Thursday, 13 November 2014

Hugelkultur - burying woody material. (1)

Spent quite some time digging on the allotment today.  The trenching on allotment 3A is going well if a little slowly.  The top spit of soil is being sieved carefully with a little chicken manure.  The second spit, clay subsoil is being taken out and put into the wheelbarrow. This subsoil is being used to make the paths where the topsoil has been removed.  The path top soil is being used in the trenches to replace the removed subsoil. The theory of replacing top soil for subsoil on the paths is to produce a path that is less likely to encourage weed growth. I am mixing in a good quantity of stones sieved from the topsoil to the path subsoil to make a more substantial and long lasting construction. The Victorian gardeners used clay and sandy subsoils to make their kitchen garden paths and I wanted to see if I could make as good a job of it as they did.  The paths at Attingham Park in Shropshire are a clay stone construction - particularly the one running along the river from the mansion.

The bottom of the trench is being forked over a spit deep before anything is added.

This trench hole has a layer of  Hedera helix and Corylus avellana prunings from the hedge. Other trench holes will have Crataegus monogyna prunings added to the bottom spit.

Ivy prunings together with hazel twigs.
The coarsest woody material goes at the bottom.  This is probably best because it keeps it out of the way when the top soil is being cultivated.   This material has a lot of air spaces in it and the increased porosity introduced to the subsoil will enable excess water to drain away quickly.  The woody material itself will become more and more absorbent as it begins to decay retaining water and releasing it to the crop plant's roots when the soil is dry.

Shredded ash tree
A load of mainly Fraxinus excelsior was delivered last week and is being added to the trenches. About six inches of shreddings is covering the Hedera helix brushwood.  About 18 inches of top soil is then raked over the shreddings.

Shreddings nearly fill the trench
This procedure raises the level of the topsoil surface about 6 to 10 inches higher than the original level.  

In most descriptions Hugelkultur is a single row of logs or brushwood with top soil heaped over them to make a humped raised bed.  There is a great deal of anecdotal evidence that this is a fairly effective method of producing a bed in which vegetables can grow well.  If it works for raised beds like this then it will work throughout the allotment garden.  The whole allotment is being or has been trenched like this and woody material added to the subsoil raising the level of the topsoil. Extra topsoil from the paths is also being added to raise the level of the topsoil further.  

I don't raise beds with Hugelkultur; I raise whole allotment gardens.  

The next trench hole had composted bindweed, mare's tail and couch grass added with some rotten wooden planks thrown on top.  10 inches of shredded ash tree covered the planks.  Now it may be dangerous to add perennial weeds like these to the trench even if they have been composted for some time.  However, they had made some particularly friable compost and not using this to improve the soil would be perverse.  

So I am giving it a go just to see if any of the weeds return to haunt me.  If they do then I will have to dig them out but that is no different to what I am doing now with the trench digging.  

From my experience it would seem that processed wood is just as good as logs, branches, brushwood and shreddings for making Hugelkultur beds.   Any useless decaying processed wooden planks are being added to the Hugelkultur trenches as additional carbon sources.  

I have moved one of the blue water butts to the end of the little greenhouse to catch more water from the gutters.  I have put a rope from the gutters to the bin because the water will follow and flow down the ropes into the water butts.  

On Saturday I will continue trenching with Hugelkultur until I run out of wood chippings.  

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