Sunday, 5 March 2017

Finishing off the hugelkultur in the potato bed.

Due to the inclement weather recently, which has cost me the roof of the peach greenhouse, I have not been able to complete the hugelkultur I started a couple of weeks ago.

The was no rush to finish it but I wanted to make sure that I had enough time to prepare some of the other beds for planting and sowing.


I had to clean the crumbs out of the bottom of the trench because the rain had washed the sides in.  Two spits of top soil were taken out of the trench and put onto the side in separate piles.  The bottom of the trench was carefully forked over another spit deep.

Then brushwood, weeds, crop residues, and logs were put into the bottom.  Composted woody shreddings were then put over the logs until the trench was nearly filled.  I got the woody shreddings from under the frames.  I moved the frames in front of the greenhouse, which will be their permanent location for the rest of the season.  Quite a few of the lettuces were still growing well but not big enough to make a sizeable meal yet.  I decided to put them into the frames about a foot apart to grow on into the spring. The radish, which was still growing well and forming good roots, I have taken home to eat.


I will have plenty of composted woody shreddings so I will not have to use any of the fresh material in the piles by the gate.

I have planted several of last year's grafts alongside the growing beds but not put espalier posts in to train them to.  I was going to have to buy them from Dobbies.  One of the blokes along the way is giving up his allotment and he came over to see if I wanted to take some of the stuff off his allotment so he did not have to take it home or to the tip.

There were several good posts which I could use to make espaliers out of plus more that I can use to support the sweet peas.  Sometimes you just need to about at the right time on the allotments.

Fetching the stuff off his allotment meant that I did not have time to complete the hugelkultur.  It just needs filling in with the topsoil now.  Although the hugelkultur will be raised I will still plant across it.  The high end alongside the espaliered fruit trees.

I have  made he high side two feet away from the trees so the base of their trunks will not be buried in the mound.  I will slope the other side into the growing bed so that I can plant at right angles to the trench.  This is so  I am able to plant the potatoes northish and southish and get the full benefit of the warmth and light from the sun.  It will also enable me to see the effect of the hugelkultur because the potato row will start on the raised area and go down into the ordinary soil of the bed.



While doing all of this, I have continued to turn the compost bins and even though they have not really become very hot during the winter, they have produced some reasonable compost.  I am going to sieve it and put it onto the top soil piles before they go into the hugelkultur trench.  It will mix in with the topsoil as I drag the soil in.

I have also planted the garlic, elephant garlic, shallots and red onions in the allium bed.  I still need to plant the onions but that can be done tomorrow.  I am planting them in planned four foot beds with a two foot shredded woody material path between them.  I am only putting a thin layer of shreddings down for the path because I did get some nitrogen drawdown last season.  Digging a trench and filling it with shreddings for paths is a little excessive.  Four or five centimeters is more than enough to keep feet clean and dry.

Furthermore, I have put concrete reinforcing wire over the pond to make it a little safer for the grandchildren.  I thought afterwards that it will be difficult to get a net through the mesh but I am not going to take it up now.  I will have to put the wire through a pipe to prevent the mesh from breaking it.  I took the opportunity to clean out the bottom of the pond and put the sludge on the compost heap with the thinnings of the water plants.  The mint around the sides of the pond have been cut back quite hard and I have taken out some of the other plants.  More rocks have been put around to cover the plastic sides.  I looks a little more presentable now and will look good in the summer when all the plants grow up.

So really, I have a good excuse for not finishing off the hugelkultur - as well as the rain.

So if the rain keeps off I will complete the hugelkultur tomorrow and then go onto planting onions.  I may use some of the composted shreddings to mulch the onions with.  They did particularly well with fresh shredding mulch last year.  I will also cover all the alliums with scaffold netting.

It was a lovely day today but rain is forecast again for tomorrow.

Saturday, 18 February 2017

Starting off a new Hugelkultur in the potato bed.

Bloke came down with a lorry load of shredded woody material and had some logs on the back as well.  He gave me the logs so I decided to make another trench Hugelkultur in the potato bed.  I wanted to raise the soil at the north end of the bed in order to create a surface water calming bank alongside the espaliered fruit trees.  The Hugelkultur trench will be a subsurface water calming structure until it decomposes. 
I dug down one spit today and left the soil on the side of the trench.



I always use garden lines because I can't keep a straight line without them.  There are lots of reasons for not digging but there is no other way of introducing large quantities of organic matter and deepening the top soil.  I will take another spit out of the bottom of the trench and then fork over the bottom which will give me three spits of turned over soil.  Loads of waste material from around the allotment will be used to put into the trench. 

The old vegetables from last season.  A few celery and celeriac together with carrots and beetroot. 

Old bits of wood that I have collected from under the hedge and in the woody chippings piles.  I will probably get some more before I fill in the trench.  I will certainly clean the bottom of the hedge a little more. 
The logs off the lorry.  These will go at the bottom of the trench.  I think they are mostly cherry laurel. 
I will move the frames off the hot bed, which has not been that hot during the winter.  The woody chippings have rotted down now and will go at the bottom of the trench.  I will put the frames on top soil now and just rely on the glass to heat the soil.

If that is not enough shreddings, I will resort to the woody chippings pile to add more woody material.
Mostly X Cupressocyparis laylandii and holly but it is all grist to the mill.  I will also be putting the cuttings from my daughter's garden in the trench too.  It will all be two spits down and can moulder there for a year under the potatoes and whichever green manure I plant after them. 

The top soil is deepening and now is more than a spit deep.  The subsoil is darkening with organic matter too.  Deeper topsoil means more organic matter, more nutrients, more microbes, more water and more air for vegetable roots to delve into. 

Now I am going to try and explain why I think that it is a good idea to introduce organic matter into the subsoil as deep as I can.  In normal conditions plants can get water and dissolved nutrients easily from the top soil.  There is usually decomposition going on and nutrients being released.  As drought conditions start to appear the roots start to forage for water lower and lower in the soil profile.  The dry top soil means that they cannot obtain nutrients from here because there is no water to dissolve them in.  Nutrients can only enter the root as dissolved ions.   As the roots pass out of the dry topsoil they pass into the moist but infertile subsoil where nutrients are much more scarce.  Little is dissolved in this water and although the plants have adequate water they begin to get nutrient shortages.  Bottom old leaves start to yellow as nitrogen is transported away to the growing tips, although the plant is not wilting.  If we can deepen the soil, adding lots of organic matter, it will make plants more able to withstand drought conditions and the shortage of nutrients that it might bring.

So that's what I have been doing today - that and turning one of the compost bins.  I will use the compost to mix in with the top soil as I rake it back into the trench. 

Wednesday, 8 February 2017

The possibilities of using slope to benefit the allotment.


My allotment slopes to the south east.  What advantages does that give to the allotment crops?  The aspect of the allotment can give quite an advantage.  Being south facing means that the sun's heat and light is a little more concentrated and will warm up the soil earlier in the year and allow crops to be grown later in the autumn. 

Path alongside the allotments looking down the south facing slope.


Although I grow crops in north south rows,  I have put in paths from east to west at right angles to the slope.  The paths have been made as mini ditches and soil has been taken out and put onto the growing areas to raise them.  The mini ditches are aligned more or less with the contours across the allotment.  Water will flow at right angles to the contours soaking in as it does.  Some surface water will flow into the ditches and spread out.   I have filled the  ditches  with woody shreddings which will soak up some of the water and prevent it from evaporating creating a reservoir of stored water. 

Espaliers planted on the top of the raised bank.



This allows surface rain water to be spread out evenly along the path, slowed down and soaked into the soil.  Although irrigation is not a particular priority in the UK climate, we still have to consider the effects of leaching and soil erosion. 



Raising the level of the soil, creating banks on the downside of the slope and planting espaliered fruit trees or soft fruit along the east west raised soil aids in the slowing down of water (mass flow) through the soil.  As the water is slowed, it allows dissolved nutrients to be taken up by plants before it is lost though leaching. 



As plant nutrients are soluble minerals they will be leached slowly as the water flows to the bottom of the slope.  I have planted comfrey at the bottom of the slope to catch as much leached nutrient as I can.  Their deep roots will absorb much of the available nitrogen and any potassium and phosphorus that is available.  The leaves and stems of the comfrey can then be composted, made into comfrey liquid or put into the worm bin to recycle the nutrients. 
It is all about slowing the mass flow of water through the soil.  This will slow leaching, allow more time for uptake of soluble minerals; capture eroded soil particles, enhance water filtration  and provide more opportunity for upward water capillary action for plant growth.


My compost heaps are at the top of the slope so that any leachate that they produce will flow down the slope and into the allotment soil.  In a similar way, I have planted perennial nitrogen fixing legumes along the top of the slope so that any nitrogen they fix will flow naturally into the allotment top soil.  I will be planting perennial legumes alongside the fruit trees and bushes on the banks alongside the paths so that nitrogen will flow with the water into the growing areas. 

Compost bins at the top of the slope so that leachate will flow into the allotment.



Laburnum and lupins planted at the top of the slope so that nitrogen they fix will
flow into the allotment growing areas.

In the UK there is often too much water flowing through the allotment.  It is necessary to put in some kind of drainage to prevent waterlogging.  I have dug out a trench at the bottom of the allotment and filled it with stone sieved from the top soil.  The stone was covered with paving slabs to make a path alongside the hedge. 
Drainage ditch under the slabs.  Path is at the bottom of the slope.   



During the driest months in summer, the soil is covered by mulches to reduce evaporation and the trench Hugelkultur further slows the soil water and retains it as a reservoir that is accessible to plant crop roots. 

So slopes can be very useful. 

Wednesday, 18 January 2017

Is mulch made from conifer wood chip or bark acidic?

I have seen it often suggested that organic mulches such as wood chip and bark from conifers is acidic.  The pH is a measure of the amount (the negative log of the concentration)of hydrogen ions and this measurement must be done in a liquid.  You cannot measure the pH of a solid unless you dissolve it in water.  As most of the solid from wood chip and bark  is insoluble in water, it is virtually impossible to measure the pH of these materials.



The woody chippings or bark could be giving off substances that acidify the soil solution as they decompose.  However, neither pine bark nor pine chippings have been found to have any effect on soil pH.  (Tahboub, Lendemann and Murray 2008) There is no significant change in soil pH for wood chip incorporated into soil measured over a three year period.   Bare soil is more likely to have a low pH (be acidic) than organic mulches.  Shredded bark and woodchip have been found to be the least acidifying of the organic mulches.

Regardless, wood chip could be shaken up in water and the resultant solution tested.  This should be done with distilled water or deionised water to make sure that you are testing the pH of the dissolved substance not the pH of the water.  Tap water contains a lot of substances although it usually has a neutral pH of around 7. 

Now, I haven't tested the pH of  woodchip solution, however I would conjecture that it would be fairly neutral or possibly slightly alkaline.  There are some that suggest that the phenolic substances secreted by the above ground structures of a plant may be acidic. I don't know. 

What I am going to do is test the soil beneath an estimated 2000 year old yew tree.  The tree is in my local nature reserve.  There is nothing growing under the tree within about a 50 food diameter. 

I would suggest that the pH of the soil is no different from the rest of the wood so I will take samples from outside the yew trees influence as well as under its canopy.  After 2000 years of falling litter surely it would have affected the soil underneath it. 

My suggestion is that there will be no difference between the soil pH from beneath the canopy of the yew tree and the soil from outside the canopy.   

The fact that there is no build up of litter under the tree would suggest to me that some invertebrates, such as worms, are feeding on the organic matter from the tree.  Worm's preferred habitat is one with a neutral or alkaline pH.

Usually scientific consensus is pretty solid, however sometimes explanations that purport to be scientific are merely based on hearsay and anecdote and need to be challenged by experiment. 

Sunday, 15 January 2017

Too much mulch?

It is self evident that if you cover a plant completely with mulch you will kill it through lack of light.  This is one of the benefits of mulching - weed control.  However, what is the correct amount of mulch to apply to crop plants? 

There is a lot of advice to suggest that heaping relatively large amounts of compost around fruit tree trunks could cause the trees to die.
http://www.mortonarb.org/trees-plants/tree-and-plant-advice/horticulture-care/mulching-trees-and-shrubs.
There is a reduction of oxygen diffusing through to lenticels and reaching respiring cells below bark in the trunk.

Now I went along with this until I though, hang on a minute.  When I put woody cuttings into soil or compost, there is a similar reduction of the free flow of oxygen to growing cells in the woody stem of the cutting.  Lenticels are covered in the same way.  So how do cuttings survive this treatment? 

My rooted willow cuttings from stems just pushed into the soil. I put quite a bit of woody
mulch on these too.
I have just been turning the composts today and found some woody stems I threw in  from the willow.  They were right in the middle of the compost and merrily throwing out new growth. 
Layering woody shrubs would not work if this were correct and we would never get Irishmen's cuttings. 
For an explanation to have credibility it must be consistent with all the data collected. Inconsistencies must lead you to question sloppy explanations. 

So here is another piece of data that does not really fit in to the " not too much mulch" hypothesis.  I tend to heap compost, manure and woody chippings around my soft fruit bushes.  They do not die throwing out lots of adventitious roots into the compost.  A little irritating because this means that the roots need to be covered again when the mulch decomposes and they are exposed. 

Blackcurrants and rhubarb with a thick woody shredding mulch.


Blackcurrants with a thick horse manure mulch.


I think that much more tree and shrub death occurs from poor planting practices than the addition of too much mulch. 

Brussel sprouts with a thick woody mulch to stop them from falling over.
Mulching brassicas with compost or hoeing them up does not kill them.  I do this to stop them from flopping over.  The Brussel sprouts produce adventitious roots that root into the mulch or soil. 

Having said all that, I have found that it is unnecessary to add more than a couple of centimeters of woody shreddings to get all the benefits associated with mulching.  Adding more does risk substantial nitrogen drawdown.  This immobilisation of nutrient does have an affect if excessive woody shredding material is used for mulching.