Hey, all! I garden on a 2/3 acre lot just outside DC that started as pure clay nine years ago. I've been putting in at least one large new bed each year, and my oldest beds are now over a foot deep in good black crumbly soil. I have a big rear-tine Sears tiller I use to prep new beds, but I also love my little Honda -- it's like handling a manic Jack Russell terrier the way that little guy can dig a hole for a new tree, and it does a great job of digging foot-wide six-inch-deep wall footings too. They are both valued friends, they just do different work.

Problem with repeatedly tilling clay is that the blades of the tiller compact the bottom surface of the bed as they scrape up the stuff they loosen -- it can create a hardpan base that's impermeable to water and roots if you're not careful. That said, running over the area once to loosen the clods six or eight inches down, then dumping on six inches of old manure or chopped leaves and tilling that in works well for me as a starting point for new beds. I've also had good luck working in bags of alfalfa pellets from the feed store (I get broken bags for half price, but I'm careful not to get stuff with a high salt content). My veggie garden gets six or eight inches of whatever good stuff I can find tilled in each spring once the ground is dry enough that a fistful crumbles when squeezed and released, but my other beds just get top-dressed with last Fall's chopped leaves plus a good dose of sheep or llama manure -- the earthworms work it in for me with a lot less effort on my part!

I'm glad nobody is talking about mixing in sand to loosen clay -- around here, sand plus clay equals cement. Organics do the job so much better! And the clay keeps the soil from parching so badly in drought.

There's been some discussion on GardenWeb that clear plastic warms the soil better than black, but when I tried it a few years back neither did much to kill weeds if the area wasn't in full sun. I had better luck with laying down several layers of newspaper or cardboard to stifle bermuda grass; I did that in the Fall and successfully planted the next Spring.

There's a lot of talk at GW too about Lasagna Gardening -- don't even bother tilling, just lay down cardboard and/or eight layers of newspapers to smother the existing growth, and heap organics alternating with some soil on top of that. Let it get acquainted with itself for a while, and plant right into that. May be worth checking out, eh?

Lynn