Friday, 4 October 2019

Compost: how to retrieve an unrotted pen

I'm very strict with my composting: all my Clients are encouraged to build a proper 3-pen system (you can read more about it here, if you wish), but from time to time I am presented with what you might call "failed composting" and asked how to put it right.

This week, I was asked to sort out a double problem: one of the three compost pens had been used for an excess of lawn clippings back in early summer, and had then been used as a dump for the long grass from the meadow area. This, needless to say, was not rotting at all (*bites tongue to prevent the "I told you so!" escaping*), and the Client was disappointed in it.

Then, the second half of the problem: the Client had collected a huge pile of bags of horse manure from a friend, about a year and a half ago, and was confidently expecting them to be lovely rich manure. But alas, they were not. Back in April I had inspected these bags, and had pointed out that they were almost bone dry, mostly because they were good strong plastic bags with no holes in them, but partly because  the contents were far from being proper "muck heap" horse poo: they were in fact stable sweepings, meaning that they were dry wood shavings with great clods of unrotted poo in them, like a sort of deranged, disgusting, bran-tub lucky dip.

We tipped the bags out, back in April, into our leaf mold pens (which were, of course, not in use back then) and watered them well, in the hopes that they would rot down once exposed to the elements - like being in their own, rather small, muck heap.

But now it's autumn, and I want to start using the leaf mold pens, so it was time to check out the horse poo.

Well, they'd made some progress: the large clods had mostly broken up, but there was still rather too much wood shaving visible for my liking.

And that leads to a point I should make: if you start at the bottom, and build your compost heap up by adding in a bucket load of weeds and debris every day or two, then you will never have this sort of problem. Problems arrive when people add too much of any one material, all in one go. This is why grass is the "usual suspect" for failed compost heaps, because people do sometimes leave cutting the grass, for various good reasons ("too busy"  "been away"  "mower broken"  "couldn't be bothered..."), and then when they do finally do it, it generates far too much material for the brandlings to deal with.

So, what to do, with my two heaps of unrotted material? Answer - bearing in mind that I'm making this up as I go along - I decided to combine the two horrible heaps into one, layering them alternately (and wetting them as I went), as suggested by nearly all of the gardening books.

As an aside, have you ever noticed the way that gardening books, when describing how to make compost, all seem to assume that "one" has a large amount of several different types of materials, all sitting around just waiting to be neatly layered into the compost pen, alternating "greens" and "browns", of course.

Out here in the real world, we have to pile on whatever we have just weeded out, as and when it arrives!

Anyway, just for a change, I had two piles of non-rotted materials laying around doing nothing: the grass is very definitely in the "greens" category (ie soft nitrogen-rich material - nothing to do with the physical colour of it), and I'd certainly classify wood shavings as "browns" (ie not nitrogen-rich, but adding texture and minerals) so I started to clear out the grass-filled pen, ready to do some lovely layering.

*waves excitedly" "Hey, Brigid, look, I'm doing a lasagne bed!" *  (My friend Brigid is heavily into eco and organic gardening, and is always telling me about her lasagne beds! OK, this is not quite a lasagne bed, but I've always secretly thought that the whole "lasagne" principle is just a fancy name for composting....)

Here we go then: oh dear, not a pretty sight.

The top layer was the long grass and of course it was dry, black, and unrotted, despite me having thrown buckets of water on it every time I visited, for the last four months.

So I heaved it all out onto the grass.

This revealed:

Urgh, an even less pretty sight: the lawn clippings from back in early spring, which are still, to this day, bone dry.

The dark streaks are where, this morning, I emptied some buckets of water onto the heap (having not realised that I was going to be asked to dig them out....) but those dark patches are superficial, and all below it is dusty and dry.

Sometimes, grass clippings get so hot that they seem to smoulder, and they almost look like ash - but it's actually just super-dry dead grass.

So, out it all came, in great flat plates and wodges.

Having found the ground level, I then started replacing it all, layering dry-as-ash grass,  long-and-dry grass. and not-very-well-rotted stable muck, and wetting each layer as I went.

In a sneaky bid to give this pile a head start, I foraged around in the "proper" compost pen adjacent to it, and added in a few handfuls of actual rotting material, with brandlings (red wiggly compost worms) as well, inbetween various layers.

I have no idea if this will work: I'm  hoping that even if the adult brandlings die off, there will be sufficient eggs in the material surrounding them to start new colonies, once the heap warms up.

Here's the finished article: the pen is six planks high, so it is just over half full, which is pretty remarkable when you think that it was four planks full of grass when I started, and I've added at least three planks-worth of horse muck.

Which just shows how dry it all was: it's the moisture which makes compost material reduce in volume, which is why a properly-working compost pen never seems to get filled up.

Right! I shall leave it now, for a couple of months: the Client has strict instructions not to add any material to the top of it, but to leave it to get on with things, so we shall see what happens! 



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  1. What a joy to read about your composting exploits. I am sure you have concocted a recipe for success. As for watering in of each layer, I would just have run a hose over the finished pile and let gravity and capillary action take it from there.

    1. Ah, but interestingly, Mal, you are wrong: and you have made such a good point, that instead of trying to explain it within this tiny comment box, I'll do a whole new article about it!


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