Yeah, That could be a lot of things, In April,I did what you did (sort of)I used cardboard right over sod and mine is 8" tall, but besides that everything is the same, and I don't have those issues, my guess is that your soil has become "water -phobic", there is a real word that describes that process, but I can't remember what it is, if it was my bed I would use my fingers to mix up the top couple of inches and water it by hand with a hose sprayer , so it is getting all over ,for at least a couple of weeks , by then it should resolve that problem.

Linked below is Pat Lanza's web site about Lasagna Gardening. I doubt that there is any specific recipe for building a bed. Here is a link that might be useful: Lasagna Gardening 101

Sujiwan, there are mentions of this all over the Hugelkultur sites. At least those that feel the need to instruct. :) From what I remember, cedar, treated lumber, walnut, locust and a couple more weren't good. Things that decompose very slowly or that have antibacterial properties such as the cedar. This was so easy. Somehow easier than the lasagna beds I made when I first moved in here, around 2002-4. Perhaps I'm braver and trust common sense that I didn't at first. ha! Either way, I'm having all the building materials moved out of my front yard, where they've been since 2005, stacked out behind the barn, and building another long bed in front. I imagine my yard as a future courtyard area, with my Japanese maples providing some shade, but definitely beautiful visual interest. Check out the resuse centers for lumber: Community Forklift in Edmonston (off Kenilworth Ave) or 2nd Chance in Baltimore. I got 12"w, 16' long unfinished pine for my kitchen floor at $0.25 a foot and 2nd chance. I'm going to check there for longer treated deck boards or just treated lumber. As a matter of fact, I think I've talked myself into going out there today. Got nuttin' better to do!

At my last house I had raised beds - 4' wide by 12-20' long with wooden sides about 1 1/2 foot tall. Over two or three years we built 8 of these large beds plus several smaller beds for perennial crops like stawberries, rhubarb, and horseradish. For that situation, there were several advantages. It allowed us to have flat areas on a hill; we terraced with rock walls and put the beds on those flat areas, surrounded by woodchips for mulch, so there was no weeding at all. The beds were sunk about a foot below the grade, and we had to sift the soil, which was shallow over fractured ledge, to get rid of all the rock, and then we filled the rest of the beds with composted cow manure, thanks to our local dairy farmer. So, we ended up with no weeds & great soil in flat beds from an area that started out mostly rock on a steep grade. Other pluses were sitting on the bed sides to plant, screwing trellises for beans, melons, cukes, etc. directly into the bed sides, and the ablility to plant early due to good drainage and early season warm-up. We also sometimes put plastic hoops over the beds, tucking the hoop ends inside the beds to hold them, to cover with spun-bond or plastic. On our strawberry beds, we put hinged wire mesh covers so the chipmunks couldn't eat the berries. Between mulch and the high organic content of the soil, we only had to water when it had been dry for a couple of weeks or more. Our current house had a pre-existing ground-level garden which we simply took over as was since the house needed a huge amount of work, so that's where our efforts and energy went. I miss the raised beds, and find that I have more difficulty with soil-living bugs like wire worms in my potatoes and cutworms crawling in from the surrounding field. I can't work in the garden as long since I have to bend more or sit on & scoot along the ground. (I'm no spring chicken!) The grass and weeds migrate into the veggie garden from the surrounding field, and the soil needs to be prepped in the fall so I can plant peas, potatoes, etc. earlier in spring since the soil stays cold and wet for much longer. There are two only advantages I can see to the ground level garden: it's easier to till with a machine like a big tiller or tractor if you want to be able to do that, and any crops that need winter warmth can be well mulched and will stay warmer in the ground. Garlic, which is a bit borderline as far as hardiness here, has better survival rates, and my leeks and root vegetables overwinter better with a thick layer of mulch when they are in the ground rather than in a raised bed. So, like Lisa, I will eventually have some of both, but with most of my garden as raised beds and a smaller part of it in the ground.