Water-efficient and discreet, drip irrigations systems positioned above ground or even the subsurface type, have evolved considerably. New types of drippers are now available and with the appropriate water treatment and an adapted legislation and accreditation, they can also be used with recycled wastewater.
Changes over the last few decades
With more and more presence on the agricultural or parks and gardens market, micro-irrigation systems are becoming increasingly efficient in the various world markets. The users are constantly looking for a better definition of the irrigation obtained, by reducing the flow available to the emitter. This is one of the reasons why the different manufacturers are prioritising drip irrigation products with built-in or integrated drippers, rather than the sprinkler systems, and developing products adapted to the different market segments (either in agriculture or the green spaces sector).
We now have the traditional in-line drippers pre-installed into a polyethylene drip tube, such as the integrated driplines (i.e. drippers factory-installed inside the polyethylene tube) with pre-set spacing, which is more robust and faster to install. There are two categories of drippers: the basic turbulent flow type (a simple labyrinth or chicane placed in the dripper slows the flow path in a way that allows the flow rate to be as close as possible to the nominal value).
These types of drippers are very dependent on the pressure exerted in the drip tube at the dripper inlet and they are quite sensitive to the risks of clogging if contaminated water is used. The second category consists of self-cleaning or pressure compensating drippers (apart from the labyrinth, a membrane regulates the pressure, and this allows for a far greater pressure range to be present in the dripline, thus ensuring that the dripper’s flow rate is equal to the nominal value).
What drives the green space (parks and gardens) market and what are the challenges
To go even further with this approach, the most high-tech manufacturers have have developed different segments of the agricultural or green space market and added special features to each of the products in the range. This segmentation has led to greater specialisation, which is essential in ensuring the success of new micro-irrigation applications.
The integrated driplines subject to this distinct segmentation are very common today in the agricultural markets as well as the green space markets. In order to bring motivations to this distinct area of segmentation, it is essential at this stage to remember the motivations and challenges that apply, for example, in this secondary green spaces market.
• Saving on water: the users much prefer a precision irrigation system that limits the amount of water applied to the target zone without losses and without projecting water onto busy roads or footpaths. With no losses into the atmosphere caused by runoff or evaporation, low flow drip irrigation generates a significant saving on water compared with the traditional sprinkler systems (nozzles or rotors).
• Discretion: by positioning it below the mulch or beneath the ground, the users aim to keep the systems out of sight and away from malicious intentions, thus reducing the risk of vandalism to zero.
• Modular and flexible: the drip irrigation systems are compact, discreet, modular and can be adapted to practically all situations.
• A creativity that is also conducive to respecting the environment: This allows for an expansion in the field of creativity and enhances the product offer in the green spaces and sports field sector, as well as benefitting the environment: the concept of a green city thus becomes achievable (combatting climate change, encouraging biodiversity, more clean air, CO2 absorption…).
The most noticeable product changes on the Green Space market
On the green space market, the packaging is adapted to the specific features of the field or site: the coils are smaller in size than those used in agriculture, being on average 50 m or 100 m in length. The nature of the polyethylene used makes the product more flexible and thus easier to lay, avoiding ovalisation of the pipes.
The flow rates are adapted to cater for an offer based on low flow, such as 1.6 l/h, 1.0 l/h or even 0.6 l/h, as the rates of 2.3 l/h or 3.5 l/h, which were very common in the 1980s and 1990s, are less and less in demand. Thus, if the dripper technology is optimal, the resistance to clogging is greater today than it was previously and there is no longer any need to have the “high flow rate” offer.
Therefore, the users are more and more professional and would not hesitate to check the quality of the offer by referring to the ISO international standards, such as the ISO 9261. This demand for an international benchmark and transparency has, for example, encouraged us, for a number of years now, to publicly display all the characteristics of our drippers, such as, for example, the dimensions of the passage of water, the dripper’s filtration area or the K and X constants, thus allowing the user to understand precisely and define the changes in the flow rate in relation to the pressure variation (turbulent-flow drippers).
Subsurface drip irrigation for green spaces and its special features
Subsurface drip irrigation is more demanding because of the labour required in the case of an incident occurring and it is important to remember that our offer differs according to whether it will be an above-ground or subsurface application.
In the first place, it is necessary to use drippers that are self-cleaning (flushing) through a large labyrinth and with pressure compensation, capable of delivering exactly the same amount along the line, from the first to the last dripper, without any risk of clogging. The wet bulb formed underneath each dripper must be available to the roots and allow the plants to achieve optimum growth. It is sometimes necessary to vary the distance between the lines according to the nature of the soil: they will be closer on a light soil and should be further apart on a heavy soil.
A strong emphasis is also placed on having the drippers provided with the anti-siphon feature: the drippers should be able to close when, between two irrigations, and on account of the slope, the water being discharged from the pipes creates a vacuum behind it, which can suck in particles from outside the dripper. This is not in any way to be confused with anti-draining, which has the feature of retaining the water in the pipes between irrigations: in any case, it is important to avoid the risk of bacterial growth, particularly when recycled water is used!
Finally, it is important, above all, to check that there is no plant water stress by ensuring that there is no risk of root intrusion, which could block the drippers. That is where, once again, the dripper technology will be important: it must have an anti-root intrusion feature. i.e. it must have a separate labyrinth at the chamber outlet to act as a barrier for root intrusion and also, ideally, the presence of a copper oxide component in the material used could improve the dripper’s resistance to root intrusion as well as bacterial growth and the emergence of biofilms.
Last but not least: the hydraulic design of a subsurface system, if specific equipment is required, must also be carried out in accordance with the industry standards. This is where a professional distributer/ installer must be called in, his or her work being to select the correct and suitable emitter products and also incorporate into the design additional components such as the flushing manifold, air vents, filters… to ensure that the solution obtained conforms to the system demands.
(2nd part of the article in the next issue)