I've prepared several beds with a layered mulch of cardboard, spoiled hay, organic amendments (mostly marine based and kitchen scraps), and landscaping straw (wheat or oat straw I presume). Oh, there are also some hardwood leaves and pine straw that my grandfather foolishly wanted to get rid of - he's just starting to remember that it should go to me instead of the dump.

Anyway, I've prepared all the beds in an effort to define the areas that will remain as paths so I can begin systematically replacing Zoysia grass with a greater diversity of more aesthetically pleasing, and maintainence free, groundcovers... I curse Zoysia grass every day, because I don't want to sheet mulch my paths and I certainly won't use an herbicide... so it gets pulled and worked out with a small cultivating fork and my hand plow. I feel like I'm scrubbing floors with a toothbrush, but I hate to cut it out, like sod, with a spade or shovel because that takes all of my topsoil and the creatures that live in it. But that's neither here nor there, sorry, I was off on a tangent. Well, it's marginally related because the sheet mulch is also to kill the Zoysia grass; to start preparing all of the areas that will be planted as opposed to the areas that will be path.

My question involves seeding cover-crops into the beds that have already been sheet mulched, where I can't fill with perennials yet or where I plan to have summer annual food crops. In preparing a larger area with sheet mulch than I could immediately plant, I now have several beds with large empty spaces or no vegetation at all - which I don't like. I want to fill in with cover-crops, to provide a sort of living mulch, and food & shelter for birds and beneficial insects. I also want to ensure that I don't have any erosion occuring beneath the mulch in areas where the weeds & grass have been killed, but nothing has been planted to replace them. So, the crux of this verbose post would be my asking whether or not I can just broadcast seed on top of the sheet mulched beds in areas that I want to cover-crop. I've seen a few seedlings of whatever annual grass crop produced my straw, so this led me to believe that I could just spread my cover-crop seeds on top of the sheet mulch and they will root through it. Those roots would have the added benefit of holding my sheet mulch in place, since bare sections have been overturned by the wind if I let it dry out. And I'm also hoping that the roots of my cover-crops will work with the sheet mulching to further loosen and enrich my soil while I am waiting to plant in those areas.

The only alternative I can see is removing the straw layer, perforating the cardboard/paper layer, spread a layer of topsoil, broadcast my seed, then spread a thinner layer of straw... and that sounds like a hell of a lot of work, considering I already did the sheet mulching once. And it especially sounds like a lot of work if I could achieve similar results by simply casting seed on top of straw.

I suppose it would help anyone who might have some suggestions to know that the cover-crops I have for seeding are Red Clover, Buckwheat, Nude Oats, and some leftover Hairy Vetch. I prefer to use the first three, due to their usefullness to myself as well as to the wildlife, but I'll buy some more Vetch or some other crop if that's what it takes to allow me to seed on top of the mulch. Any advice would be greatly appreciated... especially if anyone has some first hand experience with seeding those crops directly into the top layer of a sheet mulched bed.