DOCUMENT RESUME

ED 106 073 SE 018 254

AUTHOR Halsey, CliftonTITLE Hinnesota's Soils and Their Uses.INSTITUTION Einnesota Univ., St. Paul. Agricultural Extension

Service.SPONS AGENCY Department of Agriculture, Washington, D.C.REPORT NA Bull-383PUB DATE [75]NOTE 33p.; Photographs related to the text may not

reproduce clearly

EDRS PRICE NF -$0.76 HC-$1.95 PLUS POSTAGEDESCRIPTORS *Agronomy; Conservation (Environment); Conservation

Education; Environmental Education; *Land Use;Natural Resources; Science Education; SecondaryEducation; *Coil Conservation; *Soil Science

IDENTIFIERS Minnesota

ABSTRACTThere is ar, increasing need for land planning and

understanding soil is one step toward assuring proper land use. Thispublication, written by soil scientists and teachers, is designed asa reference for high school teachers. It is designed to be acomprehensive collection about Minnesota soils (although theinformation can be applied to other areas) that non-experts canreadily nse. Discussed are topics such as the composition of soil,the importance of soil, soil profiles, soil classification, soilformation, soil variation, soil types, and using the soil.Illustrations, photographs, a diagram of the sulfurs, and nitrogencycle, maps, figures, and tables are included. A glossary ofsiil- related terms used in the text and suggested references areincluded. (TX)

Minnesota's Soils and Their Uses

U S DEPARTMENT OF HEALTH.EDUCATION &WELFARENATIONAL INSTITUTE OF

EDUCATIONTHIS DOCUMENT HAS BEEN REPRODUCED EXACTLY AS RECEIVED FROMTHE PERSON OR ORGANIZATION ORIGINAT,NG IT POINTS OF VIEW OR OPINIONSSTATED DO NOT NECE:SARILY REPRESENT OFFICIAL NATIONAL INSTITUTE OFEDUCATION POSITION OR POLICY

By Clifton Halsey,:xtension ConservationistSoils

GLOSSARY OF SOIL-RELATED TERMS USED IN THE TEXT

acidity, soil acidity the concentra-tion of hydrogen ions (Hi) in the soilsolution.

aeration, soil aeration the exchangeof air in the soil with air from theatmosphere.

aerobic, aerobic organisms - living oracting only in the presence of mole-cular oxygen.

aesthetic - relating to beauty.

alkalinity, soil alkalinity - the con-centration of hydroxyl (OH-) ions inthe soil solution.

amino acids nitrogen-containing or-ganic compounds which are the chiefcomponents of proteins.

anaerobic, anaerobic organismsliving where molecular oxygen isabsent.

artificial drainage a system for re-moving excess or undesirable surfaceand/or groundwater. using ditches,underground tile, or both.

aspect, slope aspect the direction aslope faces.

autotrophic - able to use carbondioxide or carbonates as a source ofcarbon and to obtain energy by oxi-dizing inorganic elements or com-pounds.

available, available nutrient, availablewater -- the portion of the supply ofau element, of a compound. or ofwater in the sod that can he taken upby plants at rates and in amountssignificant to plant growth.

bearing strength the soil's ability tosupport weight without shJting ormoving.

bedrock - solid rock.

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hog an area of organic soil (peat ofmuck).

calcareous soil containing enoughcalcium and /or magnesium carbonateto be alkaline.clay - refers to either the submicro-scopic mineral soil particles less than0.002 millimeters in diameter or a soilmaterial that contains 40 percent ormore clay, less than 45 percent sand,and less than 45 percent silt.close-growing or close -sown crops -farm crops such as oats, wheat, grasses,and legumes. Their seeds are plantedclose together, either randomlyscattered or in close rows.compaction - any process by whichsoil particles are packed closelytogether, reducing the space betweenthem and increasing the density of agiven volume of soil.

conifers - trees with cones and needle -shaped or scalelike leaves, usuallyevergreen.

contouring, contour tillage - perform-ing fieldwork at a right angle to thedirection of a slope.contour strips even-width strips ofcrops at a right angle to the directionof a slope, alternating closesown cropssuch as oats and alfalfa with row cropssuch as corn.crop residues the portions of annualplants left in the field after harvest.deciduous plants perennial plantsthat shed all their leaves each year,usually in the fall.deposition - accumulated materialwhich was dropped by slowing wind orwater.

depression - a low area of terrainsurrounded completely by land of ahigher elevation that prevents com-plete surface drainage of water fromthe low area.drainage - the removal of surfacewater or groundwater from land.

32

drop spillway - a structure made fromconcrete or a similar material overwhich water falls to an apron below.drouthiness - inability of a soil tohold sufficient water for good plantgrowth.

erodibility - the degree of a soil'ssusceptibility to removal by wind orwater.

erosion - detachment and removal ofsoil by wind or water.

fertility, soil fertility - soil's level ofnutrients available for plant use.

fertilizer - any material added to thesoil to supply nutrients for plantgrowth.

fill - soil deposited in a depression.

filter field, disposal field, drainfield,soil absorption field - an area used fordisposing of sewage liquids by placingthese liquids in the soil through asystem of perforated pipes or looselyspaced tile.

frost boil. frost heave - raised ordisintegrated road surface caused bythe accumulation and subsequentthawing of ice in soil beneath the road.

granulated - having numerous clustersor aggregates consisting of many soilparticles adhering to one another.granule - a cluster of soil particlesadhering to one another and havingmany characteristics of a singleparticle.

grassed waterway - a natural or con-structed shallow drainageway ccveredwith grass.

gully - a deep channel cut by flowingwater from rains or snowmelt.heterotrophie - able to obtain energyonly through decomposing organiccompounds.horizon, soil horizon - a layer of soilapproximately parallel to the soil sur-face and distinctly different from thesoil above and below it.humus - the dark-colored, well-decomposed, more or less stable por-tion of organic matter in mineral soils.igneous rock - formed by solidifica-tion of molten (extremely hot, liquid)mineral matter.impermeable, impervious - resistantto penetration by water, air, or roots.infiltration - the flow of water intothe soil.

internal drainage - rate of movementof water through the soil.

lacustrine deposited in lake water.leach - to remove materials from soilby dissolving them in water movingdownward through the soil.liming spreading agricultural lime-stone or similar material on the soil toreduce the soil's acidity.

loam - the name for soil containingmoderate amounts of sand, silt, andclay (7 to 27 percent clay, 28 to 50percent silt, and less than 52 percentsand).

loess - soil material consisting mostlyof silt-sized particles that have beentransported by wind.logarithm the exponent or symbolthat tells the number of times a factor(called a base) occurs in a given prod-uct (or number). If N = bX, x is thelogarithm of N to the base b. (Ex-ample: 1,000 = 103; the logarithm tothe base 10 of 1,000 is 3.)

macronutrient a chemical elementnecessary in relatively large amountsfor plant growth.

manure animal excrement with orwithout bedding or litter.micronutrient - a chemical elementnecessary in very small amounts forplant growth.

microorganisms - forms of life toosmall to be seen with the unaided eye.

mine tailings - waste materials frommined mineral processing.

mottle - spots of color different fromthe color of most of the material in asoil horizon.

mulch - a layer of plant residues orother material on the soil surface.

open ditch an uncovered channelconstructed to convey drainage water.

organic matter - the part of the soilconsisting of dead plant and animalmaterial.

organic soil - a soil containing morethan 20 to 30 percent organic matter.

outwash, glacial outwash - materialcarried by glaciers and later sorted anddeposited by water flowing from themelting ice.

overflow - water which periodicallyflows from higher ground to flood alower aea.

oxidation - combination of a chemi-cal with oxygen.

parent material - the unconsolidatedmineral or organic material fromwhich the soil profile is formed.

pasture an area established foranimals to graze.

peat soil material primarily con-sisting of slightly to partially decom-posed plant material which has ac-cumulated under conditions ofexcessive water.

percolation - downward movement ofwater through soil.

percolation rate - 'the rate at whichwater moves downward through sod.

permeability - a soil's ability to allowwater and air to move through it.Permeability is measured as the rate offlow of water through a unit area inunit time under specified temperatureand hydraulic conditions.pH - a numbered expression of theacidity or alkalinity of a soil; the com-mon logarithm of the reciprocal of thehydrogen ion concentration of a solu-tion.

plant nutrient - an element esse-Jialto the life and growth of a plant andused by it in elaboration of its foc 1and tissue.

plasticity - the case with which aportion of soil can be molded orreshaped.

ponded - kept or held in an undrainedor slowly draining depression.

pore space - the fraction of the totalspace in a volume of soil not occopiedby solid particles.

porosity - the percentage of totalvolume of soil not occupied by solidparticles.

practice - a customary way ormethod.profile, soil profile a vertical crosssection of soil through all its horizonsfrom the surface into the parentmaterial.

reaction, soil reaction - the degree ofa soil's acidity or alkalinity.rangeland - large areas of nativegrasses used for grazing livestock.

riverwash - unproductive soil de-posited by streams and subject toshifting when it's flooded.rotation, crop rotation - growingdifferent crops in recurring successionon the same land.row crop - a crop planted in rows sothat the soil between the rows may hecultivated.runoff, surface runoff - the portion ofrain and snowmelt water that flowsover the surface of the land.

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sand individual soil particles havinga diameter between 0.05 and 2.0 milli-:neters.

seepage - water escaping through oremerging from the surface of the soil.silt - individual soil particles having adiameter between 0.002 and 6.05millimeters.slope - the incline of the surface of asoil from level.strip crop - having a systematic ar-rangement of strips or bands of differ-ent crops to reduce wind or watererosion.

structure, soil structure - the com-bination or arrangement of individualsoil particles into units or groups ofparticles.

subsoil - the soil horizon (called 13horizon) beneath the layer of darker-colored topsoil. It does not include thealtered or unaltered parent material orunderlying layers unlike the parentmaterial.

surface inlet - a surface opening to anunderground tile to help remove sur-face water; much like a storm sewer.terraces - ridges and channels con-structed across sloping land surface onor at a slight angle from the contour toprevent erosion by diverting surfacerunoff to a prepared outlet.

texture, soil texture - the relativeproportions of various sizes of indi-vidual grains in the soil. It refers to theproportions of sand, silt, and clay.

till, glacial till - unlayered ,,oil ma-terial which was deposited directly bymelting glaciers.

tillage, tilling - digging and looseningthe soil in preparation for planting orto control weeds.

tilth the physical condition of thesoil affecting the soil's ease of tillageand fitness for the growth of a speci-fied plant or sequence of plants.

topography - the shape of an area'ssurface.

topsoil - the darker surface layer ofsoil, often the plow layer.undulating - having a wavy appear-ance.

watershed - all the land surface fromwhich water drains into a commonoutlet.water table - the surface of ground-water or the level below which the soilis saturated with water.windblown - transported and de-posited by wind.

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FOREWORD

Minnesota's Soils and Their Uses isa reference for high school teachers.It's designed to be a comprehensivecollection of technical knowledgeabout Minnesota soils that noncxpertscan readily use. There is an increasingneed for land use planning in the state.Minnesotans need to know about thestate's soils to assure proper land use.

1. Soil provides basic ingredients for life and growth of all living things.

Such learning should begin in theschools.

Several soil scientists and teachershave contributed to the publication.The author is thankful for the reviewsand suggestions by the University ofMinnesota Soil Science Department.Special thanks go to Drs. James Swan,Rouse Farnham, Richard Rust, andHarold Arneman and to the Soil Con-servation Service assistant state soilscientist Ed Bruns. Thanks also go toRonald Clendening and Charles Burn-ham of the Coon Rapids Junior HighSchool science department who re-viewed the manuscript and suggestedimprovements.

The Emil Conservation Service andthe Minnesota Highway Departmentprovided many of the photos.

Finally, the author thanks the pub-lications editors and artists of theUniversity of Minnesota AgriculturalExtension Service for their help withthis publication.

4 5

SOIL IS IMPORTANT

Sunlight, air, water, and soil pro-vide basic ingredients for life andgrowth of all living things. Life as weknow it would not exist if one of theseparts was missing. Let's consider soil.The roots of almost all plants are insoil. Soil furnishes plants with water,mineral nutrients, and support oranchorage. Plants using elementsand water from the soil, the carbondioxide from the air, and radiantenergy from the sun produce foodon which all animals depend.

Soil also provides:

homes for microscopic or-ganisms and for many largeranimals;

minerals that arc carried intolakes and streams to nourishaquatic life;the foundation, the minerals,and the construction materialsneeded for many of man's activi-ties and structures.

FIGURE 2. Moist, fertile soil contains many living things.

COMPOSITION OF SOIL

Most people think soil is finelyground rock. A closer look reveals thatsoil is much more. It has depth, andfrom the surface downward, soil maybe different in color, in size of par-ticles (texture), and in other charac-teristics. Soil contains microorganisms,fungi, crawling animals, and insects.The soil contains oxygen for theseanimals to use. Soil also containswa ter.

A surface soil good for most plantscontains about 45 percent (by volume)of mineral matter particles. Another 5percent is dead and decaying plant andanirml material. The remaining half ofsoil is space occupied by gases andliquid.

Mineral matterLet's take a closer look at the

mineral portion of soil. Depending onthe soil's texture (coarseness or fine-ness). we may sec small stones or

gravel particles. These are rock frag-ments. If their corners are rounded,these fragments have been rolled andworn by flowing water and/or glaciers.Particks of sand (which can be seenwitslout magnification) are mostlyoriginal mineral particles. These par-ticles were once part of massive rock.Smaller particles individually visiblethrough a microscope are called silt.The finest particles, clay, are visibleonly through an electron microscope.Some silt particles, like sand, areoriginal primary mineral particles fromweathered rock. The rest of silt andmost of clay are secondary minerals.These minerals have been chemicallyand physically changed after thou-sands of years.

AnimalsMoist, fertile soil zontains many

living things. The following list' showsthe number and variety of micro-

5 6

organisms that may be found in 1/4teaspoon of fertile soil.

50 nematodes microscopicparasites and predators:

62.000 algae microscopicplants:

71.000 amoebae:

111.000 fungi;

1.910.000 actinomycetes;

/5,/80.000 bacteria.Bacteria, alone, in I acre of soil is

estimated to weigh I ton or more.(The average weight of an acre of top-soil 7 inches deep is 1,000 tons.) Oneacre of moist, loam soil may containmore than a million earthworms.These earthworms weigh a total ofmore than 1,000 pounds (I acre con-tains 43.560 square feet).

I Waksman, Selman A., 1952. SOILMICROBIOLOGY. John Wiley, NewYork.

This chart lists the more importantorganisms in soil.

Kinds of soil organisms and their roles

1. Animals

11. Plants

A. Macroorganisms

B. Microorganisms

1. Feed largelyon plantmaterials.

2. Mostlypredatory (eatliving unimals).

Predatory, parasitic, or.1 feed on plant residues.

( Roots of higher plants.1 Algae green, blue-green; diatoms.

Fungi mushrooms, yeasts, molds.Actinomycetes.Bacteria.

Microorganisms cat and decomposeplant and animal material. Decomposi-tion releases this material's nutrientsfur re-use by higher and lower formsof life. Remaining organic matter(humus) increases the soil's infiltra-tion. aeration, water-holding capacityand resistance to erosion. Almost allnematodes are microscopic. A fewfeed on the roots of higher plants suchas potatoes and carrots. Some preda-tory nematodes eat other an, ,ai life.A third group feeds on decaying or-ganic matter.

Protozoa are one-celled, microscopic animals. They are grouped ac-cording to their development. Theflagellates are most common in soil,followed by amoebae and then ciliates.Most soil protozoans feed on deadorganic materials. Some may feed onbacteria.

Rot ifers are also microscopicanimals. They live in moist soils andare especially abundant in swampyland. Their importance in soils is un-known.

Millepedes, sow bugs, mites, slugs,and snails feed mostly on relativelyundecomposed plant tissue. Millepedesare especially active in peat soils.

Earthworms are very important tosoil. They take in the soil, digestingboth organic and mineral soil particles.In loam soils high in organic matter,earthworms eat as much as 15 tons ofsoil per acre each year. This activityhelps plants in several ways. It in-creases the soil's content of decay-resistant or residual organic matter(humus), makes more plant nutrientsavailable, and increases soil aerationand drainage.

Vegetable matterPlant life in soil is even more impor-

tant than animal life, especially in itsfinal decomposition of the organicn ttter. Animals in soil perform mucho the initial decomposition- micro-flora carry it much further.

Algae are most numerous near thesoil surface. Grasslands and water-logged soils are favorite sites for biue-green forms, and diatoms are 3bundalitin old gardens. Algae contribute someorganic matter to soil. Fungi transformorganic matter into fungal tissue,especially in acid forest soils. Actino-nrycetes are especially numerous inneutral mineral soils high in organic

6

Small mammals groundsquirrels, gophers,woodchucks, mice.

Insects springtails,ants, beetles, grubs, etc.

Millepedes, sowbugs, mites.Earthworms, slugs, snails.

Moles, shrews.Insects many ants,

beetles, etc.Mites, in some cases.Centipedes.Spiders.

Nematodes,protozoa, rotifers.

matter. They are able to use the moreresistant and complex residual organicparts in the soil, reducing these frac-tions to simpler compounds.

One billion to three billion bacteriamay be in 1 gram of soil. Bacteria arevery small, less than 0.005 millimetersin size. Smaller bacteria are about thesame size as individual clay particles.When growing conditions are favor-able, the bacteria multiply on soil par-ticles. There they form colonies in theshapes of mats, clumps, and filaments.Autotrophic bacteria obtain theirenergy by oxidizing ammonium, sul-fur, and iron compounds. Their carboncomes from carbon dioxide. Auto-trophic bacteria are important becausethey convert nitrogen and sulfur tocompounds used by higher plants.Heterotrophic bacteria derive theirenergy and carbon from soil organicmatter. Bacteria are perhaps the mostimportant form of life in soil becausethey are responsible for three life-sustaining transformations: nitrifica-tion (nitrogen oxidation); sulfur oxida-tion; and the fixation of nitrogen fromthe soil air.

Plant roots are an important sourceof organic matter in soil. They are the

Partial sulfur cycleair from combustion

Torption

SulfateSO24

From plant residuesand microorganism;

%44......--1)xidized byThiobacillus bacteria

rmallellal ilallabibmillisb

From soil minerals

Sulfur compounds

(Adapted from Nature and Properties of Soils, page 468.)

FiGURE 3. Soil microorganisms recycle plant nutrients.

ultimate food source for much soillife. Even when the roots are living,they actively dissolve nutrients andexcrete amino acids at their surfaces.The number of organisms may be from10 to 100 times as great in the im-mediate root zone as in other pzrts ofthe soil.

Soil airPlant roots and other soil life need

air for respiration. These roots alsorelease carbon dioxide. Gases it thesoil spaces (these spaces are calledpores) must move freely so life canexist in the soil. The pores in soil are amaze of small open spaces. Part ofthese spaces is occupied by water.

Air in the soil is not pure. Moist soilis nearly saturated with water vapor.The carbon dioxide content in soil airis several hundred times greater thanth in the air above ground. Oxygenmay be no more than 10 to 12 percentin soil air. It is about 20 percent in theair we breathe. Soil air also containsammonia, sulfur dioxide, and othergases not found in the air aboveground.

Poorly aerated (ventilated) soilscontain reduced compounds (com-

Partial nitrogen cycle

Nitrogen in soil air

Soil organisms

Soil organic matter

3 Changed by a varietyNi ate ion

of soil organisms

Certain bacteria,blue-green algaeand fun i.

gNitrogen fixation

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A

Changed by nitrosomonasand nitrobacter (bacteria)

Ammonia ion

Adapted from Nature and Properties of Soils, page 440.)

FIGURE 4. Flooding restricts the amount of air in the soil for the growth of corn(SCS photo).

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pounds from which oxygen has beenremoved) poisonous to higher plants.These reduced compounds form whenanaerobic organisms take oxygen fromoxides for their own use. Poor aerationcan be caused by flooding, poor inter-nal drainage, and compaction.

Soil waterSoil water is complex. It is not

pure, but is a solution containing dis-solved gases, plant nutrients, livingthings, and occasionally compoundstoxic to plants. Too much water in soil

7 8

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pores restricts the a:nount of air forplant growth. However, too littlewater is also restrictive.

1' _sc.

Soil water may be measured interms of saturated capacity of the soilto hold water (all pores filled); theamount of water that soil will holdagainst the force of gravity; and theamount remaining in soil when plantsbegin to wilt. The most practical measurement is available water, that whichcan be used by plants at significantrates.

FIGURE 5. Each well-developed soil has its own distinct profile. The top photoshows a very drouthy prairie soil, and the photo above shows a forest soil.

FIGURE 6. (Below) This illustration shows the horizons in a soil profile.

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SOIL PROFILES A LOOK FROMTHE SURFACE DOWNWARD

Soil has depth as -Atli as surfacearea. Soil is classified according to par-ticle size (texture), organic matter,color, and other characteristics fromthe surface down to the unchangedparent materials or to other geologicstructures or def:osits below the soil.The arrangement of these soil com-ponents is the "soil profile." Indi-vidual layers in the soil profile arecalled "horizons." Each well-devel-oped, undisturbed soil has its owndistinct profile. These profiles are usedto classify soils according to theirsuitability for various uses.

The upper layers of soil are usuallydarker than lower ones because theupper layers have accumulated organicmatter. These layers are called "top-soil." Lower layers are "subsoil." Sub-soil usually has three bands: an uppertransition layer; a middle layer con-taining materials carried down bywater from above; and a bottom layerof nearly unchanged parent material.Soil horizons are described in figure 6.

0 horizon raw and partially decom-posed organic materialabove the mineral soil.

A horizon surface mineral layers,including the zone ofmaximum accumulationof decomposed organicmatter within the min-eral portion and thezone of maximum leach-ing or removal of clayparticles, mineral com-pounds, and organicmatter.

B horizon the zone of maximumaccumulation or depositof materials removedfrom the layers above.

C horizon layer of material belowthe zone of maximumaccumulations and notmuch affected by thesoil-forming factors. Thislayer may be slightlyweathered parent ma-terial much like the ma-terial from which thesoil above it was formed,or it may be unrelatedmaterial unlike theparent material.

Similar soils in different locationsmay be identified through detaileddescriptions of their profiles. Similariils in separate !orations will respond

in the sanne way tt the same uses andland treatments. A Hubbard sandyloam in one 1.,:atian will be as goodfor a septic ta..k driinfield as the samesoil in another ;cation. A Floyd siltyclay loam in one county will he just aswet for corn and ai poor for a septictank dra infield as tit: same type of soilwould be in another county. Soilscientists name specific types of soilafter locations where these soils can befound.

Identification and classification ofsoils according to ph:'sical and chemi-cal characteristics of soil profiles helpsin planning land use management.

SOIL CLASSIFICATION

Soils throughout the United Statesare classified in a a mpreaensive sys-tem developed by the U.S. Depart-ment of Agriculture. The most recentrevision of this classification system,called Cie Seventh Approximation,was adopted in 1960. Classification isbased on soil properties in the fieldproperties that can be measured quan-titatively. Color, texture, structure,organic matter, type of clay, pH value.soil depth. internal drainage, andchemical compounds are some proper-ties that may be considered.

Soil scientists record their findingson aerial photographs. Soil survey re-ports have been printed for more than

52 of the 87 Minnesota counties. Theymay be found in libraries or at officesof the Agricultural Extension Serviceor soil and water conservation dis-tricts. Some older reports are out ofprint. Recent survey reports may bepurchased from the Superintendent ofDocuments in Washington, D.C. Thesereports describe individual sods ingreat detail. Recent reports also in-clude information about the suit-ability. use, and management of soilsfor agriculture, forestry, wildlife,roads, buildings, and recreation. Soilsurvey reports are an excellent sourceof technical information for planningland use.

FIGURE 7. This soil survey map shows detailed soil characteristics of a small portion of Fillmore County in southeasternMinnesota.

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SOIL FORMATION IN MINNESOTA

Nlivnesota has 80,000 square milesof land and 4,00e square miles ofwater. inch.ding 15.000 lakes. Thereare lulls and valleys. rivers and peathugs. rock outcrops and waterfalls. Wecrop fertile farml.nds, quarry graniteand limestone, mine iron ore, harvestthe forests, and hunt the wildlife. Thesod 'antis greatly from one part of thestate to another.

Much of the northwestern area usne-irly level with a fine-textured, dark-colored soil. Although part of it floodsand its excess water drains awayslowly. northwestern Minnesota is afertile agricultural area.

Extreme southeastern Minnesota isrolling to hilly. Water runs off rapidlyand can erode the soil. This area's siltloam soils are well-drained. and thegentler slopes can produce bountifulcrops. Steep slopes are suitable onlyfor forests and wildlife.

In some parts of the state. soils dif-fer greatly within short distances.Changes in the slope. internal drainage,and texture may be very abrupt orsudden. There are short, steep hillswith ponds at the bottom. There aresloping lands with medium-texturedsoils adjacent to very sandy, nearlylevel areas.

Why is there such variability in thesoil?

Most of Minnesota's present land-scape was shaped by continentalglaciers. The last g;acier melted about11.000 years ago. These glaciers

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FIGURE 8. Continental glaciers cov-ered much of North America. (FromMinnesota's Rocks and Water:, page155.)

formed during long periods of coldweather as snows accumulated todepths of many thousands of feet. Theextreme weight i the accumuiationcompacted the bottom lay ors into ice.This ice became somewhat fluidlikesimilar to cold sy rup and spread outin all directions over the continent.The thick ice mantles slowly movedover hills and valleys. mountains andplains. scraping and gouging enormousamounts of rock and soil ranging insize from house-sized chunks to finedust. The basins of many Canadianborder lakes are a result of thisgouging. Glaciers entering Minnesotafrom the northwest carried limestonematerials from southern Canada.Glaciers flowing froin the northeastremoved and crushed bedrock andother materials from Ontario andnortheastern Minnesota.

The glaciers melted as the climatewarmed. Remaining rock and mineraldebris were left in varying arrange-ments of sorted and unsorted ma-terials. South central Minnesota wasmostly an undulating expanse ofmixed. unsorted materials depositeddirectly as the ice melted uniformly.At intervals, belts of hills interrupt thisexpanse. These hills consist of gla.1a1debris formed by temporarily st; Lededges of the retreating glaciers.

Large luantities of water were dis-charged at the edges of the meltingglaciers. These glacial streams de-

FIGURE 9. The melting glaciers leftmineral debris in varying arrangements.

10

posited well-sorted layers of sand andgravel (called "outwash") alcag themajor river.. such as the Minnesota andMississippi. They also created large,flat sandy plains. The glaciers, actingas dams, created la.ge lakes such asglacial Lake Agassiz, which includedthe area now called the Red RiverValley. The lake bottom sediments arefine-textured clay materills. The lakeedges or beaches are sandy or gravellymaterials.

Southeastern and southwesternMinnesota have ortensive areas of siltymaterials (called "loess") which wereblown about by the wind before vege-tation became established.

The differences in the materialslimestone deposits to nonlimc bed-rock, particle sizes fro:n house-sizedboulders to submir-ascopic clay. andheterogeneous mixtures of particlesizes to well-sorted sizes of particlesproduced a wide variety of parentmaterials from which Minnesota soilwas formed. Understanding these dif-ferences will enable the user homeowner or road contractor to employthe soil the best advantage ofeveryone.

The climate where soil is forminggreatly influences the speed of forma-tion. Running water and extremechanges in temperature cause physicalweathering Of disintegration of mineralparticles. Alternate freezing andthawing of water in cracks as well as

Moraines

Glacial Lake

FIGURE 10. Glaciers, acting as dams,created large lakes.

heating and cooling of rocks areexamples of temperature effects. Drierclimates favor prairie grasses ratherthan forests. Warm temperatureshasten the decay of organic matter.Heavier precipitation increases move-ment of elements from the surface tothe subsoil. It also increases the rate oferosion of the surface of sloping soilsto more level areas.

Topography and climate are closelyrelated factors influencing soil fonrra-lion. The steepness of a slope affectsthe amount of water that soaks intothe soil and that runs off, possiblycarrying surface soil with it. Hilltopsusually have shallower topsoil for thisreason. The direction of slope( "aspect ") affects the temperaturenear the soil surface. North- and cast-facing steeper slopes are cooler andfavor forest vegetation. Warmer south-and west-facing slopes favor prairievegetation. Level areas having slowinternal drainage accumulate organicmatte: because the water in the soilinhibits bacterial oxidation anddecomposition.

Native vegetation interacts withclimate and topography to form soil.The most obvious effect is on the soil'sorganic matter content as indicated bysoil color. Although drier climatesfavor prairie grasses. fire was impor-tant in restricting expansion of theforest into prairie land. Roots ofgrasses are short-lived, and organicmatter formed from them accumulatesto develop a deep, dark topsoil, Rootsof the forest trees are long-lived; it ismostly the leaves and dying branchesthat form organic matter on the sur-face of the soil. The decaying remainsof forest vegetation causes soil waternear the surface to become more acid.This acid solution dissolves chemicalcompounds and organic matter andcarries them down into the soil. There-fore, little accumulation of organicmatter results in surface soil under-neath forest vegetation.

Time, in terms of hundreds to thou-sands of years, is required to I'm in soil,Older soils are more developed thanyounger ones formed under the sameconditions.

These factors parent material,climate. topography, vegetation, andtime are "soil-forming factors."

17

At-

V

4 41

a1. .44...

ON

I

Je

FIGURE 11. Topography is an important soil characteristic.

SOIL DIFFERS GREATLY FROMSoil varies greatly from one loca-

tion to another, sometimes within afew feet. Changes in parent materialand topography are responsible formuch of the variation over short dis-tances. Time, climate, and native vege-tation cause changes from one regionto another.

Topography

One of the first features we noticeabout landscapes are their topography.Some are nearly level. Most land in

II 12

PLACE TO PLACEMinnesota slopes. elopes may vary insteepness, length, and aspect (directionthey face). Topography may be evenor uneven and irregular. The elevation,as related to the surrounding area (topof the hill, hillside, or bottom), is im-portant, too. The amount of slope orsteepnessof the soil is important whendeciding how soil can be used.

S ;ope may be expressed in severaldifferent ways. Tables I and 2 (nextpage) illustrate them.

Table 1. Expression of slope.

Regular topography Irregular topography Percent slope Letter designation

Nearly level 0-2 AGently sloping Undulating 2.6 BModerately sloping Rolling 6-12 C

Moderately steep Hilly 12.18 DSteep 18-25 E

Very steep 25 or gre F

Table 2. Expression of slope.

Slope ratio Percent slope De gm

1:1 100 452:1 50 263:1 33 1/3 18

4:1 25 14

Slope percentage is the verticalchange in elevation between two loca-tions divided by the horizontal dis-tance between them and multiplied by100. Slope percentage is the change infeet of elevation between two points100 fe2t apart. Soil scientists designateletters to represent the ranges of slope."Slope ratio" (a term used by engi-neers) is the ratio of the horizontal dis-tance between two points to thevertical change in elevation betweenthem.

Steepness affects: the amount andspeed with which water runs off thesoil; the amount of water remaining tosoak into soil and water-bearinggeologic formations; the depth of soilon the slope; and the amount ofnatural and man-accelerated erosion. Ifslope percentage is doubled, the soillost by erosion is about 2 1/2 times asmuch.

Length of the slope is importantbecause it affects erosion. The longerthe slope, the more water flows overthe lower part of the slope. If slopelength is doubled, soil loss per unitarea increases by about I 1/2 times.Larger amounts of water can carrymore soil until it reaches the pointwhen soil is dropped on the lowerslope or, if the water is concentratedin narrow channels, gully erosionoccurs.

Direction of slope influences soiltemperature and soil water availablefor plants. South and west slopes facethe sun for longer periods and duringthe warmer part of the day. Therefore,they are warmer and drier than northand east slopes. The kind, and quali-ties of plants growing on these siteswill reflect these differences.

Uniformity of the slope is a com-bination of direction, length, andsteepness. Uniformity influences thetypes of soil-conserving practicesfarmers can use.

Relative elevation of the 1.1nd com-ared to the surrounding area in-

,luences flood hazards. Plant speciesvary in their tolerance to flooding interms of the season, duration of sub-mersion, and frequency of flooding.Flooding also affects the land's suit-ability for wildlife and for structuraluses such as homes and streets.

Watersheds are a result of topog-raphy. A watershed is the land areawhich contributes all the runoff waterflowing into a body of water or past acertain point (more specifically,through the cross-sectional area) of astream, ditch, or other waterway. Forexample, all the land from whichwater flows into the Blue Earth Riverin southern Minnesota is a part of theBlue Earth River Watershed. That riverand several others flow into the Minne-sota River. Each river receives runoff

12 13

water from a specific land area becauseof the directions of slope within thearea. Thus, the Minnesota River Water-shed consists of numerous smallerwatersheds. The Minnesota RiverWatershed is a part of the MississippiRiver Watershed.

Flooding, pollution, and sedimenta-tion into a lake or stream are causedby actions within its specific water-shed. Solving these problems fre-quently involves the entire communitywithin the watershed.

TextureA very important but less obvious

feature of the soil is its texture. Tex-tur is the fineness or coarseness ofsoil Texture is the relative amounts ofthe various sizes of mineral particles inthe soil. There is a very great range inthe size of soil particles. Gravel referstr particles larger than 0.08 (1/12)in...i in diameter. Twelve part: ofthat size laid side by side wove ,a line about 1 inch long. Clay refers toparticles smaller than 0.00008 inch,one-thousandth the size of the smallestgravel particle. It would take morethan 12,500 clay particles side by sideto form a line 1 inch long. This linewould be so thin that it would takemore than 250 lines side by side toform a line as wide as a pencil mark.Table 3 shows the relative sizes of soilparticles.

A clay particle enlarged 500 timesmay be as large as the period at theend of this sentence. Sand particles en-larged 500 times could be from 1 inchto more than 3 feet in diameter.

Table 4 shows the sand, silt, andclay content of three Minnesota soils.

The shape of soil particles is respon-sible for many characteristics attrib-uted to soil texture. Gravel particlesare usually somewhat rounded. Sandand silt particles may be rounded orquite irregular, depending on howmuch they have been worn by wateror wind. Soil particles do not fittightly side by side like a stack c`blocks or bricks. They are more likemarbles of various sizes in a container.Smaller ones fit into the spaces be-tween larger ones; clay particles are inthe spaces between sand particles.There is much space (called porespace) between these particles. Whenthe soil is dry, this space is mostly air.When the soil is very wet, the porespace is filled with water.

MississippiHeadwaters

FIGURE 12. (Above) A stream's water-shed is all the area from which waterdrains into that stream.

..........

Coarse Sand --.ClaySilt

FIGURE 13. (Above) Here are therelative sizes of three kinds of soil par-ticles enlarged about 500 times.

Table 3. Sizes of soil particles.

Range indiameterof particles

Particle in millimeters

Approximate numberof particlesrequired to forma line 1 inch long

Gravel More than 2 12 or less

Sand 0.05 to 2 12 to 500

Silt 0.002 to 0.05 500 to 12,500

Clay Less than 0.002 More than 12,500 Less than 0.04

Rana: indiameter ifenlarged 500times (in inches)

More than 40

1 to 40

0.04 to 1

Table 4. Percent of sand, silt, and clay in threa Minnesota soils.Sand

Range indiameterof particlesin inches

More than 0.08

0.002 to 0.08

0.00008 to 0.002

Less than 0.00008

Silt Clay

Fargo silty clay (Red River Valley) 1.2 48.9 49.9

Zimmerman fine sand (Sherburne County) 93.7 3.0 3.1

Nicollet loam (Sibley County) 40.1 38.0 21.9

The various textures of soil have beenarranged in more than a dozen classes,

Range in percentTextural group Sand Clay

Fine

Moderately fine

Medium

Moderately coarse

Coarse

Organic

100% CLAY

40°10+

>

0

FIGURE 14. A soil's textural class is determined by that soil's respective per-centages of sand, silt, mid clay. To use this figure, follow the respective percentagelines for sand, silt, and clay to their appropriate intersections with the figure. Forexample, a soil with 35 percent clay, 30 percent silt, and 35 percent sand is classi-fied as clay loam.

13 14

but they may be combined into sixgroups:

Textural Class

More clay 4--- -+ More sandClay, silty clay, sandy clay

Clay loam, silty clay loam, sandy clay loam

Silt, silt loam, loam, very fine sandy loam

Fine sandy loam, sandy loam

Loamy sand, sand

Mostly decayed plant material

Large sandparticle

Edge of granule Edge/

of sandparticle

FIGURE 15. Soil has a mixture ofparticle sizes. This drawing illustratesloam soil enlarged 500 times.

Clay particles are thin, flat sheets.Innumerable clay particles can fit be-tween larger soil particles so that thespaces between larger particles arealmost completely filled. The re-maining pore spaces, although verynumerous, are very small.

Plasticity is a quality of soils con-taining much clay. Fine-textured soilshold considerable water, which acts asa lubricant between particles. Such soilis easily molded when it is wet. Someclay soils also shrink and swell con-siderably as moisture co_itent changes.Texture influences the amount andsize of air spaces (pores) between soilparticles. Pore space influences the:

speed with which water canmove into and through soil(percolation rate, permeability,infiltration rate, internaldrainage);

amount of water the soil canhold for plants (available water-holding capacity):

amount of air the soil can pro-vide for plant roots (a(1..ition):

bearing strength of the soil (solidsupport for heavy loads orweights).

Depd.Soil's der:ii above bedrock, a water

table, or porous sand and gravelgreatly influence.; the soil's suitabilityfor various uses. These effects are de-scribed under later headings: Soil airand water.. and Using the soil.

Organic matter contentSod's organic matter content is im-

portant for some land uses. Organicmatter is the dead remains of plantand animal life. The most obviouseffect of organic matter is soil color.The darker the soil, the more organicmatter it contains. Organic matter ac-cumulates in soil as a result of theamount and type of vegetationgrowing in this soil and the rate atwhich the material forms and decom-poses. Soils formed under prairievegetation are much darker than thosedeveloped under forests. This is be-cause a much greater proportion of theprairie grasses is below ground as rootsand, therefore, accumulates faster. We tsoils where poor aeration inhibits aero-bic decomposition will be much darkerthan very drouthy

Organic matter holds soil particlestogether in granules. This makes thesoil less erodible, improves soil aera-tion and porosity, and creates a moresuitable seedbed for gardens, lawns,and crops. Organic matter also im-proves soil's water and nutrient-holding capacity and the amount ofnitrogen available for plant growth.

StructureSructure is the natural arrange-

ment of individual particles in the soil.Very minute orga_lic and mineral par-ticles have a gluelike quality. Clay par-ticles stick together in clusters ("aggre-gates") of various sizes and shapes.The aggregates' resistance to breakingapart or disintegrating into single par-ticles in water is important. Decay-resistant organic matter increases theaggregates' stability. Surface soilshaving a granular (grainlike) structureare relatively easy to till and cultivatefor crops and gardens. Air and watermove more readily through granulatedsoils. Soils containing relatively largeamounts of organic matter and havingstable aggregation are more resistant toerosion than similar soils containinglittle organic matter. Cultivating suchsoils when they are wet or continuallypacking them with heavy foot andvehicle traffic destroys the aggregation

and reduces these soils' pore space.Plants may not grow as well on com-pacted soils, and excess soil waterdrains away more slowly.

Soil air and waterWaterholding capacity may be mea-

sured two ways: the amount of waterthat soil can hold before it is satu-rated; and the amount that soil canhave available for plant use. This sec-tion considers the water available forplant use. Available water is influencedprimarily by the soil's texture, organicmatter content, and depth. The greaterthe soil's clay content, the more waterit will hold. Part of tLe water con-tained in the soil is not available toplants; it is held too tightly by the soil,especially by the clay particles. Whenthe water content of a soil is reducedso that only unavailable water is left,the plants wilt. Therefore, the greaterthe clay content, the more unavailablewater the soil will hold. The deeperthe soil above bedrock, porous sandand gravel, or compacted layers im-penetrable by roots, the more waterthe total soil can hold for plants. Or-ganic matter in the soil influences theamount of available water in twoways: organic matter holds severaltimes its own weight of water; and itincreases granulation and porosity

FIGURE 16. Oak trees on soil with a low available-water capacity grow extremelyslowly. These trees may be 100 years old (SCS photo).

I4 15

which help hold water for plants.Medium-textured soils (loam, silt loam)hold the largest amounts of wateravailable to plants.

The amount of water available forplant use influences the species ofplants that will grow well in the soil.Soils with a low available-watercapacity are more likely to havenatural vegetation tolerant to drouth;prairie grasses are more tolerant thanmost trees. The quantity of plantgrowth is greatly affected, also; burroak trees on Zimmerman sand may be100 years old and only 20 feet tall.

Available-water capacity is usuallyexpressed as inches of water that a soil5 feet deep can hold. The texture ofsoil from its surface to a depth of 5feet may vary considerably. Hence,surface texture alone does not alwaysindicate the soil's capacity to holdwater for plants. Table 5 shows theaverage amounts of water that soil tex-tural groups can hold for plants.Available waterholding capacity forsoil to 5 feet deep may be expressed asfollows: good - more than 9 inches(22.9 cm.); fair 6 to 9 inches (15.2to 22.9 cm.), poor less than 6 inches(15.2 cm.).

Permeability describes the ease withwhich gases and liquids pass through asoil profile. The sizes and amount ofpore space (spaces between soil par-ticles) influence the speed at whichwater passes through the soil. Sandysoils have relatively large pores, andwater can move downward and side-ways within the soil rapidly as morewater is added. If there are no imper-vious layers in the soil and the water(able is not a factor, most of the waterfalling on a sandy soil will drainthrough rapidly. The greater the pro-portion of fine particles (clay) in thesoil, the smaller are the pores and theslower water will percolate or flowthrough them. Clay is almost im-permeable.

The internal drainage of a soil is itsnatural wetness. Internal drainage indi-cates the ease with which water and aircan move and the amount af air avail-able to plant loots. This soil qualityaffects many structural uses. Internaldrainage is a result of several other soilcharacteristics, most of which havebeen discussed. They are steepness;relative elevation; texture; structure;and the depth to impervii.us bedrock,compacted soil layers, water table, or

Table 5. Average amounts of water that soils can hold for plants.

Textural group

Fine (clays)Moderately fine (day loams)Medium (loams)Moderatcly coarse (sandy loams)Coarse (loamy sand, sand)Organic (peat)

Range in inches of waterper foot of soil (30.5 centimeters)

Inches Centimeters

1.1 to 2.01.7 to 2.62.0 to 2.91.3 to 2.20.2 to 1.44.2 to 8.4

2.7 to 5.24.3 to 6.75.2 to 7.33.4 to 5.50.6 to 4.3

10.7 to 21.4

Table 6. Permeability rate and class for several typical Minnesota soil types.

Soil type

Zimmerman loamy fine sand (SherburneEstherville sandy loam (Sherburne Co.)Barnes loam (Stevens Co.)Glencoe silty clay loam (Wright Co.)

Fulda silty clay (Swift Co.)

Rate of water infiltrationinches of water per hour

More than 20Co.) 6 - 20

2 - 60.6 - 20.2 - 0.6

0.06 - 0.2Less than 0.06

Permeabilityclass

Very rapidRapidModerately rapidModerateModerately slowSlowVery slow

Table 7. Relationship between soil (internal) drainage condition and soil color.

Soil (internal) drainage condition Description of subsoil color

Excessive Coarse texture, yellowish brown

Well-drained

Somewhat poor

Uniformly brown, dark brown, yellowishbrown, dark yellowish brown,or reddish brown throughout the subsoil

Mottled upper subsoil, lower subsoil greyor mottled

Poor or very poor Dull grey or olive color, some mottles maybe present

very porous sand and gavel. Internaldrainage affects aeration, availablewater, runoff, and soil color.

Aeration and soil color are dis-cussed in following sections. Table 7illustrates the influence of soildrainage on the color of subsoil. Thecolor of subsoil can indicate thequality of the soil's internal drainage.

Soil aeration is important forplants, whether the plants are lawns,gardens, or crops. Roots need air forrespiration; if insufficient air is

present, compounds develop that aretoxic to plants. Ferrous oxide, man-ganese oxide, and nitrites areexamples.

ColorSoil color is easily seen and indi-

cates some soil qualities. The darkness

15 16

of soil and tut depth of the dark colorreflect the amount of organic matterpresent. Surface soils under prairiegasses may have a dark color 12 to 14inches deep. Soils under forests willhave a very thin dark-colored surfacelayer. Soil's natural nitrogen content isclosely related to the organic mattercontent (and therefore color) of thesurface soil. The depth of the darkcolor in prairie soils ma: indicate theamount of erosion or deposition thathas occurred. As surface soil is washedaway, the remaining depth of surfacesoil becomes less. The eroded soil maybe deposited at the bottom of the hillwhere the slope is less steep. As a re-sult, the depth of the surface soil willbe increased there. Minnesota surfacesoils range from black to very lightbrownish grey.

Soil color. especially that of sub-soil. indicates the internal drainage orease with which water and air maymow through the sod. Internal drain-age was discussed in greater detail inpreceding paragraphs.

Sod contains iron. When the son: iscontinually wei-drained. there is

enough air (and consequently oxygen)in the sod to oxidize iron and give thesubsoil a yellowish to reddish browncolor similar to rusted metal. If thesubsoil is continua II). saturated withwater. there is little air in it. Then theiron is not oxidized. but reduced. Thesoil Lolor is then dull or bluish grey.Soils that are intermittently dry andwet are splotched with grey and red oryellow (mottled). The color of Nlinne-sota subsoils varies from reddishbrown to grey.

Surface runoff and erosionSurface runoff is the rainwater.

snow melt. or irrigation water that runsoff the surface of the sod. The steep-ness of th^ slope affects how muchwater can soak into (infiltrate) thesoil: the steeper the slope. the fasterthe water flows downhill. lessening itsavailable time to infiltrate the soil.Vegetative cover impedes the flowdownhill, giving the water more timeto infiltrate. Soil texture and structureaffect infiltration and percolation.also. The coarser the soil and thegreater the granulation. the larger thepores in the soil will be and the morerapid will be the percolation. If thesoil is not saturated when water isapplied, the depth of soil above im-permeable layers may also be a factor.It affects the amount of water that caninfiltrate before runoff begins.

Soil's erodibility (the ease withwhich soil is removed by wind orwater) is greatly influenced by the per-meability and the structural stabilityof the surface soil. Well-granulated sur-face soils resist the beating action ofrains that can break up the granulesinto individual particles and carrythem downhill. High levels of residualorganic matter promote stable,erosion-resistant aggregates (granules).The same factors that affect surfacerunoff affect erodibility. Doubling theslope increases erosion by 2 1/2 times.Doubling the velocity of the watertheoretically enables the water tomove particles 64 times larger. makingerosive power 4 times as great and in-

FIGURE 17. The left photo shows a forest soil. Its surface layer is dark-coloredand relatively thin. The right photo shows prairie soil. it has a much thicker dark-colored layer.

FIGURE 18. Lack of vegetative cover and a long slope encouraged this erosionduring a heavy rain. A grassed waterway would have helped prevent the gully.Some of the eroded soil remains at the bottom of the hill (SCS photo).

IMEMMill1111111111M161

16 g

creasing carrying power 32 times.These factors are unportant whereverland is used, in town or in the country.

Vegetative cover serves as anenergy-absorbing canopy. Raindropsstrike the grass or leaf litter and runmore slowly onto the soil than whenthese raindrops strike bare ground.

The degrees of erodability are:Slight: During average conditions

of weather and use, there islittle chance of excessiveerosion. Slopes are gentle;internal drainage is good.

Moderate: Medium or finer texturedsoils on slopes of 2 to 6percent and longer than300 feet could havemoderate erosion prob-lems. Shorter slopes maybe as much as 12 percentand still have moderateerodibility.

Severe: Slopes exceed 12 percentwith soils having amoderately coarse to finetexture.

Wind erosion is closely related tosoil moisture content, the amount ofvegetative cover on the soil, and theexpanse of land not protected fromthe wind. Large areas without vegeta-tive cover, such as the Red RiverValley in the spring, are subject toconsiderable wind erosion. Drouthysoils, such as the Zimmerman sands inSherburne County, are noted for theirsusceptibility to wind erosion. In-tensively cultivated peat soils developinto finely divided, light particles thatare easily moved by the wind.

Soil reaction acidity alkalinitySoil reaction is the soil's degree of

acidity or alkalinity. Reaction refers tothe relative amount of hydrogen andaluminum ions and other acid-formingelements compared to the amount ofhydroxyl ions and base-forming ele-ments such as calcium and magnesiumWhen the acid- and base-forming ...e-ments are balanced, the soil is neutral.Soil reaction results from soil-formingfactors: parent material and its con-tent of acid- and base-forming ele-ments: the climate as it affects leach-ing through the soil; the vegetation orcrops growing on the soil; and time.

Soil reaction is usually expressed in"pH." The pH scale is logarithmic (seeglossary for definition) from I to 14.A pli of 7 is neutral, neither acid noralkaline. A pH below 7 is acid; above 7

FIGURE 19. (Above) Unprotected dry, sandy soils are easily eroded by wind(SCS photo).

FIGURE 20. (Below) Field shelterbelts and striperosion (SCS photo).

afr-01^44.1,tra( if .."

Na+ +

Mg+2 n

Ca+2K+Soil particle

Al(OH)+2NH +4 Ca+2

KH

H+ Soil solution(Water, liquid)

Ca+2

H+

NH4+

H+

Na

Ca+2

Mg+2

OH. OH-

AI(OH)+2

OH H+1(OH)+2mg+2

Soil particle

Al(OH)2+ K+

xyL

H+

NO3

Ca+2

mg+2

Soil partic.e

Na+ NH4+

K+

H

a+NH4

OH.

FIGURE 21. Acid- and base-formingions are in the soil solution and areattached to soil particles.

17 18

*rapping help control wind

r:f 7'-`-

i. t.

041. Pii`frA

Sod reaction pH scale Common solutions

-o

I Hydroctdonc acid

LemonsVinegar

Tomatoes

5 Boric acid

Milk7 NEUTRAL

8 Sea waterElicaibonate of soda

10 Milk 01 magnesia

Ammonia

Lowest pit - -most mineral sods

Strongly sodModerately aced

Range found Slightly andin Minnesota Very slightly and

Very slightly alkalineSlightly alkalineModerately alkalineStrongly alkaline

Highest pH for--most mineral sods

2

3

4

6

9

12

13 Lye

14

FIGURE 22. This scale shows soilacidity terms used in Minnesota andthe pH values of some common solu-tions.

pH

Nitrogen

Calcium, Magnesium

Phosphorus

Potassium

Sulfur

FIGURE 23. The width of each bandshows the relative availability of someplant nutrients as they are influencedby soil reaction.

it is alkaline. For example:

Average native levels ofphosphorus available to plants:Area 1. LowArea 2 Low to mediumArea 3, MediumArea 4. Medium to highArea 5 High

dll

Amxy native levels ofpol.ssslufn available toplants

Alt, 1 LowArea 2 Low to mediumArea 3 MednumArea 4 Medium to highArea 5 MO

From Soil Test Summaries

-

Approximate area of highestprobable sulfur deficient sods

Relative native reactionof Minnesota soilsArea 1 Mostly acidArea 2 VariableArea 3 Alkaline

FIGURE 24. These maps show soil reaction and relative native levels of phosphorus,potassium, and sulphur available to plants in Minnesota.

a call of 7 represents 1 x 10- 7(1 0.000,000

)gram equivalents of hydrogen per liter.

-a pH of 6 represents I x 10- ( I

01.000,00) oram equivalents of hydrogen per liter.

a pH of 5 represents 1 x 10 5 (I 00,000) grain equivalents of hydrogen per 1:tcr.

A soil with a pll of 5 is 10 times moreacid than one with a pH of 6. Minne-sota soils vary from strongly acid (pHof 4.5) to moderately alkaline (pH of8.5). The eastern two-thirds of Minne-sota has mostly acid soils. The westernis primarily alkaline.

Correcting soil acidity for plantgrowth is discussed in the section en-titled Using the soil.

Soil fertilityPlants require 16 different ele-

ments. Carbon. hydrogen. and Oxygencome from air and water Plants obtainnitrogen, phosphorus. potassium, cal-cium, magnesium. and sulfur in rela-tively large amounts from the soil.they are called macronutrients. Iron.

manganese. boron. molybdenum,copper, zinc, and chlorine in soil arenecessary in relatively small amounts:they are referred to as micronutricnts.A fertile soil contains a sufficientsupply of all these elements in an avail-able form. Several factors affect thenutrient content of soil:

dark-colored soils developedunder prairie vegetation containmore natural nitrogen than soilsdeveloped under forests:

coarse-textured sods, such as

sands and sandy Wins, usuallycontain less nitrogen and potas-sium than finer-textured loamsand clays. The greater porosityof coarse-textured soils causes,

IS 19

the elements to be rapidlyleached into the subsoil beyondthe reach of most plant roots;

soil reaction influences the avail-ability of many nutrient ele-

ments

the acid soils of caster!! andnorthern Minnesota contain moremailable phosphorus than do the alka-line soils further west and south.

Micronutrient deficiencies occur toa limited extent in sonic Minnesotasoils. Plant nutrients are discussedfurther in a following section, Usingsod for agriculture.

TYPES OF SOILS IN MINNESOTA

Repeated glacial coverings of Min-nesota left a wide variety of parentmaterials from which the state's soilswere formed. There are differences inthe bedrock materials carried in andalso in topography, vegetation, andclimate. Numerous soil types havebeen identified in Minnesota. These

SOILS OF MINNESOTA

Locations of soil group combinations:

Area 1. Northwestern

Area 2. Northern

Area 3. Northeastern

:Wig Area 4. Western

1.11 Area 5. North Central

1111 Area 6. East Central

1f4

ElArea 7. South Central

Area 8. Southeasternand Southwestern

Area 9. Scattered primarilyalong major streams

FIGURE 25. This map shows the locations of 15 broad soil groups in Minnesota.

types have been classified into 57 dif-ferent associations according to relatedcharacteristics such as adjacent loca-tion, amount of slope, and parentmaterial. Tte associations have beencombined irto 15 broad soil groupsconsidering location in the state, tex-ture, and native vegetation. Severalgroups have been combined for thefollowing description. Table 8 summar-izes the distribution.

Northwestern areaThe soils in and along northwestern

Minnesota's Red River Valley com-prise about 12 percent of the state'sland area. Most of these soils wereformed on the level bottom andbeaches of glacial Lake Agassiz. Theparent material is calcareous (containsmuch calcium -arbonatc); the nativevegetation was prairie. The soil textureranges from loam to clay. Both soilsurface and internal drainage are dis-tinct problems in the heavier soils. Thesoils are usually alkaline, medium tolow in phosphorus, and high in potas-sium.

The Red River Valley is well-knownfor its farm products: small grains;sugar beets; and potatoes. Much of thearea is unsuitable for septic tanksewage disposal drainfields. Poor in-ternal drainage causes seepage prob-lems in basements and foundation

problems in building and road con-struction.

Northern areaSignificant portions of north

central Minnesota and Aitkin and St.Louis Counties were also covered byglacial lakes. These areas are generallylevel and include much peat. The tex-ture of the mineral soils varies fromsandy to clay. The area covers 13 per-cent of Minnesota's surface. The nativevegetation on the upland areas wasforest, and a light-colored soil devel-oped. Some soils are drouthy. Othersare poorly drained because of theirclay subsoils or a high water table. Allcontain lime (calcium carbonate) inthe parent material. The soils aremedium to low in phosphorus andmedium in potassium. The better 'areasproduce small grains, legumes,potatoes, and forest products.

Northeastern areaNortheastern Minnesota soils, com-

prising 9 percent of the state. vary intexture from coarse to fine..The landis rolling to hilly with many outcrop-pings of basic igneous rock. Much ofthe area is a sandy-stony glacial till.Soils along the Canadian border andLake Superior were formed from limyglacial lake clays. The vegetation wasforest. The primary uses are forestryand recreation; there is very littleagriculture.

19 My

FIGURE 26. (Above) Sunflowers area common crop on the level land innorthwestern Minnesota (SCS photo).

FIGURE 27. (Above) Large peat bogsare common in northern Minnesota(SCS photo).

FIGURE 28. (Above) NortheasternMinnesota is mostly forested and hasmany lakes.

FIGURE 29. (Below) Much of westernMinnesota is covered with gently roll-ing glacial till (SCS photo).

11110,.....

"-

sviv; a.rC t11.1.1

FIGURE 30. (Below) Light-coloredsoils developed under the forests ofnorth central and east central Minne-sota (SCS photo).

f.

FIGURE 31. (Below) Southern Minne-sota's dark-colored soils are excellentfor corn.

1

Western areaAn irregular band of fertile. mostly

prairie soils in western Minnesota ex-tends from Clearwater County in thenorth to Nobles County in the south.It includes I I percent of the state'ssurface. The slope of these soils variesfrom nearly level to rolling. The soilswere developed from limy glacial tilland are dark-colored. The texturevaries from loam to clay loam; internaldrainage ranges from good to poor.The soils are generally alkaline,medium to low in phosphorus, andmedium to high in potassium. Corn,soybeans, and small grains are the pre-dominant crops.

North central areaIn north central Minnesota, there is

a large area of light-colored loam tosandy loam soil that developed underforest vegetation. This area coversabout 9 percent of Minnesota's sur-face. The parent material is a limyglacial till, and the area has an undu-lating to hilly topography. Lakes andpoorly drained mineral and organicsoils occupy the depressions and levelareas. The soils are somewhat acid andmedium to high in available phos-phorus and potassium. The usual farmcrops are legumes and small grains.Forestry and recreational enterprisesare also common.

East central areaEast central Minnesota has a wide

variety of t. Is developed under forestvegetation. The parent material of thisarea, about 10 percent of the state,contains mostly limy grey and redglacial till and nonlimy red till withsmall lakelaid deposits and some out-wash gravels. The topography rangesfrom level to rolling. Most of the soilsare light-colored foams and sandyfoams. There are some areas of siltloam, clay loam, and peat. Drainagevaries from excessive to poor; how-ever, most of the land is well-drained.The soils are usually acid, high in avail-able phosphorus, and medium to lowin available potassium. Dairying is themost common agricultural pursuit.Second growth timber, such as aspen,covers much of the area.

South central areaSouth central Minnesota has a large

area of very productive agriculturalsoils. This area comprises 16 percentof Minnesota's surface. The topog-raphy is mostly level to gently rolling.

20 21

Dark-colored soils have formed underprairie vegetation, and moderatelydark ones were formed in the forest-prairie borders. Most of the soils arewell-drained loams formed from limyglacial till. Depressional areas are clayloarns haviiig poor drainage. The top-soils are somewhat acid. The prairiesoils are usually medium to low inavailable phosphorus; the prairieborder soils are usually high. Most ofthe area contains medium amounts ofavailable potassium.

Agriculture consists of cash graincrops, dairy, beef, and hog farming.(Cash grain crops are those sold ratherthan being fed to livestock on the farmwhere the grain was raised.)

Southeastern and southwestern areasSoils formed from windblown

parent material blanket parts of fourcounties in extreme southwestern Min-nesota and parts of 13 counties in thesoutheastern part. The variety ofcharacteristics requires three groups tobe considered separately.

15artions of the four southwesterncounties are blanketed by dark soilsdeveloped from a windblown limysilty material under prairie vegetation.The land is sloping and has good sur-face and internal drainage. The soil isslightly acid, medium to low in avail-able phosphorus, and high in availablepotassium. Cash grain crops and live-stock feeding predominate. The areacomprises 1.5 percent of Minnesota'ssurface.

The southeastern counties havingwindblown soils may be divided intotwo groups. Eight counties on the easthave silt ' )am soils that may be deepor shallow to bedrock. Slopes varyfrom gentle to steep. The light-coloredsoils were formed under forest vegeta-tion; dark ones were formed underprairie. These soils are well-drained.Ten of the 13 southeastern countiesalso have shallow, windblown, siltysoils over a medium-textured glacialtill. The slopes are mostly gentle.Dark-colored soils formed underprairie vegetation; moderately darkones formed in the forest-prairie bor-der. Internal drainage varies from goodto poor. These soils are usually acid,high in available phosphorus, andmedium in available potassium. Cast,grain, dairy, and livestock farming areimportant on all but the steep land.These soils make up 6.5 percent ofMinnesota's area.

Scattered primarily along majorstreams

The melting continental glaciers leftmany areas of glacial outwash through-out Minnesota. When the edge of aglacier remained stationary for con-siderable time, large quantities of waterfrom melting ice deposited well-sortedlayers of sand and gravel. These out-wash areas cover about 12 percent ofMinnesota and are scattered through-out much of the state, especially alongthe major rivers. Prairie vegetationdominated the southern and westerndeposits. Forests grew on the north-eastern and eastern ones. Topographyvaries from nearly level to rolling.Color may be dark or light, dependingon naive vegetation. Most of the sur-face soils are sandy; in many places,they are shallow over gravel. Thesesoils are mostly drouthy, acid, high inavailable phosphorus, and medium tolow in available potassium. These soils,unless irrigated, are usually unproduc-tive for farming.

.rh 11, 2111.0,..

,f-44' ,=zeiesterfr149,-.-

FIGURE 32. When irrigated, some sandy outwash plains in Minnesota produceexcellent crops (SCS photo).

Table 8. Distribution of soil groups in Minnesota.

Area of Minnesota Percent of state

Northwestern (Red River Valley) 11.6Coarse to fine-textured prairie and organic soils of the glacial lake plains

Northern 13.0Coarse to fine-textured forest and organic soils of glacial lake plains

Northeastern 91Coarse to finetextured forest soils and rock outcrops

Western 11.3Medium to fine-textured prairie and prairie border soils

North central 85Medium-textured forest soils

East central 10.4Coarse to fine-textured forest soils 1 8%Coarse to medium-textured forest soils 6 5%Finetextured forest soils 2 1%

South central 15.6Medium to fine-textured prairie border soils 5 2%Medium to fine-textured prairie soils 10.4%

Southeastern and southwestern 8Windblown, silty forest and prairie soils (S.E ) . 4.1%Windblown, medium-textured prairie and prairie border soils (S.E.) 2 5%Windblown, silty prairie soils (S.W.) 1 5%

Scattered, primarily along major streams 12.4Glacial outwash, coarse to mediumtexvired prairie soils 5 4%Glacial outwash, coarse to mediumtextured forest soils 7 0%

100.0

Peat organic soilsFifteen percent of Minnesota's

80,000 square miles of land is peat (or-ganic soil). Peat am..., are scatteredthroughout Minnesota, but the largestdeposits occur in the northern part ofthe state. Some characteristics of peat

are much different from those ofmineral soils. Organic soils containmore than 20-30 percent organicmatter that formed during the pastfew thousand years. They formedfrom accumulat;ons of aquatic vegeta-tion in water. The water acted as a

&

FIGURE 33. (Above) When drained, some peat soils are excellent for manyvegetable crops (SCS photo).

FIGURE 34. (Below) Many peat soils produce excellent sod for new lawns (SCSphoto).

;-- .

23

preservative, restricting oxidation ofthe dead material. Thus, peat accumu-lates in marshes. bogs, and swamps asthe partially decomposed remains ofpondweed, cattails, sedges, reeds,grasses, mosses, shrubs, and trees. Thethickness of the deposits ranges from atoot or so to as much as 80 feet ormore.

To quite an extent, the originalplants from which peats are formeddetermine the characteristics of thesesoils. Often, such plants as sedges,mosses, grasses, and cattails form veryraw fibrous peat soils. Trees and brushbecome woody peats. Raw peat isusually tan, brown, or reddish brown.Decomposition of bog plant remainsaccelerates when the soil is drained ortilled, and continuing tillage reducesparticle size. Particles in the upperlayers turn darker with time, eventu-ally becoming black. Peat soil is rela-tively light in weight. A cubic foot ofpeat soil contains from 4 to 30 poundsof dry matter; mineral soils averageabout 84 pounds of dry matter percubic foot. An average peat soil canhold 6 to 10 times its dry weight inwater; mineral soils have a water-holding capacity only one-fifth to two-fifths their dry weight. Thus, peat soilmay hold about twice as much avail-able water as the same volume ofmineral soil. Most peat soils that havebeen drained are porous and easy tocultivate. When tilled, peat soilsreadily dry out and may drift in thewind. Dry peat burns readily, and peatfires are difficult to extinguish.

Peat soils vary widely in their soilreaction (acidity). Reaction dependson the vegetation, topograrhy, andchemistry of mineral soils surroundinga bog. Peat in a depression may bealkaline or calcareous because thedrainage waters flowing into the bogcontain calcium from the surroundingland. Peat at bog surfaces on relativelylevel land may be acid because ofmuch leaching. Peat soils, because oftheir high organic matter content, con-tain considerable nitrogen. They havelow amounts of phosphorus and potas-sium available for plant use.

Peat soils that can be drained ade-quately are excellent for vegetablesand for sod and grass seed production.Shallow peat over clay soil is well-suited for wild rice paddies.

Peat is a very unstable foundationfor buildings and roads.

FIGURE 35. (Above) The long slopes of this Class II land havebeen terraced to control erosion (SCS photo). FIGURE 36.(Top right) Tile lines have been placed underground in thisClass II land to improve drainage for crops (SCS photo).FIGURE 37. (Right) Strip cropping is used on this irregularClass iii land to control erosion (SCS photo).

USING THE SOIL

Using soil for agriculture capabilitiesand management

Farming is by fal the most impor-tant use of Minnesota soil. About 28million of Minnesota's 51.2 millionacres of Laid are farmland Crops areharvested from about 17.5 millionacres. About 20 million acres of Min-nesota's land are covered by forests.About 4.8 million acres of this forestland are on farms.

The Soil Conservation Service ofthe U.S. Department of Agricultureclassifies agricultural land throughoutthe United States into capabilityclasses. Classification is based on de-tailed soil survey s. individual soil map-ping units are identified according tosoil type and landscape The eightcapability classes show. in a generalway, the soils and landscapes mostsuitable for aviculture. These classesare based on limitations and haiards ofusing eah soil and the risk of land midcrop damage when the Lind is not usedwithin its Lapability and heated forproper erosion and soil moisturecont rota

Pte,

About 4 percent (1.8 million acres)of Minnesota is Cava I. Most of this isin the southern and southwestern partsof the state and is used as cropland.Class I lands have few limitations re-striding their use for i_ultivated crops.pasture, woodland, and wildlife. Theyare deep. moderately well- to well-drained. and are easily tilled. Theyhave good available -water capacity forplants and are either quite fertile orcan be readily made productive. Theyare not subject to damaging overflowsor flooding and have a favorablegrowing season for common fieldcrops. Good management fin intensivecropping may include fertil-izing. maintaining a high level of activeorganic nutter. and rotating adaptedcrops,

About 35 peftent of .Minnesota(17.7 million acres) is Clam // land.nu, Lind has .1 few limitations for cul-tivated clops. pasture. woodland. orwildlife. About two-thirds of this Lindis cropland. nearly 3 million dues ofthe Class II land is forested. Limiting

23 21

features may include. gentle slopes.sonic susceptibility to erosion; some-what shallow soil. less th,ut moderateper meability occasional damagingoverflow or flooding; poor internaldrainage, and a shorter growing season.

Good management of Class 11 landfor continued high production anderosion control may require: croprota t ions. including close-growingcrops and/or legumes: tillage practicessuch as contour strips. strip cropping,contour tillage. and terraces: grassedwaterways: and artificial drainage.

About 19 percent (9.9 millionacres) of Minnesota's land is Class ///.More than half of that (5.(a millionacres) is Cropland. 2.7 million acres isforested. Class III land. although simi-lar to Class II. has moie severe cloplimitations. 1 hese limitations may be.moderately steep slopes, great sus-ceptibility to erosion. continued nu-perfeLt inteinal drainage. even aftertiling or ditLlung, or shallow soil overrock, sand, or gravel, or impervious soillayers that restrict root gsowth and the

Ail

FIGURE 38. (Above) This steeper-sloping Class IV land is used for pasture ratherthan for crops (SCS photo).

FIGURE 39. (Below) This steeply sloping Class VI land may be used for pasturebut it should not be overgrazed (SCS photo).

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FIGURE 40. (Above) Rough Class VII land is suitable for wildlife (SCS photo).

FIGURE 41. (Below) This Class VIII land has several rock outcrops. Such land mayhave aesthetic value (SCS photo).

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soil's waterholding capacity for plants.Management practices needed for ClassIll land are similar to those for Class IIland: however, they must be usedmore intensively.

About 16 percent (8 minion acres)of Minnesota land is Class IV land.This land has very limited suitabilityfor cultivated crops, such as corn andsoybeans, because of these character-istics: steep slopes; severe suscepti-bility to erosion; severe effects of pasterosion; shallow soil; low waterholdingcapacity for plants; and excessive wet-ness. Soil conserving tillage practiceson this land are difficult to apply andmaintain.

Class V land has little or no erosionhazard, but has other limitationsseverely restricting its use for culti-vated crops. These limitations may befrequent overflow, stones, and pondedareas. Correction of these hazards isimpractical, but such land is suitablefor pasture, woodland, and wildlife.Four percent (2.2 million acres) ofMinnesota's land is in this category.

Slightly less than 4 percent (1.8million acres) of Minnesota land is

considered Class VI. This land isgenerally unsuited for cultivation, butit is suitable for pasttire or range,woodland, or wildlife food and cover.Limiting characteristics may be steepslopes, severe erosion hazard, effectsof past erosion, stoniness, shallow soil,wetness or flooding, or drouthiness.Vegetative growth may be improvedby seeding, liming, fertilizing, or watermanagement.

Class VII land includes 7 percent(3.7 million acres) of Minnesota's landarea. The limiting characteristics aresimilar to those for Class VI but aremore severe. It is impractical to usevegetative improvement practices. Ifthis land is carefully managed, it canbe used for grazing, woodland, or wild-life.

About 1 percent (700.000 acres) ofMinnesota land is Class VIII. This landis not suitable for commercial plantproduction because of its erosionhazard, wetness, stoniness, or drouthi-ness. Rock outcrops. sandy beaches,marshes, river wash. mine tailings. andother nearly barren lands arc includedin Class VIII. The land may have wild-life and aesthetic values.

The amounts of Minnesota laud inthe eight capability classes are summarized in table 9.

25 24

Table 9. Capability of Minnesota land for agriculture.

ClassMinnesota Land

Millions of acres Percent of state

I 1.8 4II 17.7 35Ill 9.9 19IV 8.0 16V 2.2 4

VI 1.8 4VII 3.7 7

VIII 0.7 1

Not classified 5.4 10

51.2 100

'consists of small water areas less than 40 acres in size, urban and built-up land,and federally owned, noncrop land.

The effect of changing soil charac-teristics on capability class is illus-trated in the following table.

Soil well-suited for cultivated cropsis nearly level to gently sloping and hasmedium to moderately coarse surfacetexture, a depth of at least 3 feet forroot growth, no flooding, and good tomoderately good internal drainage.Soil well-suited for permanent grasspasture would be nearly level tomoderately steep or hilly and havemedium to moderately fine surfacetexture, a depth of at least 3 feet, atleast moderately good drainage, andflooding not more than four timesannually for short periods.

There are numerous practices thatcan be used to overcome undesirablesoil features.

Level or low land having poor sur-face drainage and subject to floodingmay be ditched, reshaped (formed), orprovided with surface inlets extendingto tile lines to hasten the removal ofexcess surface water.

Sloping land with erosion hazardsmay be terraced to shorten the effec-tive length of slope and to lead surfacerunoff to grassed waterways or tilelines. Contour tillage helps controlerosion on even or regular slopes.Some slopes are too irregular for con-

Table 10. Changing soil characteristics as they influence land capi.rility class.

Characteristic

Slope

Degree ofpast erosion

Class I

nearly level (0-2%)

Class VIII

increasing steepness

some accumulation to1/3 of original soil increasing pastremaining erosion

Erosion hazard slight increasing hazard

Depth of soil more than 6 feet decreasing depth

Available waterholding i good to very goodcapacity l (9 inches or more)

decreasingcapacity

Internal drainage well to moderatelywell-drained poorer drainage

Permeability moderate to moderatelyrapid (0.6 to 6.0 inches --.- slower permeabilityper hour)

Flooding oroverflow none increasing frequency

or duration

Climate satisfactory snorter season, lowertemperatures

25 26

tour farming with modern equipment.Staying on the contour would requireturns too sharp to make with today'smachinery. In such cases, alternatingstrips of close-sown and row crops arefarmed across the general slope. Thesame practice helps control-wind ero-sion. On steeper irregular slopes, smallgrains and hay are grown almost con-tinuously to control erosion.

Soil texture influences availablewater capacity and soil aeration, there-by affecting plants, seedbed prepara-tion, erodibility, irrigation, and otherfactors. On a large scale, changing soiltexture is even more impractical thanchanging the slope. 'Farmers shouldchoose crops and practices to fit thetexture.

The depth of soil favorable to rootgrowth and its influences in agricultuiehave been discussed previously. Cropsdo vary considerably in their rootdepth. Although most roots are in theupper 1 foot of soil, field corn rootscommonly grow to 5 feet deep; alfalfaroots under arid conditions may godown 20 feet.

The value of organic matter in agri-culture has been recognized for cen-turies. Farmers maintain organic mat-ter levels in soil by using soil-conserving tillage practices, spreadingmanure, and incorporating cropresidues.

Many soils are too wet for goodcrop growth. Where it is practical,farmers use underground tile lines oropen ditches to remove excess water.

Soil reaction (acidity and alka-linity) is a major factor in plantgrowth. Some plants, like alfalfa, can-not tolerate acid soils; others, such asblueberries, thrive on acid soil. Mostplant species prefer a soil that hasnearly neutral reaction. Soil reactioninfluences:

adapted crops and their produc-tivity;amount of lime needed on acidsoil to grow other crops produc-tively;

efficiency of nutrients applied asfertilizer;amount of "mineral" nutrients(nitrogen, phosphorus, potas-sium, micronutrients) availablefor plant use.

Maintaining a near neutral pH is im-portant on Minnesota's acid-pronesoils. Farmers have their soil testedand may apply as much as 6 tons of

Soil pH4 5 5 5.5 6 6 5

Bluefloweredhydrangea

Azalea

White potatoes

Blueberr: .,

Strawberries

Cucumbers

Tomatoes

Snap beans

Corn

Many grasses

Oats

Soybeans

Asparagus

Lettuce

Peas

Red clover

Spinach

Alfalfa

7 75

--1111111111---

(Adapted from SOIL, 1957 Yearbookof Agriculture, U.S.D.A.)

FIGURE 42. Plant species have varyingtolerances to soil acidity.

ground limestone per acre to correctacidity and raise the pH from 5.7 to6.5. Alkalinity is not a major problemin Minnesota soils, although in somewestern Minnesota locations, free limein the root zone inhibits the uptake ofiron by soybeans and causes plants toturn yellow.

Farmers can meet most plantnutrient needs by applying commercialfertilizers and/or manure. The primaryelements added are nitrogen, phos-phorus, and potassium. The amountsneeded depend on the level of avail-able nutrients in the soil, the produc-tive capacity of the soil, the crop to bt,grown, the yield level desired, andsimilar factors. For example, a south-ern Minnesota farmer wants to growcorn for the second consecutive yearon soil testing low in phosphorus andmedium in potash. He would apply120 pounds of nitrogen, 50 pounds ofavailable phosphate, and 25 pounds ofpotash per acre of land. A farmer innorthwestern Minnesota wishing togrow wheat in a soil medium in phos-

phorus and high in potassium wouldapply 60 pounds of nitrogen and 30pounds of phosphate per acre and nopotash.

The major elements in plants arecarbon, hydrogen, and oxygen. Plantsobtain these elements from water andcarbon dioxide. Nitrogen is a constit-uent of every living cell; it is a part ofall proteins, chlorophyl molecules, andsome enzymes. Phosphorus is also apart of every cell. It is important inplants' energy transformation fromstarch to sugar. Potassium is essentialin cell metabolism; it has specific rolesin plant functions such as respirationand transpiration but is not a part ofplant compounds. Calcium is a part ofcell walls. Sulfur is a part of someamino acids. Several of the micronu-trients magnesium, iron, manganese,copper, and zinc are important inplant enzyme systems. Enzymes facili-tate or prunote complex chemicalreactions in plants but do not becomea part of the resulting compounds.

Micronutrient (nutrient elementsrequired by plants in relatively smallamounts) deficiencies for agriculturalcrops occur to a limited extent insome Minnesota soils. On some sandysoils low in organic matter, a borondeficiency limits the growth of somecrops such as alfalfa and sugar beets.Zinc deficiencies have occurred in cornand other crops on poorly drainedsoils high in lime. Additions of mag-nesium and molybdenum have beenbeneficial on some acid soils. Addi-tional iron has improved crops onsome alkaline soils.

Many plant species show specificvisual symptoms when certain nu-trients are deficient in the soil and,therefore, in the plant. For example,the bottom leaves of corn deficient innitrogen will be yellowish down themiddle of the ieaf. A potassium defi-ciency produces yellow edges on cornleaves. Phosphorus deficiency causespurplish leaves. A deficiency of anynutrient limits the growth of plants.

Farmers may determine fertilizerneeds by having their soil tested by areliable testing laboratory. Such alaboratory will also make recommen-dations for the specific crop a farmerwishes to grow.

Suitability and use of soil for otherpurposes

When people build a community,they change the land. Buildings, side-

26 27

walks, streets, and parking lots coveras much as half of the land in a com-munity. Most precipitation falling onthose areas is diverted by gutters andsewers into streams and lakes. Duringbuilding construction, heavy equip-ment removes absorbent topsoil andcompacts the remaining surface, thusreducing the ability of future lawns toabsorb rainwater. Wise communityplanners and developers carefully con-sider these effects as they plan andbuild a community.

In general, soil that is ideal for com-mon agricultural crops is ideal forhome lawns, gardens, shrubs, andtrees. The slope will be nearly level togently sloping (0 to 6 percent). Thelawn will have a slope of at least Ipercent away from the house so waterwill not seep into the basement.Gentle slopes are less subject to ero-sion. There is more time for water tosoak into the ground for plant use,resulting in less surface runoff. Lawnsare more difficult to seed on steepslopes; to resist erosion, new turf mayneed to be staked or otherwiseanchored until the roots develop morefully.

The texture of ideal soil will be be-tween a clay loam and a sandy loam.Such soils can hold considerable mois-ture for plant use. They are permeableso surface runoff is not excessive andso aeration is adequate for plant roots.Finer soils have poor aeration; coarsersoils are drouthy and need to bewatered more often. A good soil sur-face or seedbed is important for a lawnor garden. Sandy soils seldom crust onthe surface, but they dry out rapidly.Clay soils remain moist longer, butthey easily form a surface crust thathinders the emergence of tender youngplants. This is especially true if thesoil's organic matter content is low.

For the most favorable root condi-tions, soil depth should be 4 to 6 feetabove compacted soil layers, rock, thewater table, or porous gravel and sand.Such a depth provides plants with suf-ficient air, water, and nutrients.

Dark-colored topsoil 10 to 12inches deep indicates a high organiciatter content. Organic matter helpsthe soil maintain a crumblike structurethat resists erosion, enhances waterinfiltration, and promotes aeration.Dark-colored soils also have morenitrogen available for plants. Some-

what red or yellow subsoil indicatesbetter internal drainage and aerationthan occurs where subsoil is grey.

Lawn grasses tolerate muleratelyacid conditions down to a pH of 5.5.If lawns are more acid than this, theywill benefit from an application offinely ground agricultural limestone.Lime may be spread at the rate of 75pounds of finely ground limestone per1,000 square feet of lawn. Most gardencrops are more productive on soils thatare neither very acid nor very alkaline.Soil having a pH lower than 6.0 can beimproved by spreading limestone at arate of about 200 pounds per 1,000square feet of garden.

Home lawns and gardens may bene-fit from applications of commercialfertilizer just as agricultural crops do.Soil beneath a lawn or garden mayvary considerably in texture and otherfeatures because of excavation andfilling during house construction.Reliable soil tests help determineneeded plant nutrients.

University of Minnesota publica-tions contain detailed recommenda-tions for improving soil reaction, fer-tility, organic matter, and other lawnand garden soil characteristics.

Soils well-suited for homes,gardens, and cultivated crops are alsowell-suited for forest trees. However,plant nutrient and water requirementsare not as great for trees as for culti-vated crops. Soil for deciduous treesshould be nearly level to moderatelysteep or hilly, have a medium tomoderately fine texture, be at leastmoderately well-drained and have arooting depth of at least 20 inches.Conifers grow better on somewhatcoarser-textured soils, need betterdrainage, and require less moisturethan do deciduous trees.

The steepness of slope is importantfor timber production. Steepness anddirection of slope (aspect) affect thesoil temperature which, in turn, in-fluences the kinds of trees present andtheir growth rates. Slope also affectsthe ease of harvesting. Logging trailsand bare cutpver areas on the steeperslopes readily erode until they areagain protected by vegetative cover.

Soil texture influences forest treespecies and their rate of growth or pro-ductivity in much the same way as soiltexture affects lawns, gardens, and

41

FIGURE 43. (Above) Forest trees tolerate a fairly wide range of soil conditions(SCS photo).

FIGURE 44. (Below) Because they grow slower and, therefore, fuller, pines grownon sandy soils make better Christmas trees than do pines grown on finer-texturedsoils (SCS photo).

270,8

agricultural crops. Maple and bass-wood do not grow well on sandy soils;red pines grow poorly, if at all, onwaterlogged soils. Pines grow sloweron sandy soils than on loam soils."those grown on sandy soils are thenbetter sv'ted for Christmas trees be-cause their sets of branches are closertogether on the trunk.

Tree growth reflects soil fertility.Fertilizer applications have not pro-duced economic gains on Minnesotaforest land, however.

Soil well-suited for homes, gardens,crops, and forest trees is also well-suited for upland wildlife. If theirother needs are also met, wildlifepopulations will be in direct propor-tion to the production of their foodson the land. Soil characteristics con-sidered good for upland wildlifehabitat are: slopes ranging from nearlylevel to steep; moderately coarse tomoderately fine texture; infiequentflooding; at least moderately gooddrainage; at least 20 inches of rootingdepth; and a fair amount of wateravailable for plant growth (9 inchesavailable water capacity). Wetlandwildlife use poorly drained land whichhas at least 3 feet of water con-tinuously and open water (free fromemergent vegetation) all summer.

Homeowners want to avoid waterin their basements, cracked founda-tions, uneven floors, sticking doors,and similar problems. Better hornesitesare on nearly level to gently slopingland having medium- to coarse-textured subsoil 5 fee: or more abovebedrock or the water tabie. Homesitesshould be in locations that will notflood. Basements built on fine-tex-tured soils may have frequent seepageproblems. It is easier for the water toseep through the wall than to move inother directions through the soil. Tiledrains may be laid along the outside ofthe house foundation's footings, andcoarse aggregate may be put along theoutside of the basement walls to inter-cept this drainage. There must be asuitable outlet or a sump pump, how-ever.

Some clay soils swell considerablywhen they are wet and shrink whenthey are dry. Buildings on these soilsfrequently develop cracked walls andfoundations and uneven floors, doorsills, and windows. Stronger founda-tions and footings can partially alle-viate this problem.

A soil well-suited for a homesewage disposal drain or filter field(also called soil absorption system)will have less than 10 percent slope,have medium to moderately coarsetexture, be well-drained both on thesurface and internally, be 6 feet ormore in depth to bedrock or water,and have no flood hazard. Design ismore complex and installation costsare greater on slopes exceeding I0 per-cent. Where the land slopes more than18 percent, the sewage may actuallyseep to the surface of the ground andflow downhill.

The subsoil percolation rate is themost critical factor for sewage d -posal. The soil must absorb at least I

inch of water per hour. Percolationrates for drainfields are usually ex-pressed as minutes per inch. The maxi-mum time is 60 minutes per inch ofwater. A sand or gravel soil may have apercolation rate of less than 10minutes per inch of water. A silty clayloam subsoil underlain by loam ma-terial may require 1 hour to absorb Iinch of water.

Slope and percolation are not theonly considerations. Rapid percolationmay cause pollution of undergroundor nearby surface water. At least 4 feetof earth must be between the bottomof the drainfield trench and the watertable or impenetrable layers such asrock.

Highway and street planners whodesign heavily traveled roads mustunderstand the engineering propertiesof soils. Streets are most easily builtand maintained where slopes are lessthan 6 percent and do not flood.Moderately coarse to coarse soil 5 feetabove bedrock and the water table willprovide good internal drainage and befree of shrink-swell problems. Onsteeper slopes, roads must be cutthrough hills, and lOw areas must befilled to reduce the slope. Clay soils,with their high waterholding capacityand low permeability, are not de-sirable. Road contractors may exca-vate the roadway and haul in coarserfill from which excess water can drain.Otherwise, the roadway may becomeuneven, frost boils may develop duringthe spring, and the road surface maycollapse under heavy traffic.

Peat soils, because of their poorengineering qualities, are a problem toMinnesota road builders. They may

28 29

FIGURE 45. (Opposite page, left) Thesehomes are on the floodplain of the Minne-sota River. FIGURE 46. (Middle) Drain tileis being laid along the outside of the housefoundation to intercept possible basementwall seepage (SCS photo). FIGURE 47.(Right) This house was built on soil notsuitable for buildings (SCS photo).

FIGURE 48. (Opposite page, left) A drain-field is being installed here to distributehousehold sewage liquids throughout a largearea of the soil. FIGURE 49. (Middle) Thedrainfield pipe has small holes in it. The rocksurrounding the pipe exposes more soil sur-face area to the effluent. FIGURE 50. (Right)Frost boils may develop in roads built onpoorly drained soils (SCS photo).

FIGURE 51. (Opposite pap, left) The peatbeing removed for the new roadbed will bereplaced with firm soil material (Minn. Hwy.Dept. photo). FIGURE 52. (Middle) Con-trolling erosion on new road slopes andditches is difficult. FIGURE 53. (Right)Until grass is established, a straw mulch isused to temporarily control erosion alongnew roads.

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FIGURE 54. (Immediate right) Over-used bike trails can uecome deep gullies,disfiguring the landscape (SCS photo).

FIGURE 55. (Opposite page) Excessiveuse damages c:mpsites. Vegetation is

difficult to reestablish.

plan routes around bogs. of they mayexcavate the peat and replace it withfirm soil material.

During road construction, precau-tions must be taken to control erosionalong the right-of-way. Otherwise,heavy rains may damage the roadwhile it is being built. Road ditchesand slopes must be designed to preventerosion. Frequently, structures such asdrop spillways and terraces are used tocontrol erosion. Vegetation is the besterosion control on roadside slopes.Where soils ate suitable, road buildersmay lay sod or plant grass. They mayuse huge blowers to spread a strawmulch for temporary protection untilnew grass grows. A wet mixture ofwood fibers, fertilizer, and grass seed isblown onto hillsides that are too steepfor planting machinery.

Utility contractors such as water,sewer, and other pipeline installersface some of the problems road build-ers do. Pumping stations are necessaryto move liquids over hills. Operatingthe construction and maintenanceequipment and moving the construc-tion supplies over steep slopes is verycostly. Controlling erosion du- lig andfollowing construction can be a seriousproblem. Ana-textured sods increasethe cost of construction, especiallyduring wet weather. Very sandy andgravelly soils do have one undesirable

construction feature. The sides of deepexcavations must have relatively flatslopes or be supported by retainingwalls to avoid caving or slides.

Minnesota land offers many oppor-tunities for a wide variety of recrea-tional activities in addition to huntingand observing wildlife. More than one-third of the land area is not suited foragricultural crops. Most of this area isforested, and much of it is interspersedwith many lakes. Suitable sites forlakeside cottages, resorts, camp-grounds, trails, and the like areabundant. However, intensive use ofthese areas must be limited to preventdegradation of the land. Recreationalareas are usually located on steepslopes and/or sandy soils not well-suited for cultivated crops. Hence,they do not produce luxuriant growthsof natural vegetation either. Whencampgrounds, primitive campsites, andtrails are overused, the resulting tramp-ling or packing from too many feetand wheels destroy the protectingvegetative cover. Less water soaks in,and more runs off, carrying soil withit. Reestablishing a good grass cover onpoorly suited sites or under trees isvery difficult.

Septic tank drainfield requirementsfor a lake cottage are similar to thosefor any other home. Home sewage fre-quently finds its way into the lake as it

30 31

flows over fine-textured soils or per-colates too rapidly through coarse-textured subsoil.

Minnesota soil varies greatly fromplace to place. There are many combi-nations of soil characteristics. Somecombinations are good for homesites,lawns, gardens, agricultural rrops, orforests. Others are good for ducks andother waterfowl. Community-mindedcitizens and community plannersshould understand the soil. Floodplains and filled-in swamps are poorlocations for homes; there is lessdamage if they are used as parks. Wide-spread removal of protective cover onsoil being developed for housing, com-merce, or industry may result in watererosion and downhill or downstreamsedimentation and wind erosion.Putting sewer and water lines on hillyland or in bedrock can be costly to thetaxpayer. We all use the soil in someway, whether watering the lawn orbuilding a freeway.

There is a wealth of informationabout Minnesota soils. The tools areavailable for Minnesota citizens toknow how to match our needed landuses with the types of soil we have. Wecan use our land properly and avoiddegrading our environment and re-sources if we learn the basics aboutsoils and use them accordingly.

REFERENCES

I. CHARACTERISTICS OF SELEC-TED HORIZONS FROM 16 SOILSERIES IN MINNESOTA, Tech-nical Bulletin 272, 1970. DJ.Pluth, R.S. Adams, Jr., R.H. Rust,and J.R. Peterson. University ofMinnesota Agricultural Experi-ment Station.

1 FERTILITY STATUS OF MIN-NESOTA SOILS AS SHOWN BYSOILS TESTS, Miscellaneous Re-port 56, 1964. John Grava. Uni-versity of Minnesota AgriculturalExperiment Station.

3. FERTILIZING THE HOMELAWN AND LANDSCAPE MA-TERIALS, Soils Fact Sheet No. 7.L.D. Hanson and C.G. Hard. Uni-versity of Minnesota AgriculturalExtension Service.

4. GUIDE FOR INTERPRETINGENGINEERING USES OFSOILS. USDA Soil ConservationService. U.S. Gov't. PrintingOffice, Washington, D.C.

5. GUIDE TO COMPUTER PRO-GRAMMED SOIL TEST RECOM-MENDATIONS IN MINNESOTA,1974. Special Report I. January1974. William E. Fenster, CurtisJ. Overdahl, Charles A. Simkins,Bob McCaslin, and John Grava.University of Minnesota Agricul-tural Extension Service.

6. GUIDE TO USE OF SINGLESHEET SOIL SURVEY INTER-PRETATIONS. MN-SOILS-2.USDA Soil Conservation Service.

7. LAND CAPABILITY CLASSIFI-CATION, Agric. Handbook No.210. 1961. U.S. Dept. of Agricul-ture, Soil Conservation Service.U.S. Gov't. Printing Office,Washington, D.C.

8. LIME NEEDS IN MINNESOTA,Soils Fact Sheet No. 10, 1968.W.E. Fenster, C.J. Overdahl, andJ. Grava. University of MinnesotaAgricultural Extension Service.

9. LIMING MINNESOTA SOILS,Extension Folder 210. 1970. JohnGrava, C.J. Overdahl, and W.E.Fenster. University of MinnesotaAgricultural Extension Service.

10. MINNESOTA SCIENCE, Volume23, No. 3, April 1967. Universityof Minnesota Agricultural Experi-ment Station.

II. MINNESOTA'S ROCKS ANDWATERS, Minnesota GeologicalSurvey. Bulletin 37. George M.Schwartz and George A. Thiel.University of Minnesota Press,Minneapolis, MN. 1 963.

31 32

-?°Itistier

-4.14,11r1

-

12. MINNESOTA SOIL ANDWATER CONSERVATIONNEEDS INVENTORY. 1971.Minn. Conservation Needs Com-mittee.

13. THE NATURE AND PROPER-TIES OF SOILS, Seventh Edition.Harry 0. Buckmai and Nyle C.Brady. The MacMillan Co., N.Y.1969.

14. RESOURCE CONSERVATIONGLOSSARY. Soil ConservationSociety of America, Ankeny, Ia.1970.

15. SOILS OF MINNESOTA, Exten-sion Bulletin 278, June 1963.H.F. Arneman, University of Min-nesota Agricultural ExtensionService.

16. SOILS OF THE TWIN CITIESMETROPOLITAN AREA, Exten-sion Bulletin No. 320. Lowell D.Hanson, et al. University of Min-nesota Agricultural Extension Ser-vice. (out of print)

17. SOIL, THE 1957 YEARBOOKOF AGRICULTURE. U.S. Dept.of Agriculture. U.S. Gov't PrintingOffice, Washington. D.C.

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