The Pleasuresof Soil Watchingby Francis D. Hole

Soil is the vital substance that supports life onland. Because it usually feels stable underfoot, we call soil terra firma but when webecome aware of the vibrational motions of

water molecules and films, of air, roots, and organ-isms in soil, we are more inclined to call it terravibrata. When storm winds bend trees, for example,the soil “dances” measurably as roots are jerked thisway and that. Soil endures, both firmly and in a livelymanner, wherever i t is well protected by a covering ofvegetation and associated natural mulch or l i t ter . Thesoil supports plants; plants protect the soil. It is acooperative enterprise, which flourishes in great for-ests and grasslands, as well as in well-managedfarms, rangelands, and gardens.

The pleasures of soil watching can match those ofbirding. Among the chief differences are that we soilobservers look down more than up, and that soil doesnot migrate seasonally as birds do, nor does i t moveabout the local landscape (accelerated erosionexcepted). We do the moving, from soil to soil . Land-scapes are natural j igsaw puzzles composed of con-trast ing soi l bodies interspersed with bodies of waterand rock outcrops.

The 1980s would be a logical decade in which to

organize a Society of Amateur Soil Observers. Thescience of soil, called pedology (from the Greek forground, pedon), was founded simultaneously in Amer-ica and Russia in the 1880s. So a centennial celebra-tion is in order. Picture city and country people alike,fanning out over a landscape (assuming that land-owners have granted permission) in orderly fashion,studying soil patterns in honor of the 100th birthday ofthe science of soi l .

As part of our celebration, we should salute a Ger-man-American professor, E. W. Hilgard (1833-1916)who in a scholarly cotton census published by theU.S. government in the 1880s, presented an early sci-entific treatise on soils. We should also applaud a pro-gressive Russian natural scientist, V.V. Dokuchaev(1846-1903), who in 1883 published a remarkablework on the Russian chernozem, which was a peasantterm, now used by scientists in a technical sense, forthe productive “black land” of the steppes. Doku-chaev used letters of the alphabet, A, B, C, to desig-nate the natural soil layers, called horizons, from thetop down. Today, a century later , thousands of soilspecial ists around the globe use concepts and meth-ods established by Hilgard and Dokuchaev for ob-serving, analyzing, classifying, and managing soils . I t

is a propitious moment for the ascent of the soilwatcher into the constellat ion of friends and defen-ders of landscapes, wild and tamed.

Most of us need some instruction in how to encoun-ter soil, aside from the all-important, intimate contactwith surface soil in gardening and farming. A naturalsoil body extends on down many feet, the full lengthof plant roots. This short article is an introduction tothe subject of “soil watching,” not just of the surfacesoil, but of entire bodies of soil, in their dark and silentdepths. These deep reaches of soil become known tous through pictures and samples. Once we are armedwith the necessary information about what to look forin the way of soil profiles and their constituent hori-zons, and how to go about it, we can join the ranks ofactive amateur soil observers. To start with, ourfocus is not on serious problems of abuse by humanbeings. Rather, we will simply allow ourselves toenjoy the vital kingdom beneath our feet. If webecome friends of the soil first, we will be better ableto act in its defense later.

Soil, though out of sight, need not be out of mind.Until our death we remain exiled and l iberated fromthe soi l , but we draw on i t for nutr ients-phosphorus,calcium, potassium, etc.-as long as we l ive. The soil

is , both l i teral ly and f igurat ively, the root domain.

I t has taken mill ions of years for enormous quan-tities of solid, seemingly unyielding granite and

related rocks to be transformed into the particulatesoil . The spaces between soil part icles make room forwater, air, roots, and animals that the rocks in theirdensity would not accept. We can be grateful that thecontinents no longer present to the sun rock surfacesextending relentlessly from shore to shore. We wouldgo hungry in such a barren wasteland. Fortunately,the soil is there for us and serves as our welcome matto l i fe on land, whose inhospitable core is safely sub-merged under a nearly continuous blanket of loam.

The word “loam” connotes a mixture of sand, s i l t ,c lay, and humus, with or without pebbles and stones.The first three terms-sand, silt, clay-stand,respectively, for (1) coarse mineral grains (sand parti-cles are 2 to 0.05 millimeters, or 1/12 to 1/500th inch, indiameter), which feel gritty when rubbed betweenthe fingers; (2) medium-fine part icles (si l t grains are0.05 to 0.002 mm in diameter), which feel like flour;and (3) very fine particles (clay particles are less than0.002 mm in diameter), which feel sticky when wet.Humus is decomposed vegetable and animal matter ,

Soil profiles inEllsworth County,Kansas (overleaf).

Rock has come a long way to reach its powderystate in the soil. Visualize a cubic foot of granite. Ithas six sides for a total of six square feet of surfacearea. Nearly all of the 175 pounds of tightly inter-locked mineral grains are isolated from the environ-ment, waiting to be set free by slow processes ofdisintegration. Once the rock is finally reduced to soil,the approximately three million sand-size grains ofminerals that made up the rock separate, and many ofthem break down into still finer sand, silt, and clayparticles. We should not be surprised that 1,000grains of sand are in a single gram of sand (about thevolume of a pencil eraser); 6 million particles of siltare in a gram of dry silt; and 90 billion particles of clayare in a gram of dry clay. Imagine that 175-pound massof granite converted to dust (sand, silt, clay) andmixed with humus. It is now soil and has increasedtwofold in volume to two cubic feet , because of addedpore space. The total surface area of the billions ofparticles now equals one square mile, or nearly 28million square feet. No wonder that the soil acts like asponge, as it takes up water and stores nutrients informs avai lable to plant roots .

Diagram of a road bankan which the layers(horizons) of a soil areexposed as a complete“soil profile." The close-up view is of a column ofsoil, called a pedon, thefront face of which is theprofile consisting of A, E,Bt and C horizons overrock (R). The topsoilconsists of dark horizon(A) over pale horizon (E).The subsoil (B horizon)has a “t” symbol thatstands for clay (Ton, inGerman), because of clayaccumulation there. TheC horizon is loose parentmaterial that has not yetchanged into true soil.

In most soils of this planet, these four kinds ofparticles-sand, silt, clay, humus-are intermixed.In fact, they are likely to cluster together in pea-shaped and block-shaped units, called peds (about aninch in diameter, to a tenth of that size). Soil scientistssound like architects and geometry teachers whenthey describe shapes and arrangements of soil peds inthe ground: granules (pea-shaped), blocks, prisms,plates (fragile wafers of soil) . These various buildingunits of soil are shaped by earthworms, moles,wasps, spiders; by growing roots; and by swell ing andshrinking as soil becomes wet and then dries, freezesand thaws.

We can become familiar with this world of peds andpart icles by examining exposures (r iver banks; newlyscraped roadsides) and samples pulled out of theground by means of special tools . Imagine a plug outof a watermelon that shows green, white, and red lay-ers (horizons). The plug is a model of a soil pedon, a

which gives soils their black, dark gray, and darkbrown colors and endows them with greater capacityto support p lant growth.

column of soil in which the horizons are all exposed toview: topsoil , subsoil , and parent material , commonlyto a depth of many feet. A single face (two-dimen-sional) of a pedon is called a soil profile or sequence ofhorizons. Each of the hundreds of thousands of kindsof soil on the planet has a unique profi le.

Now let us consider the nutrient chain, from rockto soil to plant to food to human beings. Calcium, forinstance, from feldspar grains of granite, or fromderived limestone, becomes available through soilformation to plants, which take up the calcium intounderground parts, then into leaves, seeds, andfruits, which we eat directly, or which cows and otheranimals eat for us. An incredibly complex array ofelements and compounds f lows in balanced fashioninto our bodies along the nutrient chain. We are whatwe eat. In a sense we are unique, moist packages ofanimated soi l .

Here I would like to take time out from ourcarefree exploration of the world of soil to dis-

cuss a l i fe and death matter . For hundreds of mil l ionsof years, l ife forms, human beings among them, haveevolved in a rich and proportioned environment ofelements and compounds. The adequacy of that mil-ieu is increasingly threatened in two ways (as hasbeen summarized recently by National Academy ofSciences member M. L. Jackson, working with C. H.Lim). First, “trace” elements, which are thoseneeded in human diet in very minute amounts, arenow deficient in intensely farmed soils. Soils of China,for example, are generally exhausted of the traceelement selenium. So also are soils of many agri-cultural areas of New Zealand and the United States.Second, industrialization has introduced into soils cer-tain substances that are dangerous contaminantswhen taken into the human body. These substancesinclude the heavy metals lead, mercury, and cadmi-um; organic toxins; and radioactive elements-all ofwhich are accumulating in soils . Some trace elementshelp the body to cope with these contaminants . Dataindicate that selenium, copper, and zinc, for example,in appropriate daily amounts help to protect a personagainst cancer and other disorders fostered by inges-t ion of heavy metals. Such supplementary trace ele-

ments may prove to be as important in human diets asiodine in table salt.

We are fortunate if we have access to food pro-duced from fertile soils of alluvium, glacial drift, andvolcanic deposits. In contrast to such soils, some lit-tle-weathered sandy soils and very old soils of highlyleached, red equatorial lands under intensive cult i-vation do not generally support crops that provide allthe elements required for human nutri t ion. An Afri-can woman in one of my classes on soils of the worldonce told me that in her region it was the custom forpregnant women to eat some soil from abandonedtermite mounds, in which the insects had stored cal-cium and other nutrients.

But our main purpose in this essay is to learn totake pleasure in the soil . I recommend that we

take a soil walk. We shall give ourselves two assign-ments , namely to observe what goes into soi l andwhat comes out.

Let us start in the countryside, where we obtainpermission in advance from the landowner to probethe soil. The list of things that enter the soil daily is animpressive one, rivaling bird lists in length. Anyonewho has walked through a maple forest is familiar withthe tufts of leaves, twisted into burrows the size ofone’s l i t t le finger: these tufts are called earthwormmiddens. Dead leaves like these are among the natu-ral debris that is pulled into the soil by various agents.Water and air also enter the soil. While standing in arainstorm, one can observe water soaking into thesoil, most abundantly at the base of a smooth-barkedtree, where stem flow increases the volume. I haveheard soft , hissing sounds as bubbles of air escapedfrom a pasture soi l during a summer downpour. Airgoes in, and it also goes out of the soil, with the pas-sage of overhead high- and low-pressure air masses.It is as if the soil breathed. (Yet soil air is kept relative-ly low in content of oxygen and high in proportion ofcarbon dioxide, as a result of the metabolism of soi lorganisms.) Animals transport material to the sur-face: some earthworms bring up globules of soil,which lie strewn over the ground like pellets of “blackgold”; these are called earthworm casts. Ants areworth watching, too. They help build topsoil in for-

ests of New England, and even work through cracksin sidewalks in cities. And aside from fauna1 activity,the soil is restless on its own, as evidenced by thecracking of soi l into polygons in dry seasons, and theclosing of the cracks again when rains come.

To monitor the constant change in microenviron-ments at the surface of the ground a soil watchermight use a row of flat-headed nails, set two inchesapart and thrust into the moist ear th with heads f lushwith the ground surface at the start of the growingseason. Sets of these nails can be placed at contrast-ing si tes, accessible to weekly or biweekly checking,but protected from traffic, human or otherwise. Awitness stake with colored ribbon can mark the loca-tion of each row of nails, and a template consisting of astrip of wood penetrated by a row of small nailsspaced exactly the same as the nails in the soi l can beused to locate the heads of the soil nails at eachinspection. The point is to record what has happenedto each nail since the last observation. Has it beenburied? Under what? Sandy soil? Moss? Deadleaves? Worm casts? An ant mound? A butterflywing? Or has the nail head been completely exposed

A-HORIZON

E-HORIZONTOPSOIL

H-HORIZONSUBSOIL

C-HORIZONPARENT MATERIAL

II-HORIZONBEDROCK

A SOIL PROFILE

Some common kinds ofsoil profiles (below). SoilsI, II, and III constitutean age sequence from avery young soil (I) to a“mature” one (III), all onupland. Soils IV and Vare wetland soils. Four(IV) is composed largelyof rock particles. Humushas accumulated in the Ahorizon, which has re-ceived deposits (+) fromthe upland by erosion.The subsoil of IV isbluish-grey (g) in color.Five (V) is a muck, com-posed mostly of organicmatter (O) or humus,which is aged (a) near thetop, and fibrous (i) below.(C) FRANCIS D HOLE

I

by soil erosion that leaves the nail standing like aspine? Or did frost push the nail up? Or a mole? Ques-tions are to be enjoyed and pondered, even if not an-swered at the moment. Who can comprehend theways of the soil? Nobody can do this entirely. Who canenjoy the process of soil watching? We can, certainly.

If we walk in a forest dominated by trees more than100 feet tal l , we might wonder what kind of soi l sup-ports such an impressive stand. We may dig a pi t toexpose the profi le of the “true” soil (down to the baseof the B horizon, at three feet, for example), that usu-ally overlies many more feet of the parent material (Chorizon). The soil horizons in a forest soil can be strik-ing: black over pale lavender over dark brown, grad-ing downward to yellow-brown. Organic matteraccumulates as dead leaves and pine needles on thesurface. Also, f ine humus gradually washes down todarken the subsoil , leaving a bleached horizon (calledthe E horizon) above, where organic acids have strip-ped away color coatings from quartz particles. Whathappens to this soi l when the forest is cut and cropsreplace trees? The color patterns become simplified,as the original horizons are blended by cultivation.The great diversity of biota in the original wild soilis cur tai led.

Some soil walkers collect specimens of soil-earthworm middens and casts, peds of various sizesand shapes, miniature soil profiles made by gluingpinches of soil from various horizons onto cardboard

strips-and carry them in egg cartons back to thegarage shelf to keep company with empty wasps’nests and interest ing stones. I know someone who,by pressing sticky paper against the forest floor,mounts collages of earthworm casts, lacy deadleaves, and other debris to set in the house besideflower bouquets as something of comparable beauty!

If we live in a city, a soil walk lets us observe inter-actions between soil and the works of humankind. It isnot unusual, in a corner of a city park, to see a gravelpath or paved walkway part ial ly overtopped by what Icall creeping soil, which bears a protective coat ofgrass with it. The soil may manage to cover half of thepavement or path in places, as instabi l i ty of the soi lunderneath dismembers the walkway from below. Ifthe crew of park workers is too busy to take action,the t respass of the soi l may continue uninterrupted.The soi l is a s low-motion sea that gradually devourswhatever it can-fence posts, gravel paths, deadtrees, decaying buildings. Maintaining a city in theface of this motion is work.

think i t is important for us human beings, who arepeople of the l ight , to surround ourselves with im-

ages of the creative realm of darkness, the supportingsoil on which we tread. There is no way that we can beexposed to such images naturally, on a regular basis ,as we are to those of sky, birds, vegetation, and a va-riety of animal forms. Several possibilities come tomind. I have already mentioned the mounting of “soilbouquets, " that is, collages of delicate earthwormcasts and circular ant mounds. The art of soil-bouquetarrangement is in its infancy, as a result of our habit ofignoring the soi l as a universe of beauty. Soil jewelryis, as far as I know, not a lost art, but rather an undis-covered one. Nature lovers of all ages have surprisedme with the attractive creations they have made onsoil walks with me, by pressing soils of differentcolors into acorn cups, with appropriate adhesives.Lengths of cord can be glued to the back of the cups,which then are affixed to clothing: conversationpieces! Home interior decorat ion with soil pat terns isanother practical means of giving us daily acquain-tance with the hidden lacerylacery beneath our feet.Framed enlargements in color of views of natural soil

ment more familiar pictures of flowers and landscapes.Exhibi ts of soi ls are notably scarce in museums. I

recently saw in the natural history museum in Vic-toria, Brit ish Columbia, a spectacular enlargement ofa porous block of soil, in which an earthworm ap-peared as large as an elephant’s trunk. I am particu-larly pleased with the idea of dioramas of large soilpits, complete with forest or grassland vegetationrooted in the soil , representing different parts of theworld. Miniature dioramas are effective and less ex-pensive than full-scale ones.

The soil has more to say to us each day than weare capable of receiving and finding words for.

Eskimos have many words for snow because they areattentive to it. We have few words for soil as an entity.Our vocabulary for communicat ing about soi l is em-bryonic. Walt Whitman recognized this when hewrote:

affections.They scorn the best I can do to relate them

With the coming of age of the young science of soil,pedology, we are in a better posit ion than the poet tospeak for and about the soil , however less eloquentwe may be. Thanks to a voluminous scientific liter-ature about soils published worldwide in the pastcentury, we in the 1980s are able to understand thisnatural resource better than ever before. The soilneeds all the friends i t can get, friends who practicethe art of soil watching, with pleasure.

Francis D. Hole is emeritus professor of soil scienceandgeography at the University of Wisconsin-Madisonand the author of several books.

Professional soilscientists examining thehorizons (layers) of a10, 000-year-old forestsoil, as exposed in a ditchbank beside a highway(above). These workersare classifying the soil ina world soil-classificationscheme. They will assignratings to the soil fornumerous possible uses ofit, ranging from wildlifehabitat to urban develop-ment. The soil will be de-signated by the name ofa local settlement.

--