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Drip irrigation

To most of us irrigation means pumps and pipes and sprinklers. But if you think a little laterally there is an alternative: drip irrigation.

In order to flourish, plants require a regular supply of water. The amount and frequency varies with the variety. Most indigenous plants, for example, require less water less frequently than the majority of exotics – plants that have been imported into a climatic zone to which they are not fully accustomed (e.g. certain roses into the dry parts of South Africa; or a protea plant into the UK). Exotics need individualised 'micro climates' created for them to survive (e.g. Kew Botanical Gardens in the UK and Kirstenbosch Botanical Gardens in SA). Plants that originate and thrive in their local environment are referred to as 'indigenous'. 

Water wastage is prolific. In South Africa long noughted rands are poured into automatic sprinkler systems that merrily encourage driveways, pavements and other inanimates to grow. This method is very cost ineffective. Another factor is that, especially when the sun is shining, much of the irrigated water is lost to evaporation. Most plants are solar sensitive and internally (metabolically) active very early in the mornings.

Drip irrigation is far more water wise. It allows the delivery of a limited volume of water to the soil just above the root zone of each individual plant, or clump of small varieties, ensuring that wastage is at an absolute minimum. For most garden plants (aside from very large shrubs and trees), two litres per plant per hour is adequate. Every drop goes to the roots, avoiding the wasteful 'feast and famine' caused by irregular soakings.

Drip irrigation  Drip irrigation

How to do it

For a complete list of BIO-SYSTEMS products click on our Product table.

  1. Plan your garden (it usually pays to consult a landscape gardener with personal experience of your locality).
  2. Set out your plants in the chosen arrangement for colour, texture, height etc.
  3. Lay a manifold of 12mm plastic pipe either on, or just beneath the soil.
  4. Fasten all joints using Full Flow™ fittings, or similar. Although slightly more costly than push-in clamp junctions, they are more reliable and cheaper in the long run.
  5. Armed with an electric drill with a 4mm steel bit, drill one hole 20mm (on the upper side) above each plant.
  6. Press in button drippers – they should be a snug, tight fit.
  7. Lead in water from your mains tap – turn one quarter turn to check pressure and ensure all works properly.
  8. Link in the gravity feed from your grey water treatment tank (see The ultimate home grey water treatment) with a switch valve and voilà! your water-wise system is ready to go.

Some pointers

  • As a general rule, running the system for two hours once a week in the late evening is satisfactory (although, early morning is better as plants resume typically recessed internal osmotic activities at sunrise). With recycled water you can operate more frequently. Simply split the manifold to suit the tank volume.
  • Limit the number of drippers per line to a maximum of 100.
  • Use drippers rated at 2.2 litres per hour for the average plant (daisy, rose bush etc.) but fit four-litre-per-hour ones for larger shrubs. Better yet, you can fit two or three extra 2.2 litre drippers, thereby broadening the discharge over the larger root zone of the bigger plant.
  • It pays dividends to mulch your open soil beds with rough bark, small pebbles, plastic, or compost. This limits water lost to evaporation (hot sunlight) and desiccation (wind).

What to watch out for

  1. Root zone. One draw back to drip irrigation is that the roots will proliferate over time in the immediate vicinity of the dripper. This may make a plant unstable as most (larger) varieties derive mechanical benefit from the spread of their roots. They also thrive as their catchment area for nutrients is increased. It's a good idea, therefore, to move the dripper pipes around every year in an effort to vary the water shed.
  2. Fertilizing. The application of fertilizer is often hampered by mulch. However, the blanket can be opened periodically for this purpose. Although, if your dripper line is just below the surface, mulch does not impede water and fertilizer – it's also aesthetically easier on the eye. Alternatively use a cylindrical slow applicator inserted into the line (Gardena make one), or dose the water supply tank with liquid fertilizer for more even distribution.

For more information on the re-use of grey water click on The ultimate home grey water treatment.

For a complete list of BIO-SYSTEMS products click on our Product table.

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