Poly tunnels

When we were offered the site there was an old frame of a poly tunnel in the field which we brought into use in the autumn of the first year. Since then we have been given two more tunnels which we have made into poly tunnels as well as the one shown below which was in rather poor condition and so we have replaced the netting and continue to use it as a growing cage. This blog describes how we have been developing and using our polytunnels.

An old frame which we were given in summer 2010 and now use as a fruit cage

Renovating the first poly tunnel

In winter months temperatures can go quite low, so the doors are always shut, with a little air filtration allowed in vents in the top of the doors. In Poly tunnel 1 we have the system which takes the warmer air from the daily solar gain, down below ground level into a covered pit of 300 water bottles which in turn warms them. Then the warmer air derived from the water bottles percolates out of the exit pipe during the night. The whole system is powered by a solar panel, battery and small fan. In the summer, we open the doors and put in the grilles to keep the wildlife out and allow the air to circulate. A Poly tunnel team was set up late in 2011 to manage the three tunnels.

Sue and Steve set up the solar gain box with 300 1pint milk bottles containing water

Warm air is extracted by a fan driven by a 12 v battery powered by a solar panel and pushed down into the solar gain box below ground level.

Currently we have three poly tunnels measuring 10m x 3.4 m, giving a total surface area of 103 sq m. In them the winter crops of Amsterdam forcing carrots, Mizuma, Mispoona, rocket, winter salad, over winter Chard are grown. It is possible to grow other crops, but not in sufficient quantities to satisfy the demand of the farm.

Good quality benching is very useful

Sue and Steve setting up the poly tunnel

Many crops are started off in our polytunnels

In the spring the main crops grown in the tunnels are tomatoes, sweet peppers, cucumbers and chillies. Crops are sown from January onwards. Sweet peppers need a very long growing season, so these are started off at home in the hot box (large propagator) by the team leader. Cucumbers are also started off with a bit of bottom heat at home, to ensure an early crop.

In the late winter and early spring one of the tunnels is available for the teams so start off their crops. Many Renovation seeds are sown here including onions, leeks, squashes and courgettes then transplant into individual pots, then harden off outside under sheets of glass before being planted into the plots.

Good husbandry is practiced and so few diseases develop in the poly tunnels. Some blight has occurred in tomatoes mainly as a result of blight on the potatoes being brought in. Now we are growing mainly blight resistant potatoes, but people who have been working on potatoes are discouraged from entering poly tunnels when the atmosphere is warm and damp. A little grey mould has been found on Cucumbers. With blight on tomatoes we have tried using Bicarbonate of soda, and eco washing liquid and olive oil in a spray, with good success on small outbreaks, but have resorted to Bordeaux Mixture in serious outbreaks, with great success.

The team uses good quality potting compost, some of which they make themselves in pots and trays. They try to apply “no dig” policy and at the start of each season when they cover the beds with manure and home grown compost. Sometimes a top dressing of chicken pellets is applied and in the case of the tomatoes, they apply tomato feed.

The team find that they can bring crops forward by at least two months using the polytunnel. Clearly the environmental conditions have to be right outside for leaders to consider planting out into plots or beds, but the fact that we can grow on plant materials earlier means that we can extend some crop seasons by as much as two months.

Thousands of seedlings start life here

Cucumbers growing in a polytunnel

At the moment the leader considers that the major obstacle to further continued development is a lack of power. We are currently using solar power to drive the pump to supply the water in the tunnels, but more could be done with more power. The polytunnel leader has considered hydroponics, but thinks that we do not have a suitable water supply for this. Currently our water supply is mainly from a pond which is shared with a model boat club who have added dyes in an attempt to suppress plant growth in the pond. The polytunnel team leader considers hygiene in the water supply is important and feels that there could be issues with our current supply of pond water. There could be a case for extracting water from the nearby River Itchen, storing it in IBCs, adding selected nutrients and letting it run slowly into the beds in the polytunnel.

Having more space, more poly tunnels and more people in the team would give the polytunnel team more crops, and a better facility for raising seedlings for external plots. We perhaps could experiment with other crops, including small melons, indoor grapes and strawberries. We would need two or three poly tunnels dedicated to strawberries in order to comply with our principle of supplying enough for 100 stakeholders. Growing in poly tunnels, by lengthening the season is very successful and productive and it is certainly an area where more thought and development is needed.

Water

Water is essential, and given the increasing instability of global weather it is probably worthwhile to think early on about how you will manage if the rainfall is insufficient during a growing period. By June 2010 some of our crops were getting seriously short of water.

Early on we purchased around 20 plastic 13 litre watering cans, which were in heavy demand during dry spells. These are too heavy for some to manage, so we also bought some smaller lighter ones.

The pond, our water supply

We took water in our watering cans from a pond about 30 m N of the first plots, but 200 m away from the last plots. Lugging water in a watering can from the pond was time consuming. Clearly we couldn't expect people to walk kilometres to draw enough water for a thirsty plot of potatoes! So, somewhat reluctantly we took the compromise decision and in June 2010 we bought a petrol operated pump from a local tools shop. With careful maintenance it is still working today. We asked the local fire service if they had any decommissioned hose pipe and they blessed us with about 200 m length in joinable sections. We investigated purchasing water butts but soon decided to buy Industrial Bulk Containers (IBCs). These are plastic tanks measuring 100cm x 100cm x 100cm with a metal frame around them. They generally hold 1 cu m of water (1000 litres).

Industrial bulk containers (IBCs) hold can 1000 litres of water

They are used often initially for holding fruit juices, but can be purchased second hand for around £40. These can collect rainwater if placed next to a shed roof, be filled with a hosepipe from a nearby tap or filled from a water source nearby using a pump. We mounted them on breeze blocks to allow a watering can to be placed under the tap near the tank bottom. These have been brilliant, they let the water flow out rapidly and so fill a watering can in about 3 seconds. The pump feeds the Fire Brigade hose and pumps water at a rate of about 500 litres min-1 to several IBCs situated around the site. Manhandling the hoses into place is a heavy task, but the reduction in time spent watering makes it worth the effort.

Developing the site

We decided to have ten teams each growing on two plots on opposite sides of the central path. Alongside these 20 plots are the polytunnels, soft fruit area, tool and pot sheds, sales area, social area, compost areas, and toilets. The vegetable growing area is constrained by a perimeter fence.

Initially we needed a shed for tools storage onsite. In addition to spades and forks, trowels and hand trowels we have found that wolf hoes are very useful for quick weed control and ground preparation. We have one or two rotivators and a few members have been trained in their safe use, but teams are generally reluctant to use them. Otherwise most of the cultivation is by hand. This has the advantage of teaching people, often with few growing skills the basic principles of growing your own food, but it does limit the area that can be cultivated and the quantity of food that is grown.

We tried to plan the site so that the communal facilities that quickly grew up were closest to the people who needed them and this plan shows how our buildings and structures developed in the first few years.



Sue, Les and Kate in our sales marquee
This was installed in our first winter 
and lasted until the seventh year when it was
replaced by another large shed 

We soon found that we were accumulating "clutter" at an alarming rate. We were quickly acquired additional materials, such as piles of wood of all shapes and size from a barn construction business on the farm, a second polytunnel, compost bins, many pots, fleece, mypex, (breathable interwoven sheet plastic), black plastic sheets, tea making facilities, seats and tables for recreation and rest, a portable loo, seeds, labels and many other things as well. Some of these materials were placed in sensible locations, others were just dumped in a convenient spot. People were suddenly incredibly generous when they wanted to throw something out - if it is easier to take it to the community farm than to the local Recycling centre they probably will. We found that all sorts of doors, window frames, broken tools, half full tins of paint etc mysteriously appeared. Some were useful, others not, so we had to be vigilant and eventually developed a policy of "No products to be brought onto site and left without first seeking permission from……"



The site developing in 2011

From the outset there has been little opportunity to increase the growing area within the first field but somehow the number of sheds, polytunnels, compost bins and additional items has managed to grow so that now this area which is situated at the side of the 20 plots looks like a small shed village! However we are fortunate that the locations of constructions reasonably correlate to the shortest paths between key installations.