montana natural resources youth camp - mnryc.org · grassland soils are often more alkaline and...

Montana Natural Resources Youth Camp 2014

87

Soils

88

Soils Notes:


89

Soils Class

Course Goals - Students will gain understanding of the complexity of soils as a physical and

biological system providing a basic resource for above ground biological systems. Students will learn

a variety of characteristics used to describe soils and differentiate different soil types. Students will

visit several different soil types and learn how each have unique characteristics that strongly

influence a wide variety of management decisions.

Topics Covered 1. Soils Are Complex Living Systems

Soil is not lifeless dirt but rather is an incredibly complex, living, breathing system!

Soils take in oxygen and expel carbon dioxide.

Water passes into, through and out of soil

Soil hosts thousands of organisms, both micro and macro-organsims

2. Humans Would Have Serious Problems Without Soils

Soils are the main medium for plant growth, especially crops. These crops include

forests and rangeland as well as fruits, vegetables and grains.

Soils support our structures - our homes and other buildings, roads, and other structure.

Soils also dispose of our wastes in landfills and with onsite sewage treatment systems

such as septic tank drainfields.

3. Soil Properties (Terms)

Soils have several main components including: mineral, water, air, organic. We will

point out some important features of soils throughout this class including:

Horizons - these are the horizontal layers of soil which you can see in a soil profile

or roadcut , and which change with depth.

Color - dark brown or black usually means high organic matter content, bright

colors (red, yellow) usually mean high iron and clay content.

Texture - the percentage of sand, silt, clay, and rocks

Sand - feels gritty

Silt - feels smooth but doesn't form a ribbon

Clay - feels smooth and sticky, will form a ribbon

Structure - (dirt clods) - lumps of soil formed by root growth, clay movement,

wetting and drying, shrink-swell

Organic matter content - mostly in the surface from roots and litter. Main source of

nitrogen, phosphorus, and sulfur.

Roots - root distribution tells you a lot about where the plants are getting their

water and nutrients. Bedrock, dense layers (glacial till), or loose sand and gravel

can limit roots.

90

PH - acidity/alkalinity. A measure of how many hydrogen ions are around.

Grassland soils are often more alkaline and conifer forest soils are often more

acidic.

Available water holding capacity - how much water will the soil hold and make

available to plants. Sands hold about 0.5 - 1 inch/foot of soil and silty or clayey

soils hold about 2 inches/foot.

Mottles - (redoximorphic features) are spots of rust in the soil which indicate

saturation. Usually from a seasonal high ground water table.

4. Soil Formation

There are five main factors of soil formation. When you look at soils, think of these factors

and try to figure out which have had the most effect. By knowing about soil forming factors,

you can figure out how the land developed throughout geologic history.

Parent Material - what the soil is made of. This includes the kind of rock and the

processes that acted on the rock and soil material, including streams, glaciers, lakes,

wind, gravity.

Streams move quickly, carry gravels and make rocks rounded, most rocks are

about the same size. Stratify layers or deposit layers of about the same size

material.

Glaciers pick up all sizes of rocks, including gravels, stones, and boulders as well

as soil and mix these up into a jumbled deposit.

Lakes deposit mainly silts and clays with no rocks, may have varves (layers of

sediment).

Wind deposits silts and fine sand, no rocks.

Gravity breaks rocks off outcrops and moves them downhill slowly over time,

these rocks are usually angular.

Topography - slope steepness, aspect, slope length, landscape position (valley bottom,

ridgetop, mid-slope).

Vegetation - forests, grassland, wetlands.

Climate - rainfall, temperature, freeze-thaw cycles, wet-dry cycles.

Time - how long has all this been going on.


91

Soils Field Trip Outline

As you visit each soil site think about what properties each soil has and how it may have been

formed.

Site 1 - Wet meadow soil - loamy-skeletal, mixed Aquic Cryoboroll

Mixed volcanic ash and lakebed deposits over stream deposits

Dark surface - grasses concentrate roots in the upper foot or so. Wet, cold soil slows

decomposition.

Mottles - rusty spots caused by seasonal saturation and drying.

Roots don't go very deep due to shallow groundwater.

Hummocky surface from freezing and thawing and animal use during wet periods.

Productive in terms of biomass.

Not suited to many trees except spruce.

Not suited for most crops but will grow lots of water tolerant grasses and sedges.

Not suited for homes, foundations, roads, septic systems.

Site 2 - Greenough soil - fine-silty, mixed Typic Eutroboralf

No shallow water table

Light colored surface layer over brighter brown subsurface. Surface not dark because less grass.

Acid leaching under conifers bleaches the surface horizon.

Silt loam layers with a zone of clay accumulation in the subsoil. Lake varves below. Lake

deposits are usually silt and clay size particles. Glacial Lake Missoula. Uniform textures are not

the most stable- you need a good mix including some clay to bind it together and some rocks

and sand for good drainage and higher friction.

Varves with platy structure. Wide light colored varves is the spring runoff sediment and the

thinner dark varves are the sediments with organic matter accumulations through summer and

winter.

Dark brown bands of clay washed down root channels and around soil peds. What if soil

formation continues? Will a clay horizon form?

Hydrologic cycle- most places in Montana rain only penetrates a few feet then is

evapotranspired by plants. The upper soil at site 2 started out wet in the spring then plants

removed the moisture as they grew. You can seed how deep the plant roots are by where the

moisture has been removed.

92

Productive in terms of biomass.

Well suited to many trees, especially pine, Douglas-fir, and larch.

Not suited for most crops due to cold environment, topography, low organic matter content.

OK for foundations if kept dry.

Poor for roads due to lack of sand and rocks.

Good for septic systems, will absorb waste water and not let it pass through to groundwater

Site 3 - Crow soil - fine, mixed Typic Eutroboralf

Great for landfills - waste pollution can't go anywhere.

What's different about the vegetation? More lush due to aspect and texture.

Slightly darker surface horizon - more grasses that site 2 but not nearly as much as site 1

Reddish brown subsoil - clay

Roots don't easily penetrate the clay but grow between peds and in cracks.

Productive in terms of biomass. Moisture perched when trees need it.

Well-suited to many trees, especially pine, Douglas-fir, and larch.

Not suited for most crops due to cold environment.

Suited to range when trees removed.

OK for foundations if kept dry but beware - over excavate and backfill with more suitable soil,

provide for drainage.

Poor for roads due to lack of sand and rocks.

Poor for septic systems, will not absorb waste water.

Site 4

As you walk to the soil pit predict what soil you will see based on vegetation, topography, and other

clues. You have seen this soil before.

"Confirm predictions - don't uncover mysteries"

Soils do repeat themselves across the landscape allowing us to map out areas of distinctly different

soils. Soil surveys are made through the USDA-Natural Resources Conservation Service national

cooperative soil survey program.

Ice-rafting and glacial erratics - Glacial Lake Ovando

Evaluate the understory and tree productivity. 800 - 1000 pounds of forage per acre.


93

Site 5 - Sharrot - loamy-skeletal, mixed, frigid Lithic Ustochrept

This is an inclusion of a shallow soil in an area that is mainly deeper soils.

Has a light colored surface layer with a thin litter layer.

Texture is similar to the rock - sandy

Little structure, not much time for soil formation

What is different about these rocks? Angular (have not bee transported)

Evaluate the understory and tree productivity. Less productive than site 4 with 400 - 600 pounds of

forage per acre.

Summary

Pay attention to soils - they have an important effect on your life. Be sure soil is considered in your personal land

use decisions (where to build a home, road, sewage system, etc.) and in public land use decisions concerning

developments, landfills, farmland preservation, mines, timber sales and other issues.

Help protect our soil resources from erosion. Man has ruined much of the land he has occupied very long. In

America we tend to look down on other cultures and think we are good land managers when actually we just

have the newest land. Our land has not yet been ruined since Ave have not been here long.

Much of the Middle East appears on our TV screens as bleak, dry, desert-like wastelands. However, Lebanon

once had 150,000 lumberjacks and a huge cedar forest. Now there are only a few acres of "forest" left.

Mesopotamia-Babylon is considered the cradle of civilization and once had 35,000 acres of irrigated cropland

supporting around 20 million people. Now the same area supports only 3 million. The city of Jerash, Syria once

had a population of 250,000 but is now covered by 13 feet of sediment. The current city only supports 3,000

people.

This leads us to an interesting revelation about the entire field of archaeology. Why are archeologists always

digging up past civilizations? Because these civilizations practiced poor land management and the upland areas

eroded down upon the cities and towns which were usually built down in the valleys.

94

Glacial Lake Missoula


95


97


99


101


103

Soil Profile

104

Soil Facts

Soils are important because......

* without soil, the ecosystem in which we live could not exist

* Soil acts as a filter to protect water, air, and other resources.

* bacteria in soil oxidize harmful methane and nitrous oxide, so they are less harmful.

* growing plants require 17 essential nutrients, and all but 3 are found in soils*.

* soil recycles residues (leaves, stalks, dead roots, animal wastes) into nutrients needed by

growing plants.

* plants need a tremendous amount of water to grow. Soil is the best storage unit.

* soil makes an excellent delivery system for water.

* groundwater is free to flow through soil to recharge other areas.

* 85 percent of atmospheric carbon dioxide comes from reactions found in soil.

* the plant, animal, and microorganisms found in soil are the optimum carbon recyclers,

promoting a healthy atmosphere for humans.

Did you know?

* A spoonful of soil contains more microorganisms than the number of people on earth.

* Actinomycetes are short strands of fungus found in soil that gives newly plowed soil its

fresh smell.

* The total weight of the living organisms in the top 6 inches of an acre of soil can range from

5,000 to as much as 20,000 pounds.

* The number of earthworms in the soil ranges from 0 to hundreds of thousands. In the

proper conditions, earthworms can have 800,000 small channels per acre that pipe water

throughout the soil after a downpour.

* A teaspoon of soil may contain over 50 million bacteria.

* More than 17,000 soil series can be found in the U.S.

* Earthworms move about 1 to 100 tons of soil per acre per year.

* Virtually all fresh water falls on soil and travels over, through, evaporates from, is stored in,

or interacts with soil to drive several chemical, and biological processes.

*Essential nutrients supplied by air and water are Carbon, Oxygen, and Hydrogen.

Nutrients supplied mainly by the organic matter in soil are Nitrogen, Phosphorus, and

Sulfur. Nutrients supplied by the mineral part of the soil are Potassium, Calcium,

Magnesium, Iron, Manganese, Copper, Zinc, Boron, Molybdenum, Chlorine, and Cobalt.


105

More Soil Facts

Here are some more interesting factoids about soil.....

Onsite wastewater treatment systems (septic systems) treat and release more than 4

billion gallons of treated effluent per day from an estimated 26 million homes, businesses,

and recreational facilities nationwide.

Shrinking and swelling of some kinds of soil damage buildings, roads, and other

structures. Repairing this damage costs our Nation more each year than repairing the

total damage from hurricanes, tornadoes, and floods.

The tips of small plant roots move through the soil with a twisting, screw-like motion.

Mature trees can have as many as 5 million active root tips.

A single spade full of rich garden soil contains more species of organisms than can be

found above ground in the entire Amazon rain forest.

Although the soil surface appears solid, air moves freely in and out of it. The air in the

upper 8 inches of a well drained soil is completely renewed about every hour.

The plants growing in a 2 acre wheat field can have more than 30,000 miles of roots,

greater than the circumference of the earth.

The wonderful "earthy" smell of newly plowed ground in believed to result from

chemicals produced by micro-organisms. One of these chemicals, called geosmin, is

produced by actinomycetes, organisms that have some properties of both bacteria and

fungi.

About 10 percent of the world's land is used to grow plants and to feed either animals or

humans. About 20 percent of the land in the United States is used to grow crops.

Soil can act as either a sink or a source of greenhouse gases. An estimated 30 percent of

the carbon dioxide, 70 percent of the methane, and 90 percent of the nitrous oxide

released to the atmosphere each year pass through the soil.

Worldwide, an estimated 25 percent of the soils used for agriculture are being degraded

at an unacceptable rate.

The American midwest has the largest area of Prime Farmland in the world. Other large

areas are in South America, in Eastern Europe, and in Russia.

There's still more.....

In the spring of 1934, a dust storm originating in the Great Plains carried an estimated

200 million tons of soil to the Northeastern United States and out to sea. This storm

caused "muddy rains" in New York and "black snows" in Vermont.

In 1950 there was more than half an acre of grain land for each person on earth. By 1990,

there was less than 1/3 acre per person. By 2030, there will only be 1/5 acre per person.

At field capacity, the amount of water available for plant growth ranges from less than

5 to as much as 50 percent, with an average of about 15 percent.

106

It takes about 4,000 to 6,000 pounds of crop residue per year to maintain the content of

organic matter in a soil.

Modern farming practices that minimize soil disturbance (plowing) and return plant

residues to the soil, such as no-till farming and crop rotations, are slowly rebuilding the

Nation's stock of soil organic matter.

Of the carbon returned to the soil as plant residue, about 5 to 15 percent become tied up

in the bodies of organisms and 60 to 75 percent is respired as carbon dioxide back to the

atmosphere. Only 10 to 25 percent is converted to humus in the soil.


107

Soil Terms


109


111


113

SOIL AWC C = 0.5-1.0”/FT MC = 1.5”/FT M = 2.0”/FT MF = 2.2”/FT F = 2.0”/FT


115


117


119


121


123


125


127


129

montana natural resources youth camp - mnryc.org · grassland soils are often more alkaline and...

Documents