New research from University College Dublin (UCD) suggests nitrogen (N) excreted from live earthworms may have the potential to replace the use of synthetic fertilisers on farms.

Experiments carried out show that N and carbon (C) movement from living soil animals to plants can be extremely rapid.

UCD Professor Olaf Schmidt said earthworms can rapidly enrich soil and plants through N excreted in their mucus.

"The real novel insight is that N from worms is going into crops really fast.

"Up to now, we assumed this involved slow decomposition processes and microbial cycling," he said.

Crop yield

Earthworm presence in the soil is already known to increase crop yield in the long run through their burrowing and feeding, which creates good soil structure and releases N that is otherwise locked away in soil organic matter.

Under laboratory and field conditions, a team of researchers from Ireland, Germany and China were able to track the nutrient transfer from earthworms into soil, wheat seedlings and greenflies (aphids) using a method called stable isotope tracers.

They found earthworm-derived N was acquired by greenflies after just two hours under laboratory conditions and after 24 hours in the field.

It suggests that earthworms probably supply nitrogen directly to crops

"This is very exciting because it suggests that earthworms probably supply nitrogen directly to crops and they do it exactly when crops need it most, because both earthworm activity and crop growth are sort of synchronised, by environmental factors, mostly temperature and moisture,” said Professor Schmidt.

Schmidt argued that the agricultural sector should maximise the financial benefits of this N supplied by earthworms as a potential alternative to synthetic fertilisers, adding that they are very costly as the world’s supply chains continue to recover from the COVID-19 pandemic and energy prices rise.

Cropping practices

"By adopting cropping practices that promote earthworms, these dynamic N benefits will also be maximised.

"We knew from previous research that good earthworm populations contribute agronomically significant amounts of N to the soil, but we did not know that they can supply crops with N in such a dynamic fashion," he said.

Schmidt said that farmers cannot always know in advance when to apply synthetic fertilisers, because crops may not need N if it is too cold or too dry.

"Then the applied expensive N is lost to the environment as nitrate leached down into groundwater or as N gases emitted into the atmosphere.

"All forms of N supplied naturally, from the soil's own stores, through decomposition and mineralisation, are economically and environmentally highly valuable and desirable, so we should maximise them,” he added.

Schmidt concluded by saying that earthworms won't replace all mineral and organic fertilisers, but that their full use as a natural nutrient supply could offset the use and cost of mineral or synthetic fertilisers.