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Are bright orange and yellow earthworms ok in garden soil?

They seem to be the same size and shape as the normal earthworms elsewhere in the garden. We noticed them when we were transplanting a deciduous tree from a pot that we had previously "saved" from our front lawn. We live in a rural area with sheep paddocks surrounding our block.

General Advice • Garden Jobs

Hi Kathryn,

Earthworm can be of various colours. If they are earthworms, they can only be of benefit to your soil.
By their activity in the soil, earthworms offer many benefits: increased nutrient availability, better drainage, and a more stable soil structure, all of which help improve farm productivity.
Improved nutrient availability
Worms feed on plant debris (dead roots, leaves, grasses, manure) and soil. Their digestive system concentrates the organic and mineral constituents in the food they eat, so their casts are richer in available nutrients than the soil around them. Nitrogen in the casts is readily available to plants. Worm bodies decompose rapidly, further contributing to the nitrogen content of soil.
New Zealand research shows that worm casts release four times more phosphorus than does surface soil. Worms often leave their nutrient-rich casts in their tunnels, providing a favourable environment for plant root growth. The tunnels also allow roots to penetrate deeper into the soil, where they can reach extra moisture and nutrients. Earthworm tunnelling can help incorporate surface applied lime and fertiliser into the soil.
Earthworms improve drainage
The extensive channelling and burrowing by earthworms loosens and aerates the soil and improves soil drainage. Soils with earthworms drain up to 10 times faster than soils without earthworms. In zero-till soils, where worm populations are high, water infiltration can be up to 6 times greater than in cultivated soils. Earthworm tunnels also act, under the influence of rain, irrigation and gravity, as passageways for lime and other material.
Earthworms help improved soil structure
Earthworm casts cement soil particles together in water-stable aggregates. These are able to store moisture without dispersing. Research has shown that earthworms which leave their casts on the soil surface rebuild topsoil. In favourable conditions they can bring up about 50 t/ha annually, enough to form a layer 5 mm deep. One trial found worms built an 18-cm thick topsoil in 30 years.



Answered: 9 Oct, 2012

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