All Things SOIL TAXONOMY

Summary

This educational video script delves into the importance of soil, explaining its formation through weathering and erosion, and the significance of its composition—clay, silt, and sand. It outlines the soil horizons and how they develop over millennia, affecting plant growth. The script further classifies soils into various orders based on latitude, climate, and other factors, highlighting the diversity and complexity of soil types across the globe. It concludes by emphasizing the intricate relationship between soil and ecological systems.

Takeaways

• 🌍 Soil is a universal substance found beneath our feet, essential for plant growth and nutrient absorption.
• 🏔️ Early Earth had no soil; it was rocky and barren. Soil formation began with weathering and erosion of rocks.
• 🔬 Soil is composed of different particle sizes: clay, silt, and sand, which determine its properties and suitability for plant growth.
• 🌿 Loam soil, with a balanced mix of clay, silt, and sand, is ideal for most plants.
• 💧 Clay soils retain more water but are less permeable to roots, while sandy soils are less water-retentive but more root-friendly.
• 🌱 Soil layers, called horizons, form over thousands of years and include the organic-rich Oh horizon and the mineral-rich B horizon.
• 🌱 Soil classification is based on the development of these horizons and other factors, resulting in soil orders like Inceptisols, Gelisols, Spodosols, and more.
• 🌐 Soil distribution is influenced by latitude, climate, and other factors, creating a diverse range of soil types across the globe.
• 🌳 Soil fertility varies by soil order, with some like Mollisols being highly fertile and others like Oxisols being less so.
• ⏳ Soil development is a slow process, with factors like climate, organisms, relief, parent material, and time (PORCHT) playing crucial roles in soil formation.

Q & A

What is the significance of soil for plants and the environment?

Soil is crucial for plants as it provides access to nutrients, and without it, the world would likely be a lot less green.

How is soil formed?

Soil is formed through the processes of weathering, which breaks rocks into smaller pieces, and erosion, which carries these smaller rocks away, usually by wind or water.

What are the three main particle sizes of weathered rock that make up soil?

The three main particle sizes are clay, silt, and sand, with clay being the smallest, sand the largest, and silt in between.

What is the ideal soil composition for most plants to grow?

Loam is considered the best soil composition for most plants, as it has a good balance of sand, silt, and clay.

What are soil horizons and how do they form?

Soil horizons are layers that form on top of bedrock as soil settles. They develop over thousands of years due to weathering, erosion, and the movement of soil particles.

What are the five distinct horizons typically observed in soil?

The five horizons are the O (organic), A (surface soil), B (subsurface), C (bedrock with some soil), and R (bedrock) horizons.

How do soil properties differ based on the ratio of sand, silt, and clay?

Soils with more clay retain more water but are harder for roots to penetrate, while sandy soils are less retentive but easier for roots to grow. Silt has characteristics of both.

What are soil orders and how are they classified?

Soil orders are classifications of soils based on the development of horizons and other conditions. They include Inceptisols, Gelisols, Spodosols, Alfisols, Ultisols, Aridisols, Mollisols, Oxisols, and others.

What factors influence soil formation according to the PORKED acronym?

The PORKED acronym stands for Parent material, Organisms, Relief (elevation changes), Climate, and Time, which are the main factors influencing soil formation.

Why are soil distributions sporadic and patchy across the planet?

Soil distributions are sporadic and patchy because factors like latitude, humidity, climate, organisms, relief, parent material, and time all play a role in determining soil types in different regions.

How do different soil orders relate to their geographical locations?

Different soil orders are found in specific geographical locations based on factors like climate, vegetation, and parent material. For example, Oxisols are found in rainforests, while Aridisols are in arid regions.

Outlines

00:00

🌱 Understanding Soil Composition and Properties

This paragraph delves into the fundamental aspects of soil, emphasizing its omnipresence and crucial role in plant growth by providing access to nutrients. It explains that soil wasn't initially present on Earth but was formed through weathering and erosion, turning rocks into smaller particles classified as clay, silt, or sand. These particles, when combined in different proportions, create soil with varying properties. The paragraph introduces the concept of soil horizons, which are layers that develop over thousands of years, and the significance of loam, a balanced mixture of these particles, for plant growth. It also touches on the classification of soils into different orders based on the development of these horizons and additional factors, setting the stage for a deeper exploration of soil types in the subsequent paragraph.

05:01

🌍 Global Soil Orders and Their Characteristics

The second paragraph expands on the classification of soils by discussing various soil orders found across the globe. It starts with the most undeveloped soils, the 'Entisols,' and progresses to more developed types like 'Inceptisols,' 'Spodosols,' 'Alfisols,' 'Ultisols,' and 'Oxisols,' each associated with specific climates and geographic locations. The paragraph also highlights unique soil orders such as 'Andisols,' rich in nutrients due to volcanic activity, and 'Histosols,' found in wetlands with high acidity and organic matter. Additionally, 'Vertisols,' characterized by their clay content and tendency to crack when dry, are mentioned. The influence of factors like climate, organisms, relief, parent material, and time (remembered by the acronym 'PORkED') on soil formation is also discussed. The video concludes with a note on the USDA soil taxonomy and an invitation for viewers to explore further with a like and subscribe.

Keywords

💡Soil

Soil is a natural body consisting of layers of mineral and organic matter that supports plant growth. In the video, soil is highlighted as the foundation for plant life, providing essential nutrients and a medium for roots to anchor. The script emphasizes the importance of soil by stating that without it, the world would be less green due to the inability of plants to access necessary nutrients.

💡Weathering

Weathering refers to the physical and chemical breakdown of rocks into smaller particles. In the context of the video, weathering is a key process in soil formation, where rocks are broken down into smaller rocks, which can then be further classified as clay, silt, or sand based on their size.

💡Erosion

Erosion is the process by which weathered rock particles are transported from one place to another, typically by wind or water. The video script explains that erosion plays a crucial role in soil formation, as it moves smaller rock particles away from their parent rocks, contributing to the layering and composition of soil.

💡Clay

Clay is the smallest particle size among the weathered rock materials, typically less than 0.002 millimeters in diameter. In the video, clay is mentioned as one of the components of soil, which, when predominant, can retain more water and be more challenging for plant roots to penetrate.

💡Silt

Silt is a soil particle size that is larger than clay but smaller than sand, usually ranging from 0.002 to 0.05 millimeters in diameter. The video script positions silt as an intermediate component in soil, having characteristics of both clay and sand but to a lesser degree.

💡Sand

Sand is the largest particle size among the weathered rock materials, with particles typically larger than 0.05 millimeters in diameter. The video explains that a soil rich in sand has poor water retention but allows for easier root growth compared to clay-rich soils.

💡Loam

Loam is a type of soil that has a balanced mixture of sand, silt, and clay particles. The video script highlights loam as the ideal soil type for most plants, as it offers a good balance of water retention and root penetration capabilities.

💡Soil Horizons

Soil horizons are the layers that form in soil as it develops over time. The video script describes five main horizons: O (organic), A (topsoil), B (subsurface), C (bedrock), and R (rock). These horizons are crucial for understanding soil composition and the processes that shape it.

💡Soil Orders

Soil orders are broad classifications of soils based on their properties and the conditions under which they form. The video script discusses various soil orders such as Inceptisols, Spodosols, Mollisols, Oxisols, and more, each associated with specific environmental conditions and characteristics.

💡Soil Taxonomy

Soil taxonomy is a system for classifying soils based on their characteristics and genetic properties. The video script references the USDA soil taxonomy, which is a comprehensive system used to categorize soils into orders, suborders, great groups, subgroups, families, and series.

💡Soil Formation Factors

The video script introduces the acronym 'PORHKED' to remember the factors influencing soil formation: Parent material, Organic matter, Relief (topography), Hydrology (water), Climate, and Time. These factors collectively determine the type and properties of soil in a given location.

Highlights

Soil is essential for plants to access nutrients.

Soil is manufactured on Earth through weathering and erosion.

Weathering breaks rocks into smaller pieces, while erosion moves them.

Soil composition varies based on the size of weathered rock: clay, silt, sand, or gravel.

Clay is the smallest soil particle, while sand is the largest, and silt is in between.

Different ratios of clay, silt, and sand give soil different properties.

Loam is the ideal soil type for most plants.

Soil particles settle into layers called horizons over thousands of years.

Soil horizons include Oh (organic), A (topsoil), B (subsurface), C (bedrock), and sometimes E (leached).

Soil classification is based on the development of these horizons and other conditions.

Entisols are young soils with no developed horizons.

Inceptisols have slightly more developed horizons than Entisols.

Gelisols are found in high latitudes with permafrost, limiting soil development.

Spodosols are acidic soils found in coniferous and boreal forests.

Alfisols are rich in iron and aluminum, found under broadleaf and deciduous forests.

Ultisols have a lot of iron, making them very red, and occur in subtropical locations.

Aridisols are desert soils with low water content and heavy sand, silt, and gravel.

Mollisols are the most fertile soils, found in grassland regions.

Oxisols have low nutrient availability but the most horizon development, found in rainforests.

Andisols are rich in nutrients and come from volcanic soil.

Histosols are wetland soils with a lot of undegraded organic matter.

Vertosols have a lot of clay and crack when they dry, preventing horizon formation.

Soil distribution is sporadic due to various factors including latitude and humidity.

The acronym PORKED helps remember factors influencing soil formation: Parent material, Organisms, Relief, Climate, and Time.

Transcripts

soil is everywhere no matter where you

go on earth soil will always be

somewhere beneath your feet and that's a

good thing without soil plants would

have no way to access nutrients and the

world would likely be a lot less green

so I think it's about time we all

appreciate soil a little more so here's

all things soils first have you ever

stopped to think about what soil

actually is well me neither but here we

go at one time in Earth's history early

on there was little to no soil on earth

instead the surface was rocky and barren

and unlike rock and water soil didn't

come to earth on an asteroid instead it

had to be manufactured here as soon as

our infantile earth cooled the process

of weathering and erosion kicked into

gear weathering is the breaking of rocks

into smaller rocks either by a physical

or a chemical process and erosion is

when these smaller rocks are carried

away from the bigger parent rocks

usually by wind or water depending on

the size of the weathered rock it can

either be considered a clay a silt or a

sand with anything bigger being gravel

out of these three though clay is by far

the smallest while sand is the biggest

and silt is somewhere in between

together these three sizes of weathered

and eroded Rock make up soil and

depending on the ratio of these three

different sizes of particles the soil

will have different properties there's

this nifty graph to help figure out what

you have based on the soils composition

so if a soil is 25 percent sand 40

percent silt and 35 percent clay it's

considered clay alone if it's 10 percent

clay 40 percent sand and 50 percent silt

it's silty loam we could do this all day

and all these different combinations

have different properties in most cases

however loam is what you want your soil

to be as it's best for most types of

plants to grow in if a soil is more clay

like it will retain more water the plant

roots will have difficulty growing

through it if it's more like sand it'll

be worse at holding water but easier for

roots to grow it again silt is kind of

just the in-between and has

characteristics of each extreme to

lesser degrees overall you want a good

balance of each one as these soils

settle on top of bedrock they form into

layers called horizons this process

takes place over many thousands of years

as Rock is weathered and eroded and

moved from one place to another and of

course things like this are never exact

as nature tends towards randomness

for most places five distinct horizons

can typically be observed the uppermost

is the Oh horizon

Oh for organic and this is where most of

the dead plant matter called detritus is

then there's the a horizon that's where

the real surface soil is it's sometimes

called the bio mantle because this is

also where most soil organisms reside

the B is the subsurface and usually is

the farthest plant roots will go for

soil the C horizon is where the bedrock

is slowly degrading into soil so it's

mostly large rocks and gravel with some

soil in between then the our horizon our

for rock it's just rock sometimes if

there's a lot of soil leaching and eve

horizon will develop this is where sand

and silt are deposited while clay will

continue further down into the B horizon

forming a thin light layer between the a

and the B and now here's where things

get fun based on the development of

these layers plus one or two other

conditions you can start to classify

soils all over the world into soil

orders there are a bunch of these so you

better strap in so in the beginning when

there's soil with absolutely no

development of horizons it's an into

salt these are very young and actually

the most common type of soil on earth

give the soil a little more time however

and it will become an inceptive salt

which has slightly more development of

its layers with the beginnings of a B

horizon then based on the climate given

more time and in scepter saw can become

a variety of different soils at high

latitudes in the Arctic or even mountain

ranges you'll have jealous Souls these

soils will have permafrost close to the

surface so the soil doesn't move around

a lot meaning its horizons remain

undeveloped as well these are found

mostly within northern Russia and Canada

moving slightly closer to the equator

well next find spawn assaults which

occur in coniferous and boreal forest

biomes these will be acidic due to pine

needles falling to the ground and

decomposing into acidic compounds

because of this they're low in fertility

these are primarily found in Scandinavia

and the Canadian East Coast then we have

alpha cells which have fair horizon

development they're rich in iron and

aluminum and are typically under

broadleaf and deciduous forests and also

some human Mediterranean climates these

are mostly in the east coast of the

United States and the Russian heartland

a low alpha cells you'll have ulta soles

which have a lot more iron in them

making them very red these occur in

subtropical locations very humid places

like the American southeast and

Southeast Asia I'm roughly the same

plane ara ridicilous while Altos all's

occur in very human places or riddles

are desert soils with extremely low

amounts of water just think arid or it

assaults these are not sanded deserts

however this is what an original looks

like and this is shifting sand they're

different because there's little to no

water in these environments most of the

small clay particles have been blown

away by the wind leaving mostly heavier

sand silt and gravel these are found in

the Sahara Arabia Australia northern

China and the western United States also

roughly in this area are mala sauce

these are dark soils and in terms of

agriculture the most fertile soil order

these occur in grassland regions like

the American Midwest the Pampas region

of South America and the steppe region

of Russia lastly in terms of latitude we

have oxisols these have low nutrient

availability and aren't a very fertile

but they do have the most horizon

development of any soil order although

it's hard to see because there's so much

iron in the soil turning every layer

this reddish orange color these are rain

forest soils linked to the Amazon and

the Congo then we have a few more soils

that don't really fit into the latitude

scheme these sort of just occur where

they occur in this vague category first

you'll have an de saucé think like the

volcanic Andes Mountains this is

recently volcanic soil ejected from a

volcano

these are surprisingly rich in nutrients

and given enough time create lush

landscapes think about the volcanic

islands of Hawaii and Japan then we have

histah Sol's

these are wetland soils that means

they're caked in water and usually

feature peat there's also going to be a

lot of undegraded organic matter which

can form an impermeable layer if too

much builds up due to the build-up of

this organic matter these will also be

highly acidic they're also unstable and

dangerous to build structures on most of

these can be found in Canada and river

deltas and lastly we have vertosols

these also have a lot of clay in them

but they often dry out when they do the

ground will crack and split and look

like this when this happens soil on top

will get blown into the crevices

inverting the soil layers and preventing

real horizons from forming the largest

concentrations of them are found in

India and Sudan there are of course more

ways to describe soil and in fact for

every order there's a sub order a great

a subgroup of family and a series but

holy crap we don't have enough time for

that here's a map of the actual

distribution of these soil types across

the planet you'll see most of the new

soils are close to the poles this is

because until recently the poles were

covered in glaciers from the last ice

age so they haven't had much time to

develop I'll leave a link for a bigger

version of this map in the description

you'll notice that the soil distribution

is kind of sporadic and patchy and

that's because latitude and humidity

aren't the only things that determine

where different orders of soil are found

in soil science there's a common acronym

porked that's used to remember the

factors that influence soil formation

first there's climate so rainfall and

temperature and also humidity the

climate of an area is largely determined

by its latitude but also elevation and

its surroundings then o means organisms

like how pine trees will change in alpha

saw into a spot us all over time with

their acidic needles also soils need

things like bacteria and fungi in order

for plants to thrive R is relief or

change in elevation mountains will

channel water into valleys so you may

find a hysto saw at a low elevation but

an alpha saw or even an errata saw

further uphill P is for parent material

so if a soils parent material is

volcanic rock you'll get an Indus all if

the soils parent material is limestone

it likely dissolved away and is

therefore probably a clay and will also

be rich in calcium and lastly T is time

given enough time the into cells and

septa cells will become more developed

soil orders I think that's it I hope you

enjoyed this video came right out of a

college notebook of mine so these are

all based on the USDA soil taxonomy and

other places might have different ways

of categorizing soils there's actually a

ton more to learn about soils also so if

you want to see a video called even more

things about soils give this video a

like and subscribe that's it for now

thanks