Mypex or black plastic?

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Barry
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Mypex or black plastic?

Postby Barry » Mon Jan 18, 2016 8:56 pm

Our brand new allotment was carved out of an old farmer's field that had not been cultivated for 20 years.

The pressure group that had persuaded the council to provide an allotment site was organic in its outlook, so turned down the offer of having the ground professionally weed-killered and then ploughed prior to gardeners moving in. The result was that 90% of those who started plots abandoned the project barely half-way through the first season, overwhelmed by weeds and tough old heavy clay.

Having run a similar site in another part of the county, I took on my new plot in July and was horrified to find that I was just about the only person doing anything in the summer.

Since the locals clearly couldn't cope with the ground conditions, I suggested we put down some very large sheets of very thick black plastic to kill the weeds "organically". Indeed, on my own plot, I managed to kill some absolute horrors after three months, with the exception of bramble roots, which clung on.

A couple of other people have used mypex, but over a 12-month period and have been successful at killing weeds, at least on the surface. They should therefore be in a position to start digging in the spring.

My question is this: depriving land of both light and water for extended periods of time ups acidity. Is this right? If so, will applying garden lime help rebalance? Do you think six months of black plastic will irreparably damage the soil, or can we get away with it?

The allotment needs to have clear plots as of the start of the season and black plastic was about the only way of ensuring this! Furthermore, we are on a hill, so even when you take away light and water from above, the water flows - downhill - anyway and therefore gets beneath the plastic, albeit at a depth.
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sally wright
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Re: Mypex or black plastic?

Postby sally wright » Mon Jan 18, 2016 10:21 pm

Dear Barry;
Mypex or non woven membrane (weed fabric) is better than black plastic for the following reason.
It is air and water permeable; this allows the soil bacteria to survive in aerobic conditions. Black plastic will either dry out areas or make them very wet which is bad and it is this which acidifies the soil. Mypex is also stronger and as it will last for many years it can be reused elsewhere. It is good to eliminate light as this that kills off the weeds

Before putting down the Mypex it is good if you can roughly dig over the area and apply a thick layer of compost and or manure. If you do this you can get a crop whilst you are waiting for the weeds to die down. Because you have dug over the area in the spring and applied compost etc the worms and the weather will help the mixing process and make it easier to dig in the Autumn.

The list of plants that you can grow this way is quite long, but by far the best is courgettes, squash and other members of the marrow family. Simply cut a slit at suitable intervals and plant into the compost/manure mix. Other plants include potatoes aubergine, peppers, tomatilloes, tomatoes, celeriac and basically anything that is transplanted. Slugs will make their home under the fabric so take appropriate measures to eliminate them.

Come the Autumn dig over the area and apply more compost; digging at this time is essential on new clay soils as the frosts over the winter will help to break up the clods. If the plants are cleared off soon enough (ie late august) late/ overwintering salads, turnips and possibly a late crop of leeks may be possible. I would not recommend overwintering onions or garlic until the soil is in a bit better condition. By all means try some broad beans if you are on a slope and there is enough drainage.

Lime is only necessary if the soil is deficient but there is a product called clay breaker or agricultural gypsum (this will be cheaper as it comes in bigger bags) which will help to break down the clods if they prove stubborn; please follow the instructions on the packet.

Next year module sow most things as there will not be a fine enough tilth to open sow seeds unless you can use some potting soil in the rows; but I think carrots and parsnips are best left until the soil is in much better nick. Even then try the stump rooted, round or chantenay type carrots and the old fashioned wedge shaped parsnips such as white king and 1/2 long Guernsey.
Regards Sally Wright.
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Re: Mypex or black plastic?

Postby Barry » Mon Jan 18, 2016 11:38 pm

Hi Sally,

Many thanks for your interesting reply and valuable information.

Sadly, I don't think I made it quite how difficult the earth is to work on our new allotment.

I've been an allotment holder elsewhere and can dig anything, but this new site is so tough that even rough digging it would defeat most people. It takes me around 90 minutes to clear a square metre of land of roots, and I often come home feeling as though even I can't go on like this. What hope somebody who has never had an allotment before? It is by far the most difficult soil I have ever worked with.

What I suppose I really need to know is how long it takes land to recover when it has been totally covered for 3 months with black plastic.

We are using mypex in some places for longer term clearance, as noted, but we MUST have 4 - 5 plots absolutely clear by the start of March, so we have had to resort to black plastic, which does the job, but at a cost.

To go back to something you said about black plastic drying out the land and killing the bacteria, surely this happens over summer when heavy clay simply dries to hard concrete and the only moisture available is at least two feet below the surface. I know this to be the case, since I had to clear land during July and August and needed a mattock to get down to that level and there was absolutely no water at all of any kind. This is why the land has been colonised by perennial weeds, whose roots go down to impossible depths to retrieve water.

I fear we are between a rock and hard place.

Regards

Barry
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Re: Mypex or black plastic?

Postby Pa Snip » Tue Jan 19, 2016 7:42 am

Hi Barry

I am intrigued enough to want to know what the members of the "organically based pressure group" that declined the councils offer are doing with their plots.
Have they not set a leading example of how to overcome the problem ?
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Re: Mypex or black plastic?

Postby Barry » Tue Jan 19, 2016 10:37 am

Hi Pa Snip,

I don't think this is really an organic or not approach proving to be right or wrong. It is more a case of naivety in respect of what people who have never grown vegetables before will - or crucially won't - do when faced with difficult working conditions. Most voted with their feet, leaving one organic grower in situ battling aginst the weeds, but still managing to grow some stuff, and a couple of others taking the long term view by laying down mypex for over a year before intending to start properly this spring.

Understandibly, the powers-that-be, which invested both time and money in the project, would like results. And that means getting at least a dozen plots under cultivation this year, which will be about one-third of the total.

Using black plastic should get people clean plots fast, although my one fear is that we may be destroying the soil in order to save the allotment! But there is no other way of getting the results wanted quickly whilst retaining something of the original organic ethos. Soil does recover fast in my experience.

But it is a challenge.

Regards

Barry
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Re: Mypex or black plastic?

Postby PLUMPUDDING » Tue Jan 19, 2016 1:34 pm

If ground isn't waterlogged you could cover the ground with sheets of cardboard, put manure and compost on top and plant into these and just tackle the weeds elsewhere by mowing or smothering them if you don't want to use herbicides. Or you could use raised beds. If you concentrate on small areas and keep them weed free it won't seem such a big challenge. If you build up the fertility on top the clay won't be so much of a challenge. You don't have to double dig or anything to bring it up and if there are plenty of worms they should help take some organic matter down eventually.

Sally's advice is excellent as always, but whatever you use if it is only for a few months the insects, worms and bacteria will recover, especially if you add manure first as she suggests, and if you do a soil test you can adjust the Ph to suit what you want to grow anyway.
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Re: Mypex or black plastic?

Postby sally wright » Tue Jan 19, 2016 7:08 pm

Dear Barry,
I don't think I was clear enough on the rough digging bit. You do not have to remove any of the weed roots, just turn over the soil in big chunks (or little ones if you cannot manage big ones). You will be covering it over to prevent them growing anyway so pulling out potential organic matter doesn't need to happen as they will die and rot down.
Regards Sally Wright.
Ps digging of this kind is often better done with a fork rather than a spade.
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Re: Mypex or black plastic?

Postby peter » Tue Jan 19, 2016 9:54 pm

Genuinely curious about the "pressure group" that persuaded the council to set up an allotment site.

Did any of its members:
    Take on a plot?
    Have gardening knowledge?
    Have allotment experience?

With hindsight the use of a weedkiller, NOT an aminopyralid based one, would have allowed the inexperienced a chance to make all subsequent progress without further weedkiller and more importantly to actually make progress.

Another missed chance would have been, weedkiller, sufficient pause for it to work, then a tractor with a subsoiler followed by a chisel plough. It would have made for "interesting" inter plot paths but again helped introduce people to something they could succeed in without needing to be heroic gardeners. At worst an area treated thus would break down over winter from opened up concrete - clay lumps into workable soil, at best a decent scattering of organic material onto the opened soil would have worked down the gaps.
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Re: Mypex or black plastic?

Postby Barry » Wed Jan 20, 2016 12:31 am

Hi Peter,

This part of Kent has a lot of new houses with very small gardens, hence many residents clubbed together and petitioned the council under the 1908 act to be allowed to have an allotment, of which there are none in the parish. Finding an appropriate site took almost five years to do and the whole process was, apparently (since I wasn't around) very frustrating, with neither side seeing eye to eye on certain aspects, including whether to use weedkiller and then plough.

I respect the stance taken by the petitioners: they wanted an organic site, but none of them had any experience at all of this type of gardening, so it was a case of "be careful what you wish for". Similarly, the council had never run an allotment before.

I first moved here last summer. Nearly all the people that had been involved in the original project had gone (there had been around 40 petitioners), including most of the key committee members. One organic gardener and one who used lots of Roundup survive from the original petitioning group, although a couple of others are still around but yet to start.

I'm now trying to use my experience in running allotments (I headed the team that rennovated this allotment in Dartford:
https://tredegarallotments.wordpress.com/ which was also down and out when I arrived there some seven years ago, but was brought back to life thanks to a terrific team of people helping me) to get the new allotment kick-started.

I too would have taken your approach in weedkilling and then ploughing. I'd possibly have waited a year and applied more weedkiller given that, even though we clear existing weeds, the ground must be smothered with seeds, so we shall all spend much of the coming season weeding just to stay in the game!

As noted above, it does, at times, become too much. An hour and a half sanitising a square metre of soil is plain daft, but I'm having to do it in places, although have deployed mypex, plastic and weedkiller on different sections of my plot as well.

But, when all is said and done, we have a brand new allotment site and there are many out there that don't, with waiting lists in areas around here that go on and on... At times, I wish we could turn back the clock and start again, but we are where we are and I do love a challenge :D

Regards

Barry
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Re: Mypex or black plastic?

Postby Ricard with an H » Wed Jan 20, 2016 6:05 am

Hello Barry, you made me feel very small with the description of your problems just creating some suitable land to grow stuff on. Even when the weeds are sorted it'll still be hard work and in my short experience we never-ever really Winn against perennials.

In the three years I have been gardening I spent three years moaning about stones, weeds, wind and moles yet compared to you I had an easy time.

Huge respect Barry.
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Re: Mypex or black plastic?

Postby peter » Wed Jan 20, 2016 7:44 am

Good on you Barry. :D
In my mind the originsl group was one of two things, religiously green, or, naive.
Looks like the latter :( which when it collides with reality sees many new allotment holdets walk away.
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Re: Mypex or black plastic?

Postby Barry » Wed Jan 20, 2016 11:37 pm

Thanks for all the encouraging words.

It is interesting to note that nobody in either the council or the petitioners had dealt with allotments before, so obviously they were bound to make mistakes. The people asking for the allotments have my full respect, though, since they had to battle hard to get a site and were successful. I know nothing about this part of the whole allotment process and there aren't that many new allotments springing up in the UK, are there? So hats off to them.

If you were trying to start up an organic allotment site, how would you do it in terms of preparing the area prior to letting plot holders start growing? How, in other words, do organic farmers clear ground if they can't use weedkiller?

I think I would have started out here by simply placing huge sheets of mypex over about a quarter of the site for 12 months and only then let people take those plots. Not all the perennial weeds would have been killed by that, but the majority would. I would then have covered up another quarter, then another quarter and then the final quarter, probably opening the allotment over a 4-year period, or something like that.

To give you an idea of one of the huge mistakes that was made out of sheer naivety, a lot of the clearance of the site was done by the petitioning group. This involved cutting down brambles and then burning small heaps of them in the area where they had come from. Within six months, that whole area had been covered with brambles again. Naturally, the potash from the fires was simply absorbed by the blackberry roots (which were not dug up!) and the plants grew back even stronger than before. Some of the members then protested that the new canes didn't produce any fruit, showing they don't understand that berries are only formed on two-year-old wood.

Actually, despite the folly of the slash and burn approach, the HUGE brambles that resulted have been brilliant in that they have suppressed many of the other weeds that were growing amongst them, which has meant that when I get bored and go and help clear the plot next door, it is actually easy, since all you have to do is hack out the main root and most of the land is then useable. If only there had been something similar to kill all the twitch!!!
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Re: Mypex or black plastic?

Postby Motherwoman » Thu Jan 21, 2016 7:20 am

Just read this thread, my goodness what an inappropriate allotment site they chose!

I have tackled a garden that was lumps of solid yellow clay, I didn't go down the covering route at all as I've seen the 'slap' effect from loose plastic which pats down the surface and makes the ground sour. I gave it a shallow turnover to get out the 'big stuff' and over the course of about 10 years laid down as much organic matter on the surface as I could get hold of. I planted in little pockets with plants germinated in pots during this time and stuff grew very well, clay can be a rich soil. I kept weeds down by hoeing the top layer.

Good luck with it Barry, I think you're in for a long, but ultimately satisfying, haul.
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Re: Mypex or black plastic?

Postby Johnboy » Mon Feb 01, 2016 1:36 pm

Dear Barry,
I have used heavy duty black polythene since it first became available which is now more years than I care to admit and I have never ever come across any sign of acidity of the soil. The soil here is PH7 which means that it is neutral and areas of my plot has been under black polythene for years.
As far as I am aware any Mypex I have ever used has been a woven fabric and unless covered with something like pea shingle any persistent perennial weeds left under the membrane will eventually find their way through the weave especially couch grass.
I am lucky that I have a constant inexhaustible supply of manures and compost and before the black polythene has been laid down the soil has been in productive use and a layer of around 3" of manure is spread and allowed to become saturated by rain. When the polythene is finally lifted the worms have taken 99% into the soil. Even with the manure I have never experienced acidification of any kind.
Perhaps Sally may be kind enough to PM me and give me some readings I may persue as regards acidification caused by black polythene.
Sincerely,
JB.
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Re: Mypex or black plastic?

Postby robo » Mon Feb 01, 2016 2:15 pm

I think I would hire a tractor and plough for a weekend, no matter how much you cover the soil in plastic you still have to dig it eventually, when we first got our plot at the time it was only half a plot I was 3 weeks of solid hard work turning over an area 10 feet square and it did not get any easier as we worked down the plot it just got wider
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