Earthworms Dig, Humans Don’t!

Earthworms improve soil fertility and aid healthy plant growth.

Earthworms improve soil fertility and aid healthy plant growth.

IN the last article on ‘‘No-Dig” garden, we established some reasons why we don’t dig the soil. Digging exposes the soil’s very delicate ecosystem to the air and ultraviolet rays of the sun, which kills the soil’s organisms. The soil loses most of its nutrients, its organic matter and as a result, does not retain water, the structure is destroyed and compaction occurs leading to hard pan formation soil erosion and the result is dead soil! One thing we haven’t mentioned so far, is that Nature digs, not in the way humans do, but far more efficiently – with earthworms!

With no-dig gardens, the soil is not compacted because it is not walked upon. Stepping on the soil destroys the soils structure by compacting it, preventing air and water penetration to the plants roots, which affects plant health, restricts plant growth and reduces productivity. Paths are constructed for people to walk on, the garden beds for plants only.

Earthworms are Nature’s wonder creatures, a tireless army of super-efficient diggers, whose abilities we humans cannot replicate, despite all the technology we have available. There is need to keep stressing that Nature does it better than we could! In Nature, soil does not need to be manually cultivated for spectacular forests to grow. What holds true in Nature also holds true in the garden. In a forest, organic matter in form of fallen leaves, twigs and branches, annual plants at the end of their yearly cycle and other plants at the end of their lives, are all deposited on the forest floor where they decompose into rich humus.

For those who need more convincing that Nature’s experts (the earthworms) do ‘‘digging” of the soil better than we ever could, here is the evidence:
One hectare of land can support up to 7 million worms, which all collectively weigh 2.4 tonnes, and in favorable conditions, they can turn over around 50 tonnes of soil per hectare each year, enough to form a new layer of topsoil 5mm deep. It has been reported that in one trial worms built an 18-cm thick topsoil in 30 years.
Earthworm burrows aerate the soil and allow the drainage of water up to 10 times faster than soils without earthworms. Uncultivated soils with high populations of earthworms have 6 times greater water infiltration than cultivated soils, which reduce earthworm populations.

Earthworms help plants grow better-burrow castings are richer in nutrients than the surrounding soil with phosphorous levels four times higher than the soil and nitrogen that is readily available to plants. Their burrows allow plant roots to reach deeper into the soil to access more water and nutrients. In addition, the burrows also contain nutrient rich worm castings.

Worm casting is richer in nutrients than surrounding soils.

Worm casting is richer in nutrients than surrounding soils.

Earthworms improve soil fertility from research conducted in various countries. In New Zealand and Tasmania, the introduction of earthworms into perennial pastures (where there were no earthworm previously) initially increased pasture’s growth by 70-80 per cent, and increased it by 25 per cent over the long term. Research in Netherlands showed increases in pasture growth of 20 per cent and in Ireland increases of 10 per cent were observed. In wheat production research in Adelaide, Australia, glass house trials showed an increase of 35 per cent, while paddock trials showed increases between 13 per cent and 75 per cent.

This clearly shows us that earthworms can dig a lot more soil than we can in a more efficient manner, but even more so they can dig soil in a way that produces additional benefits. When we dig the soil, we damage it! That should be enough convincing that it’s best to let the earthworms do their job, and it is to our benefit to build no-dig gardens.

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