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Setting up a subsurface drip irrigation system: guiding principles and recommendations

A subsurface irrigation system targets a greater level of agronomic efficiency by applying the necessary resources closer to the plant for it to be allowed to develop, while reducing the growth of weeds.
it is essential to change the maintenance programme from a corrective approach (dealing with the problem when it arises) to a preventive or even predictive approach (anticipating the onset of a problem and making plans for any intervention

Whether it is used in agriculture (citrus fruits, olives, grapes, shelled or stones fruits, cereals, sugar cane…) or for watering Parks and Gardens (lawns, shrubs or flower beds, sedum for green roofs…), subsurface irrigation has many advantages, which are becoming more and more understood and appreciated by the clients. This is shown by the many enquiries we have received at shows such as SITEVI 2017 in Montpellier or PAYSALIA 2017 in Lyons, these not being the result of the clients’ curiosity but rather a desire to see the projects take shape in the short term.

Why use a subsurface irrigation system?

We must remind ourselves of the reasons for imple­menting this type of system:

• Targeting a greater level of agronomic efficiency by applying the necessary resources closer to the plant for it to be allowed to develop (water and fertilisers), while reducing the growth of weeds (reducing and even eliminating altogether the need for herbicides).

• Making tangible savings (water, energy, fertilisers, her­bi­cides, pesticides, labour… working on the land) by taking advantage of the improved efficiency of the system.

• Increasing the operational effectiveness by protecting the system, making it more discreet and increasing its life span by shielding it from mechanical damage (vandalism, mowing…) and UV rays.

• Making life easier for the users thanks to automation and the centralised control of the irrigation system and fertiliser application, thus avoiding the constraints of having to be present in the field and being better able to cope with global warming while generally having more time to concentrate on the core business and main tasks in hand.

• Improving the environment by allowing, for example, the use of recycled water, which could contain patho­gens, without allowing them to come into contact with people working in the Parks and Gardens.


A review of the basic principles

Of course, an efficient and sustainable subsurface irriga­tion system does not operate in the same way as an above ground system. There are a number of constraints, which must not be overlooked. These include, in particular:

• More serious consequences in the event of partial or total clog­ging of the installation. It will be more complicated to replace all or part of the system. The nature and techno­logy of the drippers used thus takes on an even greater importance.

• A different approach must be adopted for designing a suitable network that differs from a traditional instal­lation in order to prevent risks and facilitate the imple­mentation of a regular preventive maintenance programme.

• Efficient and precise irrigation management is requi­red, so as to avoid prolonged periods of water stress, which is the main cause of root intrusion.

• Greater financial investment is required, but this will generate a higher return on investment, albeit after a lon­ger period of time… requiring more elaborate calcula­tions and deliberations before arriving at any decision.

For example, we can quote the question most often asked by any candidate for the adoption of this new technology: how to reduce the risk of root intrusion in the drippers?

The dripper technology. It should be entirely suitable for this particular system. In our experience, there is a lower risk of encountering clogging problems with the incorporation of concepts that NETAFIM has been developing for many years:

• drippers with prefilters and water inlet located towards the centre of the tubing

• self-regulation with a flexible and efficient silicone membrane that facilitates the self-cleaning of the dripper

• anti-siphon (AS) device, which prevents particles from entering the dripline after irrigation

• the incorporation of an anti-root intrusion chamber or compartment

• taking agronomic factors into account (type of crop, soil, depth, tillage…)

• using copper impregnation technology (particularly copper oxide, XR)


THE REVOLUTIONARY AS XR NETAFIM™ for subsurface drip irrigation applications: Its secret is the revolutionary process of mixing copper oxide directly with the constituent material used in the anti-root intrusion barrier of the NETAFIM UNIRAM / UNIWINE / UNITECHLINE / BIOLINE XR dripper models. The XR concept has been developed exclusively by NETAFIM in order to provide its subsurface drip irrigation applications, for each market segment (irrigation in agriculture and parks and gardens, recycled waters), with the best protection against root intrusion and biological growth, without any chemical emissions and, therefore, without there been any negative impact on the environment. This provides a more efficient subsurface irrigation, with a more sustainable product, in a preserved environment.


The specific characteristics of the hydraulic design.

The hydraulics are not at all the same when a drip system is buried underground. Apart from using drippers designed and manufactured for this purpose, a number of other factors must also be taken into account:

• an advanced filtration system (when a domestic water supply is not available), which can better protect the drippers (sand or disk type).

• an efficient fertilisation system, which can help to pre­vent problems with the mixing process and the forma­tion of different agglomerates (excessive applications, incompatibility of certain substances with others, sediments…).

• perfect pressure control in the system (using control valves or pressure regulators to ensure proper obser­vance of the pressures calculated during the hydraulic system analysis), which is essential for a subsurface irrigation system

• the inclusion of methods of measuring and monitoring the physical variables, such as, for example, the flow rates, using water meters or pressure gauges (mano­meters), so as to control and anticipate any variations (example: actual flow rate lower than the theoretical flow rate = risk of partial clogging, actual flow rate higher than the theoretical flow rate = risk of leaks in the system). Moisture sensors must also be used so as to be able to better control the applications.

• air vents, which can help to prevent the development of low pressures in the system as well as high pressures linked to the presence of air, or they can facilitate the movement of air between the outside and inside of the system.

• a connection suitable for the constraints that are present in the soil.

• the incorporation of flushing solutions for the system during irrigation in order to facilitate the extraction of accumulated materials and prevent the physical risk of clogging.

These last two points are very critical because they are by far the most technical. We have never resorted to "grommet-type" connections, rather we used the technology of a holding clamp + QFLEX extension. It is more expensive, but infinitely more robust given the movement of the soil under surface irrigation conditions, especially when the soil is of the stony clay type. These products prevent the formation of leaks, which are very harmful for the performance of the subsurface system.


New NETAFIM QFLEX™ product for subsurface drip irrigation systems: a new range of couplings that ensure the quality and rapidity of the connection in a subsurface or above-ground drip irrigation system. There are many variations and they consist of flexible non-deformable tubes (no ovalisation or crushing) and different types of couplings at the ends, for connecting to a supply manifold (Polyethylene, PVC or FLEXNET™ type flexible tube) fitted with holding clamps and thin-walled or even thick-walled driplines, for applications on any type of terrain. More reliable, longer lasting, with less time spent on site! NETAFIM has systematically carried out its tests with the aid of computer simulation tools (IRRICAD software) and they are always seeking to improve the design of these aspects. For example, they were committed to the design of a head-end, including a pumping station capable of correctly suppling the network, in spite of the flow-rates required for the necessary flushing process, and also guaranteeing that the pressures at the end of the line are able to maintain the minimum speeds required for flushing the system.


Our recommendations: monitoring the irrigation…. corrective maintenance becomes preventive maintenance

Good irrigation management is very important with subsurface irrigation. We recommend the expertise of an agronomist for the design phase (assisting in deciding on the positioning of the driplines in the soil) and also when beginning operations. Taking into consideration the agronomic (soil, crop) and climatic factors will enable the farmer to optimise the irrigation and fertilisation phases throughout the whole season and thus avoid plant water stress.

Apart from the special characteristics of the network, which have an influence on its management, it is essential to change the maintenance programme from a corrective approach (dealing with the problem when it arises) to a preventive or even predictive approach (anticipating the onset of a problem and making plans for any intervention). A suitable periodic maintenance programme should be implemented. This must include a flushing routine for the system, with regular checks carried out on the physical variables (pressure, flow rate…), cleaning the filtration media (automatic or manual) and finally applying a weak acid solution (Nitric or Citric) as a treatment to remove any physical deposits or even oxygenated water or chlorine to remove any biodeposits.


And the future prospects?

The practice of burying a drip irrigation system underground has been carried out by Netafim for several decades in a number of different locations. Today, we are able to note with satisfaction that French agricultural producers, as well as players in the landscape sector, are willing to try and catch up in this respect with other countries that use this method to produce certain crops (Italy/grape vines, Israel/turf grass, USA/Maize –corn, Spain/Fruit trees…). We believe that the new generation of drippers, the growing profes­sionalism of the installers, the development of crop management technologies (sensors/controllers/ centra­lised systems) coupled with meticulous agrono­mic monitoring, will considerably facilitate the development of this innovative form of irrigation, making it even more commonplace in France in the years to come.

However, it is also evident that the high financial commitment means that there will always be the risk of some producers and local authorities being disappointed, while other potential clients will have certain doubts and suspicions. That is why we are urging the professional players in this market to meet the prerequisites required for this innovative and also very demanding practice! It is only in this way that we will be able to realise its true value on the irrigation market, both in France.