivation to connect with the materials being presented. Soil science is a field where we are constantly battling the “it's just dirt” mindset. The seductive detail can be a useful tool in proactively generating interest in our field. The collection above is admittedly unstructured—loosely tied to the topic of cultural aspects of soil. For the lay audience and for students having their first exposure to soil science, that cultural perspective can link soil science to the very fabric of human life—seemingly a key characteristic for a seductive detail in any of the sciences. Commenting on a 2014 SSSA-sponsored Bouyoucos Conference that explored soils and ecosystem services in a societal context, Mary Stromberger of the Department of Soil and Crop Sciences at Colorado State University noted that “the study of soil from a human-centric point of view is key to getting public and ultimately government support for long-term soil conservation and management” (Soil Science Society of America, 33). In both the classroom, and in dealing with the broader community, adding novel human-centric perspectives—ones that moves beyond the now-tired image of cupped hands holding soil and a seedling—can enhance the effectiveness our dialog. Sadly, the systematic assembly and usage of such materials in soil science is rare. The best example that comes to mind is Mary Beth Kirkham's placement of biographical sketches of key historical figures at the end of each chapter in her book Principles of Soil and Plant Water Relations (Kirkham, 16). Leaf-cutting ants in Louisiana excavate soils for the construction of belowground chambers in which they grow fungi on the harvested plant material. Photo courtesy of iStock/Global P. I present below what are, for me, a new cache of seductive details in soil science, with the hope that others will add to them and provide a pool of “stories untold” for classroom, outreach, and other efforts. The story of Selman Waksman and the production of streptomycin by soil actinomycetes in the 1940s is well known. The search for such compounds during this era was based on culturing methods. Over the last two decades, molecular methods have greatly expanded our ability to screen the biological pool within the soil for natural products of use to humans as biocatalysts of industrial interest such as amylases, lipases, and proteases and as bioactive compounds such as drugs and insecticides. With a 30-g soil sample now known to contain more than 500,000 species, soil still represents a largely untapped resource for useful microorganisms (Daniel, 7). Examples of soil-derived natural products from the earlier era include spinosad, a metabolite produced by the actinomycete Saccharopolyspora, which has been shown to be effective against mosquitoes and other insects (Jiang and Mulla, 13). This microorganism was isolated from soil collected in 1982 at an abandoned rum distillery at a sugar mill in the Virgin Islands by a vacationing chemist from the Natural Products Research Group at the Eli Lilly pharmaceutical company (Mertz and Yao, 21; Thompson et al., 36). Coumarins are a class of compounds of widespread occurrence in vascular plants (Neish, 26), and hence, in plant residues in soil. They are responsible for the sweet smell of freshly mowed hay, and synthetic coumarin has been used in perfumes, including Jicky, created in Paris in 1889 (Museum of Arts and Design, 24). Consumption of moldy silage made from sweet clover that has spoiled during storage has been found to produce sometimes fatal bleeding in cattle. The “hemorrhagic factor” responsible for such cases was found to be a substance produced by the degradation by the fungi of the genus Aspergillus, whose primary ecological niche is soil or decaying vegetation (Dagenais and Keller, 6). It is the conversion of the abundant coumarin in the clover to a mycotoxin known as dicoumarol that inhibits coagulation in cattle feeding on it. This same conversion to dicoumarol also occurs as plant residues decompose in the soil, and with its accumulation in soil microenvironments, some toxicity to native bacteria may occur (Smyk and Van, 32). Selman Waksman. Source: Wikipedia. Warfarin is a synthetic derivative of dicoumarol that is widely used today as an anticoagulant in human medicine (best known by the brand name Coumadin) and as a rodenticide. Besides this scientific linkage of soil science to human health, there is also a fiscal linkage. The research that led to the development of warfarin was funded by the Wisconsin Alumni Research Foundation (WARF). The name “warfarin” was derived from WARF, plus the “arin” from coumarin (Pirmohamed, 30). WARF funded the Ph.D. thesis work of my colleague and officemate Del Fanning (personal communication), and undoubtedly that of other University of Wisconsin soil science graduates. Not all of those who study soil science make it their career home. But the skills acquired with soil science training can certainly have carry-over value to other fields; such was the case for three major figures in 20th century science: Vladimir Vernadsky (1863–1945), the acknowledged founder of biogeochemistry, is often claimed by ecologists and geologists as one of their own. But Vernadsky was mentored by Dokuchaev at Saint Petersburg University during his student years (1881–1885) and later research; his intellectual lineage to soil science is clear. Dokuchaev's integrative and interdisciplinary approach to science in general and his view of the importance of organisms in the creation of soils were guiding principles in the development of Vernadsky's concept of the biosphere (Bailes, 2; Ackert, 1; Guegamian 9; Ivan Vtorov, personal communication). Rene Dubos (1901–1982) was born in France and gained international fame as a medical scientist at the Rockefeller Institute in New York City and as an environmental activist; he coined the iconic phrase “Think globally, act locally” (Kingsland, 15). Soon after graduating from the Institut National Agronomique, he began work as a technical editor at the International Institute of Agriculture (IIA; the forerunner of the Food and Agriculture Organization of the United Nations) in Rome. The IIA hosted the founding meeting of the International Society of Soil Science (now International Union of Soil Sciences) in May 1924, and here he met soil scientists Jacob Lipman and Selman Waksman from Rutgers University. The visit spurred him to study bacteriology over the summer and to take on outside translating work in order to earn money for a trip to America. With apparently no firm plans upon departure, he happened to be on the same ship as Waksman, who was returning from Europe in September 1924. Waksman offered him a position at Rutgers and escorted him there upon arrival in New York. Dubos obtained his Ph.D. under Waksman in 1927 for research on the decomposition of cellulose (Note: Hans Jenny was a post-doc with Waksman in 1926–1927—now that was a laboratory lineup!) Vladimir Vernadsky. Source: Wikipedia. Dubos’ work soon shifted from the New Jersey Agricultural Experiment Station to Rockefeller Hospital in New York City, and he was tasked with seeking a cure for bacterial pneumonia. The capsule surrounding the pneumococcus was, like cellulose, a polysaccharide. Using the soil enrichments from a New Jersey cranberry bog, Dubos isolated an enzyme that destroyed the capsule and rendered the pathogen susceptible to phagocytosis by white blood cells (Moberg, 22; Moberg and Cohn, 23). In preparation for a 2010 Earth Day presentation on soils at the Arlington Arts Center in Virginia, I thought about showing the browning reaction—the enzymatic formation of quinones from phenols in fruit such as apples when cut and exposed to air; the quinones polymerize to melanins, a brown pigment. My idea was to then use this browning of a cut apple as a demonstration and an analog to organic matter transformation that occur in the soil. Using “soil science” and “browning” as search terms, I inadvertently came across a memoir by Earl Reece Stadtman (1919–2008), a noted biochemist at the National Institutes of Health, entitled Sixty Years of Research: From Soil Science and the Browning of Dried Apricots to the Biochemistry of Metabolism.” Stadtman graduated from high school in San Bernardino, CA in 1937 and enrolled at the local junior college, hoping to learn the basic science required to set up a soil testing lab (Park, 28). He soon realized that more training was needed and transferred to the University of California at Berkeley, where he earned a B.S. in soil science in 1942: “… this proved to be a rewarding experience because the soil science curriculum included courses in organic, inorganic, and analytical chemistry, physics, bacteriology, human and plant physiology, plant nutrition, soil physics, colloidal chemistry, agronomy, and soil microbiology. The latter course proved critical to my scientific development” (Stadtman, 34, p. 625). The soil microbiology course was taught by biochemist and microbiologist Horace A. Barker; Stadtman's wartime work with Barker on the rapid browning spoilage of dried apricots sent to troops in the South Pacific initiated Stadtman's career shift from soil science to a lifetime of work in enzymology. He was awarded the National Medal of Science in 1979 by President Jimmy Carter and mentored two physicians at the National Institutes of Health who went on to win Nobel Prizes (Goldstein and Brown, 8). Joseph Needham was a biochemist by training but is best known today as the founding author/ encyclopedist of the series Science and Civilisation in China (SCC; 1954–2008). The genius of Needham has been chronicled by popular author Simon Winchester in his 2008 book The Man Who Loved China: The Fantastic Story of the Eccentric Scientist Who Unlocked the Mysteries of the Middle Kingdom. In the volume of SCC focused on botany, Needham goes into considerable detail on the soil forming processes and the geographic distribution of soils in China. Describing podsolization and the translocation of iron and organic matter, Needham's roots in biochemistry and his powers of synthesis come through in a footnote: “Perhaps the method of chromatographic analysis, which has so greatly revolutionised modern biochemistry by making it possible to separate and identify organic chemical compounds, whether pigments or not, in extremely small quantities, adsorbing them differently on columns of solid substances in powder or granular form, or upon strips of filter paper, and then eluting (eluviating) them with different solvents … was one of the greatest indirect contributions of soil science. In view of the outstanding position of Russian scientists in the development of modern pedology, it may be no coincidence that the central figure in chromatographic history was also a Russian, Michael Simeonovitch Tswett (1872–1920)” (Needham, 25, p. 69). Was the botanist M.S. Tswett (Livengood, 19; Tswett's death date is now generally given as 1919) acquainted with and possibly influenced by the earlier soils studies of Dokuchaev and/or his students? Did he see soil profiles as analogs for the laboratory columns that he set up around 1901 for the separation of plant pigments? Expert opinion does not support Needham's speculation (Jonathan Livengood and Ivan Vtorov, personal communications), but it is, nevertheless, thought provoking and can be used to introduce the concept of historical context when considering the path of scientific discovery. The discussion above has focused on text material. But images can also provide powerful seductive details. Such imagery may derive directly from science—for example, the snowflake photomicrographs of Wilson Bentley and Alexander von Humboldt's artistic use of vertical exaggeration in depictions of the biogeography of equatorial plants (Barrow, 4). Morphed images, only loosely tied to scientific reality, such as the Man in the Moon in the 1902 French silent film A Trip to the Moon by Georges Méliès, can also excite the imagination and be sparks for discussion and dialogue. Soil science is rich in captivating imagery—see, for example, the wonderfully illustrated European Atlas of Soil Biodiversity (EASB; Jeffrey, 12), with its micrographs of rock-eating mycorrhiza, mycogenic oxalate minerals (EASB, p. 38-39), and parasitic and carnivorous fungi (EASB, p. 43 and 94). One can rightly be in awe of charismatic megafauna (whales, eagles, elephants, etc.), but claw-legged tardigrades—a new group of soil invertebrates for me (EASB, p. 100)—have both shock value and universal appeal for all ages—a charismatic, microfaunal soil superstar! Soil pore architecture and root distributions being explored with new methods and devices adapted from engineering and medicine (including borescopes and laparoscopic samplers) and advanced, three-dimensional tomographic imaging techniques offer new opportunities to engage audiences. Snowflake photomicrograph of Wilson Bentley, 1890. Source: Wikipedia. Most of us have had this experience. You are at a party and somebody asks what you do. You respond “I'm a soil scientist”; they look confused and ask “social scientist?” Well, saying “pedologist” may not be any safer. At our neighboring university, Bowie State, the use of “pedology” in the curriculum comes from an alternative definition, taken from the medical dictionary, meaning the scientific study of the life and development of children (http://www.merriam-webster.com/dictionary/pedology). Thus, Bowie State University has courses such as Pedology 250: Child and Family Life Skills Development. And at my alma mater, the University of Minnesota, the College of Homeopathic Medicine and Surgery's second year students in the 1887–1888 academic year studied “Paedology”—what today would be termed “Pediatrics”—the diseases of children (Wilson, 38, p. 57). Tardigrade (“water bear”), Hypsibius dujardini; scanning electron micrograph by Bob Goldstein and Vicky Madden, University of North Carolina–Chapel Hill; http://tardigrades.bio.unc.edu/. Having come to soil science from geology in 1970, at the time of the wonderfully mysterious-sounding “7th Approximation,” I knew that soil classification was a complex and evolving scientific endeavor. But an earlier iteration escaped my attention until recently. It came from Cyril Hopkins and a colleague at the University of Illinois in 1908 and employed a variation on the Dewey Decimal System, familiar in library usage, in the classification of soils. The soils of Illinois were divided into 14 great soil areas based upon age or general method of formation; these were assigned numbers in increments of a hundred, from 100 to 1,400. Within each of these units, the soils were assigned to general groups based upon texture, then subdivided into individual soil types based upon color and stratification, with special consideration of peats and mucks. Numerical values at this level ranged from 0 to 99 (with decimals employed as needed for further distinctions) and were attached to the higher-level classification. Thus, a brown silt loam on gravel (26.4), developed in an unglaciated area of Illinois (100), would be designated as 126.4 (Hopkins and Pettit, 11). As Hopkins was a bitter enemy of USDA Bureau of Soils Chief Milton Whitney (Landa, 18), any hope for this Illinois system making it to the national stage was dead on arrival. In the broadest sense, we can consider any account of scientific results to be a story, and indeed, storytelling has a long tradition in the sciences (McCloskey, 20; Phillips, 29). “Surprise stories with unexpected emergences” are just part of that spectrum (Karasti et al., 14). What to tell? This is an area where our instincts are our best guides. If it surprised, entertained, and informed us, it is likely going to do the same for our audience. And how much? There can be too much of a good thing, and we are warned that seductive details can be diverting: “… such anecdotes may indeed attain the desired level of increasing motivation, but they pose a risk if precious attentional resources flow to processing the motivating information and away from the conceptually central information… a phenomenon known as the ‘seductive detail’ effect. This undesired effect can be diminished by limiting and demarcating anecdotes” (van den Broek, 37, p. 455). Again, our instincts are likely our best guides as to when and where to place such stories. Among our colleagues—from students and early career soil scientists to established workers and emeriti—are undoubtedly some gifted storytellers. We need only look to our neighbors in plant pathology for a role model in E.C. (Ernest Charles) Large (1902–1976). His 1940 book The Advance of the Fungi, a history of plant pathology written with “a tone of fiction” for a mass audience, was reprinted on at least three occasions over two decades. This was preceded by a highly imaginative science fiction novel, Sugar in the Air (1936). Large summarized its central storyline as “transmuting the manufacture of colloidal fungicides into that of making carbohydrates from water and carbon dioxide from the chimneys of power stations.” The book was a best seller in the U.K. (Bailey and Kinross 3). Nine decades later, when we are reading about making plastics from air-bound methane emissions from energy facilities (http://www.newlight.com), Sugar in the Air shows the power of scientific imagination and its ability to stimulate dialog about issues in science, technology, and the environment. Sugar in the Air was published by Jonathan Cape (now part of Random House); they published books by Ernest Hemingway [including A Farewell to Arms (1929)] and Sinclair Lewis [including Elmer Gantry (1927)]. Large mingled with the likes of George Orwell, T.S. Elliot, and Pamela Travers (author of Mary Poppins and made famous to modern audiences in the film Saving Mr. Banks), as well the rank and file of the British Mycological Society (Colhoun, 5; Bailey and Kinross, 3). Who will be the E.C. Large of soil science? Soils touch virtually all aspects of the human experience, and we have stories in our heads, hearts, and back pockets that can hook individuals out there. On a daily basis, we are privileged to explore and experience what C.C. Nikiforoff (27) called the “excited skin” of the earth. Let's share the excitement. Sincere thanks to: Jonathan Livengood, Department of Philosophy, University of Illinois, and Ivan Vtorov, Department for the History of Geology, Vernadsky State Geological Museum, Russian Academy of Sciences for discussions on the work of Vernadsky, Tswett and Dokuchaev.

The definition of soil is an important part of communication about soil, and it is important to have effective communication with other scientists, politicians, an interested public, and others with an interest in utilizing soil information. Initially soil science was focused primarily on agricultural applications, but in recent decades the use of soil information has expanded to include areas like land use planning, environmental applications, human health, and food, water, and energy security. Pedologists now include urban and other anthropogenically disturbed environments in their studies in addition to the traditional natural and agro-ecosystems. With these expansions in the application of soil information it is natural that some have raised the question of whether a new definition of soil is needed. Here we investigate that question by exploring whether the traditional pedologic definition of soil is meaningful in the modern world, with its expanded applications for soil knowledge. The current pedologic definition of soil includes the following key elements: (i) soils are natural bodies, (ii) soils are both spatial and temporal, (iii) soils form at the surface, (iv) soils are the result of complex biogeochemical and physical processes, (v) soils are capable of supporting life, and (vi) soils can be mapped at appropriate scales. We conclude that a definition that includes the six key elements listed above, with perhaps some minor modifications, is able to incorporate the expanded applications of soil information in the modern world.

The first soil maps were made by geologists, and many early soil maps were surficial geology maps. After soil science became established as a scientific discipline, there has been a continued interplay between geologists and soil scientists, both fields benefiting from advancements made by the other. In the 1940s and 1950s, researchers began to use soil information and soil maps to assist in the improvement or construction of various types of geologic maps. There is strong agreement between preliminary geology maps created from soil maps and traditional geology maps. This is primarily due to the influence of parent material on soil formation and may also be due in part to the importance placed on parent material in some soil classification systems. Despite the results obtained when using soil maps to create surficial geology maps, there is a need for more quantitative studies to assess the degree of compliment between soil-based maps and traditional geology maps, expansion of the technique into a wider range of geologic and climatic environments, and more research in locations that use classification systems other than US soil taxonomy.

Physico-biochemical processes occurring in soil are difficult to predict because the knowledge of local soil properties such as soil moisture and temperature is often limited. Therefore, soil moisture and temperature regime classes are necessary for US soil taxonomy and other classification systems. The goal of this study is to develop a modeling tool to predict soil moisture and temperature at multiple soil horizons and to code the Keys to Soil Taxonomy in a Soil Moisture and Temperature Regime Classification (SMTRC) module for automatic identification of soil moisture and temperature regimes. The Environmental Policy Integrated Climate (EPIC) model was extended as the EPIC–SMTRC tool for this purpose. Field data from the Soil Climate Analysis Network (SCAN) sites and the Wye farm site in Maryland for validation of soil moisture and temperature predictions. Results indicate that predicted daily soil temperatures are in close agreement with observed values with R2 values ranging from 0.73 to 0.98 and Nash–Sutcliffe efficiency (NSE) from 0.50 to 0.96. Predicted soil moisture by EPIC–SMTRC captured observed trends reasonably well. Testing results at the Wye farm indicate that the predicted daily values of water content are satisfactory, with R2 values ranges from 0.66 to 0.88 and NSE from 0.51 to 0.84. The EPIC–SMTRC tool demonstrated the ability to automate the identification of the soil moisture and temperature regimes as currently defined in the US soil taxonomy and can be used to classify soils and to be utilized for other sites.

The following article is a continuation of the story of Turtle (Indorante, 9), a fictional field soil scientist in the later stage of an enjoyable career (Fig. 1). New technologies like GIS, multi-spectral imagery, high-resolution elevation data, etc. have emerged, while new colleagues have entered into Turtle's life. The new techniques and data fit right in with the tasks required of field soil scientists. However, new ways of thinking are required to utilize the new tools effectively. The latest chapters of this pedological tale explore these new technologies with a few new colleagues Turtle has gained. Turtle and Bear reviewing their latest GIS/RS soil mapping efforts. In Part III of the series, Turtle was advised by Eagle and Bear to carry on the study of the spatial component of soil mapping using the current tools of the geographic disciplines. Some of the more important topics discussed by the curious earth scientists follows. Eagle (E): What is a soil map? Turtle & Bear (T&B): At the most basic level, a “good” soil map groups soils geographically that are similar and separates soils geographically that are different. All: What could be improved? All: Soil map accuracy and precision could be improved by applying digital tools to a traditionally analog process, within the context of understanding the soil–landscape relationships. E: Expand on that. B: As Hudson (8) stated, it is the predictable pattern of soil occurrence that has allowed us to map large acreages with minimal observations of the soil itself. The process of consistently identifying similar landform segments is what has and remains to be the most difficult step in producing a good soil map using analog techniques. For example, the ability to identify areas that have concave profile curvatures in lower side slope positions with slopes less than 5% is a straightforward proposition using GIS/RS software. In addition, the results would be repeatable and easily expressed to end users in the form of rules, e.g., this soil occurs where profile curvatures are less than A, with a relative position between B and C on slopes less than D. We were confident in providing qualitative descriptions in the pre-GIS/RS days but were never confident that we could say that a particular setting as described was mapped with accuracy and precision within a soil survey project, let alone across soil survey projects. T: There is no question that if the present day data, software, and skills were available during my early days of mapping, I would have made better soil maps. I would also have been sure there was consistency among my crew. That is not a knock on the work we all did. We produced the best product possible given the tools available at the time. We had hand probes, sharp shooters, clinometers, USGS topos, and stereo paired aerial photos. We used the clinometers, topo maps, stereo pairs, and our walking feet for topographic control. We thought we had it made! The present day tools are more like a surgeon's scalpel, while the older tools were more like a stone ax. E: If Dukuchaev, Glinka, Hilgard, Marbut, or any of the early pedologists had GIS/RS tools in their day, I absolutely think they would have used them. I think the early soil surveyors that mapped a county over the course of one field season would have used these tools too. E: Why is slope class a criterion for mapping soils? T&B: Well, it is important to remember that the maps in a soil survey report are not soil type maps but are soil management maps. Map units are intended to delineate uniform management areas, not uniform soil areas. Slope gradient is an important potential limiting factor, and in the past, there wasn't much information related to things like slope gradient. It was not that long ago that USGS completed the 1:24,000 scale topographic quadrangle map series for the continental states. We remember when the 1-inch-to-the-mile topographic maps were common. Having a slope class phase was important as a matter of characterizing the landscape for the USDA as part of the soil survey program. At the same time, soil scientists were gaining a better understanding of the relationships between soil distribution and slope characteristics (e.g., soil landscape). In the 1950s, 1960s, and 1970s, regional soil landscape projects were carried out in various parts of the United States (Nettleton and Lynn, 18, 19; Fenton 6), with the goal of understanding soil landscape relationships to improve the speed, utility, and accuracy of soil survey. These regional studies were critical in the birth and acceleration of modern soil survey (Indorante et al., 11). The history and impact of these studies is recorded in the legacy soil maps, soil classification, and soil surveys in the areas of the respective studies, as well as in refereed scientific literature. T: Historically, a soil map with slope classes provided a huge amount of information that was desired for characterizing soil and land resources for the nation. This information was not available anywhere else as a synthesized product. In addition, slope class became very important as USDA programs began to put conservation requirements on some agricultural producers starting in the mid-1980s. Over time, it was discovered that slope was a very strong predictor of soil distribution. The soil-forming glasses that Dr. Owl prescribed helped me focus on soil–landscape relationships that helped segment the landscape, grouping similar soils and separating dissimilar soils geographically. Dr. Owl emphasized the importance put on the proper use of the genetic glasses with flip-down taxonomic glasses. Use the pedogenic glasses first, and then use the flip-down taxonomic glasses—flipping back and forth between the glasses helped to make a good soil map. E: That explains why it was done in the past, but what about present day, considering the increased availability of high-resolution elevation data derived from LiDAR? Wearing glasses to map soils seems so yesterday. T: All of the new GIS/RS tools are just modern technology versions of the original pedogenic glasses prescribed by Owl, optometrist in the town of Even. The “earth” glasses that let us see GIS/RS data are a much more powerful prescription, but like any prescription, they can be used properly or abused. E: What do you mean by used or abused? T: Take the slope (topographic) factor in the pedogenic glasses prescription. My glasses were able to identify landscape, landform, and landform component level units. The current GIS/RS data layers (e.g., LiDAR) are very detailed, and it is possible to focus too closely on the micro-scale topographic variability at the expense of viewing the connectivity and continuity and cross-scale relationships of natural landscapes (Roecker and Thompson, 20). There is a distinct possibility that the “hole mappers” of traditional soil survey could now morph into “pixel mappers” of the current era of digital soil survey. E: So it is possible to have too strong a prescription? T: For now, yes. I think that Bear has something to say on this subject. B: It is a given that slope gradient is a factor in soil genesis. It helps us group similar landscapes and landforms, which in turn, helps us separate and group soils accordingly. All soil series have slope parameters as a range in characteristics, with some series confined to the low or high end of the slope spectrum and others spanning a wide range of slopes. After our many talks with you Eagle, we think it would be preferable to dispense with slope phase and just map the soil series or class. When we develop slope maps from high-resolution DEM and compare them to our legacy polygon slope classes, we are often discouraged. We can see many areas defined by the slope class maps that are outside of the slope classes defined by soil polygons. It has been common to see discrepancies occupying 40 to 50% of the area when we have compared SSURGO slope classes to slope classes derived from high-resolution DEM. At first, we thought the data were suspect, but we can't recall many cases where the LiDAR was wrong and we were correct. We think the improved data will allow us to shift to a higher level of precision for slope estimation, improving mapping consistency. A soil scientist is no match for accurately determining and mapping slope gradient when compared with LiDAR. Once upon a time, we soil scientists could feel pretty good about our abilities to define and delineate slope classes with our stereo photo pairs and clinometers when compared with a 30-m DEM. We can no longer make that claim when dealing with LiDAR, and the more we think about it, the more convinced we are that slope phases just complicate the soil map. E: Are the slope class phases the problem or is it the map unit polygon data model? T&B: A little of both, since they are related. The map unit polygon data model was the only option available in the past and has proven to be quite useful. We have discussed the imprecise nature of delineating polygons. Cartographic generalization is inherent with the map unit polygon model. There is also the issue of what is conveyed to soil survey users by the hard boundaries of a polygon, which soil scientists have accommodated with descriptions and lists of components present within delineations. Users would like to see more precisely where these components occur across the landscape, and the polygon model is not the best data model for providing these potential details. However, it bears repeating that these polygon soil maps were created to convey information on management interpretations to the users, not the precise locations of specific soil types or the precise values of specific soil properties. As for the slope classes, soil scientists were often asked to generalize slope classes, thereby compromising the task of mapping a natural landform segment. Given the increased availability of high-resolution DEM, it would be possible to dispense with slope class phase altogether. An end user could group slopes any way they see fit using DEM and combine them with a raster soil map. In fact, a new raster-based system could be developed that uses raster versions of all variables related to particular interpretation and output cell-based ratings or interpretations. E: That is a big change, but I think I can see this…. T&B: Yes it is, but data and software available today provides a tremendous opportunity that was not available in the past. Legacy or current soil surveys were developed as a data synthesizer, since there were no other sources available. Now that new tools are available that perform the job better, the need to synthesize things like slope class equally for all map unit polygons is less important and may not be appropriate to include in legacy soil geographic databases. E: There would need to be an educational effort in how to use a soil map that may be more detailed compared with a map unit polygon map. There are different scales of precision and levels of confidence for each variable used in an interpretation or rating. The system of fuzzy logic currently used for soil interpretations provides a nice framework for continuing something like a completely raster-based system. New terms will also need to be developed and defined to enhance communication among soil scientists and soil survey users. T&B: That could work well. As you said, this would be a big change from the current system, but it should be a change that provides great benefits to the user. Furthermore, there is already some evidence that users are ready for raster soil maps (Grunwald et al., 7). E: We have discussed the raster data model for some time. Would it work? T&B: The raster data model seems to be the next logical step. Large amounts data in standard formats are becoming available in raster form like imagery, elevation, LiDAR vegetation derivatives (canopy height, biomass, and vegetative density), electromagnetic induction, gamma spectrometry, and climate, to name a few. The use of data like these for mapping soil classes and properties is well documented (McBratney, et.al, 15). Keeping the output data in the same format as the input makes sense. Raster soil survey products have been reviewed favorably (Grunwald, et.al. 7). We have a 100-plus year history using the polygon model and a vast infrastructure designed to support it, so it will take a period of time to transition from our current polygon model to a raster model, especially when considering the associated database. E: Speaking of the attribute database, how valuable is a perfect database if the geographic representation of soils on the ground is flawed? T&B: Both are required to have the best product possible. With regard to data management, there is a tendency to treat the spatial and tabular data as separate entities. A large emphasis has been placed on the tabular, and rightly so, but the spatial has often been ignored or neglected. E: I always chuckle at the old soil mapping analogy, “would you rather map soils on the back side or the front side of an aerial photo?” Does that apply in the present day? T&B: That analogy is timeless. Aerial photography and stereo-photography, in particular, revolutionized soil mapping. Much can be inferred from an aerial photo, and it was an indispensable tool that helped us inventory much of the USA. Given the tools available today, spatial data processed with GIS/RS can be considered the “front side” of a symbolic aerial photo while a plain orthophoto occupies the “back side.” That statement is a little extreme, but the capability to synthesize, categorize, and classify these various raster datasets for the purpose of mapping soils should not be underestimated. T&B: These GIS/RS-based tools could help us convey soil–landform relationships to soil scientists more effectively than oral tradition and on-job training. E: You mean arm waving only goes so far? T&B: Right, when you can describe something qualitatively in the office and show it in the field, it is effective. When the qualitative is defined quantitatively, mapped in the office, downloaded to a device, and taken to the field, it becomes even more effective. E: Don't forget the inverse operation: collecting georeferenced data in the field and coupling it with data in the office to help quantify the setting of soils. T: Good point. The ability to collect, define, and “project” one's understanding of the soil-forming environment is something we could not conveniently do in the past. The software today is more suited to that task than blackboards or whiteboards. E: Will these powerful tools and data without geopolitical limits eliminate field work? T: No. In the past, we would sit over a stereoscope to map our lines. That time can now be spent developing relationships with our data and documenting soil distribution using GIS/RS. B: The stereoscope was only effective when the user above the scope had an understanding of soil–landform relationships. GIS/RS is the same way. When GIS/RS is coupled with a knowledgeable soil scientist, it can be thought of as a smart stereoscope. An understanding of soil–landform relationships is required to make effective use of GIS/RS. E: You make GIS/RS sound too good to be true. T&B: We don't mean to, and we are aware that there is no silver bullet. We have both mapped in areas that are unpredictable, and using these techniques may be more time consuming than doing things the traditional way. B: There have also been situations where the soil–landscape relationships may be able to be determined and mapped via GIS/RS, but their extent is so small that by the time you figure out the soil–landscape relationships, it is effectively mapped. T: Some of the GIS/RS work I see just looks like a pretty map. Is it really useful? B&E: There is no question we can produce eye-pleasing maps with GIS/RS. But, which is the “pretty map”—one produced under a stereoscope that has been redrafted two or three times to produce “cartographically” pretty polygons on its way to becoming legacy SSURGO, or a map with quantitatively defined extents and settings produced using GIS/RS? Neither procedure advocates more or less field work. Both procedures require the same understanding of soil–landform relationships. The difference is the GIS/RS procedure can be explained, defined, and reproduced by others. The polygon map can be explained but falls short when it comes to definition and reproduction. If we assume a common understanding of soil landform relationships, the tasks becomes determining the most effective means to “project” that knowledge spatially. GIS/RS is the tool designed to facilitate this task. Not using GIS/RS is akin to playing darts while one's eyes are blindfolded. T&B: What about measures of accuracy and confidence with these new techniques? E: What metrics are available for the present SSURGO? T&B: Nothing stated in the tradition of accuracy assessments or confusion matrices exists for SSURGO. The reason for that, in our experience, is the practice did not exist for much of the time period when the soil survey was taking place. In addition, there is an assumption in most soil surveys that every delineation was visited and the named soil was observed within the confines of the polygon. Some soil survey reports presented information summarizing map unit composition based on transect data (Doolittle, et al, 4; Linsemier, 12). There are many examples in the literature related to assessing the variability and accuracy of conventional soil maps (Amos and Whiteside, 1; Brown, 3; Wilding and Drees, 22; Edmonds and Lentner, 5; Mausbach and Wilding, 14). The component table provides data related to map unit composition, and there are ranges provided for the physical and chemical properties. E: I suppose that gets at the issue a bit, but these new techniques typically have the development of an accuracy assessment assumed as part of the process (Malone et al., 13; Nauman and Thompson, 16). It is a more straightforward way of reporting the information than SSURGO. T&B: Our procedures have been in place for a long time, but there is no reason accuracy assessments could not be incorporated in the future products. E: Regarding the ranges of physical and chemical properties, I've always wondered what a representative value (RV) is, how it is determined, and if everyone across the USA uses the same criteria to make that determination. T&B: Very good question. The RV is not defined statistically. As a result, it may not be consistently defined or applied across the country. E: What if these were defined statistically so that the data could be populated and interpreted consistently? T&B: Indeed, if we have enough data, we use something like the mean and two standard deviations for the RV, low and high values. When we don't have enough data, we have to rely on our best professional judgment and expert knowledge. We are open to suggestions. E: I like your option when you have enough data but only if the data are normally distributed. Another option could be as simple as selecting the median as the RV and the low and high ranges as a quantile, like 20 and 80%. It would sure make it easier to interpret for users like me. T&B: It would definitely make it easier for us to explain to users too. E: Get back to me when that gets resolved. T&B: Well, we do edit our tabular data quite a bit, so maybe we can get that implemented. T: It is too bad all of these neat tools are coming at a time when the inventory is nearly complete. B&E: Well, do you throw your knife away when it gets dull, or do you sharpen it again? T: That is true; refining the product we have created sounds good. B&E: It is always a challenge to improve an existing product. The existing product will be a huge knowledge base for new maps. Given the choice, a violinist would rather fix a Stradivarius than buy a brand new violin. When you think about it, there is no data set in the world that can match the NRCS soil survey for the extent of coverage, level of detail, or intensity of observation. There is an excellent foundation to build upon. This quote by R.S. Smith, Director of the Illinois Soil Survey, on 27 Sept. 1928 is as appropriate now as it was back then: “I hope the answer to your question is clearly indicated in what I have written. It is that the soil survey will never be completed because I cannot conceive of the time when knowledge of soils will be complete. Our expectation is that our successors will build on what has been done, as we are building on the work of our predecessors” (Smith and Wascher, History of Illinois Soil Survey, Department of Agronomy, University of Illinois at Urbana-Champaign, unpublished, 1967). T: How would it work? B&E: Like any new endeavor, the first step is to think a bit, plan a bit, do a few trials, evaluate the results, and then repeat. It will take a few years to work out the details, but there are examples of methods being developed that incorporate legacy maps as inputs for the DSM process (Nauman and Thompson, 16, Nauman et al., 17). Once that is done, a reasonable protocol could be implemented for others to follow. We believe harnessing these new tools for evaluating the soil–landscape will help to improve our understanding of soil systems. T: Who wants to map and refine from the office? B&E: We all want to get out more often. There will always need to be time devoted to field work to build and verify the work done on the computer. These tools offer the potential to make our field work more targeted and efficient. However, there is no way these tools preclude field work. A soil scientist is required to make it all come together. One example of such work is what is being called disaggregation. The result of a disaggregated soil map is a more refined representation of the soil–landform relationships (Nauman and Thompson, 16; Nauman et al., 17). T: Maybe we will be able to spatially represent what we currently just list in the component table. B: That would be the good goal. E: Since we are talking about refining, I will be a little provocative and ask a somewhat loaded question. When I look at the plethora of soil series and read the Official Series Description, I would ask you to explain, “What are the differences between the hypothetical James, Seamus, Giacomo, Jacob, Hagop, and Jaime soil series?” T&B: We thought this was going to be a friendly discussion! The ability to split on minutia may exceed our ability to explain why it is important to do so or if the splits are functional pedogenic breaks that make sense and are predictably identified on the landscape. Brevik and Hartemink (2) show the growth of soil series over time (Fig. 2). No doubt, mapping in new landscapes during the acceleration of the soil survey added to the numbers, but at some point, it may be helpful to see if these series are actually unique, or if some could be aggregated, deactivated, combined, etc. The growth of soil series in the USA over time. Figure courtesy of Dylan Beaudette, USDA-NRCS, California Soil Resource Lab. E: You know I like spending time with you, but it can get frustrating to not get a straight answer on something like “What series is this—delta or alpha?” and have you answer, “Well, this is kind of like a deltalpa.” Make a decision. T&B: We do that to get your goat most of the time, but you have a point. E: By the way, the soil series is a powerful concept that I hope is maintained. T&B: We agree, and we need to talk about that when we have more time. E: I don't know about you, but I've had enough yapping—let's head the field, so we can get educated, eh? T&B: You bet—make sure you bring the “earth” glasses. Adopting and using GIS/RS, GPS, and data to better understand the distribution, pattern, genesis, and behavior of soils has enhanced the endeavor for Turtle and Bear. The technology required a learning curve, but it did not get in the way of the process. The many methods available for data mining and classification will ensure the need to stay abreast of new techniques and continued exploration of their respective strengths and weaknesses for use in soil survey operations. The pedogenic glasses that Dr. Owl prescribed Turtle 28 years ago to help make soil maps are still useful, but the more modern and powerful tools from Eagle and Dr. Owl help Turtle do a better, more consistent job. Oh, and one more thing. A pair of reading glasses from Dr. Owl (Fig. 3) in the town of Even can still come in very handy when reading Chapter 5 of Soil Taxonomy–Application of Soil Taxonomy to Soil Surveys (Soil Survey Staff, 21). The traditional “hole mappers” and the more recent “pixel mappers” are likely to become “whole mappers,” after a good read. Dr. Owl, the optometrist, in his office in the town of Even Numbers (Indorante, 10).

On 30 Oct.–1 Nov. 2014, the Victorville MLRA Soil Survey Office; Dr. Bob Graham (University of California–Riverside, UCR), and Dr. Brenda Buck (University of Nevada–Las Vegas, UNLV) hosted the Desert Pedology, Land Use, and Wild Lands—Las Vegas to Long Beach two-day tour. The tour was planned and executed by Leon Lato and the rest of the Victorville MLRA Soil Survey, Region 8 team with a special thanks to Carrie Ann Houdeshell who originally initiated the effort before she transferred to her modelling position in Region 2. From Las Vegas, NV to the outskirts of the Los Angeles Basin, CA, there is a wide range of desert landscape, remote wilderness, unique vegetation, and soil formation. This area represents isolation and preservation and, at the same time, promises for the future of open space for renewable energy production, food and fiber production, watershed renovation, and alternative uses for new minerals for green infrastructure and modern technology. The tour started in Las Vegas at the University of Nevada with a lecture and lab tour from NCSS cooperator Dr. Brenda Buck. Her lecture on “Naturally Occurring Asbestos: Potential for Human Exposure, Southern Nevada, USA” was illuminating and a good start to understanding the issues of dust in the Mojave Desert and the southwestern U.S. to humans and the difficulties of studying the subject in an urbanizing environment. The group travelled on to California to the Mojave National Preserve (MNP). Dr. Mandy Williams of UNLV and Dustin Detweiler, NRCS ecological site specialist, started the field discussions with examples of biocrusts, ecological site descriptions, and the function of dust in these systems. Dr. Daniel Hirmas, Kansas University, explained his Ph.D. UCR thesis of Eolian deposits on mountains, and Leon Lato, NRCS soil survey project leader, Mojave National Preserve, led the discussion of the playa soil of Soda Dry Lake. The group stayed at the Desert Studies Center in Zzyzx, CA (named by Dr. Springer, owner of this famous 1930s health spa as the “last” word in health). On the second day, the group visited the basalt flows in the Cima volcanic field with Dr. Yvonne Katzenstein, which illustrated the potential of 1 to 3 m of dust (eolian fines) inflating the landscape over measured geologic time. A highlight of the tour was the taxonomic discussion and illustration of the new master V horizon by Dr. Robert Graham, UCR. This site shows how the V horizon developed from eolian deposits under a desert pavement surface. The vesicular pores and platy structure of the silt loam surface (V horizon) contrasts strongly with the gravelly-sandy material below. The final stop was at the eastern side of the Kelso Dunes with an explanation by Dr. Katherine Kendrick, USGS, on desert dust and dune processes. Pre-meeting SSSA Pedology Tour 2014 group picture on the eastern edge of the Kelso Dune field in MNP in an area stabilized by big galleta grass. Playa soil on Soda Dry Lake looking south at the Desert Studies Center in Zzyzx, CA—coarse-loamy, mixed, superactive, hyperthermic Oxyaquic Udorthents. The tour brought together students, soil scientists, and soil taxonomists from China, Iraq, Syria, India, Europe, Canada, Australia, Africa, and throughout the U.S. Those who attended came away with a clearer understanding of the importance of the V master horizon and dust in desert environments as well as congenial memories of NRCS's work in the region. They enjoyed the spectacular weather including some overnight rain and relatively light desert breezes for the trip. Tour participants scrutinizing samples of the V horizon in MNP. Desert pavement with a V horizon in MNP—sandy-skeletal, mixed, thermic Typic Haplocalcids.