Providing tax breaks for grow-your-own gardens would stimulate a great interest in creating more local food production chains, also stimulating more employment in this industry. (In the UK, for example, this would take the form of a council tax break - the tax you pay on your residential property to fund local government activities and services.) If you don't have time to grown produce, why not offer up your free space to those without available land who want to grow food - you get the tax break and they get access to soil and fresh produce.
A buy-back scheme would ensure that you are able to also guarantee selling on your produce to the local store ( or swapping it on a points system perhaps for other products) or to a super-local veg box scheme - perhaps done by street. Growers would then be able to collaborate on a very local basis as to who should grow what, perhaps encouraging specialisation to complement others' efforts and increase community network resilience.
** Picture credit: http://askaxworld.com/