I would stop worrying and just plant what is recommended for your area now. Sounds as if you could also try garlic, peas, chard and brassicas. Deal with problems if they arise and don't bother about what Gaia's garden says if it's just confusing you. IMO this kind of 'information' sounds interesting but in an ordinary domestic garden situation it is unnecessarily complicated and not particularly useful.

As long as you have reasonable soil stuff will grow. To get reasonable soil make and add compost. Add a bit of manure if you can get it. Plants are fairly tolerant things and do not require precision treatment for you to get a fair crop.

As it happens favas, or any kind of bean, are nitrogen fixers and will also attract insect pollinators. I doubt you could get an 'imbalance' of nitrogen by planting nitrogen fixers. You'd need to be planting acres of them over a period of years. None of the other crops you mention need pollination since what you eat is either the leaves or the roots not the fruit or seeds.

So stop agonising and get gardening! Good luck.

I would suggest you get your soil tested and see what you're working with. Contact your local Cooperative Extension Service and ask for the Master Gardener. He/she will know where to get your soil tested; it runs about $10.

WHICH Zone 8 are you? The PNW Zone 8 (coastal WA/OR) with cool temps, lots of rain and acidic soil, or the Texas Zone 8 with hot temps, less rain and alkaline soil?

Although in either place, you're not likely to overdo the nitrogen with cover crops... in the PNW, the nitrogen gets washed out by the rain, and in Texas, it gets burned out by the heat.

Gardening of any kind is a world of trial and error, so don't plan on getting it all right anytime soon. 8-) Try it, if it works, continue; if it doesn't, try something else. If you read about something that sounds interesting, read up on it and see if it might work FOR YOU. Just be aware that some plants are invasive in some areas, not in others. Google "(your state) invasive plant list".

To get an idea of what plants attract beneficial insects, just Google "plants attract beneficial insects", a lot of info will show up. In general, most of the plants that have tiny flowers massed together in flat-topped clusters are beloved by insects that both pollinate and feed on harmful insects. Achillea and Queen Anne's Lace are two that come to mind. Just don't grow Queen Anne's Lace if you intend to grow carrots and collect their seed, because they will cross and you'll get stringy carrots the next year.

There is a nice book on cover crops that explains what each one does, called "Managing Cover Crops Profitably". It is usually available in library systems, but it is also free online (see link below). It was written for farmers, but there's lots of useful info in it for backyard gardeners, too. Easy to read and understand.

There is also an Australian Permaculture site that might be useful to you, discussion board and all. I can't post the site because this board will wipe it out.

Keep reading and keep experimenting.

Sue

Here is a link that might be useful: Managing Cover Crops Profitably

Make a list of plant you like( vegetables,herbs, berry plants).Then make a search for companion plants.
Basil repels insects from tomatoes & asparagus.beans like beets,corn,cucumber,potatoes.Carrots like leeks,onions. Lettuce-garlic-tomatoes.The 3 sisters-corn-running beans-squash( nasturtium around the the edge).
Never heard of soil builders causing an imbalance. You must have some powerful compost, if clover,peas,peanuts,beans, even comfrey could over do it.
Getting the most from your Garden from Organic Gardening Magazine is good.
http://www.howtogardenadvice.com/garden_info/companion_gardening.html
You should rotate soil builders with heavy feeders with light feeders.

Here is a link that might be useful: Companion chart