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Soil 101 – The Basics

Photo credit: Joi Ito, Creative Commons.

Soil Basics

Soils are intricate mixes of minerals, water, air, organic matter, as well as numerous microorganisms that are the dead remnants of once-living things. It develops on the surface area of land and it is the “skin of the planet.” It is vital to support terrestrial plant life and to life on earth in general. In addition, it has the potential to soak up carbon dioxide from the atmosphere. So next time you look down and think it’s just a bit of dirt, think again.

What is the Difference between Soil and Dirt?

What is dirt? Apart from what we call the material that gets under our fingernails, needs washing off our cars and generally peeves the proud house-owner,  dirt is generally soil that has died. It’s also soil contaminated with man-made materials, especially in cities. Can dirt become soil again? It would seem that we can, yes, regenerate damaged urban soils (dirt).

It is soil that runs the earth. It carries out a multitude of crucial functions in virtually every ecosystem. These include: agricultural land, forests, meadows, marshes, suburban landscapes, and so on.

Here are 8 basic duties that soils carry out:

  1. Soils function as the media for development of all type of plants
  2. Soils change the air qualities by giving off and also soaking up gases (co2, methane, water vapour, and so forth) and also dust.
  3. Soils also enable animals to exist by providing habitat for part-subterranean creatures like snakes, mice, rabbits, and groundhogs as well as organisms  such as bacteria and mushrooms.
  4. Soils take in, store, release, change, as well as purify the majority of groundwater.
  5. Soils process recycled nutrients, to ensure that living organisms can utilize them many times.
  6. Soils are used for building and construction of structures, (see our article on earthbag construction) roads, dams and so on.
  7. Soils work as a living filter to purify water prior to it relocating into an aquifer.
  8. Soils contain the primary plant nutrients of nitrogen, phosphorus and potassium along with a host of minor nutrients that help spur on plant growth.

Different Types of Soil

There are various kinds of soil, each with it’s own distinguishing characteristics. Dig deep into any type of soil, and also you’ll see that it is constructed from layers, or horizons. These horizons can consist of O, A, E, B, C, and R.  Together the horizons create a soil profile. Each profile lets us know about the background story to the soil – how it developed, where it came from, and what it consists of, for example. Every soil has it’s own individual background and makeup. The majority of soils have horizons A, B and C, and the most fertile ones have and organic horizon (O).

What are the Soil Horizons?

O – (humus ) Organic is mostly raw material such as decaying fallen leaves and dead twigs, but also manure, and wood chips. Also called humus, it has a negative charge meaning that a lot of the nutrients plants need adhere to humus, including ammonium (source of nitrogen), calcium, magnesium and phosphorous. This humus holds onto these nutrients and prevents rain from washing them away. In a nutshell, humus acts as an organic chemical free fertilizer for your garden that releases slowly over time.

A – (topsoil) Mostly minerals from parent material (see below) with organic material integrated. It is great for plants and also various other microorganisms to live in. This layer of soil is two to seven inches from the surface and it vital to life.

E – ( eluviated) At this horizon clay, minerals, as well as raw organic materials have drained away. Silt, sand and quartz mainly remain. This layer is present in older and woodland soils.

B – (subsoil) This horizon is mineral rich. These minerals percolated down from A and E (where present)

C – (parent material) Earth’s surface area from which soil develops.

R – (bedrock) Underneath the parent material, this the mass of rock such as granite, lava, quartzite, sedimentary rock or sandstone is not soil.  It can create soil if it is sufficiently close to the surface to break down due to weathering.

Obviously the availability of mineral nutrients in the soil either limits or encourages plant growth and yield, so it is in a grower’s best interest to create the best conditions for soil regeneration and improvement.

In later blogs we will look into this is more detail. In the meantime, if you would like to share any comments you have or share your growing experience, we’d love to hear from you! 

1 Comment

  1. Mick Poultney on October 25, 2016 at 10:16 pm

    My update on making compost …… https://www.youtube.com/watch?v=7HvQ-gmZ_qg

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