The subsurface system (SDI)

As the name suggests, subsurface drip irrigation, or SDI for short, is drip irrigation applied underground. There are two forms of SDI: shallow and deep. Shallow burial refers to the burial of the drip lateral a few centimeters below the surface (see the Seasonal/multi-season system and Permanent system).

The goal of deep burial is multi-season use with the same drip line/tape being used from a few years to over 20 years. The burial is generally 20–30 cm (8–12”), with thicker drip line/tape (minimum 12 mil and up to 45 mil) used to ensure that the product will properly function for many years.

Additionally, pressure compensated (PC) drip lines may be used to achieve extra-long run lengths, or to irrigate on sloping ground. This SDI method has a wide range of crop applications, including cane, corn, cotton, vineyards, tomatoes, orchards, and alfalfa.

There are many variations of SDI systems. Below are examples for both row-crop and orchard/vineyard applications.


Deep burial can provide an excellent solution for crop rotation of broadacre/full cover crops. The following provides a wide wetting pattern on many soils, and does not require GPS guidance for placement.

Flex-Rotation Crop SDI System

SDI is the most advanced form of irrigation. Although there is more complexity in setup, there are significant advantages that warrant covering here.

Save water – no evaporation
Irrigation applied underground eliminates surface water evaporation, which can be as high as 45% with sprinkler irrigation

(Measurements of evaporation during sprinkler irrigation, University of Southern Queensland, 2012)
Minimize weeds
By applying water directly to the plants, no water is being
applied to the interrow. Less water in the interrows or on the
surface means fewer weeds, and lower costs (herbicides) to
eradicate the weeds.
Stronger root structure
When a drip lateral is buried 20–30 cm (8–12”), roots need to “chase” the water. This leads to a very healthy root structure
that penetrates deep into the ground, as opposed to concentrating on the surface.
Reduce plant disease
A noticeable difference with SDI is that, while the plants are irrigated, the top soil remains relatively dry. Compared to sprinkler irrigation, or even surface drip irrigation, SDI enables you to irrigate right up to harvest. Furthermore, a drier surface results in less humidity and therefore less risk of fungal disease.
Easy field access and harvest
When drip laterals are buried, field access is easy, as SDI eliminates the need for irrigation pipes on the surface. For harvesting of nuts where mechanical sweepers are used, any irrigation on the surface can be a problem, which is eliminated with SDI. Furthermore, you can irrigate right up to harvest without the normal risk of bogging in crops such as sugarcane and alfalfa.


Better water and air distribution

SDI improves water movement and air–soil–water balance as water distributes in a sphere of 360 degrees away from the drip lateral.


Comparatively, when a dripper is on the surface, the water can only distribute in a 180-degree pattern

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