[Blowin]

Towards the end of last summer, as I lifted the crops from a particular area, there were already weeds poking their heads up so I placed a large sheet of black polythene, probably 4m x 8m, over the whole lot and weighed it down with blocks.

After something like 8 months, I took it off a few weeks back and was faced with a completely weed free patch (the intended result) and a beautifully friable soil that just needed a rake over to prepare it for sowing/planting. The only 'livestock' I found was the odd slug. Presumably, with no rain to compact the soil, it's remained loose and, similarly, nutrients won't have been taken down deep into the subsoil, hence no need for green manure.

Having cleared the last of my spent borecole plants, I piled up large quantities of lawn mowings on part of the plot and moved my polythene over to cover all of it, weeds and all, but this practice seems so perfect, space permitting, that I'm wondering if there might be a down side that I don't know about? Can anyone provide an answer or have I hit a mini-jackpot?

[maigheomac]

Sounds like a great way to do it. I would say you will get a great crop with all the lawn mower fertilizer.
My soil is like tar when wet and concrete when dry so for the first time this year (and to save my back the digging) I rotivated the lot.... it made an absolutely great job of the soil. It is now like powder, ten years of digging would not have given me soil this good.....
Anyway, only down side is that I have multiplied/spread the weeds. Maybe I will use your polythene approach next year... Good luck with the season ahead!!

[James Kilkelly]

Blowin, you've done something the the garden chemical manufacturers would prefer nobody finds out about.
Expect a visit from a hitman in the next few days......

[Greengage]

now look what you've done, given away a big secret, monsanto and Dow will not be happy I think James should ask you to leave the site for giving away the big secret.

[kernow]

Some years ago I took on an allotment (in England) and the weeds were waist high ( I think it must be a law that no allotment is rented until they are that high) I was advised by some of the more experienced to forget this years growing and to cover the entire site with cardboard (weighted down) old carpet or black plastic. I did that and ended with weed free site. All it needed then was the communial (?) rotavator and then I was in business.

[medieval knievel]

i thought covering the soil with plastic was a well known trick?

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74145.html

[Blowin]

Thanks all of you, particularly the last post with the scientific explanation which I read with a lot of interest.

I'm glad I started the thread.

[My Potatoes]

The term for this is "mulching". We normally associate this term with surrounding plantings with bark, compost, fabric, etc. to suppress weeds and retain moisture. But it is also used for blanket covering ground with plastic such as black polythene.

I've done it for years and it works great. It prevents weed growth on vegetable beds over the winter. It also kills weeds on future beds; it takes about six months to achieve this but the weeds are completely killed off and their roots are dead and weak, leaving the soil clod free.

Also, as it's impermeable, though it might have been raining for weeks the soil underneath is dry and workable (which will not be the case if you use fabric/Mypex). Should you need the rainwater elsewhere (such as a pond) it can be easily diverted.

The only downside is if the wrong plastic is used. It needs to be thick, impermeable and opaque. I know of people that have used light black polythene, no heavier than a supermarket poly-bag. Such light polythene gets pulverised by the rain, leaving shreds of plastic everywhere. You need to use thick heavy plastic. It can be bought in most builders providers; it comes with a gauge but I'm not sure what the value is.

Soil Sterilisation is a completely different practice relating to IPM.

[Good guy]

A good source of suitable polythene is your local farmers co-op. Ask for a small silage cover. In my experience its the cheapest way of buying the right stuff.

[medieval knievel]

[My Potatoes]