Irrigation

Irrigation

Regardless if you believe in climate change or not you cannot deny our weather is becoming more unpredictable.  In the past we could rely on steady spring showers watering all our newly planted seedlings. Nowadays the spring can be one of the driest months of the year and without vigilant watering newly planted crops can suffer.  For the busy (or even the lazy) gardener this is a real bind as they may have to make special trips to an allotment site far from home or spend time watering when they have other things to do.

This problem is not a new one, the first recorded garden, the famous ‘Hanging Garden’ in Babylon, had to have a complex irrigation system to water plants on continued terraces.

Thankfully, gardeners and allotment keepers need not install a complex ancient irrigation system as there are much simpler alternatives.

 Leaky pipe

Starting with one of the most expensive, yet effective systems, those with a bit of cash behind them could install a ‘leak pipe’ system.  The leaky pipe system is the most common method of irrigation used large scale greenhouse and polytunnel growers.  Some garden centres and field growers use the same system and scaled down versions are available for the home grower.

The leaky pipe consists of a hose pipe running the length of a bed, the pipe is attached to a regulator and a measured amount of water will ‘leak’ out of holes along the length of the pipe. This method is great for those on a water meter as it delivers the water right where they need it, minimising losses from evaporation.
I’ve used these in a polytunnel and found them to be very effective for salad growing. They are easy to put in place and you can sow or plant at the same spacing as the holes which deliver the water.

You can shop around for these and like anything else you usually get what you pay for. I have come across second hand systems for sale as sadly during these times many growers are going out of business and selling off cheaply all kinds of things they would have spent and are and a leg on.  Look on ebay and in the local newspaper for auctioned off systems – you may just pick up a bargain.

Homemade leaky pipe

A similar system can be rigged up at home at a fraction of the cost of a true leaky pipe system.  It consists of a length of PVC pipe with holes made at the same spacing as the plants you wish to sow or plant. The pipe is laid on a bed alongside the crop – a hose is then attached to one end and the other end is either blocked or it is attached to another length of hose which then in turn is attached to another PVC ‘leaky pipe. If enough of them are attached together then a whole garden can be irrigated this way.   When you need to water the garden the tap is simply turned on, the garden is watered and the tap is turned on again.  Even simpler methods can be made by placing a hose pipe where it is needed and cutting holes in the pipe – the down side to this method is it will permanently damage a hose and it is more inclined to be knocked and disturbed than a fixed PVC pipe.

In the hose or PVC pipe method effectively you act as the regulator of water but again as the water is being delivered where it is needed your water bill should be reduced.

Similar systems can be rigged up to work on waterbutts rather than mains water. These tend to only work if there is enough water pressure present.

Wicking bed

Wicking beds are very well known in Australia, especially in permaculture circles. Their theory is very simple – plants tend to ‘wick up’ water through their roots so, having a water source from underneath will theoretically be more effective than watering from the top down.

A wicking bed will have just such a reservoir of water for a plant to draw on which should minimise the watering time for the gardener.

It is no surprise it was Australians who adopted the wicking beds system it is thought to be most useful in warm dry conditions. In the UK we have high rainfall across most of the country so wicking beds would might not be necessary on a large scale outdoors but small beds may well be worth experimenting with.

This method of irrigation holds the most promise for container growers and those growing under protection (such as greenhouses or polytunnels) as plants can all too easily dry out in these conditions.

The ‘reservoir’ consists of a agricultural (porous) piping or similar improvised homemade pipe covered with absorbent material such as coir or compost. This sits at the bottom of a bed or container and plants are sown into soil or compost above.

A step by step guide is as follows -

Step by step

1. Find four plastic bottles – Tonic, cider or coke bottles are best –( if you don’t seem to have any it could be a good excuse to throw a barbeque).  Cut the tops and bottoms off three of the bottles to make a pipe lay these flat and use the third as an upright (cutting a hole in the side to fit the three bottle pipe to it).  Alternatively find a length of agricultural piping.
2. Using a pin make a number of holes in the horizontal pipe.  As pipes can get clogged use old sacking or porous weed suppressant material to allow water out but not soil in.
3. Place the constructed pipes into a polystyrene fish/vegetable container with holes made at one end. Or if you wish to use this in a larger bed place you should try to make a raised beds lined with impermeable plastic and dill drainage holes each end
4. Next cover piping with course organic material – coir, straw or compost will do. For larger beds you might want to use expanded clay balls or volcanic rock similar to those used in water retaining layers in green roofs.
5. Next is the layer your plants will be rooting in so fill with potting compost or top soil mixed with well rotted manure.
6. Plant your seeds or sow your seedlings.
7. Water into the upright around twice a week or when the pot/bed dries out.
   

Plastic bottle irrigation

When I first saw plastic bottle irrigation on an allotment site it confused the hell out of me. There in the middle of a bed on someone’s plot was a half submerged plastic bottle – at first I thought it was some kind of slug trap. After much head scratching an equally confused allotment neighbour said to me, ‘She pours water into to’ and added, ‘she’s got loads of them’.  The plot holder emerged before the end of the day and filled us both in to the theory behind the plastic bottle irrigation system.

They are an adaptation of much early method using an unglazed clay pot. The theory is a submerged vessel is filled and will gradually leak water into its surroundings.

As unglazed clay pots are quite hard to come by outside of rural Africa the next best thing is to use a plastic bottle. The plastic bottle turned upside down with the base (or top as it is upside down!) cut off and holes pierced in the lid.  The whole thing should resemble a semi submerged funnel.  Plants are planted or seeds are sown in a circle surrounding the semi-submerged bottle and the bottle/funnel is filled with water.

This directs the water where it needs to be and prevents plants getting a big soaking at once.

Plantings around the plastic bottle can include a ring of smaller plants such as salad leaves and radishes or you can put single ones in place for larger plants such as tomatoes.

Plastic bottle irrigation systems may be suitable for container growing and might help regulate watering if you need to go away for a long weekend.

Plant pot irrigation

An adaptation of this method involves semi-submerging a flower pot half filled with gravel or vermiculite. Seedlings are sown around the pot in the same way and the gravel or vermiculite gradually releases the water to the thirsty roots of your crops.

When irrigation is not needed

If we continue to have summers similar to those we have been having in the last few years there will be little need for any of these irrigation systems in outdoor beds. However, during the lead up to summer dry conditions have prevailed in the UK in recent years and if this is set to continue, an irrigation system of some kind will be paramount to ensuring a good harvest.   Like most growers this year I will pray for rain but pray most of it comes at night!