The earthworms selectively fed on slow-germinating, nitrogen-rich seeds and seedlings, actively ingesting the plant material, killing the young plant.

BBC: Earth News - Earthworms eat live seeds and plants, scientists find

During this time, trees drop their leaves, providing nitrogen-rich mulch, and they are then cut and harvested for poles or firewood.

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The animals then converted the fish into a nitrogen-rich fertilizer for grapevines.

NPR: Fishy Vines Produce Great Wines

Some species are only found where the air is very clean, whilst other species thrive in the nitrogen-rich, less clean air that we find in our cities.

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On the dry seabird islands off the South American and South African coasts, immense deposits of bird droppings, rich in nitrogen and phosphorus, had accumulated over centuries.

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