Topsoil – There’s Lots Going On Under Foot

Topsoil is the name given to the uppermost layer of our earths surface, This fine layer, often only 15cm in depth is what gives life to all plants, flowers & trees on our planet and is home to hundreds of thousands of different insect species.

The surface layers of our planet are broken into 5 distinct regions, O, A, B, C & R. O stands for the Organic layer – this is the layer of decaying organic life that will eventually breakdown into humus in the earth’s topsoil layer. A is the topsoil layer and this is where plants & insects are most active. It is in the topsoil layer where plants can obtain all the necessary plant nutrients, air & water. What makes one topsoil better than another is the balance of water, air & the availability of nutrients

Topsoil Facts

  1. Topsoil is home to a huge variety of life from micro organisms to earthworms, insects & burrowing mammals. This diversity makes topsoil a very important ecosystem
  2. 1 teaspoon contains over 1 billion bacteria
  3. Soil is basically a substrate that contains all the essential elements for root & plant growth. These being water, air & nutrients. The ideal balance of these elements in soils is 25% water, 25% air, 45% soil substrate & 5% organic matter (humus)
  4. Soil is an endangered natural resource. Through poor agricultural practices, intensive farming, deforestation & flooding, we are destroying this precious resource at an alarming rate. Currently approx. 40% of the worlds topsoil is considered ‘degrading’ & at current rates it has been suggested that within the next 70 years we will have destroyed 99% of the earth ‘growing layer’
  5. It takes 1000 years to make 1″ of topsoil. The processes under which topsoil forms, involves the weathering of bedrock material (limestone, sandstone, etc) & the decomposition of organic material (grass, forests, insects, fish & animals)
  6. The A layer stores carbon dioxide – It is believed that 10% of the worlds carbon dioxide is stored in topsoil. As our topsoil is degraded, this carbon dioxide is released into the atmosphere
  7. Some of the bacteria & fungi in soils has a symbiotic relationship with plants. These micro organisms sit on plant’s roots are allow roots absorb essential plant nutrients that would otherwise be unavailable to plants
  8. The tallest of coniferous trees only require a 30cm layer to grow & achieve their soaring heights
  9. If soil degradation is not controlled in the next 20 years it could lead to a drop in worldwide food production of up to 30%

Because soil is such an important natural & limited resource, we need to do everything possible to maintain it & protect it. In the garden there are a number of simple steps that we can do to ensure the quality of our soil is maintained. A lot of these principles are the corner stone of organic gardening

  1. Reduced cultivation
    1. Excessive cultivation can lead to soil erosion, death of earthworms & micro organisms
    2. When preparing vegetable plots you should only loosen the top 3″ of soil – Leave the rest to rest!
  2. Use of cover crops in winter & green manure
    1. In winter, bare soils are a problem
    2. Bare soils mean less insects in your soil & more risk of soil erosion
    3. In autumn, once you have harvested your crops you should sow green manure on your plot
  3. Reduce & control use of chemicals
  4. Crop rotation
  5. Use of soil renewal products such as soil renew & use seaweed based fertilisers
  6. Protecting the earthworm
    1. Earthworms are essential for healthy soils. They improve air air flow & drainage, they help to breakdown organic matter & they help to recover soil nutrients
    2. Protect earthworms by reducing cultivation, reducing chemical usage & by using garden forks instead of garden spades
  7. Avoid mixing soil layers
    1. Top soil is distinct from subsoil in many ways (most notably colour). When working soils, digging & renovating homes & gardens it is essential to not mix topsoil & subsoil
  8. Stay vigilant to invasive weeds
    1. Always be on the look out for weeds such as mares tail & Japanese knotweed. These weeds will quickly take over soils & render them useless
    2. If you find mares tail & Japanese knotweed, please contact the garden shop for advice on how to remove it safely & effectively