cheap option for sectioning off allotment

Hi guys
weve got an allotment, all dug over and rotivated, we now need to section it off to grow things, people have suggested decking boards but they are quite expensive. Does anyone know of any cheap alternatives? or what do you guys use?
Cheers

Used scaffold batons if you have a pretty big scaffolding company near you they sell off battons that are bit shoddy or have a bit notched out. They are not allowed to use them on big construction sites by all accounts due to health and safety.

Forgot to add normally only a couple of quid each.