Table of Contents
Subsurface drip irrigation: how to choose the right dripline according to soil, climate and crop
Subsurface drip irrigation is a highly efficient irrigation technique that delivers water and nutrients directly into the soil volume explored by the roots. Compared to surface irrigation, it reduces evaporation, limits wetting of the vegetation, helps control weed development and simplifies many mechanical field operations.
Because the dripline is installed below the soil surface, the system design requires particular attention. Once buried, the system must ensure uniformity, reliability and long-term durability, without the possibility of direct visual inspection.
Choosing the right dripline for subsurface irrigation cannot be based on a single parameter. Diameter, wall thickness, flow rate, emitter spacing, installation depth and emitter technology must all be defined according to three main factors: soil type, climatic conditions and crop characteristics. Only the right balance between these elements makes it possible to create a stable and continuous wetting pattern, consistent with root development and the plant’s water requirements.
The role of soil: how water moves through the profile
The first factor to consider is soil texture, because soil determines how water spreads from the emission point. In a subsurface drip irrigation system, the aim is not simply to “bring water underground”, but to build up, over time, a wetting pattern suited to the crop, avoiding both deep percolation and the formation of dry areas or localized waterlogging.
In sandy or very loose soils, water tends to move downwards more rapidly than sideways. The wetting pattern therefore becomes narrower and more vertical, with a higher risk that water may move beyond the root zone before the plant can use it. In these conditions, it is preferable to choose lower-flow emitters, closer spacing and short, frequent irrigation cycles.
In loam, silty or clay soils, on the other hand, greater capillarity promotes wider lateral redistribution. This can allow wider emitter spacing or greater distances between driplines, but it still requires careful assessment of infiltration rate and soil drainage capacity. In heavy or compacted soils, flow rates that are too high or irrigation cycles that are too long can create root asphyxia conditions, especially during growth stages when the crop is more sensitive to stress.
For this reason, in subsurface irrigation, emitter flow rate should never be considered separately from soil assessment. As a general rule:
• sandy soils require lower flow rates, closer spacing and frequent irrigation;
• loam soils require a balance between flow rate, emitter spacing and root depth;
• clay soils require careful attention to waterlogging, irrigation duration and root-zone oxygenation.
Installation depth must be defined in the same way. If the dripline is installed too close to the surface, it may encourage evaporation, weed development or mechanical damage. If it is installed too deep, irrigation may be less effective during the early stages of crop development or in crops with a shallower root system.
In tree crops, installation depth must be consistent with the area of greatest root activity. In field crops, it must also take into account sowing, tillage, rotations and machinery management.
Tree crops and field crops: different needs, different choices
The second variable is the crop. In orchards, vineyards, olive groves, hazelnut orchards and other tree crops, subsurface irrigation is used in permanent systems, alongside root systems that develop over time. In these cases, the dripline must guarantee consistent performance for many years and withstand the main risks associated with buried installations: root intrusion, clogging, suction of soil particles, pressure variations and more complex maintenance.
In tree crops, the objective is not to wet the whole soil volume indiscriminately, but to create a continuous moist strip along the row, positioned in line with the active root zone. This allows the plant to access water and nutrients regularly, helping maintain a more stable vegetative and productive balance. Precision is particularly important in crops that are sensitive to water stress or excess water, such as vines, olives, fruit trees and hazelnuts, where irrigation management can affect not only yield but also final product quality.
In field and forage crops, such as maize, soybean, irrigated cereals or alfalfa, the design approach is different. In this case, subsurface irrigation must integrate with larger surfaces, row spacing, rotations, mechanical operations and the economic lifespan of the investment. The system must ensure uniformity over long lines, reduce waste and allow efficient distribution even in complex plots.
The expected lifespan of the system also influences product choice. In an orchard or vineyard, where the system is designed to remain in place for many years, thicker walls, reliable emitters, specific protection systems and materials suitable for long-term management are required.
The installation distance of the buried dripline — which may be doubled in orchards with row spacing greater than 3 meters — must also take into account the risk of constriction caused by the crop’s main roots.
Positioning the dripline just a few tens of centimeters from the plant can be an advantage in the post-transplanting phase, supporting establishment and rapid early growth. However, as the root system develops, larger roots may begin to interfere with the dripline and eventually compromise its functionality.
To reduce this risk, it is always advisable to install driplines at an adequate distance, so that they can effectively intercept most of the absorbing root hairs even when the plant is fully mature. To ensure optimal establishment during the first phase, an auxiliary surface dripline, even a lightweight one, can be used and then removed in the second or third year, depending on the characteristics of the rootstock.
Climate, water requirements and irrigation frequency
Climate is the third decisive factor. In areas with long summers, high temperatures, frequent winds and irregular rainfall, subsurface irrigation helps reduce evaporation losses and maintain more stable moisture levels within the soil profile. This advantage becomes particularly important in Mediterranean environments, where crops face prolonged periods of water stress and water availability is increasingly variable.
In hot, dry climates, the choice of dripline must support regular and controlled distribution, avoiding excessive fluctuations in soil moisture. More frequent irrigation cycles and well-calibrated volumes help keep the root zone active without generating waste. In these conditions, pressure-compensating emitters and systems capable of maintaining constant flow rates are especially useful, particularly in plots with slopes, uneven ground or long lines.
Irrigation frequency is another factor that must be carefully assessed. Some crops and soils require short, repeated cycles, while other systems can operate with longer and less frequent irrigation events. In short irrigation cycles, it is important that the dripline responds quickly when the system opens and closes, avoiding unwanted drainage at the end of the cycle and keeping the wetted volume stable.
Water quality requires the same level of attention. Water containing suspended solids, carbonates, iron, organic matter or a high biological load increases the risk of clogging. This is why the choice of dripline must always be supported by a proper filtration system, periodic flushing, air release valves and careful fertigation management. In subsurface irrigation, prevention is essential: a buried system must be designed to minimize problems before they occur.
Irritec solutions for subsurface irrigation: Multibar® C Rootguard® and Multibar® F a.s.
Within the Irritec range, two solutions specifically meet the needs of subsurface irrigation in tree crops and field crops: Multibar® C Rootguard® and Multibar® F a.s., also available in the a.s. – d.s. version with Drop-Stop system.
Multibar® C Rootguard® is the ideal solution when protection against root intrusion is a priority. It is particularly suitable for multi-year subsurface irrigation systems, especially in tree crops, orchards, olive groves, vineyards and hazelnut orchards, where permanent root systems can gradually move closer to the emission point.
Rootguard® technology protects the emitter, helping maintain system efficiency and reducing the risk of clogging caused by root growth. In this way, water is distributed by capillarity through the soil profile, creating a continuous and stable moist zone along the row.
Multibar® F a.s. is a dripline with a flat pressure-compensating emitter and anti-siphon system. The pressure-compensating emitter maintains a constant flow rate as pressure varies, thanks to its internal silicone membrane, ensuring uniform distribution even in uneven topographic conditions, long lines or fields with differences in elevation.
The anti-siphon system helps prevent impurities, soil particles and contaminants from entering the emitter, which is a fundamental requirement in buried installations.
The Multibar® F a.s. range includes diameters from 16 to 25 mm, wall thicknesses up to 47 mil and nominal flow rates from 1.00 to 3.80 l/h, with recommended filtration at 130 microns. The available configurations make it possible to adapt the dripline to tree crops, olive groves, vineyards, nurseries and subsurface irrigation applications, as well as to field crop contexts where uniformity, strength and long-term reliability are required.
When the project requires short irrigation cycles and even more precise management of the system closing phase, the Multibar® F a.s. – d.s. version with Drop-Stop system can be considered. This technology stops the flow at the end of the irrigation cycle, preventing the dripline from emptying and helping reduce waste. It is particularly useful in systems where irrigation frequency, distribution precision and stability of the wetted volume are decisive factors.
The choice between Multibar® C Rootguard® and Multibar® F a.s. should not be seen as a rigid alternative, but as a technical evaluation based on the specific project conditions. Where the main risk is root intrusion in permanent systems, Rootguard® provides a targeted solution. Where pressure compensation, anti-siphon protection, uniformity over long lines and the management of frequent irrigation cycles are decisive, Multibar® F a.s. and Multibar® F a.s. – d.s. offer configurations suited to complex conditions.
In conclusion, designing an efficient subsurface irrigation system means assessing soil, climate and crop together. The best dripline is not the one with the highest performance in absolute terms, but the one that best matches the hydraulic behavior of the soil, the depth and extension of the root system, the plant’s water requirements and the expected lifespan of the installation.
Only this integrated assessment makes it possible to achieve uniform distribution, reduce waste, protect the system over time and fully enhance the advantages of subsurface drip irrigation.
