I'm planning to try out some permaculture concepts in our organic vegetable patch this year. To be specific, I want to build a raised bed and fill it with sheet mulch, as described in Toby Hemenway's book, "Gaia's Garden".
As I understand, the final two layers of a sheet mulch are compost and mulch. However, I usually grow almost all my veggies from seed and I'm a little confused about how to sow them in the raised bed.
Here in the Netherlands, we are told that it's not possible to start seeds in compost, as it contains so much nutrients it actually 'drowns' the seeds and kills them. So I'm not sure that sowing seeds in the raised bed - by brushing away part of the top mulch layer - will work.
I have a feeling that this is mainly a translation issue, but I'd like to be sure. When starting seeds at home, I usually use a bag of "potgrond", which translates as "potting soil/potting compost". Compost in Dutch is pure, composted vegetable matter, which is very high in nutrients.
So, I guess my question is, can anyone tell me what exactly the compost-layer of a sheet mulch is made of?
The compost can be whatever you have available. If it's a half-rotted pile of kitchen scraps, fine. If it's a well-groomed and finished pile of black gold, use that. It's very easy to get carried away with the ratios and chemical composition of a sheet mulch project, but really all you're doing is trying to smother what you don't want with a biodegradable layer of stuff that will double as a fertilizing medium in which to grow what you do want. If someone tells you that compost kills seeds, then they need to start a pile with squash scraps and see what happens.
Just try the technique using the materials you have, and figure out what the plants need in your area. Don't be afraid to bend the "rules".
Compost is too much for some seeds I tend to think in terms of seed size: big seeds can handle it. Many brassicas, beets, coriander, legumes, cucurbits...
Lettuce, celery etc, maybe not.
It might be worth planting big seeds straight in the garden and starting small seeds in pots.
In our first attempt at sheet mulching we ended up with the top layer being straw. We created very small pockets (about the size of a fist) of a soil/compost mix and planted directly into them. We had great success and are constantly expanding! Have fun!
If you're worried about it, consider making furrows (small trenches, 2-3 inches wide) down the length of the of the finished sheet mulch bed, and fill them with soil, or a half soil/half compost mix and then plant into that? It's worked for me.
Or, make the bed by creating small mounds along the length of the garden area, of hay and/or grass clippings and/or tree leaves and/or compost, 3-4 inches wide and 4-6 inches high with 2-3 inches of space between each mound to be filled in as I've described in the first paragraph. After 7 years of sheet mulching, this is how I construct my beds if I'm doing direct seeding. I made this modification because I didn't see the sense in creating a typical sheet mulch, only to 'mess it up' by creating the furrows after the fact. I've found that weed suppression is just as good as the method described by Toby Hemenway.
@Travis: interesting alternative you came up with there. it would however mean for me that i've been breaking my back finding and dismantling woodpallets to build the raised bed 'container' for nothing!
you all must have crazy compost, i start 95% of my seeds in nothing but my homemade compost.
as for starting seeds in mulch systems, you can either make seedballs and toss them out, them lightly rake the mulch to shake those seeds to the soil level, they will find there own path for light and such.
or just toss seeds out and let nature do its thing. its what i do most of the time. as long as the mulch is mature and not like 6 inches of fresh straw you will be ok.
if you just put down the mulch you should start seedlings elsewhere and transplant. or let the mulch start to balance out. i prefer to mulch new beds in the fall and toss seeds out late winter.
The ultimate goal of farming is not the growing of crops, but the cultivation and perfection of human beings. - Masanobu Fukuoka