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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.
Ken
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.
Ken
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.
Ken
The allotment which my partner and I took on three years ago is clay and I am struggling to persuade my partner (who is a life-long gardener and regards me as a troublesome retiree with too much time on his hands) to consider some of the newer ideas which I keep reading about.
I managed to persuade her to use some permeable membrane to protect what would otherwise have been bare soil over winter and I planted two small areas with green manure. I’m working very hard to create lots of compost and I’m hopeful that my partner is coming round to the idea of protecting the soil as lovingly as she tends the plants.
There is a neglected half-sized plot close to ours and I have applied to take it on so that I can use it purely to create green manure to use on the main plot and in the compost bins. If it works out, I would plan to set up a four- or three-yearly rotation whereby one third of our total square meterage would always be used for growing manure.
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