It can be done. You will want to consider several fators:
-You will very likely be collecting rain water for this, in which case you MUST add calmag.
-Algae is going to be a factor and a light-proof res is a must if you want to avoid this.
-Heating/cooling the res is only minimally possibe and you will need to plan for this. A res that is partially sunk in the ground and shaded from sunlight will stay cooler than one on the surface.
-It's a bit obvious lol!
-Apart from algae, you are likely to get grit, bits of dry leaves and grass, insects, etc. in your system and if it is an active system, filtration is important. Again, something to plan. Passive systems such as styrofoam float over a trough, or a DWC-type configuration, are less likely to be affected by the presence of foreign objects.
-Pests are more difficult to control; however, the natural predators that prey on pests will follow them to your plants too... so you'll just have to see what the little ecosystem turns into lol! It's hard to predict.

So anyway there are other things to think about but those are big ones. I highly recommend reading the magazine 'Growing Edge', which highlights hydro food production in every issue and has great ideas for indoor AND outdoor systems.
foxysox Reviewed by foxysox on . outdoor hydro? is a outdoor hydroponic possible? Rating: 5