Tuesday, 17 February 2015

Permaculture Design Course with Geoff Lawton

So, I have started the online permaculture design course with the greening of the desert man Geoff Lawton.

What do I think of it?  It is a very intense course with a very steep learning curve.  A lot of the information I had heard of before and had a general understanding, however the detail that the course goes into is quite daunting.  Some of the terms used such as energy and entropy are on the edge of scientific definition and, although this could be irritating, it is still understandable within the context of permaculture.

Some of the concepts such as; 'always make the problem the solution' and 'gardening can solve all problems'  I like!

Even though; I still cannot find a solution for Equisetum arvensis that does not involve removing it completely from the garden.  There must be an easier way of controlling it and working it into a viable sustainable system.

The best thing about the course is that you can see what is being talked about and there are a number of good examples where people have got it right and everything is working together.  Is it a cliché  to quote the Loess Plateau in China?

Also, I was pleased to see that Geoff uses a tractor and plough to turn over his main crop vegetable garden.  Appropriate technology as Mollison would say.

What is the downside?  The culture of the celebrity is such an irritation.  Geoff Lawton knows things that I would like to know and he explains things quite succinctly. After more than forty years of experience he gets things right more than he gets things wrong.  This does not mean that he should be 'celebritised'.  The comments that verge on the sycophantic irritate me to distraction.  

I have stopped reading the comments now.  I know that I should be joining in with the chatter but I really don't find it a learning process.    Maybe I am just a grumpy old man.

So, is it applicable to cool temperate maritime climates?  Definitely.

Let's qualify that a little.  We have it easy in the Uk because there is rarely a scarcity of water on the allotment.  If there is a lack of rain, then water capture and storage in water butts can usually be counted on to provide enough water to see most plants over the drought.  I rarely water any of my vegetables and still get a very good crop.

For many years I have been cursing the three springs on my old allotment garden.  I drained the soil with commercial drainage pipes not really realising the fantastic resource I had.  Just thinking about the flushes of vegetation around springs should have alerted me to the potential but I had never connected the springs on my allotment to those flushes on the hillside.

Accepting that in the Uk we do not usually have a lack of rain water, there are still benefits to controlling water flow on the allotment.  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.

Also, having my comfrey bed at the bottom of the hill on the old allotment meant that all the nutrients washed down by water from the allotments up the hill could be taken up and harvested. This is what I am going to do on the new allotment but probably using a much smaller catchment area.

Water is not really a limiting factor in the UK although light is.  I really don't want to plant on contour.  The planting rows need to be running north to south so that plants can get maximum light.

Saturday, 7 February 2015

Concrete slabs are slippery beggars.

As the soil has been rock hard due to the frosts, I decided to get the last of the concrete slabs from the old allotment.  They are two inch thick two foot square slabs.  I have some two inch three foot by two foot slabs but these are far too heavy to be moved easily.  They are really evil beggars and will fall on your foot as soon as look at you.

So what safety precautions did I take before attempting the move?  Steel toed boots were worn.  I got these for the RHS practical gardening course and they are invaluable mainly because they keep your feet warmer than wellingtons.  However, I was glad of them yesterday.

Thick gauntlet gloves enables you to grab hold of rough surfaces without tearing your hands and I wore them.

I could have used my slab trolley but it was easier to walk the slabs down the path and that was my downfall.

Although the ground was rock hard in most places, down the side of the old allotment was very wet due to the spring on the top half.  So the slabs got very wet and muddy as I was walking them to the car.  I have a technique to lift the slabs into the car that involves using my leg muscles rather than my back so I was not worried about how to get them into the car.  I had put an old pallet in the car to make sure the weight was evenly distributed over the back axle.

I got the slabs into the car without incident, which is good because there was nobody on the site except for me and, if I had an accident, it would have been a little worrying as I found out later.

I got to the new allotment without incident and had a think before I did anything.  My gloves were caked in wet soil which was very slippy.  I have at least three pairs of gardening gloves in the shed so I went to discover which hidey hole I had hidden them in.  (I hadn't hidden them, however it always seems that I have because I can never find anything in the shed.)

First pair I found were the very big ones that I lost and this was the reason I bought the new ones. Well now I know I have two good pairs of garden gloves. The problem with the big gloves was that soil kept on falling inside them and filling the fingers.  I could not fit my little fingers in because of the soil in them.  I hit each of the fingers with the hammer to crush the solid lumps of soil and they fell out quite easily.  So a good pair of dry gloves.  No health and safety problems.

I go back to the car and begin taking out the first slab without any problems, put it on the ground using my leg muscles and walked it down the path to where I was going to use it.  Same with the second slab.

However, the third and last slab decided to be a little more irritating.  The lovely dry gauntlet gardening gloves had become caked in the slippy soil from the other slabs and I didn't have as much grip  as I had on the  other two slabs.  Taking the slab out of the car, I felt a sharp pain in my back and thought I had better put this down quickly and carefully.

It slipped out of my gloves and onto my foot, which was no problem due to the steel toe cap. However, I had lost control of it and it slid right down my leg scraping the skin.   That could have been worse, however my back now had a pulled muscle,  a discomfort that still persists, I have a bruised foot and a grazed leg.    

Just as at the old allotment, there was nobody  on the new allotment site. Fortunately the slab was on the side of the trackway and out of the way of any vehicles that needed pass by.  So I made my way home as best I could.  Sitting and lying down are the most painful so I am walking around and standing quite a bit at the moment.

So what lessons have I learnt?

Keep your mobile telephone fully charged all the time and take it with you to the allotment.

Always have someone with you when you are moving concrete slabs especially this time of the year when there are few people that brave the weather to work on their allotments.

I was very glad of wearing my steel toed boots because the accident could have been much more serious if I hadn't.

Always wear dry gloves when moving slabs.  I could have got another dry pair out of the shed if I had been thinking clearly.

Concrete slabs are evil beggars and need to be treated with respect.

Do not think that you are still 19 and can do everything because you are getting older.


Monday, 2 February 2015

Nitrogen fixing bacteria.

Atmospheric nitrogen is notoriously unreactive having a very strong triple bond between the two atoms in the molecule yet it is vital for all living organisms.

The bacteria and probably the archaea are the only organisms that can ‘fix’ nitrogen from the atmosphere.  Some of these bacteria are always free living like the Azotobactor.  However, it is suggested that free living nitrogen fixing bacteria do not contribute significant amounts of nitrogen to the soil.

Rhizobia are free living heterotrophic bacteria that can form symbiotic relationships with leguminous plants.  There are many different species of Rhizobium; some which can form symbiotic relationships with many plants and some which are specific to certain plants.  They are nitrogen fixers but only when in a symbiotic relationship with a leguminous plant.

Some non leguminous plants can form symbiotic relationships with other genera of nitrogen fixing bacteria; such as alder with Frankia alni.

Rhizobia are able to fix nitrogen from the air using the enzyme nitrogenase.

These  bacteria are able to produce ammonia from atmospheric nitrogen and plants can use this to make amino acids and eventually proteins.  Nitrogen fixed by bacteria can also be used to make plant nucleotides.

Nitrogen is used to make amino acids that are the building blocks of proteins.  The majority of cell components in bacteria, fungi, plants and animals are made from proteins.  Contrary to the common misconception, lettuce does contain protein.

As the nitrogen fixed in this way is essential to the plant and bacteria and has been gained through the expenditure of lots of energy, none is lost to the rhizosphere.  However, nitrogen is lost as proteins when cells are sheared off during root elongation and possibly by protein rich root exudates.  There is a great turnover of roots and when they die they add nitrogen to the soil in the form of proteins and nucleotides.

However, the greatest amount of nitrogen is added to the soil when the plant dies. The proteins and nucleotides in leaves, stem and roots are decomposed by bacteria in the soil releasing the nitrogen originally fixed by rhizobia.  This nitrogen enters the soil and is available for other plants to take up. A proportion of the Rhizobia in the root nodule escape back into the soil when the host plant dies but they will  not be able to fix nitrogen when living in the soil.

So, this is why you need to dig in the tops as well as the roots of your peas and beans.  Do not burn the tops or you will loose all your hard earned nitrogen in the form of nitrogen oxide gases.

Saturday, 31 January 2015

Dynamic Accumulators? This gobbledegook does nothing for the reputation of permaculture.

I have been using comfrey, both Symphytum officinale and Symphytum x uplandicum, as a green manure and liquid fertiliser for about forty years now without knowing it is a 'dynamic accumulator.'  Henry Doubleday and Lawrence Hills both researched and promoted the use of comfrey as a fertiliser.

Comfrey leaves in the butt.
The comfrey butt is a large water bin, which contains lots of comfrey leaves rotting down and producing a dark thick liquid.  I also add Urtica dioica and Myrrhis odorata to the mix to add a little variety.  These leaves rot down in the butt to a liquid that can be used as a fertiliser.
Comfrey liquid being collected from the butt.

Myrrhis odorata added to the comfrey butt
Comfrey growing and green comfrey butt.

I find the term 'dynamic accumulator' confusing. I cannot find any scientific research papers that refer to dynamic accumulators.


There is a lot of information on various different permaculture sites with long lists of dynamic accumulator plants. However, there is no referencing to scientific research or an indication of whether all these suggested plants are of any use at all.  Ken Thompson's book (2006) "Ear to the Ground" says that comfrey is rich in the big three mineral nutrients, nitrogen, phosphorous and potassium. However, comfrey is not unique in this and some plants may be a little better including Stellaria media, Urtica dioica, Myrrhis odorata, Chenopodium album, Gallium aparine and Alliaria petiolata.   

One of the advantages of using comfrey is that it all rots down very quickly producing a very humus looking liquid which is easily diluted and applied to the soil with a watering can.  However as White (2006) says in his book "Principals and practice of Soil Science"; 'The long term effect of green manuring on soil organic matter is minimal since the succulent residues are rapidly decomposed and contribute little to the soil humus.  Similarly, beneficial effects on soil structure through the stimulation of microbial activity are ephemeral.'

It is suggested in permaculture that dynamic accumulators are deep rooted and obtain their nutrients from deep in the soil.  I can find no research that indicates that deep rooted plants have a higher proportion of nutrients than shallow rooted ones or where the nutrients have come from in the soil profile.  Indeed,  Urtica dioica is not deep rooted but it is a valuable addition to the comfrey butt.

I do not confine my additions to the compost heap to those plants with deeply penetrating tap roots. I put all sorts of plants on the heap.  They all accumulate nutrients - they have to to live.
I am told that grass mowings are high in nitrogen and you have to do all sorts of complicated things to compost them as a result; and grass has very short adventitious roots.

Why is turf so fertile and why does grass seems to accumulate relatively 'large' amounts of nitrogen? Many monocotyledons start off with a normal 'root' as they germinate but this soon withers away and is replaced by adventitious roots that form from buds from nodes at the crown. These adventitious roots are very fibrous and form a dense sward full of roots. This denseness of root compounded by stolons, rhizomes and ramets seems to be a highly efficient Hoover of nitrogen. One could call it a dynamic accumulation; however I would not use the word dynamic in relation to plants without taking a lot of advice. The point is; short, thin, fibrous roots accumulate relatively lots of nitrogen compared to long, thick tap rooted ones.

The term may have come from the study of plant nutrition and the storage of heavy metals in plant cell vacuoles.  Some plants can accumulate high levels of certain heavy metals and these plants are called metal hyperaccumulators.  Some hyperaccumulators can live in highly polluted soil and can be used to remove heavy metal contaminants.
See Prasad  (2003) "Metal hyperaccumulation in plants- Biodiversity prospecting for phytoremediation technology"

There are other plants that are tolerant of heavy metal contamination but these do not store large quantities of heavy metals within their leaves.  They regulate the uptake of these metals through control measures in their roots.

Whether they have deep tap roots or adventitious roots seems to be irrelevant.   McCutcheon & Schnoor 2003 in , "Phytoremediation." New Jersey, John Wiley & Sons pg 19 say that mustard is a hyperaccumulator of strontium, cadmium, caesium, nickle and zinc - and mustard roots seldom penetrate subsoil.

There is evidence that elements such as potassium are lifted up the soil profile by the action of some pine trees in Argentina.  Also the lifting of manganese by eucalyptus trees.    These elements are taken to leaves and stems and deposited on the soil surface when plants loose leaves, loose branches or die.

Jobbagy and Jackson (2004) "The uplift of soil nutrients by plants; biogeochemical consequences across scales."

However, all plants have some heavy metals within their structures and will deposit them on the surface of the soil when they die or shed leaves. That is why chop and drop is an effective way of adding nutrients to the top soil.  To say some plants do not accumulate nutrients seems to be illogical.  They must do to grow.  We are also talking about tiny, tiny amounts even of the major nutrients like nitrogen, phosphorus and potassium so the relative accumulation of nutrients is a comparison of milligrams.  What are we comparing anyway the amount of nutrients accumulated by an oak tree compared to comfrey?  I think that I know which would be the dynamic accumulator in this comparison.

I know there has been research done on Symphytum officinale and Symphytum x uplandicum but has there been any research on other plants?
Hills L.D. (2008) "Comfrey:Past, Present and Future"
Hills L.D. (1955) "Russian Comfrey Report No1"

Hills did indicate that he thought there were other beneficial plants that could be used for fertiliser and at least tried to do this systematically.
See http://eap.mcgill.ca/publications/EAP67.htm

From the blog "One thing leads to another"
https://portageperennials.wordpress.com/2014/03/18/nutrient-accumulators/
It seems that people are just repeating gobbledegook and just like  a game of Chinese whispers adding plants to lists as their flights of fancy takes them.
This does no service to permaculture.

All plants accumulate nutrients but not necessarily in the same amounts, however the amounts are minute and differences may not be significant.  Comfrey is useful because it decomposes quickly and the resultant liquid can be used easily to fertilise the ground.  Comfrey does not necessarily have "more" nutrient than any other plant.

Tuesday, 27 January 2015

Destroying Soil Structure

I have been busily destroying soil structure; killing microbes; and depleting nitrogen from my allotment soil today.  ( Am I just being facetious?)
Taking out the second spit 
The second spit was taken out of the trench and used to make the path behind the large shed.   The fork was used to break up the bottom of the trench another spit deeper.  I was still removing mare's tail rhizomes even from this depth.
The wooden edging supports had rotted
away so I had to replace them.  
Either there was a hard pan or I had reached the bed rock because there was a hard layer beneath this which I broke up as much as I could with the fork.

Once the trench was big enough, lots of organic matter could be buried.  In this case several branches; lots of rotten processed wooden planks and bits of wood, tops of herbaceous perennials; cardboard and non rhizomal weeds.  This is a little like hugelkultur.

Guaranteed to produce nitrogen deficiency? 
This rough organic matter was covered in
subsoil and leveled out.
Can you add too much organic matter to your soil?  This amount of undecomposed organic material is sure to deplete the soil of nitrogen locking it up in the bodies of microorganisms and fungi.
Partially decomposed woody chippings 
So I added six barrow loads of woody chippings for good measure.  These were leveled and worked into the subsoil. Was this enough organic matter to cause nitrogen depletion?
Adding comfrey liquid to the trench.
A watering can full of neat comfrey liquid was then watered over the woody chippings to add a little nitrogen.

Six inches of top soil were put on top of the chippings and leveled. Then four barrow loads of farmyard manure were added to the trench.  I will cover the farmyard manure with sieved top soil and a little chicken manure tomorrow to a depth of at least 30 centimeters.  Probably enough organic matter now to cause nitrogen depletion.

Have I been causing nitrogen depletion?  Although most of the scientific papers I have read are ambiguous about this, I probably have caused some nitrogen to be locked into the bodies of microorganisms.  However, most of this is happening in the subsoil where vegetable plant roots do not normally penetrate and thus will not affect cropping.  I am adding organic matter during the winter allowing it time to rot down and add some nutrient to the soil  for the summer months.  The nitrogen that is being scavenged by the microorganisms and fungi during decomposition has been mainly leached from the top soil. So this gives me a means of capturing any nitrogen losses that might occur from the top soil.

Therefore I am; adding nutrients locked up in organic matter; capturing leached nitrogen from the top soil; increasing the cation exchange capacity of the soil, and increasing the population of soil microorganisms which all lead to increased fertility.

What goes around comes around.  I will continue to add copious amounts of organic matter to the soil by digging.

So, have I destroyed my soil structure?  The soil structure is how sand, silt and clay are arranged in soil particles and how they adhere to each other in aggregates.  It determines the bulk density and the water and air filled porosity of the soil.  (How well it drains and allows oxygen to enter - among other things) This is what some gardeners call friability of the soil. Experience and reading has convinced me that adding organic matter to the soil produces lots of humus that will aid in the forming of useful soil aggregates; increasing water and air filled porosity and reducing bulk density. To destroy the existing soil structure  moisture, clay and organic matter needs to be removed. Wind erosion, takes away the lightest soil components of clay and organic matter.  Mulching prevents this from happening particularly in hot climates.

In temperate countries such as England the ground is seldom dry in January and I am adding copious amounts of organic matter.  Although I don't think that I am destroying the existing soil structure because I am not loosing clay, organic matter or moisture; soil aggregates will continue to be produced through adding organic material.

Soil compaction occurs when soil particles are squashed together reducing air and water filled pores.  This can occur on allotments when the ground is very wet and walked over.

However, I sieve the soil through an old bread tray which brakes up large sods of soil allowing organic matter to be thoroughly mixed in.  The sieving adds lots of air, and by default oxygen, to the soil which aids in the decomposition of organic matter. Most of the organic matter is being mixed with the subsoil where there is little evidence of any previous organic matter.  When the added organic matter decomposes, it forms a very friable, top soil like material. Thus I am deepening the top soil.

Therefore, I would suggest that I am increasing water and air filled porosity by encouraging the formation of additional soil aggregates.  I am improving the soil structure.

There is some evidence that cultivation reduces the number of soil organisms.  For example, the population of worms is greater in grassy swards than in tilled soil.  This I can understand because, although the proportion of worms killed during digging is very small, there are some that inevitably die because of the operation.  However, there are copious amounts of worms living in the woody shreddings and farmyard manure and these are being added to the soil.  In addition any worms I find in parts of the allotment that are not growing areas - in storage areas, under the hedge and under paving slabs of the path - are put onto the top soil in the trenches to find their own way into the soil.  All these worms may not be species that live permanently in top soil, however a population of some of these species may find a more long lasting habitat because of the amount of organic matter I add to the soil each year.

The difference in population of worms seen in cultivated and grassy areas may be due to a habitat preference by the worms rather than a result of digging. Also the number of worms in compacted soil of paths seems to be much greater than in cultivated soil.   So worms seem to like soil with a relatively high bulk density.

Digging may well reduce the numbers of fungal hyphae in the soil.  However, the amount of fungal hyphae on and in the rotting wood added to the bottom of the trench was prodigious.  Not only have I added a significant number of hyphae, I have also provided a source of nutrition for them to use and reproduce in.

Whenever plants are planted in the allotment, I add mychorrhizal fungi spores to alleviate the possible reduction of fungi due to cultivation.  It is now suggested that there are plenty of mychorrhizal fungi already in the soil and adding spores is unnecessary.

Well you can't have it both ways.  Either I am reducing the amount of fungi in the soil through digging and need to add more spores to ameliorate this or digging has no effect on the soil population of fungi and adding fungi spores is unnecessary.

I will continue to add mychorrhizal spores.

Microbes are far too small to be affected mechanically through digging so they are probably only affected if the soil is allowed to dry.  Even this will only lead to them going into a more resistant dormant form.

Digging does not sterilise the soil.  The reduction of organic matter through erosion; addition of excessive nitrogen; mixing in of oxygen and stimulation of the microbial element leads to sterilisation of the soil.

I am told in a round about way not to increase the population of soil microbes by adding undecomposed organic matter because this leads to nitrogen being locked away in their bodies.   I am also told not to dig because it reduces the numbers of microorganisms.  Therefore it is bad to both increase the number of microorganisms and also to decrease the number of microorganisms. You can't have it both ways.

Some heterotrophic microorganisms are autonomous nitrogen fixers which add nitrogen to the soil. Their energy source is the dead organic matter in the soil.  These are the Azotobacter, Bacillus, Clostridium and Klebsiella. While it is suggested that they don't contribute a great deal of nitrogen to the soil, every little helps.  Adding organic matter to the soil will increase the populations of these anaerobic bacteria.

I will continue to add organic matter.

And I will continue to dig.