Project 9 ‘Permaculturing’ the Polytunnel (2011-2013) Summary and Lessons Learnt This project developed from problems experienced with a conventional polytunnel set up – and has dramatically increased the efficiency, productivity and overall sustainability of our food growing system. As result of the simple changes implemented in 2012 (one of the worst years for tomatoes by all other accounts) the polytunnel produced a crop of tomatoes that we are still eating (frozen, no tins of tomatoes needed) from summer 2012 to March 2013. Further seasons will show if this was a fluke or not, but the effort and savings in terms of reduced watering in itself have been a great success. Ethics Earth Care – The polytunnel is part of our sustainable, low energy input food production system. It has recycled waste materials such as bottles and paving slabs, and uses renewable resources such as solar gain and captured rainwater. People care – The whole system is providing food for the family plus extending the growing season so that I can provide winter salads and later harvests to provide more home grown, organic vegetables for the family. Fair Share – this has been a major point of interest for people visiting my plot when I run open days. As a demonstration project in the future it will hopefully allow others to see how increasing solar gain and sustainable watering can be easily applied to their own situations and enable them to gain a yield. Surplus produce is often given away. Criteria & Principles Demonstrated This project has been designed with OBREDIMET and has also demonstrated the use of Observation and Evaluation skills, Incremental and Rolling design, Functions and Elements analysis. It demonstrates the following Key principles :- Catch and Store Energy, Obtain a Yield, Produce no Waste, and Integrate rather than Segregate (by integrating the house roof to the polytunnel watering system). Page 1 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor ‘Permaculturing’ the Polytunnel Observation & Boundaries The Starting Point When we moved, a prime focus for me was to have a polytunnel. Siting it was done with permaculture principles in mind, especially after hearing the story of Many Pullen’s polytunnel at Ragman’s Lane. So when I sited it I used the following criteria: Close to house as possible but away from light excluding trees including oak in garden, for ease of picking on evening route East/west orientation to give hot side, cooler side for salads North side of property to avoid hedges and neighbours shading in winter Least windy site as possible, or at least not directly against SW wind or wind sock to it Close to chicken and duck area for receiving bedding, duck water, chucking weeds/ surplus greens over to feed chickens, letting them in when cleared for pest control. Problems/ Limiting Factors Although the relative location has remained the most optimum I can think of, problems with the polytunnel soon started appearing. 1. Watering Watering with a watering can proved time consuming and ineffective quite quickly which meant I was using the hosepipe connected to mains more often than I wanted. Even this is time consuming and only seems to water the top inch of soil so I tried using a sprinkler – BIG mistake, the humidity in the tunnel increased dramatically and blight became a serious threat to all tomato production. Surface watering was not penetrating and the soil was losing moisture even under mulches of grass mowings – all dessicating to nothing very quickly. Page 2 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor 2. Nutrient Loss After the first few years I noticed that crops were getting poorer growth despite the regular application of compost mulches, green mulches (mainly mowings) and use of comfrey and nettle homemade feeds. The sandiness of the soil coupled with the lack of moisture due to poor watering was drying and dissipating mulches very quickly and the soil seemed hungry. The worm situation was very poor again due to the dryness I suppose. I came to the conclusion I needed much thicker and richer mulching. 3. Voles After the first year or so, I noticed tunnels appearing under the soil, usually following along the plant roots. Following the tunnels I found chewed holes through the sides of the plastic! These little tunnels were voles happily munching on my peas and other produce, but worst of all causing plant wilt as roots were left suspended in vole tunnels. 4. Frost After a while I realized that my whole garden is sitting in a slight frost pocket caused by air flowing down from the hills surrounding our property. Although not at the lowest point in this plane we seem to be at a frost stopping point as the buildings next door seem to trap the frost. Also the trees, trellis and climbers surrounding the garden act as another frost brake I think. List of Requirements – Addressing the above Limiting Factors From all of the above observations, I developed the following list of requirements to address these limiting factors and improve the polytunnel:1. 2. 3. 4. 5. 6. Improve the soil nutrition, soil life and get worms interested! Protect soil from heat and water loss Get rid or at least hinder the vole tunnels Create a self-watering system which didn’t rely on my time or mains water Reduce air humidity caused by watering Extend the frost free season as much as possible Resources The following resources were available on site or in the local area. Old paving slabs, breese blocks, recycled wooden boards Wine bottles! Old guttering and downpipes Page 3 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Existing soaker hose Recycled containers & existing water butts Local manure & mushroom compost, urine from compost toilet, poultry bedding and dirty duck water Large sheets of plastic from previous polytunnel covering, some holes Needed – timber for posts and guttering support, guttering stops Evaluation The list of functions that the design had to accomplish was then easy to breakdown into systems and elements. Clearly the analysis was showing the obvious opportunity for multiple function design - raised bed edges could perform several jobs at once by increasing mulch capacity, excluding voles, and increasing solar thermal mass. Functions Systems Elements Automatic, non mains watering that reduces humidity Rain water harvesting & ground level delivery Buried soaker hose Large capacity water storage House water diverters Delivery Hose to/from storage containers Polytunnel roof collection system Frost Protection Solar thermal gain system Increased mass around beds Reduce heat loss somehow? Vole Barrier Soil Improvement Planting barrier Barrier mechanism Better recycling nutrients within larger system Barrier to heat and water loss Increase tree/fenceline planting along north/east edge of property Buried barrier at edges of polytunnel Raised beds, Source rich source of compost Recycled duck water Poultry manure & bedding, human urine Page 4 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Design and Implementation The design for ‘permaculturing’ the polytunnel evolved in response to problems over several years. The first design was purely to capture water from the ‘roof’ of the polytunnel after several retailers told me it was not possible to do this. First Polytunnel Self Watering System Design (2005) An initial early on design had been to capture rainwater from the polytunnel roof and direct it immediately into the tunnel. The rainwater was collected by means of a strip of plastic sheeting taped (greenhouse water resistant tape) to the sides of the polytunnel. The strip then sat in a free standing guttering angled to deliver water to four water butts standing at the corners of the polytunnel. This is another reason I sited the polytunnel within a ‘furrow’ section to enable water from these butts to be delivered to the slightly lower beds within the polytunnel. This design was implemented early soon after the polytunnel had been built in 2005. Page 5 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Problems with this design however soon became obvious. The tape broke down every year and needed to be replaced due to sunlight and the wind. It also left a glue residue on the plastic, which became dirty and meant you couldn’t re-stick on it very well. Insufficient height to pressurise a dripper hose – the water butts were just off ground level which was ok for can dipping but too low pressure to use a dripper hose which clogged up very quickly. The guttering distorted and twisted in the sun causing water to spill Improved Polytunnel Self -Watering System Design (2012) Page 6 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor In 2012 we had to replace the old plastic covering that had been on the tunnel for 7 years and this made me start thinking about a new system for capturing the water on the roof and delivering it directly into the tunnel. The new plastic was more insulating but could I also increase the heat loss without damaging the sunlight by covering this again with the old plastic and using this to catch the rain on? This would give a sturdier structure and very much improve water capture, but could it also provide an extra insulation layer, though in low winter sunlight the south side of the tunnel would still be open to full light at ground level where winter salads would be. Maybe in summer when the tunnel can get too hot, the extra plastic will keep things cooler? My main concerns are algae greening in between the two layers and wind lifting the whole thing out of the ground – NOTE June 2012 - 4 months and several storms later, not yet happened. Water being captured very quickly with improved design – soaker hose seems to be leaking slowly from this height of water, but often problems occur later on if the hose ever dries out. Page 7 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor House Rainwater Harvesting and Delivery Design To increase the amount of rain water I can use in the polytunnel and for watering of chickens and ducks (especially the refilling of the duck pond), and avoid all mains water use if possible, I quickly realized I needed to save as much water as I could from the house roof as well. An initial design used a solar pump to move water captured from the roof of the house and stored in two 1000 litre containers to a third container that was raised 3 feet off the ground close to the polytunnel. This was then attached to the soaker hose. Page 8 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor However again problems soon developed: – The solar PV proved insufficiently powerful and we ended up having to attach the pump to the mains electricity. The diverters were normal water but diverters and they were not collecting much water when it rained heavily so the tanks never filled up in heavy rainstorms. They also clogged up very quickly with debris. Too much effort was involved in remembering to pump the tanks so I ended up using the mains tap still. Final Integrated Polytunnel Self Watering System Design 2012 To increase the water capture rate during summer downpours, we needed diverters that would not be overwhelmed and divert water down the drainpipe. Page 9 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor The largest capacity diverters I could find were from Germany and called Giant Rainwater Diverter on the internet. They are supposed to be able to divert 90% of all rain and have a self cleaning stainless steel mesh that directs debris down the downpipe rather than the collecting pipe. Also, I realized that if we delivered the water using gravity rather than pumping I could deliver it to half way up the vegetable area, providing we attached the diverters as high as possible on the down pipes so that sufficient head of water can gather to generate sufficient pressure to move the water quickly. I also increased the bore of the delivery pipe from a normal hose to a 2.0cm blue water pipe so a greater volume of water could be moved, and this is also less likely to freeze or split than hosepipe. Some interesting steeping down was needed from the German diverter to anything hose-like in the UK, which I managed with waste pipe connectors! Using step ladders and filled water hoses we managed to find the furthest point in the garden we could deliver water at a fast rate of flow and marked it. I wanted to move the water tanks as far up the garden as possible to take advantage of the natural slop upwards, which could add pressure when delivering into the polytunnel watering system. Page 10 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor This optimum delivery point just happened to coincide with being close to the neighbours stable block which made me think I should also capture and store from their roof as well. Currently I only have a normal water butt diverter attached to the tanks at this point but I am hoping to get permission to increase the capacity with a Giant Diverter if necessary – ie if I am not regularly filling tanks from the house roof and I need more water. To allow greatest flexibility and maximize soil moisture for plants with different root depths I have kept the original soaker hose, now buried about 10 cm below soil level, which the 1000 litre tanks usually connect to. The polytunnel collecting butts are attached to the newer therefore higher system which is now under another 10 cm of mulch, therefore watering at top level. These systems could be interchangeable and indeed I may find the lower pressure polytunnel butts work better on the deeper system. The house roof has two more downpipes which are not connected to this polytunnel system. One feeds directly into the greenhouse, the other which takes approximately quarter of the house roof water is currently under-utilised with a normal diverter feeding to a patio 300 litre water butt. The garage roof is likewise used. There is therefore capacity to extend the system greatly and if over the next few years I find I need to store more as I’m using mains water regularly, especially in hot summers, then I will increase the capacity. This will probably require an additional 2cm bore blue pipe however, plus extra 1000 litre tanks, giant diverters and attachments so has quite an additional cost involved – so I’ll wait and see first! Page 11 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Raised Bed/Solar Thermal Mass Design Clearly raising the beds over the sandy soil, above ground level would help in improving soil quality, water retention and keeping the voles out but the brainwave was to recognize I could add a lot of solar gain by choosing the right materials. Slabs The decision to use slabs at the polytunnel perimeter was obvious – I had lots on hand and I could bury them upright – but to maximize solar gain I placed the taller ones on the north side, and the smaller on the south. The south ones therefore don’t cast a long shadow over the beds but they do act as radiators absorbing heat through the plastic. When I replaced the water collection system with a double layer of plastic I raised the catchment height a little (even though this might mean less water) so that when the sun is low in the winter the rays will enter through the single layer of plastic, and having the low slabs on this side does not inhibit the sun. Hopefully though any rising heat will be slightly insulated by the double plastic layer overhead. Page 12 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor The bigger north side slabs will also act again as radiators, collecting sun rays from low winter sun but also reflecting the light back into the beds, and they might go some way to insulating from heat loss from the soil and air on this shady side. Voles seemed to dig just under the surface so I am hoping that the 8 inch depth that I have buried the slabs will be sufficient. (August 2012 – no holes yet!) Bottles I also decided to keep the original ‘bendy’ internal bed shape by using bottles – an old permaculture classic now – but what if I filled them with water to increase the thermal gain? Would they shatter in winter? A trial over winter showed that bottles with water were much warmer on cool evening than those without – and if filled 2/3rds full they would not shatter at -10 degrees. Full ones did however. A happy time was spent over the winter collecting bottles from friends and the local pub! Over 200 were malleted into the ground, a big job but very satisfying to behold! December 2011 April 2012 Bottle edging filled with water gets quite warm on sunny winter days – overwintering broad beans and salad and early peas do seem to have done better this year with less signs of frost damage on beans than previous winter. Fig still frosted tips in April however. Page 13 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Other ‘Permaculturing’ additions to the polytunnel system Permanent fencing/trellis made from odds and sods begged borrowed and found, to increase useable vertical growing space. ‘Hanging’ gardens – hanging guttering from roof bars to give mouse free pea germination space, using old bread trays for extra and moveable temporary growing space. Here very early strawberries. All planting is planted through previous plant debris which is cut and left on the surface. Fine seed such as salad is grown by spreading fine compost on top of rough mulch and sowing into this. Nov – broad beans planted through cut tomatoes, May/June – broad beans cut , tomatoes, chillis,cucumbers planted through July/August – tomato prunnings left on surface for extra moisture protection Page 14 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Old thread spools picked up free from a visit to a woollen mill make a handy feed delivery method to individual tomato plants reducing surface watering and therefore humidity. Maintenance/Monitoring Maintenance of the watering system is ongoing and requires the following: Cleaning of house guttering and diverters to remove debris to ensure maximum throughput of water ( every 6 months) Adaptors need replacing now and again, taps on IBC tanks are prone to breaking – so far not replaced any parts but ‘turn off’ by lifting hose ends up above water line when not in use. Soaker hose – ok when kept damp, seems to dry up when empty of water and need to poke small holes around plant roots when replanting in the spring. Might need extra pressure to work better, see below. Additional water capture plastic covering on polytunnel will need replacing after several years I would imagine – this can be recycled/reused for cloches, extra insulation over seed trays etc, and every time replace full polytunnel plastic (costs£100 every 7 or 8 years) we can use this for the rain capture sheet as this can have holes, etc. I should imagine though the new covering will last longer with the added protection of the rain capture cover. Bottle edging – now again needs the odd bottle to be hammered back in gain. Can replace ad hoc. Page 15 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Evaluation & Tweaking The evaluation of the design against my original requirements shows some 1. Improve the soil nutrition, soil life and get worms interested! Since raising the beds and adding the soaker hose plants in 2012 have gone mad. However I do seem to have some yellowing on tomato leaves and think it may be due to magnesium deficiency possibly caused by too much comfrey/potassium rich plant feed in past. Thinking of adding Epsom salts to watering system. Soil life – under mulch the ground is damp yet no obvious signs of plentiful worms at this level yet. Will continue to monitor. 2. Protect soil from heat and water loss Overwintering plants do seem to have coped better at ground level than in previous two winters but this may be just due to warmer weather this year. More years of winter cropping need to be observed before I can conclude. What I have noticed is that I have not Page 16 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor seen any plant wilt due or tomato splitting due to erratic watering, but then this year has been a fairly atypical year. But all that rain we’ve had is at least getting inside the polytunnel without my effort! 3. Get rid or at least hinder the vole tunnels Hurray – so far no voles !! 4. Create a self-watering system which didn’t rely on my time or mains water So far this summer I have not had to water by hand at all, only for giving plant feed to tomatoes when I bail out nutrient rich duck pond. My work load in watering has completely reduced and I have been happy to leave the polytunnel unattended to water itself when I go on holiday so this has been easier for the neighbours! 5. Reduce air humidity caused by watering Despite blight in potatoes outside the polytunnel, touch wood, I have not had blight inside on the tomatoes and there does not seem to be any cucumber mildew either which I have always suffered from before by August/September. No sign of mildew or blight (fingers crossed). Notice mulching with any green material produced in tunnel, eg tomato plant prunnings, as I am building carbon and raising bed level by direct composting. 6. Extend the frost free season as much as possible I still need time to assess this. I feel the stone and glass warm under touch on sunny spring days – so this heat must be being released. I have seen and felt the soil in the raised beds as being warmer than outside soil and have found the water in the bottles unfrozen when it has been -5 degrees outside. All sign of success but how much is due to heat of still composting mulch or not I don’t know. Page 17 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Further improvement s/Tweaking:The soaker hose is still operating very slowly and I occasionally poke more holes at plant root stations when I am planting to encourage a better distribution of water. I feel the hose closes up after a period of non-use, ie. when the butts are dry and the pressure is still fairly poor when distributing water from the polytunnel collected rainwater which are at lower height and size than the IBC containers. One idea is to reuse the solar pump we had for the original system and pump water from these collecting butts to a higher cistern raised on a platform, like pumping to a toilet cistern. Something to think about for the future if I find that the soaker hose needs more pressure to work efficiently. Duck water delivery system – I am still considering how to use this nutrient rich water without the effort it requires at the moment, whereby I fill watering cans and direct water. Usually this is when I add comfrey/nettle juice too. Most of the time this water goes directly to the willow patch via an old cistern and tubing, but is and when I need to get it into the polytunnel it is a bit of a faff. It is very dirty water however and I am loath to send it down my soaker hose. Ideas still to think about! Winter 2012/13 – extreme gales this year broke some of the screws that fixed the wooden batons to the planks, but luckily the plastic was not torn. For added strength extra fence posts were added (now 6 per length) and deeper planks with bolts through the batons and planks (instead of screws and washers) now hold the plastic sheeting in place. . Page 18 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor Things I have learnt from this project Water is the most important element of land base design – I knew this in theory but this design has made me realize how precious and necessary having water in the right place in your system is in practice. A tremendous amount of effort and energy can be spent if the water part of your system is not in a useful place! It also made me realize how effective watering is so important for nutrient cycling – dried composts are useless. Without damp soils organisms needed for the conversion of dead matter to plant nutrient just do not operate. Wildlife – slugs or voles, you take your choice! On clay you get slug damage, on sand you get voles! That you shouldn’t give up on a design – you can always improve on your original ideas and eventually things begin to work! Page 19 of 19 ‘Permaculturing’ the Polytunnel Design by Alison Ensor