ISO 9001 does not differentiate between full-time and temporary personnel.
And there's no reason why it should. The requirement is for people to be competent, if they're doing work that affects product/service quality. As a customer, I'd be under-impressed if told 'sorry about the product/service problem, but it was done by a temp/contractor'. Not good enough.
The question for the organisation, however, is: how can I meet this requirement effectively? Doing the kind of performance assessments that fulltime/permanent employees undergo is unlikely to be cost-effective for the organisation.
As to how and what... can you provide more details on what field you're in, and what kinds of work the contractors are doing?
PS I don't understand what you mean by them being 'organic' at all. That means 'living' as in 'organic material' (I'd hope your contractors are alive!

) or 'produced without the use of chemicals and with fertilisers strictly of vegetable/animal origin' as in organic foods or an organic restaurant.