Basics – soil

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Soil is about as basic as you can get.

Soil is everywhere.  It’s so familiar that we take it for granted, yet it’s vital for producing all our food.

But what is soil, actually?  And what does it do?

Soil composition

Soil is made up of three main components:

  • rock particles, either from the rocks in the surrounding area, or transported from distant locations by rivers or glaciers;
  • organic matter, mainly the remains of dead plants and animals, and manure;
  • organisms which live in the soil – worms, insects, fungi and bacteria.

 

What soil does

To quote one farmer: ‘The job of soil is to make a plant’s life as easy as possible.’  That pretty much sums it up.

Like humans, plants need air, water, food, warmth and a place to live.  Good soil provides all of these things. Without just one of them, plants would die.  Some of the food plants need they actually make themselves from sunshine, through photosynthesis; however, they also need specific nutrients from soil.

Micro-organisms such as bacteria help to break down organic material and minerals, making them available for plants.  They can also help to break down chemicals such as pesticides, and to convert nitrogen into forms which plants can use.

Plants – incredibly – obtain carbon, hydrogen and oxygen from air and water.  Other necessary nutrients, especially nitrogen, phosphorus and potassium, all come from soil.

Nitrogen is derived mostly from organic matter – material from dead plants and animals, and animal manure.  Plants use it for making amino acids and cells, and to make chlorophyll for photosynthesis.

Rock particles provide the soil’s basic structure, as well as supplying essential minerals. Potassium is derived mainly from these minerals.  It helps photosynthesis, protein production in leaves, starch production in roots and helps to form a strong stalk structure.

Phosphorus is obtained from both mineral and organic sources.  It plays a vital role in cell development and energy storage in cells.

Good soil has air spaces to provide oxygen for the living organisms.  Without air, the organisms can’t survive.  Compacted, airless soil is practically useless.                                                                                                                                                                             soil with seedlings close-up

There are many types of soil.  Whether light and sandy or heavy clay, soil can make an enormous difference to the types of crops that can be grown and to the yield of the harvest.

Soil facts

  • There are over 4 billion micro-organisms in one teaspoonful of soil.
  • Soil can act both as a source of carbon transferring into the atmosphere, and as a ‘sink’ to absorb it.  The amount of carbon in soils is about 3.2 times the atmospheric ‘pool’ of carbon and 4 times the biotic (biological) ‘pool’ – all the plants, insects and animals on earth.
  • Research conducted at Rothamstead Experimental Station in England has estimated that even poor soils may have 250,000 earthworms per acre (62/sq m), while rich farmland may support 1,750,000 worms per acre (432/sq m).
  • There are many different types of soil, which require different farming techniques – sometimes completely different types can even be found in the same field.
  • It can take 500 to a thousand years for an inch of soil to form and become fertile.  This happens more quickly in warm wet regions than in cool, drier ones.

 

Good quality soil is crumbly with many small pores within the structure to help the movement of air and water.  Poor soil has either no structure at all, or hard lumpy clods which prevent air and water moving through it.

So – there is an amazing amount of activity going on across the world, right under our feet.

Soil is one of the most important elements of farming, so we will be looking at it in future posts.

 

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