Types/ Categories of Micro irrigation

Micro irrigation systems can be grouped in six main categories:

a. Systems with drip lines (operating pressure: 0.5–2.0bar; flow rates 0.5–4 litres/hour.

• This category includes the common perforated hoses, consisting of a thin tube of polyethylene (generally0.15–0.20 mm) with holes at a fixed distance.
• The perforated tubes do not have a flow rate control system and, therefore, they do not guarantee uniformity of distribution, which tends to be quite uneven due to frequent clogging of the holes.

b. Systems with drippers (operating pressures: 1–4 bar; flow rates 2–20 litres/hour).

• These systems consist of low density polyethylene tubes (diameter 16–25 mm) on which drippers are inserted at a proper distance based on the crop requirements.
• Button-type or arrow-type drippers may be used.
• Button-type drippers allow a certain uniformity of the flow.
• Also in this case, the self-compensating models provide a constant flow regardless of changes in the working pressure

c. Systems with emitters (operating pressures: 1–3 bar;flow rates 6–30 litres/hour).

• These systems are characterized by high unitary flowrates (6–30 litres/hour, with operating pressures of 1-3bar).
• The main advantages of these systems are the reduced incidence of clogging, as a consequence of the higher operating flow rate, and the greater wet surface compared with systems with classic drippers.
• These features overall allow more uniform growth of the root systems.

d. Systems with capillary tubes (operating pressures: 1–2.5 bar; flow rates0.7–7 litres/hour).

• These systems are becoming widespread due to their low cost and the possibility of having the lines already pre-assembled by the manufacturer, with considerable labour saving.
• This system consists of a polyethylene tube of 20–25mm diameter, on which are inserted capillaries of 0.5–1.5 mm internal diameter with adequate length to reach the point of dispensing.
• In these cases, for a given pressure, the flow rate is directly proportional to the diameter of the capillary and inversely proportional to its length.

e. Systems with micro-/mini sprinklers

• Sprinklers are conventionally classified as follows:

i. Microsprinklers (flow rate 30–150 litres/hour)

ii. Minisprinklers (flow rate 150–350 litres/hour)

• The sprinklers require operating pressures of approximately 1.5–2 bar and have emission holes calibrated between 0.8 and 2.3 mm. Therefore the flow rates are considerably higher than those used with the drippers and the infiltration rate (i.e. the rate at which the soil is able to absorb irrigation water) is slightly lower.
• Also the sprinklers can be standard-type or self-compensating, with the same features as described for the drippers.
• Micro-/minisprinklers systems can be divided as follows:

i. Dynamic, if they have parts that move during irrigation (also called micro sprinklers or mini sprinklers, depending on the flow rates) providing a circular wetting area with a greater radius than other systems.

ii. Static (no moving parts), also known as sprayers, able to provide wetting areas of different shapes (circular, semicircular, sectors).

f. Subsurface drip irrigation.

• Subsurface drip irrigation refers to the use of drip hoses positioned underground at a certain depth.
• This system consents to directly wet the underground root zone and reduce the evaporative water loss at the soil surface (higher water-use efficiency).