You could easily add forum board recipe section, and I think it would be very fitting. I'd keep the allotments4all web address though and divert from the other site address to this one.
On another note. Have you considered having a local allotment issues section, so that members can find other members from sites under the same local authority?
For example, the allotment site I have a plot on, is one of the 115 Birmingham City Council sites. Different authorities have different rules and so on, so it would be useful for people to be able to post cetrain questions to an audience interested in a certain regional area.