I have a couple of new raised beds that are deep. I know I don't need the depth for the roots, but the point for me was to raise the height so there is less bending.

They are sturdy, but I am still questioning what to put in them (it will take a lot). I have lots of compost/manure mix, but it is heavy. Any suggestions on what I could mix it with to lighten up the weight and increase drainage? Or, do I need to?

I was thinking Peat, because it's inexpensive, quick, and easy for me to purchase.

I would add perlite. Peat would just to the heaviness.

I agree on the perlite. Some independent nurseries or farm stores might carry the biiig bags. I would avoid the brands that have added fertilizer to the perlite.

I certainly agree. Peat not only would add to the weight but also increase the acidity. I purchase super coarse perlite by the 4 cf. bag. That's a lot of perlite. Because perlite is so light, even a huge bag like this ships for a moderate amount. You could also add something like cypress or another hardwood mulch. This adds organic matter which will break down over 1-2 years. Until it breaks down, the mulch will open the soil.

Thanks you guys, I have both of the ingredients you suggested.

How much perlite? Is there a percentage like 1 part per X part soil?

I have a big pile of hardwood mulch too ............ sounds like you have solved my dilemma. ;)

If you don't need the depth this site puts milk crates on the bottom covered with hardware cloth and landscaping fabric.
http://www.rodalesorganiclife....

I think you could add perlite at 1/4 to 1/3 of the total volume. Do mix it in well. The wood mulch - I would keep that towards the bottom of the bed.

A friend suggest Milk Jugs or Styrofoam etc ... but I was concerned about the beds being top heavy.

Thanks so much for the link to the page that suggest milk crates ..... so many ideas out there that I would never have thought of myself.

In my opinion, it matters not where the hardwood mulch/bark is. I see little value if it is simply dumped into the bottom, where few if any roots will even penetrate. I use it liberally in my raised garden as well as the super-coarse perlite. My terrestrial orchid mix has cypress mulch mixed in, and those plants do well with it in the media. In my experience, cypress will outlast pine (which I never use) and regular hardwood mulch 2 to 1.