Rain "mulch"

This topic contains 10 replies, has 6 voices, and was last updated by  Ken Adams 2 years, 11 months ago.

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    Hi All,
    I am setting up our no dig beds here in Pembrokeshire.
    It is chucking it down here, again.
    This has got me thinking about how much goodness gets washed out of our beds during the winter. I am sure I have enough area to keep my winter plants in certain areas allowing me to cover the rest with plastic sheet. I am thinking this will keep in the goodness of the compost, keep out the light and keep out the excessive water. Just wondering what other people think about rainwwater leaching?



    Hi Wellies,

    According to Charles, the nutrients in ripe compost is NOT water soluble, and thus does not get washed out by rain. I use black plastic cover when establishing new beds, on top of the compost mulch and pasture, to block out all light and rain (i’m not really sure why Charles recommend keeping out rain when establishing new beds, but is expect it is beneficial for the decomposition of the compost into readily absorbable nutrients and soil micro life and structure in general (fungi etc)



    Ken Adams

    I haven’t visited the forum for a while, but here I go again.

    Firstly – I have seen Charles’s comments that the nutrients in ripe compost are not water soluble. Another point of view is that the nutrient value of compost is not its main purpose and, in any case, compost is so variable in its makeup that its nutrient value is hard to guess.

    Secondly – I have only recently started to get active with my partner’s lifelong interest in gardening and my understanding is divided between (a) my partner’s very ‘old school’ approach and (b) more recent ideas (which I have only read about) about how best to look after the soil. After only two years ‘experience’, I cannot claim to know what I am talking about!

    However, my suggestion to Wellies would be to consider growing some green manure. It’s a bit late right now but if, next autumn, you are anticipating that there will be an area of bare soil over the winter, then green manure may be a good way to defeat rainwater leaching whilst also establishing networks of all sorts of good things in the soil. Not only will the green manure protect the soil from physical assault, it will also take up the nutrients which might otherwise be leached. Additionally, a deep-rooted green manure will lift nutrients which might not be otherwise available to the following year’s crop(s).

    Some will say that green manures need to be ‘dug in’ but, actually, all you need to do is cut it down and cover it in the same way that you cover a new no-dig bed.

    I think that Charles’s main resistance to green manure is that he prefers to be growing vegetables as intensively as possible but I don’t think that maximum yield is everybody’s top priority.

    Good luck to us all! Ken



    Hi Ken,

    Basically I can’t see the benifits of growing green manure. My thinking is that the greenry takes out nutrients from the soild when growing, and after decomposing, the same amount of nutrients is returned to the soil, i.e. netto addition of nutrients is zero.

    Growing deep-rooted green manure might be beneficial to the soil structure on very compact and heavy soil, but i think applying no-dig and adding an anual mulch of compost will give the same benifits – mayby after a few years.

    I could be wrong 🙂




    Rain water leaching doesn’t concern me in my veg growing personally. With a thick mulch of compost I am happy that my winter beds are sufficiently ready for spring planting and sowing as is. Plastic sheeting can’t hurt…other than encourage slugs in our damp climate. This relates to green manures too as the slimey critters enjoy vegetation to live in – another potential reason for not bothering with them on a small scale allotment etc.

    Green manures can be very beneficial though depending on your circumstances and different green manures bring different benefits. Elliot Colman is convinced that the roots of grass do something very beneficial to soil, especially for a following veg crop. He grows on a larger scale though than most of us and often combines green manures with veg crops – but in a drier climate.

    Chap called Pete on here from years ago grows a lot of green manures very successfully and Iain Tolhurst does this too, with his vegan veg ethos.

    There’s a lot of variables….it’s up to you and possibly your time constraints. Good luck with the coming season.


    Ken Adams

    I think that Green Manuring is as controversial as No Dig Gardening and, arguably, they are both part of the same set of ideas. Lots of gardeners use rotovators and packaged nutrients and Charles appears to use neither – but his compost includes quite a lot of imported raw ingredients. Charles’s priority is maximum yield with minimum work and who can argue with that? Charles is a commercial grower.

    As far as I can understand these things, growing green manure is not primarily intended to increase the availability of nutrients – its purpose is to prevent the unnecessary loss of nutrients whilst protecting the soil from surface erosion and improving sub-surface soil structure.

    I may be wrong, but I think that all forms of cropping will remove nutrients in the short term – if we want to grow vegetables intensively, then there has to be a way to quickly replace the previous crop’s depletion of nutrients. Deep-rooting green manure might be a part of the answer – simply ‘Not Digging’ will not, on its own, create a source of fresh nutrients.




    This is kind of a vicious circle. Surely ,as if energy, nutrients cannot be ‘created’ ,but simply transferred from one crop or place, to another, or ‘mined’ from the mineral soil. Imports from other places supplement the circle (like a working capital).
    It is very difficult to become 100% self financing. Yes, one might grow composting materials on extra land, but that only delays the issue. Does it matter that a given plot is self sufficient? Do any of us really have time in our lives to be so ‘puritanical’ ,so as to be’smug’ in knowing that we make no demands of others?


    Ken Adams

    Hi Cleansweep – I take your point but I think I would prefer to regard gardening as a game of ‘swings and roundabouts’ rather than as a ‘vicious circle’!

    Iain Tolhurst (mentioned by Stringfellow earlier in the thread) is very focussed upon trying to eliminate the need for brought-in fertility. He farms a dozen or two acres on vegan principles and operates a 7 year crop rotation two of which are devoted to green manuring which, presumably, has zero cash value. But he appears to have no problem at all with using all sorts of diesel-powered machinery. I highly recommend his book ‘Growing Green’ which is refreshingly non-dogmatic whilst setting out a huge amount of information and knowledge for gardeners and farmers alike.

    My own point of view is that, if we wanted it to, our allotment would probably be capable of growing enough vegetables to satisfy all the requirements of our entire extended family throughout all twelve months of the year. But it is easier, cheaper, and much more reliable, to go down Tesco’s.

    As a 70-year-old newbie, I am mostly enjoying learning about composting and managing the soil and eco-systems. Right now, most of the plot is still covered by permeable membrane but there are three beds of roughly 2 metres by 2 metres which look really nice. One of them is ankle deep in lush green growth which has survived the winter and which should soon start to produce masses of poached egg flowers to attract the bees etc. The other two mini-plots were sown last November with field beans – they took a long time to come through and they are still widely spaced and I am not yet convinced that they will be a useful green manure. But they definitely look much nicer than permeable membrane would have done.




    Interesting comments here, thanks. Over the long term we are now saving money by growing our own in quantity but it would certainly be easier to use the supermarket! However, you’d miss all those other lovely benefits of growing your own food, my primary two motivations being health followed closely by taste.

    Regarding green manures equalling a zero sum return, wouldn’t organic matter and fertility have never naturally increased any where if this was the case? Energy is taken in from the sun and you end up with a physical addition to the soil – possibly a bit like the difference between taking a vitamin and mineral supplement instead of eating veg/ fruit that provides both the former and with the addition of fibre too.

    It’s nearly time for the gun to go off, although it seems Charles has already started! Enjoy the coming season all.



    Nice comment Stringfellow. And I started a bit early because of other commitments this weekend, am in Sussex just now.
    On Wellies original question, undecomposed manure/slurry/dung/fresh poo does leach nitrogen.
    Compost in my experience does not, judging by subsequent growth over long periods. Compost which is not necessarily perfectly ripe, but mostly decomposed, it’s not a black and white definition.
    And yes green manures are great if you don’t want maximum output. But they are work to manage, leave often a residue of slugs and take time to decompose under a mulch. Except for mustard Synapsis alba, killed by frost.
    Green manures add organic matter, which is often overlooked in discussions which centre on nutrients.
    Lastly membranes… I don’t like them, so polluting unless handled carefully (threads) and with no dig you don’ need it.


    Ken Adams

    Hi all – for me, this conversation is becoming extremely interesting and useful.

    Charles said that ‘undecomposed manure/slurry/dung/fresh poo does leach nitrogen’ and I think it is true to say that all of those things are uncompromisingly ‘green’ in their contribution to any kind of composting process. But a thick mulch of, for example, comfrey leaves would be specifically intended to ‘leach’ its chemical constituents into the soil in the same way as a re-incorporated green manure. Obviously, a thick mulch will also suppress the growth of unwanted plants (weeds) and also provide protection against physical soil erosion. Maybe we need to make a distinction between leaching nutrients ‘into’ the soil and leaching nutrients ‘out of’ the soil!

    Charles also says that ‘green manures add organic matter, which is often overlooked in discussions which centre on nutrients’ and, for me, this relates directly to the idea of making comfrey tea etc. I don’t yet understand the purpose of soaking comfrey leaves in water and then pouring the water into the soil – why not just place the leaves directly onto the soil?

    Finally (for now!), I also don’t much like using plastic sheeting and, last October, I covered a 4.5 metre by 2 metre bed with thick cardboard and lashed it down with netting. Right now, the appearance of the cardboard has hardly changed but, if I touch it, it has decomposed into little more than a thin smear which easily rubs into the underlying soil. My partner’s intention is to use this bed for growing potatoes in the conventional manner and I am tempted to remove the netting and spread a layer of chopped up green leaves and grass cuttings etc in order to complete the decomposition of the cardboard.

    Tomorrow’s job is to get my newly-bodged 6’x3′ cold frame out of my son’s back yard and over to the allotment – most of the family will be involved and I daresay there will be a well-earned pint or two afterwards.


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