Subsurface drip irrigation – trendy technology in Moldova’s fruit sector!

Subsurface drip irrigation or SDI, is currently one of the best investments available to fruit growers, regardless of country. Over the past five years, the cost of this system has effectively converged with that of conventional drip irrigation, while offering numerous advantages over surface-laid systems.

In this article and accompanying video, Ion Ciobanu, a farmer operating what is considered a small farm by Moldovan standards, demonstrates his subsurface drip irrigation (SDI) system to colleagues from Uzbekistan. He speaks openly about its advantages and limitations and shares detailed information on costs.

The farm visit was organised under the FAO/EBRD initiative on climate and environmental sustainability in the agrifood sector, within subcomponent 2.2.3, “Greening the fruit and vegetable value chain in Uzbekistan”, with support from FARM, the Federation of Agricultural Producers of Moldova.

The orchard and vineyard were established around five years ago, while the owner decided to switch to subsurface irrigation at a later stage. He installed the system last year and carried out a substantial share of the work himself, from trench preparation to pipe connections and equipment assembly.

Unlike a conventional drip line laid on the soil surface, the laterals here are installed at a depth of approximately 40 centimetres. In the orchard, they are positioned around 50 centimetres from the tree trunks. With row spacing of about four metres, this layout leaves sufficient room for tractor operations and reduces the risk of damage from agricultural machinery.

According to Ion, subsurface placement offers several practical advantages. The pipes are protected from birds and animals, shielded from sunlight and mechanical damage, and deliver water and nutrients directly into the root zone without wetting the soil surface or encouraging vigorous weed growth.

The owner also highlights the substantial reduction in water losses through evaporation. In his assessment, under surface irrigation a significant share of the water may evaporate or be distributed away from where plants need it most. With subsurface delivery, water and dissolved fertilisers are directed straight to the roots.

One of the most interesting points in the video concerns the expected service life of the system. FAO irrigation consultant Serhiy Alba, who has many years of experience with irrigation systems, states that a high-quality, rigid dripline, if properly designed, can remain operational for up to 50 years. He explains that underground installation keeps the material in a dark and relatively cool environment, protects it from ultraviolet degradation, and prevents repeated exposure to machinery and animals.

The 50-year estimate is based on experience from the United States, where comparable systems have reportedly operated for 50 years or more without requiring replacement. Manufacturers’ warranties are typically around 20 years. Actual service life will depend on pipe quality, water quality and filtration, operating pressure, effective root intrusion control, correct installation, and the ability to flush the lines.

The project economics are equally noteworthy. According to the owner, the subsurface irrigation system covering eight hectares cost approximately EUR 25,000. However, nearly all installation work was completed by the owner himself; the actual project cost would likely have been higher if contractors had been engaged. In this case, the cost per hectare appears relatively high because the farm is small. On larger farms, the cost per hectare generally falls, as a substantial share of total investment relates to fixed infrastructure such as the water storage reservoir, pumps, and the fertigation unit.

Serhiy Alba estimates that the overall cost difference between subsurface and conventional surface-laid systems is only around 5–7%. According to him, the specialised dripline itself is approximately 3% more expensive than a standard one. When costs are assessed over several decades of operation, he believes that the subsurface system may therefore be considerably more economical.

The drip lines deliver not only water but also fertilisers. The system therefore performs both irrigation and fertigation functions, allowing nutrients to be supplied directly to the active root zone.

The participants discuss in detail how subsurface irrigation affects root development. Under surface irrigation, a substantial proportion of the root system tends to remain concentrated in the upper soil layer where water is available. With subsurface water delivery, roots develop more deeply. In the view of the specialists participating in the discussion, a deeper root system can reduce plant stress during hot and dry periods. This is particularly relevant in Uzbekistan, where high temperatures and limited moisture can slow fruit development for prolonged periods. In addition, during the cold winters that regularly occur in Moldova, deeper roots may be better protected from frost damage.

The discussion includes an example from Uzbekistan, where apples exposed to severe summer heat stress may remain almost unchanged in size for two months despite very high water use. Participants associate this with insufficient access to water and nutrients. Subsurface irrigation is considered one way to deliver moisture deeper into the soil profile and create more stable conditions for the root system.

On his farm, Ion applies approximately 50–60 cubic metres of water per hectare in a single irrigation event. The farm is divided into three independent zones: one orchard block and two vineyard blocks. Each zone is irrigated separately, approximately once every three days under the regime currently used by the owner.

The participants emphasise, however, that neither irrigation volume nor frequency should be transferred automatically to other farms. They must be calculated with reference to the crop, plant age, weather conditions, soil structure, rooting depth, and actual soil moisture.

A separate part of the discussion focuses on whether subsurface irrigation can be used on the sandy and saline soils found in Uzbekistan. Ion notes that loamy soils predominate on his farm and that he has no direct experience of operating the system under highly saline conditions.

Water may move differently through sandy soils than through loams, so installation depth, emitter spacing, and irrigation duration should be determined after assessing the specific site. This reinforces one of the video’s central messages: even an effective technology cannot simply be copied without adaptation to local conditions.

In the vineyard, the dripline runs approximately along the centre of the inter-row space. Ion explains that grapevine roots can extend considerable distances in search of water. According to him, individual roots may reach six, seven, or even eight metres.

Water may spread approximately one metre or more around the buried lateral, although the actual wetted zone depends on the amount of water applied and the physical properties of the soil. The greater the irrigation volume, the wider and deeper the wetted profile becomes.

The participants also inspect the technical components of the system. The main line is connected to a pump, filters, pressure gauges and distribution valves, which allow the owner to select the zone to be irrigated. Additional filters are installed upstream of individual zones. The farmer monitors pressure at the inlet and after the water passes through the filtration equipment, adjusting pump operation as required to maintain the necessary pressure in the drip lines.

At different points in the discussion, operating pressure in the distribution system is reported at approximately 2.2–3 bar. The owner notes that longer rows require higher pressure to ensure that water reaches distant sections evenly. When two drip lines are installed, Serhiy Alba recommends offsetting the outlet positions, with one directed to one side and the other to the opposite side. In his view, this helps create a more uniform wetted zone and prevents all water from being concentrated in a single location.

According to the owner, the system requires very little routine maintenance. Once a year, he opens the flushing valves and runs water through the lines until it is clean. When the system is started, air is released through a dedicated valve, which closes once water reaches it.

Ion and Serhiy also describe the method used on the farm to prevent roots from entering the emitter outlets. According to them, a small amount of herbicide is injected through the system once a year in early spring to suppress roots immediately around the emitters. In their assessment, this fully resolves the problem.

One of the main conclusions of the discussion is that the performance of subsurface drip irrigation depends not only on pipe quality or pump capacity. Professional system design is critical. Row length, elevation differences, operating pressure, mainline diameter, flow rate, emitter spacing, and the division of the farm into irrigation zones all need to be calculated correctly. On sloping land, excessive water may reach the lower part of the field while the upper section receives too little.

According to the participants, rows of around 100 metres are easier to manage for uniform irrigation. Longer rows impose greater demands on system design, pressure and regulation and may therefore require more powerful and expensive pumps and other equipment.

The video presents subsurface drip irrigation not as an abstract concept but as a functioning system with clear advantages, costs and limitations. Participants are able to examine the entire chain, from dripline placement and root development to pumps, filters, sensors, valves and line flushing.

Ion’s experience is particularly valuable because he installed the system himself and is now assessing its performance for a second season. In his view, the modest increase in initial investment is offset by lower evaporation losses, better pipe protection, reduced weed growth, deeper root development, and a potentially very long service life.

At the same time, the video emphasises that outcomes depend on professional design, soil type, water quality and precise irrigation management. Solutions that perform well on one farm therefore need to be tested and adapted before being applied under different climatic and production conditions.