Friday, 23 June 2017

Small Pond Installations for Irrigation and Wildlife - Part 2 - Liners

Welcome to part 2 in a series of posts covering the installation of small irrigation and wildlife ponds. Part one can be found here and covers planning and digging a pond.

During this post we'll look at liner options and the steps you need to take to install a liner for your pond.



Lining the pond in Ataraxia

Pond Liner Options  


The majority of ponds will need some kind of liner to stop water seeping into the surrounding soil. For ponds in lowland with a high water table on clay soils, or ponds with a perennial source of water that can flow into and out of the pond, a liner is not necessary, but for rain fed (either direct or via roof/land catchments) ponds, or for ponds with an ephemeral source of water in climates with long dry seasons, a liner will be needed.

We commonly use tri-laminate LDPE liners for our ponds as they are relatively light, easy to install and good value.

Tri-laminate LDPE liner


However, there are a variety of pond liners available to suit your site conditions and budget and before looking at how we install our liners we'll go briefly over the options starting with the natural liners.    


Natural Liners


Puddled Clay - Using clay to line a pond is a great idea if you have the right kind of clay soils on the location of the pond or very near by. Otherwise given the large quantity of clay required the excavation and transport costs probably make it not worth considering. You also need to be sure you have a constant water level if using certain clay that will shrink and swell. This is because when the water level drops cracks will appear and water will drain into the cracks when it refills.

Clay cracking when water levels drop 

Another thing to consider if you are adding a clay layer on top of permeable soils such as sandy and stony soils is that aquatic plants with expansive rhizomatous roots such as reeds, sedges, watermint and yellow flag can easily damage the clay layer creating holes that will lose water.

Some soils are unsuitable for clay . Gravelly, silty and peaty soils are affected by ground water and move. The puddle clay will also move, resulting in cracks and leaks.


Bentonite Clay Liners are a composite product manufactured using the naturally occurring Bentonite clay resource. The powdered Bentonite clay is sandwiched between a woven and non woven geotextile, resulting in a very strong robust product. The biggest advantage of bentonite is that it can self-heal and expand around punctures if it’s installed correctly. The biggest disadvantage is that it's relatively expensive, extremely heavy (making delivery costs high) and often heavy machinery is required to place the liner.   

Gley The idea behind a gley liner is to produce an anaerobic layer in the soil underneath the pond that forms a bio film that should prevent water from soaking into the soil. It's something I came across in the Permaculture Design Manual and having tried it on three occasions I can safely say it does not work.  

Following instructions for the gley method we applied approx 2 tonnes of manure to our pond in the Paulownia garden, covered this with a layer of vegetation and added a further cover of  tarps and carpets. It did not hold water and we eventually added a tri laminate LDPE liner.

Synthetic liners 


Tri Laminate LDPE - These are the liners that we use for our ponds. They have two basic benefits – they are very economical, and they are tear proof and flexible so can be used to line ponds with various depths, shelves and peninsulas i.e wildlife ponds. The liners are made of low density polypropylene and they are made to last for years.

Tri Laminate HDPE HDPE geomembranes are tough and non-flexible. In cold weather conditions the handling of HDPE geomembranes is a big handicap and not being very flexible they only work on basic shaped ponds.

Rubber Liners - like LDPE these liners can be easily shaped to fit the unique contours of any pond, thus allowing more design flexibility. There are two main types of rubber liners EPDM and Butyl. They are both synthetic rubber membranes and both liner types have similar properties despite having different chemical compositions. EPDM is a less expensive product to manufacture and as a result its popularity has surpassed that of Butyl. EPDM pond liners are guaranteed fish-friendly and they don't contain any additives or release chemicals that affect fauna or flora. These liners are slightly more puncture resistant than the LDPE and HDPE and PVC liners.

PVC pond liners – PVC pond liners are usually around 0,5 mm thick. The liner is stretchy and flexible , however it's not tear proof, so if the material is punctured, it may get worse over time.  They are more expensive than LDPE and HDPE but just as vulnerable and more so to UV exposure,  so I don't see much upside to this liner.

Preformed fiber glass pond liners – As the name suggests, these liners are preformed. You dig the hole to fit the shape. They are relatively expensive and are probably one of the easy ponds to install.

Cost comparison for Liners 


I made a quick cost comparison for a 18 m x 18 m liners. It's by no means exhaustively researched but it does provide a fair representation of the varying costs of liners.    


Liner Price based on a 18m x 18m liner
324m2
Price per m2 Source Notes
Rubber Liner - Butyl£1,940.76£5.99http://watergardeningdirect.comnot including delivery
no underlay
Rubber Liner - EPDM£1,710.72£5.28www.aqualinersdirect.co.uknot including delivery
no underlay
Bentonite Clay Liners£1,101.60£3.40www.bentomat.co.uknot including delivery
no need for underlay
PVC £842.40£2.60www.aqualinersdirect.co.uknot including delivery
no underlay
Tri Laminate LDPE£533.60£1.65ebay.co.uk including delivery and underlay
Tri Laminate HDPE£223.56£0.69China - Alibaba
(could not find a European source) 
not including delivery and customs tax 


We've been using tri laminate LDPE liners in our ponds for the last 6 years and have lined 4 ponds with it.  The first pond we made still holds water well although I expect that the ground under the liner will have formed a natural impermeability by now due to anaerobic microorganisms creating a bio film. 

Our first pond 

I've noticed that the material does weather when exposed to sunlight so we keep the liner covered with a layer of sand/soil and this also provides good rooting medium for aquatic plants. Wildlife appears to flourish in the ponds and I have no reason to believe the material is toxic in any way.  

Wildlife from our ponds 


Sizing the liner 


To calculate how big your liner needs to be you can use the following equation.   

Length + Depth + Depth + 2m = Length of Liner
Width + Depth + Depth + 2m = Width of Liner

You can find an online pond liner size calculator here  in imperial and metric units :) 

Often the ponds we create have varying depths and beaches as we are designing habitat into the ponds. In this case you can take the longest length, depth and width to be sure you have enough liner. The off cuts are useful for doubling up areas of the pond that may receive foot traffic or for creating very small tyre ponds.

Tractor Tyre pond lined with an off cut from the main pond liner 


Applying  the liner


Here are the steps we took to line the pond. For how we dug the pond and planning the location of the pond see our previous post here.

1. Remove sharp stones and other debris 
2. Level the banks of the pond 
3. Establish the outlet and overflow management 
4. Add Protective Underlay 
5. Place the liner 
6. Fill the pond 



1. Remove sharp stones and other debris 


Remove all stones and sharp objects from the area where the liner will be placed

Just one of the piles of stones we removed from the pond.



2. Level the banks of the pond 


Following the excavation it's a good idea to allow and deposited soil around the edges of the pond to settle. 2 weeks is adequate time for the soil to settle.  The next step is to level the bank of the pond .


Using a transit level we go around the pond perimeter adding or removing soil until we have the same level all round.


3. Establish the outlet and overflow management 



Create the outlet of your pond (where the pond will overflow). It's very important you have considered where the pond will overflow and have managed the overflow properly to avoid the water causing damage on or beyond your property. In our case we made a 2m x 1m marshy bed that drains into a 10m long by 1m contour swale that can disperse and overflow into the fields below planted with perennial crops. 

The outlet -  We then lowered the area of the wall that will serve as the outlet. In this case we made the outlet a 30cm wide channel that is approximately 10 cm lower than the rest of the wall.   

4. Add Protective Underlay 


If you have stony ground like we had on this pond, you can spend days removing the stones only to unearth more below. In such cases I recommend adding a layer of vegetation or straw, old clothes or carpets before adding the underlay. The idea is that this layer will decompose and form an anaerobic bio film that will prevent seepage if the stones happen to puncture the liner.

15 cm layer of straw applied to the surface 

Now is time for the underlay that generally comes in rolls. We placed the underlay along the longest side and overlapped each section by at least 20 cm and then taped the sections together. Working on a calm day without wind is a good idea when placing the underlay. Soaking the rolls in water also helps as the material is heavier and falls into place easier.


Rolling out the black carpet. 

5. Place the liner 


Unfold the liner and pull it into place ensuring you have adequate overlap on the sides. Push the liner into place to hug the contours and ease out any small wrinkles and neatly pleat any larger folds.

Liner in place with adequate overlap and folds where they should be.


Do not start work on finishing the pond edges until the pond is full. This is because as the pond fills with water the liner will be compressed to fit the pond floor and sides, and some slack on the edges allows the liner to move without stretching.  When the pond is full you will also be able to see whether your levels are correct and make any final  alterations before adding the pond border detail and fixing the liner to the border.

6. Filling the pond 


We filled the pond by diverting a stream from a nearby river. We channeled the stream to the pond and buried the liner under the channel to direct the water into the pond. The pond can hold approx. 150 m3 and took over 40 hrs to fill.

Here you can see the water just about to enter the liner  that is buried under the channel 


The stream is diverted onto the liner and the water flows into the pond. This pond took over 40 hrs to fill 

Almost full

If you would like the pond for wildlife then adding a bucket of water from a nearby wild pond will provide a range of microorganisms, aquatic plant seed and aquatic animals. Aquatic life is very fast to establish and in no time the pond will be full of aquatic insects.

It's best to keep the water level right to the top but this is not always possible. This will require regular topping up in summer as evaporation can reduce the levels. A pond liner that is exposed to the elements will have a shorter life and be more prone to mechanical damage.

Once the pond is full you can check you have the bank levels correct and make any adjustments that may be needed before adding the pond edging.

7. Edging The Pond Banks


The excess liner can be trimmed off allowing at least 50 cm of overlap that can be tucked under to provide a double layer around the edge of the banks. We have lots of stones and boulders around our site and place these on top of the liner and fill the gaps with sand and smaller stones. This makes the pond look natural and protects the liner from harmful UV from the sun.   

Rock borders with plants well established in  our wildlife pond 

For this pond we'll be experimenting with cascading plants such as Vinca spp. and Hedera spp. placing them around the edge of the pond to cover the exposed liner. More on that in part 3 where we'll be looking at wildlife habitat and planting out the pond.

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References 


  • Geosynthetic Clay Liners Bentonite - http://www.bentomat.co.uk/
  • Clay Liner - http://www.gardeningmasterclass.co.uk/how-to-garden-ponds/puddled-clay-ponds/
  • PVC vs HDPE http://www.geomembrane.in/comparison.html
  • Pond liner calculator - http://www.pondlinersonline.co.uk/pond-calculator/ 

Wednesday, 7 June 2017

5 Ways to Prepare Beds for Tree and Shrub Planting - Which One is Best?

During this post we will be looking at various ways to prepare beds for planting, specifically for planting trees and shrubs. I'll introduce you to a trial we started this spring where we're looking at 5 different bed preparation methods to see which method works best. We'll go through how to implement each method, why they are useful and finally look at the criteria we are judging the effectiveness of each method by.  We'll start with an introduction to the trial garden where we are undertaking this comparative study.

In April 2017 we began the development of our new trial garden (Ataraxia). The garden will be used for a range of perennial polyculture trials and experiments in order to discover the best practices to produce nutritious affordable food while enhancing biodiversity.


Ataraxia - Balkan Ecology Project-  New Polyculture Trial Garden


The first of our trials begins with the development of the planting zones. We want to discover what is the best method to establish a planting bed for the perennial plants such as fruit trees and shrubs and perennial vegetables.  The aim of the trial is to discover methods that are inexpensive, time efficient, least disruptive to the existing wildlife and that provide the optimal conditions for the incoming plants.

When planting trees and shrubs into grassland or fields previously used for agriculture, I prefer to prepare the area at least 6 months ahead of planting, 12 months is even better. We often prepare the planting zones in early spring for late Autumn planting.  I call this "advance planting preparation".

Advance Planting Preparations - (APP) 


What is it ? - It's basically the addition of organic matter into the planting zone 6 - 12 months before planting to improve soil conditions for the incoming plants. This can be in the form of mulches that suppress existing growth and decompose in situ or in the form of green manures that replace the existing growth and improve the soil. 

Why do it ? - 

 The benefits for advance planting preparations include the following :-
  • Mulches - It's generally acknowledged that early succession plants such as grass and forb prefer bacterial dominated soils whereas trees and shrubs prefer fungal. By preparing soils in advance of planting you can alter soil conditions to that which trees and shrubs are more accustomed to. A great way of shifting the soil ecology from bacterial to fungal is to deep mulch the planting zone with high carbon material such as wood chip (preferably ramial wood chip) or with straw at least 6 - 12 months before planting. If you live in urban areas ramial wood chip should be very easy to get hold of from your local tree surgeon (often free of charge). In rural areas straw should be available and spoiled straw that has been exposed to the rain during winter is often freely available as it cannot be used for animal bedding.

Wood chip - The smaller diameter the source wood is, and the more green material in the chip, the faster it will decompose. Chip from small diameter source wood is called ramial wood chip and is the best material to use for mulch in APP. Photo credit David Domoney 

  • Mulches - Grass can compete vigorously with trees and shrubs for nutrients and water. The application of heavy mulches reduces or in some cases eliminates the existing vegetation without the need of heavy digging work or the use of tractors and machinery. The vegetation that is suppressed by the mulch decomposes along with the mulch and adds to the fertility of the soil and improves soil structure. 
  • Mulches -  You can reduce the expense of time preparing compost or the cost of purchasing it by using fresh manure or other fresh organic matter layered as sheet mulch. Doing so 6 - 12 months ahead of planting allows enough time for the material to decompose in situ to levels that are not harmful to plants.
  • Mulches -  The mulch provides good habitat for a range of invertebrates many of which are beneficial in our garden ecosystems. Slugs and snails will also shelter in the mulch and this often attracts slow worms, toads, frogs and lizards that feed on them under the safety of the cover. Ground beetles and a range of spiders will also make home in the mulch and perhaps the most beneficial of all the soil dwelling organisms, earthworms, will settle and multiply under the mulch slowly bringing the material down into the soil improving structure and creating some of the best plant fertiliser around, vermi-compost.         
  • Green manures - Can improve the soil fertility, relieve compaction, improve the soil structure providing better drainage and water retention, suppress weeds and attract beneficial insects and pest predators. 

An excellent green manure - Sainfoin - Onobrychis viciifolia


Some Considerations


  • You need to apply large quantities of mulch and manures and for large areas this will often mean importing from offsite. If you can tap into local waste streams (as mentioned above) this is fine but it some places it can be expensive to purchase and transport these materials. 
  • Plants that grow via rhizomes and runners such as brambles and couch grass may grow through or around the sheet mulches and green manure cover. This can be overcome by removing these plants before mulching, or spot weeding as they reappear. If the area is dominated by pernicious weeds it's probably best to take the time of removing them before mulching.
  • On heavy clay (especially compacted clay) applying organic matter to the surface (mulching) is not very effective as the clay layer forms a barrier or "pan"  that is restrictive to the plant roots and the organic matter is not easily naturally incorporated into the clay. In these cases it's necessary to incorporate the organic matter into the soil via double digging or deep ploughing the area, adding the organic matter and then rotary tilling. The initial work is intensive but following this applying organic matter to the surface will work (so long as the area is not compacted again).
  • On any compacted soils it's worth breaking the compaction and relieving any pan that may be present before mulching.
  • It's necessary to prepare a seed bed when using green manures and this often entails ploughing and tilling the area for large areas or digging over and raking for small areas. 
  • Always apply a mulch following periods of heavy rain or water the area well beforehand to ensure the soil is well soaked. This will activate the microbiology in the soil that play a critical role in the decomposition process.

So now let's take a look at how to set up the beds and how to implement the various methods of advance planting preparations we are trying out. 



Setting up the Beds 


The position of the beds on the site were dictated by the aspect and topography of the land i.e we wanted to position the beds to receive as much sunlight as possible (west - east axis in our N.hemisphere) and to utilise the natural slope of the land to assist with irrigation. We laid out the beds on an area that was more or less on contour so we could flood irrigate from the stream water that can be diverted into our site from the NW. We also selected the planting location slightly lower then the proposed location of a pond so we may irrigate from the pond if the stream water is unavailable.


Perspective view of broad area showing the mountain river that is used to irrigate pretty much all of the plots on the south facing slopes to the west and east - The garden is marked Ataraxia on the above map. The river shown on the map can be channeled via gravity pretty much anywhere on this 53 ha landscape.  

Digital terrain models such as above are great for selecting locations and planning. Once we are ready with our design we carry out a ground topography survey to physically peg out contour lines and positions of the design elements on the site.

A benchmark contour line at the high end of the site is marked as the position for the first bed and we offset from that line at regular intervals to ensure we have regular sized beds and paths.  I like to use regular size beds and pathways for our trials so that they can be replicated easily and perhaps more importantly they suit the modular basis of our designs and allow us to scale up and down our designs easily. 

Pegging out contour lines on the site during our Regenerative Landscape Design Course 



We then peg out the top corner of the first bed and measure down to the edge of the east side of the beds marking 1.5 m wide beds, 50 cm internal pathways and 1m external pathways (to allow easy turning for the mower).The length of each bed in this case is 25 m. For beds any longer than this it's probably a good idea to make lateral access so movement within the garden is easy.


Fergus and Gabriele pegging out the beds and pathways

Once we have the location of the beds worked out the next step is to clear the bed and pathway area from shrubs and young trees.


Digging out the shrubs and saplings from the area and piling the material on the perimeter of the area.   

The removed vegetation is piled onto the edge of the garden to serve as shelter to lizards and other wildlife seeking refuge from birds and other predators. The lizards quickly made use of the cover.



Lacerta spp. taking cover in the brush piles we made on the edges of the beds with the plants we had to remove to create the new beds. 

We attached string to the side of the pegs which clearly indicate the footprint of the beds and paths. Before going any further I tried the lawnmower within the pathways to test how comfortable it is at turning corners at the ends of the beds. 1m wide external paths make for easy turning of the corners with a standard 45-50 cm wide lawn mower. 


Beds pegged out and defined with string. The mini digger in the background is digging out the pond at the highest point of the site.



With the six beds clearly defined we now set about implementing the advance planting preparations for each bed.


Our five methods for advance planting preparations


1. Inverted Sod and Mulch - (Soil - Straw)
2. Green Manure - (Plough - Till - Sow White Clover - Sainfoin and Marigolds) 
3. Dig over and Sheet Mulch - (Card - Manure - Straw)
4. Sheet Mulch - (Card - Manure - Straw)
5. Straw Mulch (Straw)

All of these methods are best implemented when the soil is moist, for example, following heavy rains when the soil profile is thoroughly soaked but has had enough time to drain i.e not water logged.

1. Inverted Sod 


Method one entails slashing the existing vegetation to ground level and leaving it on the surface. A layer of inverted sod is then applied to cover the surface of the bed. In some cases you may wish to dig out the top soil from the pathways and this can be inverted on to the bed area. In this case we wished to leave the pathways grassed and used top soil removed from a pond excavation on site. Following the top soil a layer of straw mulch is applied approx 10-20 cm deep.


Inverted Sod applied to surface. This is followed by a layer of straw


2. Green Manure 


Method two removes the existing vegetation and replaces it with plants that can improve the soil for the incoming plants. For example on sites with low fertility soils nitrogen fixing green manures are great way to lift Nitrogen (N) to appropriate levels. The green manures can also add significant quantities of organic matter to the soil improving structure and drainage and can serve the needs of beneficial insects.

To boost the organic matter content of the soils, the green manure should be cut at regular intervals and plowed into the soil or covered with a straw mulch before planting occurs. In such cases the green manure used should be a fast  growing annual cover.  An alternative is to sow a perennial cover, cut back at regular intervals (once established) and plant the crops directly into the living mulch.

We sowed the following seeds onto the  prepared bed on the 18th May.

Trifolium repens - White Clover 200 g - Perennial 
Tagetes patula 100 g - Annual
Onobrychis viciifolia - Sainfoin 100 g - Perennial

We'll probably need to irrigate this bed from July onward for a good cover to establish and we'll cut the vegetation in late summer and decide whether to mulch before planting in the Autumn or plant directly into the mulch based on the performance of the cover.

To prepare for sowing we ploughed and rotary tilled the area to provide a good seed bed.


1.5 m wide plough followed by rotary till prepares the bed for green manure 


We then hand sowed the seed onto the surface before a rainy period was forecast.

Hand sowing the cover crop onto the surface


The use of cover crops to prepare beds for perennial polycultures is something we'll be experimenting more with in the future.


3. Fork over and Sheet Mulch 


Method three entails slashing the existing vegetation to ground level, forking over the surface of the beds and then placing a card/cloth layer to cover the soil surface and a layer of manure on top of the card/cloth. We used approx 30 L of manure per m2 and finally topped this with a 10-20 cm  layer of straw.

Digging over the bed, placing a layer of card and cloth, adding 30L of manure and covering with 15-20 cm layer of straw.


4. Sheet Mulch- Cardboard layer, manure layer , straw layer


Method 4 is the same as above but without forking over the beds

5. Straw Bales 


Method five is quite simply slashing the existing vegetation to ground level and applying a 20 cm layer of straw to the surface. A simpler way is to place a straw bale on the location where each tree will be planted and this works really well if you are only planting a tree layer, however for these beds we intend to plant out 4 layers; trees, shrubs, perennial vegetables and bulbs so it makes more sense to mulch the entire area. 


Placing bales on the planting locations of the trees clears the weeds from the planting zone, encourages a fungal population of soil microbes and within 6 - 12 months the surface of the bale at ground level  will decompose providing a light layer of compost for the newly planted tree/shrub.


The Pathways 


The pathways are left undisturbed and the grass cover is mown at regular intervals throughout the growing season and can be applied as mulch (as long as it's not full of ripe seed). We allow 1m wide access at end of beds to allow easy turning with the mower.

In some cases we have removed 10 - 15 cm of soil from the paths and applied this to the bed surface and then sowed the paths with a perennial cover such as White clover - Trifolium repens, but in this case we wanted to keep the grass cover as it makes a good durable surface and can provide a regular supply of trimmings for mulch when we mow throughout the year.  


The perennial polyculture trial beds -  6 beds - 1.5m wide and 25m  long with 50cm internal pathways and 1m wide periphery pathways

How we are measuring the effectiveness of each method 


As mentioned above the aim of the trial is to discover methods that are inexpensive, time efficient, least disruptive to the existing wildlife and that provide the optimal conditions for the incoming plants.

The criteria we are judging the effectiveness of the methods and how we will measure effectiveness  is as follows:
  • The smallest amount of effort for the greatest benefit i.e in labour, materials. - Record of Inputs 
  • The least expensive method (without sacrificing quality) - Cost Analysis 
  • The least disturbance to the existing ecosystem - Entomology Survey
  • Mineral analysis compared to base sample  - Mineral Analysis 
  • Physical analysis compared to base sample  - Soil Test Card 
  • The beds should provide great soil conditions for the incoming plants i.e, free from competitive neighboring plants, good structure, moist and fertile, free draining. - Observational Report  


Will be publishing the results of our trials in the winter.


What will we be planting in the beds 


I'll write about the planting schemes for these beds in more detail in a future post but here's a quick overview of our planting plan for the beds.

Beds 1, 3  and 6 are designated as biomass beds and will be planted out with pioneer species of nitrogen fixing trees to supply biomass to the productive beds 2, 4 and 5. The productive beds will consist of 4 vegetative layers of productive and supportive plants.  Mainly fruit and nut crops in the upper canopy, a  lower canopy/shrub layer of fruiting shrubs. a herb layer perennial vegetables and a ground layer of bulbs.



While light is abundant in the early stages of the garden development the goal is to use the biomass beds 1,3 and 6 to supply biomass to the productive beds via chop and drop pruning and fast coppicing practices. As the system matures the productive beds will overshadow the biomass beds at which point they will be replaced with shade tolerant productive crops and support species.

Overview of Bed Plantings and APP Methods used for each bed  


Ataraxia Bed Layout and Setup
6 Beds
25m long x 1.5m wide
(APP) Methods
Bed ABiomass1
Bed BPolyculture2
Bed CBiomass5
Bed DPolyculture3
Bed EBiomass5
Bed FPolyculture4
Advance Planting Preparation (APP) Methods
1. Inverted Sod and Mulch - (Soil-Straw)
2. Green Manure - (Plough - Till-Sow)
3. Dig over and Sheet Mulch - (Card-Manure-Straw)
4. Sheet Mulch - (Card-Manure-Straw)
5. Straw Mulch (Straw)


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