Nursery irrigation

Modern systems are simple to operate, offer greater efficiency and can save a huge amount of time, Sally Drury reports

Harley Nursery: uses labour-saving irrigation system by specialist Flowering Plants - image: HW
Harley Nursery: uses labour-saving irrigation system by specialist Flowering Plants - image: HW

We all know that irrigation is key to plant production, whether you have two or 102 hectares, and it can be costly. Yet many nurserymen still rely on old inefficient systems, wasteful of electricity and water. In many cases smaller nurseries and retailers still carry out a great deal of watering by hand. One nurseryman in Shropshire knows how expensive that can be in terms of time.

Sitting high in the hills between Shrewsbury and Much Wenlock, the 2.2ha Harley Nursery is owned and run by Nick Murphy. The small, family-run retail concern was purchased by Murphy's late father, Duncan. It was he who in 1970 bought rose grower Edwin Murrells and, together with business partner Percy Thrower, set up the first garden centre in Shropshire. In 1990 Duncan Murphy sought a change in direction, acquired the site at Harley, developed the 1970s nursery and expanded the range of plants.

With horticulture in his blood, Nick Murphy gained an honours degree at Pershore and returned to Harley with ideas for improving and growing the business. Together with his partner Debbie, Murphy specialises in plants not found in most garden centres.

Diverse product range

The majority are propagated and raised on site. Along with a wide range of herbaceous and climbing plants, he grows formal and bare root hedging, a wide range of unusual shrubs, soft-fruit bushes and 125 varieties of ornamental trees. Fruit trees include 45 varieties of apple grown from mother stock originating from old manor houses in and around Shropshire.

With such a wide product range in a relatively small space, applying the correct amount of water of suitable quality at the right time was always an issue. Until recently most irrigation was done by hand, and in summer that took up much of the day. Over the past two years Murphy has been adopting Florimats 2 and 3 from Flowering Plants.

"Until a couple of years ago it used to take me eight-and-a-half hours just to do the watering. One of us was serving customers and one of us was always watering, so nothing else would get done. If we needed to do any maintenance it always got put back to the autumn," he recalls. "Then I took a £1,000 punt on Francis Richardson's system and realised how good it is - how labour-saving it is. From then on we just kept ploughing money into putting in more and more of his systems."

Francis Richardson is managing director of Flowering Plants. The firm has specialised in irrigation since 1976. Having read the work on sand filtration systems by scientist Dr Tim Petitt at Efford Experimental Research Station in the 1990s, Richardson developed the Manchester System of biological filtration.

"The biggest hole in Nick's budget was time wasted on hose watering and the place where most value was lost was on the retail benches," says Richardson, pondering his first communications with Harley Nursery. "We used to lose most of our potted rhubarb crop," Murphy confirms. "Now, using the Florimat 3 system on the benches, excess water is pulled out."

Collection pool: air added to rainwater before being pumped to nursery as required - image: HW

Rainwater collection

Today rainwater is collected, via guttering, from the polytunnels and discharged along with surface water into a surprisingly small pool at the lower end of the nursery. Until recently mains water was also used but now a borehole supplies additional water to the lined pool, which is just 6ft deep but contains some 60,000 litres. Air is added through a perforated pipe lying on the bottom and water is then pumped up to the nursery as and when required.

"The water is cleaned both mechanically and biologically. If you get the air right, the calcium right and the medium right, nature will do the rest and the plants will thrive," says Richardson. "We have a formula for calculating the size of reservoir required and it can be quite small, providing you know the sunshine hours, rainfall and wind - factors that govern evapotranspiration."

Murphy adds: "We didn't have any electricity on the site until last October so we relied on petrol pumps and mains pressure. Now everything goes through a pump supplied by Francis. It is so nice just opening up a valve when you see a bench needs watering. Five minutes later, it's job done."

For Murphy the first step was to introduce the system on 12 benches of herbaceous in the retail area. It saved so much time that he decided to invest part of the time saved into extending the system to the remaining retail benches. Those benches, 1.1m wide, have a 25mm fall from back to front, are covered with polythene, then the capillary matting and topped off with a cover. A standard drip line, fed from a main pipe underground, runs along the back of each bench and water is pulled, by gravity and capillary action, across the benches. A wick hanging under each bench ensures that any excess water is pulled away and returned to the holding pool. Plants on the nursery get watered first thing in the morning, at the turn of a valve.

Perfectly happy plants

It's easy to tell if plants are being overor under-watered. However, on the Florimat systems the tops of the pots normally look dry. Murphy says: "Customers would tell us the plants needed watering and I would pick up a pot and ask them to feel the weight. The plants are perfectly happy." You can see at once whether the growing medium is consistently too dry - it shrinks away from the pot. All you have to do then is shorten the relevant wick.

I was surprised by the lack of moss, lichen, algae and liverworts, especially in winter. Richardson explains: "When you first start capillary irrigation, providing the alkalinity is right, the mosses should start to turn grey within a week. The capillary action works like rising damp, lifting the fertiliser salts up to the surface. If the medium is dry enough for long enough, the osmotic pressure prevents those problems.

"It also prevents plants from rooting through. Sucking up water from underneath means the fertiliser stays in the pot, it's not washed through and with the right cation-exchange capacity the growing medium keeps it in the pots. The only thing moving from pot to pot, as the crop dries, is water."

Murphy adds: "Weeds don't germinate on the top, eliminating extra work for us." However, it does mean that every six weeks or so plants under cover need watering from above to wash the fertiliser back into solution in the pot. Rainfall takes care of the situation outdoors. Growth is excellent, as indicated by silver birch planted as 60/80 whips last year and now providing 2m-tall young trees of quality, balanced habit. It is also uniform growth.

Water use is less - Florimats have been shown to bring about a 75 per cent reduction in the reliance on water from sources other than rain - and there is no Pythium or Phytophthora on the nursery, despite using recycled water. That is down to the microflora in the water. The "good guys", notably the fluorescent pseudomonads, prevent infectious diseases. Spanish work has shown eight ways in which they do this.

System extended

With less time spent on watering, Murphy extended the system into the polytunnels last year. It required more than 140 tonnes of hardcore to attain the correct levels and create the necessary "islands" for the system to work. It is important not to bridge the gaps between the islands to prevent siphoning. Capillary action allows bedding, geraniums and fuchsias to look after themselves on a shared system. Flat-bottomed hanging baskets also did well, simply sat on the matting.

Murphy is now using time saved on watering and weeding to install benches with Florimat 3 for the A-Z shrub sales area. He finds that the system allows customers to "browse with their hands". It also allows the nursery to apply water to plants without deterring customers from spending their money.

The system is expandable and adaptable, for retail or production, on benches or on the floor. It can be small-scale or large. Not far from Harley Nursery is a 50-acre plot of Florimat 2. The average price for these systems tends to work out at around £5 per square metre.

Continuing to develop the system and accessories, Flowering Plants will soon have a new tray available to allow direct contact with matting. Components include a drip line that expands when water flows through it but lies flat when empty and stainless-steel hand lances with a range of roses that pass two times the amount of water as a standard rose but at one-third of the velocity. "You don't want to wash compost out of pots," Richardson explains.

Obviously the type of nursery, species of plants grown and source and availability of water have to be taken into account when choosing irrigation and the diversity of the industry and its products means a variety of systems have evolved. Overhead irrigation using sprinklers remains common but increasingly growers are turning to systems, such as Florimats, that are less wasteful of water, time and money.

Suppliers of nursery irrigation systems include:
Access Irrigation: 01788 823811
Arden Lea Irrigation: 01772 812433
Briggs Irrigation: 01536 260338
City Irrigation: 020 8462 4630
CMW Horticulture: 01430 422222
Delta-T Devices: 01638 742922
Denton Automation: 01903 892715
EJ Woollard: 01992 623232
Electronic & Technical Services: 01516 458491
Evenproducts: 01386 760950
Field Irrigation: 01344 891731
Flowering Plants: 01280 813764
Hortech Systems: 01406 426513
Horticultural Solutions: 01482 665449
HortiSystems: 01798 815815
Irrigation & Water: 08455 538410
Irrigation Online: 0800 316 0532
Irrigation Technical Services: 01202 874216
Javelin Irrigation Systems: 01507 607175
JD Ultasonics: 01924 378448
LBS Horticulture: 01282 873333
LS Systems: 01772 812484
Mitchell Technical Services: 01202 892402
New Leaf Irrigation: 01772 691896
Northern Polytunnels & Horticultural Supplies: 01282 873120
Wise Water Solutions: 01905 828142

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