The Origin and Depletion of SoilThe Origin and Depletion of Soil

Liberty Ag.Fall 2011

IntroductionIntroduction

Less than 3 percent of the population in the United States is employed in production agriculture.

Yet, 2/3 of the population is engaged with agri-business.

In other words, the majority of the population is likely to neglect the soil, unless they are educated on it’s importance.

Soil vs. DirtSoil vs. Dirt

What is the definition of Soil:

The top layer of the earth's surface, consisting of rock and mineral particles mixed with organic matter that supports plant growth.

Any foul or filthy substance, as excrement, mud, dust, etc.

What is the definition of Dirt:

Factors in Soil FormationFactors in Soil Formation

Parent Material

Topography

Climate

Native Vegetation

Time

Parent MaterialParent Material

Definition: the material from which soil develops.

The parent material can often be found at the soil surface or a few feet below the surface of the ground.

Parent material can consist of Limestone, Sandstone, Shale, Peat, etc.

Parent Material (cont.)Parent Material (cont.)

Not all parent material is formed in place, or residual soils.

Parent material moved by streams are call Alluvial deposits.P.M moved by lakes are call Lacustrine deposits.P.M. moved by the winds are call Loess deposits.Colluvial deposits are moved by gravity.Glacial deposits are moved by glaciers.

Parent Material (cont.)Parent Material (cont.)

The parent material and how the material was deposited influences the soils fertility and texture.

ClimateClimate

The climate effects the rate at which the parent material weathers.

Climatically factors include:TemperaturePrecipitation (amount and type)Location (Is the area on a slope, ridge or valley?)

TopographyTopography

Slope:Effects the material being moved and material left behind by pulverizing it.Exposes subsoil at the upper portion of the slope.Effects the distribution of water on the Earth’s surface.

Topography (cont.)Topography (cont.)

Drainage or Lack ofOn non-level ground water runs off the surface and takes some soil with it.On level ground, water soaks in and moves through the soil in a process called percolation.Soils that are well drained are usually gently rolling hills, and are productive for row crops.

Drainage or Lack of (cont)Drainage or Lack of (cont)

Soils that are poorly drained are less productive, because of high water table.

– The soil becomes saturated so that little to no air is present. This causes the fungi, bacteria and other organisms to slow down or die.

Native VegetationNative Vegetation

Animals and micro-organisms mix soils and form burrows and pores.

Plant roots open channels in the soils. Different types of roots have different effects on soils.

Grass roots are "fibrous" near the soil surface and easily decompose, adding organic matter. Taproots open pathways through dense layers.

Native VegetationNative Vegetation

Micro-organisms affect chemical exchanges between roots and soil.

Humans can mix the soil so extensively that the soil material is again considered parent material.

How is it possible that humans can mix the soil so much it is considered parent material?

TimeTime

Soil formation processes are continuous. Over time, soils exhibit features that reflect the

other forming factors.Such as recently deposited material from a flood, that do not show any signs of soil development

Soil TextureSoil Texture

SandSilt

Clay

Soil TextureSoil Texture

The definition of soil texture is: the size of individual soil particles.

The larger the soil particle the courser the material feels when rubbed between the fingers.

The largest soil particle is sand, and the smallest particle is clay.

Soil Texture (cont.)Soil Texture (cont.)

Soils are rarely composed of pure sand, silt, or clay. They are usually composed of a mixture of all three components.

Loam Soil: Less than 52% sand, 28 to 50% silt, and 7 to 27% clay.

Soil Texture (cont.)Soil Texture (cont.)

SandLargest soil particle2mm to .05mm in diameterExtremely poor water holding capability.

Soil Texture (cont.)Soil Texture (cont.)

SiltSmaller particle than sand..05mm to .002mm in diameter.Help hold water in the soil.

Soil Texture (cont.)Soil Texture (cont.)

ClaySmallest soil particle.Less than .002mm in diameter.Has a negative charge.Helps hold water in the soil.Important to soil fertility.

Relative Size of Soil ParticlesRelative Size of Soil Particles

Soil Texture (cont.)Soil Texture (cont.)

Course-Texture (Sandy) SoilLoose and single grained.When squeezed in the hand while dry, it will fall apart when released.When wet, it will form a cast, but will crumble, when touched.

Soil Texture (cont.)Soil Texture (cont.)

Medium-Text (Loamy) SoilRelatively even mixture of sand, silt, and clay.Feels somewhat gritty, but yet smooth.When wet, it will form a cast and can be handled easily without breaking.

Soil Texture (cont.)Soil Texture (cont.)

Fine-texture (Clay) SoilForms hard clods when dry.Very sticky then wet.Forms a long flexible ribbon when moist.

Soil Texture TriangleSoil Texture Triangle

Soil StructureSoil Structure

Soil StructureSoil Structure

Soil Structure is the tendency for soil particles to cluster together and function as soil units or aggregates.

Aggregates or Peds contain sand, silt, and clay and are held together by a gel material formed from organic matter.

Soil Structure (cont.)Soil Structure (cont.)

Advantages of a good soil structurePeds absorb and hold water better than single particles.They also hold nutrients and influence chemical reactions.Resists damage from falling raindrops.

Soil Structure (cont.)Soil Structure (cont.)

DisadvantagesDispersed soil particles run together and form a crust on the surface of the soil.Crust prevents air and water from entering or exiting the soil.

Soil Structure (cont.)Soil Structure (cont.) Granular

Resembles cookie crumbs and is usually less than 0.5 cm in diameter. Commonly found in surface horizons where roots have been growing.

Soil Structure (cont.)Soil Structure (cont.) Blocky

Irregular blocksUsually 1.5 - 5.0 cm in diameter.

Soil Structure (cont.)Soil Structure (cont.) Prismatic

Vertical columns of soil that might be a number of cm long. Usually found in lower horizons.

Soil Structure (cont.)Soil Structure (cont.) Platy

Thin, flat plates of soil that lie horizontally. Usually found in compacted soil.

Soil HorizonsSoil Horizons

Soil HorizonsSoil Horizons

O horizon Surface layer.

Comprised of organic matter and some mineral matter.

May or may not be present in all profiles. R

Soil HorizonsSoil Horizons

A horizonTopsoil

Dark in color.

Many not be present or maybe several inches deep.

Contains organic matter and is high in nutrients.

R

Soil HorizonsSoil Horizons

B horizonSubsoil

Usually lighter in color than the topsoil.

Influences percolation of a soil.

Can contain a Hardpan. R

Soil HorizonsSoil Horizons

C horizonParent Material

R

Soil HorizonsSoil Horizons

R horizonBed Rock

R

Label the HorizionsLabel the Horizions

Label the HorizionsLabel the Horizions

Soil pHSoil pH

Soil pHSoil pH

Soil pH is the measure of how acidic or basic it is.

pH scale runs from 0 to 14 Acid 0-6 Neutral 7 Basic 8-14

How do soils become acidic?How do soils become acidic?

Leaching of nutrients.

Crop removal of nutrients.

Acids formed by fertilizers.

Soil pH (cont.)Soil pH (cont.)

Certain crops may have problems growing in soils that are too acidic or basic. Therefore producers run soil tests to measure the soil’s pH and nutrient content.

What would the producer add to his fields if the soil was too acidic? Lime

Soil pH (cont.)Soil pH (cont.)

Some crops, like blueberries require a acidic soil (4.0 to 5.0) a sulfur based material is added.

The pH range for most soils, range from 4.0 to 10.0.

pH ScalepH Scale

pH scale for ForagespH scale for Forages

pH scale for Row CropspH scale for Row Crops

Soil EcosystemSoil Ecosystem

Plant Life,Microorganisms,

& Macroorganisms

Soil EcosystemSoil Ecosystem

Ecosystem: is all of the plant and animal life that live in an area.

All plants and organisms depend on each other to provide food and other environmental factors.

Soil EcosystemSoil Ecosystem

Plant LifeThe soil provides a support for the root system.Majority of all nutrients used by the plant are found in the soil.The area that contains the roots of a plant is called the rhizosphere.

Soil Ecosystem (cont.)Soil Ecosystem (cont.)

MicroorganismsThey live in the rhizosphere.Many live off plant roots.Help decompose dead material.– Carbon Cycle

Carbon CycleCarbon Cycle

Common MicroorganismsCommon Microorganisms

BacteriaRhizobia – Nitrogen-fixing– Found on the roots of legumes.– Converts nitrogen in the air to a plant usable form.– Can be transferred to other fields by transplanting the

legume.

Common MicroorganismsCommon Microorganisms

FungiPlant-like organisms that contain no-chlorophyll.

Size: microscopic to large mushrooms.Aid in the break down of dead plants.– Especially the breakdown of lignin, a primary component

of wood.

Common MicroorganismsCommon Microorganisms

NematodesOne of the MOST important microscopic animals.They have smooth round bodies that are not segmented and move by fluid pressure.

Nematodes (cont.)Nematodes (cont.)

Three groups of Nematodes

Consume decaying organic matter

Consume other microorganisms

Consume plant parasites MOST IMPORTANT!!

NematodeNematode

MacroorganismsMacroorganisms

EarthwormsEnhance the soil by– Burrowing– Pulling Organic matter from the surface down into the soil.– Castings

MacroorganismsMacroorganisms

Grub wormsFeed on plant roots, and can become Very Destructive!

MacroorganismsMacroorganisms

Groundhogs, moles, chipmunks, and other burrowing animals

They create large passages that allow air and water to enter the soil.Help incorporate organic material into the soil.Very Destructive to plants.Holes and burrows can be hazardous when operating equipment.

ErosionErosion

ErosionErosion

Define Erosion.

The wearing or washing away of the soil.

Main Kinds of ErosionMain Kinds of Erosion

Wind Erosion Water Erosion

Sheet ErosionRill ErosionGully Erosion

Splash Erosion

Wind ErosionWind Erosion

What is it?Wind erosion is the movement and deposition of soil particles by wind.

What causes wind erosion?What causes wind erosion?

A sparse or absent vegetative cover A loose, dry and smooth soil surface Large fields Strong winds

Wind Erosion ModelWind Erosion Model

Are their any soils resistant to wind erosion?Are their any soils resistant to wind erosion?

Loams, clay loams and silt loams are generally more resistant to wind erosion.

Soils with more organic matter are more resistant to wind erosion.

What type of soils are least resistant to wind erosion?What type of soils are least resistant to wind erosion?

Ways of Decreasing Wind Erosion.Ways of Decreasing Wind Erosion.

No-till Avoid burning fields Do not overgraze pastures

Water ErosionWater Erosion

Mechanism of water erosion

Detachment– Example: Raindrop hitting the soil surface.

Transportation

Deposition

Splash ErosionSplash Erosion

Impact of rain drops soil granules.

Detaches and transports soil.Up to 2 feet by air.3-5 feet by water.

Splash ErosionSplash Erosion

Sheet ErosionSheet Erosion

Soil is removed uniformly from every portion of the slope.

This type of water erosion in not very noticeable.But can be recognized by soil deposition at the bottom of a slope.

Rill ErosionRill Erosion

The most common forms of erosion. The removal of soil by concentrated water

running through little streamlets. The rill channels can temporarily be removed by

tillage.

Gully ErosionGully Erosion

Severe soil erosion. Large rills that cannot be crossed with

equipment. Carry large amounts of water after rains.