Black Sheet Plastic To Kill Weeds - can I leave it down ?

Then cut openings for my plants. I have drip irrigation system so watering is not a problem. Don't know if that might be bad idea? Did not plant the veggie garden last year for whatever reason - had weeds & clover all over but put sheet plastic down recently.

It is not great. Wherever it is exposed to the sun it will rot, then you will have smaller and larger bits and pieces of plastic in the soil and blowing around the garden.
Plus, if you can pick it up you might be able to use it another time. Keep it out of the sun.

There is also an issue with aeration in the soil. Plant roots need oxygen, as well as water. If the plastic keeps the soil too wet for too long the plants may not like that. Heavier soils may have this problem, I doubt sandy soils would. Might help a sandy soil.

i would actually go with a couple layers of newspaper--as it breaks down overtime it would be harmless to the soil as opposed to plastic

Any sort of mulch, applied thick enough, will discourage weeds, then rototill it in before you plant.

If you know you will be planting soon (a few weeks to a few months) then use soil conditioner or the finest mulch you can find. Manure with plenty of stall sweepings (rice hulls, sawdust) is good.

If you know you will not be planting for a few months to a year, then you could use a higher % of manure, or slightly coarser mulch. The chips from a tree pruning company can work, if they are high in green matter, so summer prunings.

If you know you will not be planting for over a year then coarser mulch, or chips from tree company prunings from the winter, with little or no green matter will last longer.

You could use newspaper under any of these. More thicknesses last longer.

Flying locksmith I do pretty much what you are talking about. The black plastic will not be as damaged by the ultraviolet rays of the sun as the clear. Actually the clear allows light to start weed and grass seed and roots to grow. That makes it a poor choice for your purpose anyway. The black starts the weed seed but then shades it to death except right at your hole.

I use 6 mill for 3 or 4 years. I always take it up at the end of the season and till the bed for the winter. Then in the late winter I till again and lay the plastic back down the black surface warms the soil. When I want to plant I just fold the slits back and loosen the soil. Plop in the plug or seeds and close the slits again.

On the subject of manure for fertilizer or mulch please do not use manure unless you have composted it for a year because of the E-coli bacteria.

Hmm, till-and-plastic-mulch.

I've been thinking for some time about how to encourage weed seeds to spout, but then kill then, to reduce the number in the "Weed Seed Bank" (i.e. the soil).

It sounds like your method would do that.

>> Then in the late winter I till again and lay the plastic back down the black surface warms the soil.

Also, where I live, that would keep the constant rain out of the raised bed soil, if I arranged for run-off down slope.

Except for subsoil wicking,and runoff from upslope into the base of the bed.

Please be careful using manure due to systemic broadleaf herbicides, that are widely used on hay/grain farms. They can get in your soil and make it unusable for years. Yes, ecoli is a problem that can be found in any soil with feces in it but systemic herbicide is brought in on hay or manure so it can easily be avoided.

I used black plastic to cover my entire garden. I covered poison ivy that was hard to get rid of. Mainly, because I am so alergic to it. Then I place my wooden planting boxes on top of the plastic, added my dirt. I have a smooth place to walk on, even barefooted, when I walk around in my garden.