As voluntary work for low risk prisoners, sure. If Orange is the New Black and every other prison thing I've watched has even a grain of truth to it, people would rather work than not. As an alternative to the mind crushing tedium of fuck all to do in very constricted environment.
I'm not in favour of conscripted chain gang sort of thing. But that would be a security nightmare and I doubt the farmer would be chuffed at the potential for squished fruit protests etc.
The British benefits system is not nimble enough to allow people to take on seasonal work. You need something like our voucher system. People on gov. assistance can earn up to 4000 € pa on top of their stipend via the voucher system. (An employer can pay a single worker up to €2000pa. It stops them replacing permenent positions with temp, precarious ones if there is a low limit a single individual can earn from one employer.)
Employer buys a voucher from the tabacconist for say €10 euros. The worker when she/he cashes it gets €7:50. The difference is contributions. It does not affect their benefits. It provides a source of additional income which motivates people to work when they can.
That would get your fruit picked AND provide unemployed people with the opportunity to take on non permanent work AND the opportunity create oneself a cushion of extra money that could relieve hardship, or go towards a much need deposit, other extraordinary pressing needs etc.
As it stands right now somebody on benefits would have to be masochist to take on seasonal fruit picking work, because the transition off and back on to benefits, bearing in mind the neglible increase in income, is too onerous to make it a reasonable option.