Your plants will welcome drip irrigation

Preserve water in the hot summer months by installing this type of system in your garden

THE HEAT is on and gardens are baking in the midsummer sun. Now is the time to consider drip irrigation as a potential solution for your garden this weekend. What is drip irrigation? It’s an irrigation method that conserves moisture by allowing water to drip slowly to the roots of plants, either on to the soil surface or directly on to the root zone, through a network of valves, pipes, tubing and emitters.

Drip irrigation is the preferred method of irrigation in all countries with a hot, dry climate, where droughts are common and water conservation is vital.

The latest equipment permits high-precision irrigation. As a result, drip irrigation is now used in commercial horticulture and private landscapes in more than 80 countries. During the 2005/06 severe drought in the Western Cape, when water restrictions were imposed, the only installed irrigation system that was permitted to be used was drip irrigation.

“The basic scientific principle underlying drip irrigation is simple capillary action,” said drip irrigation expert Philip Botha, from Cape Waterplant. “A common misperception is that water only moves downwards through the soil, pulled by gravity. In fact, water movement is also determined by capillary action – a force of attraction between the water and the soil particles that causes the water to move upwards and outwards into the microscopic spaces between soil particles. This capillary moisture is the primary source of water for plants.”

Botha has been installing high precision drip irrigation for more than a decade, monitoring each installation closely.

“In all soil types, ranging from heavy clay soils and ‘oily’ soils to sandy types, a sub-surface drip irrigation system penetrates the soil much better than overhead surface type systems,” he said. “Loamy soil, which contains equal proportions of sand, silt and clay, is ideal. However, plants can thrive in a very broad spectrum of soil textures when subsurface watering is applied at the proper rate, with appropriate spacing.”

His estimation is that drip irrigation can save 65 percent on water consumption in a garden.

The primary benefit of drip irrigation is that it uses water extremely efficiently. The major difference between sprinkler and drip irrigation systems is the percentage of water being utilised by the plants that are irrigated, and water lost to evaporation.

Although a drip system may cost more to install than a spray system initially, it does capitalise itself soon when running costs are considered.

“It is usually possible to convert existing sprinkler installations to a drip type installation, which is cost effective. And a correctly installed drip system requires low maintenance as it is self-cleaning and flushes itself out automatically before and after each running cycle.” He said research has shown that: ● A drip irrigation system irrigates a bigger area than sprinklers, using the same amount of water.

● A drip system achieves uniform water coverage over the area being watered. When spaced correctly, the same amount of water is applied per square metre throughout. This applies whether the drip lines are sub-surface (for lawns) or flat on the ground. Roots do not grow into the sub-surface drippers when they are properly installed.

● Water normally comes out of the sprinkler nozzle at high pressure, causing atomisation of the water and breaking it up into very fine particles, which are too light to fall to the ground immediately. Much of it evaporates long before it gets anywhere near the ground.

● A properly designed drip system can eliminate evaporation losses from the soil surface, with correct installation and proper surface mulching being used.

● Losses to evaporation in a conventional spray type system can be considerable.

“During the hot summer months in Cape Town, and with the southeaster blowing, this can range up to nearly 100 percent, with water literally evaporating faster than it can penetrate the soil, especially when the soil is dense,” said Botha.

A frequent problem associated with sprinklers in gardens is obstructive plants. Young plants thrive initially, growing rapidly until the plant gets bigger and denser, disturbing the original spray pattern. This invariably results in some parts being overwatered and other parts being left completely dry, because the water sprayed cannot penetrate the growth. In comparison, drip lines are laid flat on the ground surface where the water enters the soil directly, and the watering pattern is not influenced by plant growth above the ground. This type of installation is especially useful when the growth is very dense.

Drip lines can include mist sprayers, for example, for areas where annuals are planted, or to allow young plants to establish. In the latter case, once the root systems of the plants are established enough, the sprayers can be removed from the line.

Drip lines are particularly useful in hard-to-water areas, for example, where the space is too narrow to be watered efficiently with conventional sprays, or has irregular curves, so that there is wasteful overspray.

This system may be ideal for areas of a garden that require frequent watering, such as the veggie garden. And if you dislike weeding, it’s worth knowing that there’s less weed growth with drip irrigation when compared with spray irrigation.

● For free information about drip irrigation, send your contact details to daretofly@lantic.net.

OUT OF SIGHT: Drip irrigation can be positioned along borders and under lawns.

PICTURE: LUKAS OTTO WATER-WISE: Drip irrigation lets water penetrate the soil around the roots of plants slowly, eliminating or reducing water lost to evaporation.

CONTAINER PLANTS: Container irrigation can be included in a drip irrigation system.

WELL-FILTERED: Drip irrigation includes pipes with tiny nozzles. Modern nozzles are fitted with a filter which prevents plants growing into the pipes.