We've started installing the raised beds in the garden area. Raised beds are a good idea for a number of reasons:
1) they keep your veggies organized and they help you space out plants appropriately
2) they resist soil compaction, which aids worms and other beneficials in tunneling through the soil the way they're supposed to.
3) you can plant earlier because the beds are raised slightly and they'll warm sooner than soil at ground level.
We've decided that with raised beds it should be easier to build A-frame plastic covered hoop houses with a defined bed. Also, fencing off or netting off particular plants will be far easier because an animal will have to tunnel under the wooden frame and then up to the surface in the bed; it's not impossible, but less likely when other food sources are undefended.
The hugelkultur concept has been highly praised as a way to save water. With my water bills being about $1200 per year, it will reduce (or hopefully eliminate) the need for watering in later summer. With hugelkultur, you simply bury carbonaceous material under the bed. Typically logs are piled on teh ground and then dirt is piled on top of the piles. Essentially, the logs act as sponges once they decay a bit. The logs hold water and the plants send roots down to the logs to sit there, mingle, and have drinks. As the wood decays it provides valuable nutrients to plants. Worms and other beneficial organisms feed on the wood and turn it into worm castings and other insect waste for the veggies to gobble up and use for their own purposes. Circle of life, right?
In our suburban version, we want it to be more tidy and more likely to escape the complaints of neighbors who probably wouldn't want big heaping piles of dirt visible over the fence. The raised beds are framed out of 2x8 lumber and measure 5'x10'. The soil was dug out of the bed to a depth of about 10".
Initially, it was thought that wood would be difficult to source out in the amounts needed to line the bottom of 10 beds. I started thinking of burying tree leaves bagged in brown paper bags like from a garden or hardware store. Craigslist solved this problem. It turns out that nobody wants their trees when they fall down or are cut down. A quick search of the Free section found a half-dozen current posts where tons of free fire wood was available. Anyways, we'll be renting a truck and going to pick up as much wood as possible.
So, once the wood is lined in the beds, the soil that is piled up neatly next to the bed will be back-filled. If 10" is dug out from the bed, and 10" of wood is filled into the bottom of the bed, there will be an extra 2" of soil to pile up on the beds to account for when the dirt and wood settles out through the winter.
One more thing: when brown things (leaves, wood, other brown-colored biomass) decay, they use nitrogen from surrounding plants; high nitrogen levels aid in decomposition. To counteract this, you need to beef up nitrogen. There are three common sources available: manure, green biomass (grass clippings, green leaves), and blood meal. Manure and blood meal will burn plants if applied directly, but will aid in the decomposition of all logs that are in the bed. Another method involves saving and using your own nitrogen-rich urine, but this may be too much for some folks.
For more information about Hugelkultur visit: http://www.richsoil.com/hugelkultur