Falling leaves on allotment

[June]

Hope this doesn't sound like a really stupid question....
We've had our allotment since January and when we took it over it was totally covered in plastic sheets of various sorts.
When we came to work the soil I thought it seemed really sour and bereft of any organic matter, worms etc., so I wanted to leave it uncovered this winter and let the soil breathe.
However a fellow plot holder advised to keep it covered as fallen leaves leach poisonous substances into the soil. I'm clearing off most of the leaves for a leaf mould bin as I come to them anyway but has anyone else come across this advice?
Thanks in advance, June

[peat]

your fellow plot holder has lost the plot. Leaves make a good overwinter mulch and help bring back the worms.
Pete

[Jenny Green]

Ditto Peat.
That kind of logic would make all the world's soil poisonous.

[June]

Thanks for the replies. To be honest I thought it sounded like rubbish when he was telling me but some of these long time plot holders speak with such confidence and authority that it seems wrong or impolite to contradict them! Plus I don't want to offend anyone as besides the dodgy advice they somtimes give out very good advice!

[Jenny Green]

Yes, sometimes the old timers advice is good, but sometimes it's based on tradition without really knowing or at least understanding the facts behind what they're saying. Such as the advice to turn up great clods of earth for the winter frosts to break down into a tilth for sowing in spring. There wouldn't be compacted soil if it hadn't been thoroughly trodden on all year. I managed to grow perfectly acceptable crops on my allotment without killing myself every year trying to dig it all (some people enjoy this I know, but I'm not one of them). Sometimes it pays to experiment a bit yourself and not necessarily immediately follow advice (though, as you say, it's nice to listen politely!). Just because something's always been done a certain way doesn't make it the best way.
I hope your fellow allotmenteer doesn't give you a hard time for not raking up the leaves.

[Barry]

A chemist on my old allotment always claimed that covering soil with old carpets actually reduced the fertility. I am not sure I remember his logic, but it seemed to revolve around there being lower levels of nitrogen. I assume because the soil was not open to the air, where I assume most of the nitrogen must come from in the first place.

[Mike Vogel]

June, I think you fellow allotmenteer may be confusing two different things. I do remember reading that leaf-mould is slightly acidic - please correct me someone?? - and so an excess of it may necessitate liming the soil when it comes round to growing brassicas. But that's not the same as being poisonous. All the same, I think you've done well to make a leaf-mould bin; leaf-mould put into the soil in the autumn will benefit your root veg the following year.

mike

[Johnboy]

Hi Mike,
Your posting is correct that certain leaves have an acidic content and some more than others. I know that Oak Leaves will contain a slight proportion of Tannic Acid but certainly not enough to poison anything or even enough to seriously alter the PH of the soil. I think the same misconception occurs when people will not use Rhubarb leaves in their compost. So Rhubarb has a high Oxalic Acid content and because should you be foolish enough to eat Rhubarb leaves they would be unwell but people erroneously imagine that these leaves can poison a compost heap. If you were to compost all Rhubarb leaves and nothing else that may well be a different kettle of fish. The other misconception is that there are no acids contained within an Alkaline soil. Certainly regular liming and I mean once every few years will be sufficient to maintain any drop in PH. If you were to use FYM every year then the PH would be far more affected than a few years of Autumn leaves.
Leaves are best composted on their own because they rely on fungal activity and the heaps do not heat up like the normal degradation process in a normal compost heap composed of herbaceous waste.
To put June's mind at rest let me say that her fellow allotmenteer is totally incorrect and that most of the top soil that we have is largely due beacuse of the addition of leaves on the surface for a few million years.
JB.

[Chantal]

I've just read the article by Medwyn Williams in the Telegraph Gardening section and he says the following:

"We will have an ample supply of leaves for the next few weeks and we need to make the most of them before they get blown away. If the majority of leaves are on your lawn, then you should remove them before they form a thick layer, to prevent possible damage to your grass. Rake the leaves up and either use them as a mulch in borders, after leaving them to decompose for a while, or compost them so that you can dig them into the soil.

The smaller the surface area of the leaves, the more quickly they will break down into organic matter which is why it is good to chop of shred them. You can do this either by running the lawnmower over them, with a bag attached to collect the chopped pieces, or by passing them through a shredder, which really does a good job. After shredding, you can use the fine material to cover over areas of your garden immediately - to protect overwintered carrots, turnips and beetroot, for example. If you go down this path, you need to be aware that the natural breaking down process of the leaves - eventually into humus - will deplete the soil of valuable nitrogen, which will have to be replaced next spring.

In my opinion, the best use for shredded leaves is as compost. The slow way to do this is to place them in a wire bin and leave them for two years, turning the pile occasionally. My method for many years has been simpler and quicker; pack the leaves into black polythene bags and make sure the necks are well tied up. If they are dry going into the bag, then you will need to apply a fine spray of water to help decomposition. Stick a fork into the bag a few times to let some are in, then stack the bags out of the way until late spring. You may be able to use the compost even after that relatively short time; if it hasn't broken down sufficiently, leave it until next autumn.

Another good idea is to add some extra nitrogen. Manure is the best nitrogen supplement,and a mixture in the region of five parts leaves to one part of manure will certainly break the mass down more quickly. Another way to add nitrogen is to put a heaped cupful of dried blood in each wheelbarrow load of leaves."

[John]

If you go down this path, you need to be aware that the natural breaking down process of the leaves - eventually into humus - will deplete the soil of valuable nitrogen, which will have to be replaced next spring.

I think that Medwyn is only partly right on this one. This is only a temporary effect. When you add new organic matter to soil there is a big increase in activity of the micro-organisms there, which will make demands on the available nutrients. There will be increased competition between plants and microorganisms for available nutrients. After a while though as the organic matter becomes completely decomposed, a balance is restored with higher levels of nutrient present, released from microorganism's activity.
For this reason manure and compost should be added to soil in autumn and winter when there is little demand for nutrients from plant roots. The incorporation of the organic matter into the soil is then hopefully complete before plants increase their nutrient uptake in the spring.

John

[June]

Many thanks for the extra info.
I think I must be doing something wrong with my postings as I always ask for notification when a reply is posted. It works at first then I'm never notified of later postings! Anyway, thanks for the advice on helping the leaf mould bin leaves compost quicker. I'm not worrying now about clearing every last leaf from the plot. I'll continue with the bin and let nature take its course on the strays!!

[Colin_M]

This thread of messages reminds what I find so good about this forum.

I have never collected leaves before (sadly, I was never really aware of their value). However last Sunday, I went out with the rake and collected 2 bagfuls. I expect this will rot down to a fairly modest pile, but it's a start.

Thanks guys - keep the pearls of wisdom coming!


Colin

[Allan]

Chantal has been using the word nitrogen when he means nitites or nitrates.In case anybody else thinks that nitrogen in the air is what is in the soil as plant food, it isn't. Let me explain. There is indeed a small amount of air in the soil of which notrogen gas forms four-fifths by volume. Plants cannot absorb this dirctly. It has to be there in a solution either nitrates or nitrites and the ions of either of these salts can pass into the plant through the roots. In making fertiliser nitrogen from the air can be combined with other elements to make the solid salts such as urea, sulphate of ammonia, ammonium nitrate, nitro-chalk etc. These or similar salts also exist in organic 'manures' and have the same effect in producing the leafy growth most noticable in cabbages, for instance.
Allan

[carlseawolf]

i collect the leaves and put them on top of my raised beds untill its time to plant so it saves me doing any weeding then i will make leaf mould for the beds