All Things SOIL TAXONOMY
Summary
TLDRThis 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
🌱 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.
🌍 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.
Mindmap
Keywords
💡Soil
💡Weathering
💡Erosion
💡Clay
💡Silt
💡Sand
💡Loam
💡Soil Horizons
💡Soil Orders
💡Soil Taxonomy
💡Soil Formation Factors
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
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