Irrigation in arboriculture

Which irrigation method to choose, which equipment...

Irrigation in arboricultureWhich irrigation method to choose, which equipment...

1. Arboriculture
2. Irrigation in arboriculture

In arboriculture, water is an input of increasing or even primary importance, depending on the region. It conditions the proper development and yields of trees, and can also play a role in disease pressure. What's more, it is becoming an increasingly important factor in the context of global warming.

This portal provides a description of all the irrigation systems used in arboriculture, and presents the advantages and disadvantages of each.

Aspersion

Sprinkling is defined as a form of irrigation that shoots water into the air, so that it falls back in a circle onto the ground, around thesprinkler, . In arboriculture, there are two different applications for sprinkling : overhead sprinkling, where the water is applied to the foliage, and underhead sprinkling, which keeps the foliage dry and distributes the water evenly around the trunks.

To a certain extent,overhead spraying can be considered as a form of frost protection.whereasunder-row spraying can be used to maintain total grass cover. Unlike localised irrigation techniques (especially drip irrigation), sprinkling is therefore characterised by its ability to influence the microclimate of orchards..

Example of preventive frost control using sprinklers in Spain - Wikipedia Commons

There are two classes of sprinkler adapted to arboriculture :

Micro sprinklers

Water is distributed by a rotating finned mechanism, over a diameter of 2 to 4 m, with an optimum flow rate and pressure of between 35 and 150 L/h, and 1.5 to 2.5 bar respectively. They are suitable for all types of planting density, and can be installed either in a pendulum arrangement on a suspended boom, or on the ground.

Mini sprinklers

These are used for more specific purposes, as they are necessarily placed on the ground and are unsuitable for high-density orchards. On the other hand, they have a higher flow rate, a larger sprinkler diameter and higher pressure (150 to 500L/h, 5 to 8m and 2 to 3 bar) and therefore generally offer better water distribution. The distribution system is a rotary turbine or beater mechanism.

Localised irrigation

In contexts where water resources are scarce, it is often preferable to use controlled irrigation, with a lower flow rate and as close as possible to the crops. In contrast to sprinkler irrigation, localised irrigation often generates less weed pressure because the soil surface is less moistened. The main point to watch out for is clogging : because of the low flow rate and the diameter of the nozzles, irrigation systems are more susceptible to clogging, so greater attention needs to be paid to filtering the water and protecting it from insects and external impurities..

There are two main categories of localised irrigation systems, which can save 20-50% water compared with sprinklers :

Micro-jets

These are devices with a relatively higher flow rate, and can be fixed to the ground or suspended, like micro-sprinklers. The distributor is a static mechanism with a deflector or turbulent system (vortex), which propels the water at a flow rate of between 20 and 60L/h, a pressure of between 1 and 2 bar, and a range of 1 to 2 metres..

Drip irrigation

Drip irrigation is characterised by a very low flow rate (1 to 2 litres per hour) circulating in a tube that may or may not be buried. Drip emitters are installed at regular intervals along the length of the tube, allowing a periodic flow of drops of water to a precise location. This technology is based on the ability of trees to draw enough water to cover their needs with only a small part of their root system..

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