I have been vegetarian for many years and try to eat organic produce, if possible. I am grappling with the issue that many organic fertilisers are of animal origin and wondering if the animals that the fertilisers are derived from are of organic origin, too? Where does it start or end? I don't really want to eat food that has been grown in a way that causes harm to animals, but I realise that chemical fertilisers and pesticides are potentially damaging to me and to the environment. Help. Are fish, blood and bone fertilisers the most commonly used for growing organic vegetables, or are there other sources? (A local organic farmer tells me that she uses only horse manure and I try to buy as much veg as possible from her ... we live in France.)

Andrea Humphreys, by email

Vegetable growers – as any keen gardener will tell testify – rely on a wide range of fertilisers and conditioners to improve the quality and composition of their soil. Wood ash, compost, seaweed, shell, rotted horse manure, comfrey, chicken droppings can all be used, in addition to the rather gruesome-sounding "fish, blood and bone". And then there are all the synthetic fertilisers widely used by non-organic farmers and gardeners alike.

But, as with so much of the food we consume, we swallow much of it down without knowing the full story about the true circumstances in which it was produced. I can certainly see why you, as a vegetarian, are anxious to know if fish, blood and bone has been used in the production of the vegetables you consume. Relying on the "organic" label certainly doesn't appear to be a guarantee that animal-origin fertilisers have not be used judging by the fact that many of these products boast organic certification. "Organic hoof and horn", anyone? Some might see this as a sensible use of a waste product, but vegetarians will view it as an aberration, I suspect.

Or, perhaps, our vegetarians and vegans readers already know where to source vegetables guaranteed not to have been grown using animal-origin fertilisers?

This column is an experiment in crowd-sourcing a reader's problem, so please let us know your views below (as opposed to emailing them) and I will join in with some of my own thoughts and reactions as the debate progresses. I will also be inviting various interested parties to join the debate too.

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