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Guide

How Is Drip Irrigation Designed for an Orchard?

Orchard drip irrigation delivers water and nutrients to the root zone of every tree, in the amount each growth stage requires. The system is designed around the fruit species, soil, tree age, tree spacing, topography and water source: the number of driplines per row, dripper spacing and flow rate, wall thickness and the fertigation programme are all set from these inputs.

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The tree grows, and the system grows with it: the right design irrigates every tree with the same precision from planting to full bearing.

What drip irrigation brings to an orchard

  • Water straight to the root zoneDrip irrigation delivers water to the zone of the tree's active roots, in the right amount and at short intervals; runoff, percolation below the root zone and evaporation from wet surfaces are reduced. Water application efficiency reaches 90–95%. According to the citrus irrigation guide of Turkey's Alata Horticultural Research Institute (TAGEM), the annual irrigation requirement is 600–750 mm under surface irrigation and 300–400 mm under drip. The size of the saving depends on scheduling and management; measurement-based scheduling keeps the gain every season.
  • Fertigation at the right timeNutrients are delivered with the irrigation water, when the tree needs them and directly to the active root zone.
  • Moisture control in the inter-rowDrip irrigation wets only the root zone along the tree row; the inter-rows and the foliage stay dry. Humidity in the orchard stays under control, fungal disease pressure on leaves and fruit is reduced and weed growth is confined to the row. Spraying, pruning and harvesting equipment can enter the orchard in any conditions, and the irrigation schedule continues on spraying days.
  • Low pressure, low energyDrip irrigation works at low operating pressure, which lowers pumping energy and operating costs.
  • Equal water for every tree: design, equipment and installation togetherUniform irrigation is built in three steps. Equipment: pressure compensating drippers deliver the same flow across a wide pressure range, so on slopes, undulating land and long rows the first and the last tree in the line receive the same water. Design: run lengths, pipe diameters, irrigation zones and the pressure variation within each zone are set by hydraulic calculation, targeting an emission uniformity above 90%. Installation: air release valves are placed at the high points of the lines, connections are checked for leaks, and pressure and flow are measured at the start and end of every zone during commissioning. Monitoring the pressure difference across the filters and flushing regularly through the end-of-line valves keep this uniformity for years.

Single or double line? Decided by the wetted area

The number of driplines per row is not set by the fruit species alone; the deciding measure is the soil volume wetted per tree (wetting percentage). FAO recommends wetting at least 35% of the root-zone volume per tree in orchards; at 5 × 6 m or 6 × 6 m spacing this corresponds to roughly 10–12 m² of wetted surface per tree. The University of California (UC ANR) recommends wetting 40–60% of the orchard floor.

Soil texture sets the width of the wetted area: the average radius of lateral water spread from a dripper is about 0.30 m in light soils, 0.65 m in medium soils and 1.20 m in heavy soils (FAO). In medium and heavy soils and dense plantings, one dripline per row can therefore reach the required wetting percentage; in light and stony soils, at wide spacing and with spreading canopies, the wetted area is completed with a second dripline or with a loop around each tree.

Research confirms this principle: in an apple study in Chile with the same amount of water, one line per row gave the highest yield on clay loam and four lines on stony loam. In a super-high-density olive orchard, one line gave sufficient results. In a citrus study in Adana, Turkey, roots concentrated on the dripline side under a single line; a double line balances root distribution on both sides of the row.

Dripline layout options in orchards (FAO, Pressurized Irrigation Techniques, Chapter 14)
LayoutHow it is installedWhere it fits best
One dripline per row (single line)One dripline along the tree rowMedium and heavy soils, dense plantings, narrow canopies
Two driplines per row (double line)One dripline on each side of the tree rowLight and stony soils, wide spacing, spreading canopies, nut crops
Loop around the treeA short pipe circling each tree, or a multi-outlet dripper, fed from a single lineWidely spaced trees, irregular planting, young orchards

The number and position of lines are calculated in the project from the soil analysis, species and rootstock, tree spacing and the target wetting percentage.

Choosing driplines and drippers

  • Thick-wall driplineIn multi-year installations such as orchards and vineyards, thick-wall driplines resist external stress and system pressure; with proper maintenance they perform the same for many years.
  • Pressure compensating dripperGives every tree equal water on slopes and long rows; on flat land and short rows, non-pressure compensating drippers are an economical solution.
  • Dripper spacing and flow rateSet by soil texture: in light soils drippers are placed closer together so that the wetted area forms a continuous strip along the row.
  • Subsurface drip irrigationThe dripline is buried; drippers that resist root intrusion and prevent soil suction when the system stops are used. It allows tillage and machinery traffic and keeps the wet surface to a minimum.
  • Suspended lineIn trellised orchards the dripline is hung on a support wire, protecting it from machinery and animal damage and making weed control along the row easier.

From planting to full bearing: growing the system with the tree

In the young-tree stage the root zone is small; in the first years water is applied close to the trunk and the wetted area is widened as the canopy develops. The head control unit and mainlines are sized from the start for the water demand at full bearing; as the orchard grows, only the water distribution per tree expands. Methods in use:

  • Opening capped drippers laterdrippers between the trees stay capped in the first years and are opened as the canopy develops.
  • Increasing the number of drippers per treestart with one or two drippers per tree in the young-tree stage and add on-line drippers to the pipe as the tree grows. For newly planted trees, FAO gives two drippers on both sides of the trunk, 35–40 cm from it, as the starting layout.
  • Moving the line outward with the canopythe dripline is laid close to the trunk in the first years and shifted towards the canopy edge as the roots spread; for this purpose lines are laid with some slack along the row. A rule used in citrus: the distance from the trunk to the canopy edge is divided into three, and the dripline is placed between the second and third parts from the trunk (TAGEM Alata).
  • Loop around the treea short loop of pipe or a multi-outlet dripper is placed around the root ball of the young tree, and the loop diameter is enlarged as the tree grows.
  • Adding the second line laterin orchards designed for double lines, the first years start with one dripline per row and the second is added once the canopy and root system have developed; submains and valves are selected for two lines from the start.
  • Temporary pipe for the first years, permanent pipe afterfor the first two or three years irrigation runs on temporary thin-wall driplines, replaced by permanent thick-wall driplines once the orchard is established.
  • Micro-sprinklers for young treesparticularly in light soils, micro-sprinklers can be preferred in the first years to wet the root zone of young trees over a wider area.

Irrigation scheduling: when and how much?

The tree's water requirement is calculated by multiplying the local reference evapotranspiration (ETo) by the species' crop coefficient (Kc): ETc = Kc × ETo. Kc changes with the growth stage; tree age and canopy cover are added to the calculation.

Irrigation timing is set more precisely with soil moisture instruments such as tensiometers and TDR probes. Controllers use these readings to run the irrigation zones on schedule.

Regulated deficit irrigation can raise water productivity in suitable species such as olive, stone and pome fruit and wine grapes, at specific growth stages and under expert supervision. During flowering, fruit set and rapid fruit growth the tree's water requirement is met in full; in water-sensitive species such as walnut, full irrigation is the basis.

Crop coefficients (Kc) for selected fruit species, FAO 56
SpeciesInitialMid-seasonLate season
Apple, cherry, pear (bare inter-row)0.45–0.600.950.70–0.75
Peach and stone fruit0.45–0.550.900.65
Almond0.400.900.65
Walnut0.501.100.65
Olive0.650.700.70
Citrus (70% canopy cover)0.700.650.70
Table grapes0.300.850.45

In orchards with a cover crop in the inter-row, mid-season values rise (1.20 for apple, cherry and pear). Values specific to the region and variety are calculated in the project.

Fertigation: feeding by growth stage

The fertigation unit in the head control unit delivers fertilizer with every irrigation at the rate suited to the tree's growth stage: the different nutrient needs of shoot growth and flowering, fruit set and growth, and the post-harvest period are reflected in the programme. EC- and pH-controlled dosing delivers nutrients evenly to the root zone. Fertigation starts once the system has reached operating pressure, and the lines are flushed with clean water at the end of irrigation.

Frost protection

The main methods for fighting late spring frosts are over-tree sprinkling, under-tree (micro-)sprinkling, wind machines and heaters (FAO, 2005). An under-tree micro-sprinkler system can also be used for irrigation. When the frost protection system is planned in the same project as drip irrigation, the water source, pumping and filtration are sized together; the method is chosen according to the orchard's location, the frost type and the water source.

Our project path

  1. Pre-design: site, species and variety, tree spacing, soil and water analysis, water source and energy options are assessed; system options and the investment balance are set out.
  2. Detailed design: crop water requirement, wetting percentage and hydraulic calculations are made; line layout, irrigation zones, pipe diameters, dripper selection, the head control unit and controllers are finalised with the bill of quantities.
  3. Installation: within the agreed scope, procurement, installation, pressure and flow testing and commissioning are carried out.
  4. Operation and maintenance: the irrigation and fertigation programme is set up; a maintenance calendar for filters, lines and drippers is prepared and support is provided throughout the season.

Frequently asked questions

How many litres of water does a fruit tree need per day?
The daily requirement is calculated for each orchard from the species' crop coefficient, local evapotranspiration, tree age and canopy size (ETc = Kc × ETo). The requirement is low in the young-tree stage and rises as the canopy develops; AGIMEX prepares the irrigation schedule for your orchard from this calculation.
How many driplines are laid per tree row in an orchard?
The wetting percentage decides: at least 35% of the root-zone volume per tree should be wetted (FAO). In medium and heavy soils and dense plantings, one dripline per row can achieve this; in light and stony soils, at wide spacing and with spreading canopies, a second dripline or a loop around each tree is used.
How is drip irrigation set up in a young orchard?
The head control unit and mainlines are sized for full bearing, and the water distribution per tree grows with the tree. Methods in use include opening capped drippers later, adding drippers per tree, moving the line outward with the canopy, loops around the tree and adding the second line later.
Which dripline is used in orchards?
Thick-wall driplines are used for multi-year service. On slopes and long rows, pressure compensating drippers give every tree equal water; in subsurface installations, drippers that resist root intrusion are preferred.
How much water does drip irrigation save in an orchard?
Savings come from reduced runoff, deep percolation and evaporation, and depend on scheduling. According to the citrus guide of Turkey's Alata Horticultural Research Institute, the annual irrigation requirement is 600–750 mm under surface irrigation and 300–400 mm under drip; drip water application efficiency is 90–95%.
How is frost fought in an orchard?
The main methods are over-tree sprinkling, under-tree micro-sprinkling, wind machines and heaters. The method is chosen according to the orchard's location, frost type and water source; when sprinkler-based systems are planned in the same project as drip irrigation, the water source, pumping and filtration are sized together.
Is there public support for orchard drip irrigation?
Support programmes open periodically, and their scope and conditions can change in every period. Water-saving irrigation investments can benefit from national or EU rural development grants and subsidised loans while calls are open. This is for information only; the official announcements of the competent authorities are binding.
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