DRIP IRRIGATION FOR ORANGE GROVE

WATER REQUIREMENTS AND IRRIGATION TECHNIQUE

The sweet orange (Citrus sinensis L.) is a particularly demanding species in terms of water and nutrition; its annual water requirement can range from 8,000 to 15,000 m3/hectare depending on the area of cultivation, the rootstock used and the textural characteristics. In order to provide these volumes to the plants in a prudent way during the spring-summer season, it is necessary to use an efficient and easy-to-use irrigation system.

Drip irrigation certainly lends itself well to these needs, as it allows water and nutrients to be localized plant by plant, maximising the use of water and fertilisers, and also making it possible to adjust irrigation volumes and shifts according to the real needs of the crop. With this system, irrigation technique is focused on short and frequent shifts so as to keep the soil that is in contact with the roots constantly moist; the flexibility of the system, especially when equipped with instruments for monitoring the water status of the soil, plant and atmosphere, also offers the possibility of setting up controlled water stress strategies, i.e., reductions in irrigation volumes at specific phenological stages, which allow water savings without compromising the productive activity of the orange grove.

Filtration system

The equipment that will filter water for drip irrigation will need to be differentiated according to the origin of the water. Irritec generally recommends grit filters with automatic backwashing for water coming from basins, lakes or open water sources, while hydrocyclone filters are recommended for water coming from wells that is loaded with sand particles.

In any case, the primary filtration system should be accompanied by appropriate safety filters (mesh or discs), sized according to the flow rate of the system.

The sizing of any filtration system must be based on a careful physical/chemical evaluation of the water.

Fertigation

The irrigation system shall, together with the water, enrich the soil with nutrients essential for the development and fruiting of the plants.

For open field applications, Irritec recommends for example Ferticlick Bypass, an accurate system for simple proportional or volumetric fertigation of a fertiliser, or fertigation benches such as Dosabox Junior Automatic, which offer the ability to proportionally manage up to 3 fertilisers.

The Dosabox Junior Advanced version, in addition to the three fertiliser channels, has one exclusively for acid; the integrated Commander NPK also allows the fertigation to be set according to pH and EC targets.

Automation

For the correct set-up of the irrigation shifts, the volumes delivered, and to maximise time and manpower on the farm (opening and closing of the solenoid valves, cleaning of the filter elements, setting the fertigation) Irritec recommends that the irrigation system be equipped with the minimum necessary automation.

The Commander EVO line, for example, is the optimal solution for meeting the irrigation needs of farms of all sizes: the three programmer models (Basic, Plus and Gold) offer a wide range of automation possibilities, simplifying the total management of the irrigation system.

Subsurface irrigation for Orange

The best performing micro-irrigation system for modern orange groves, in which the number of plants in the row is often increased (e.g. a 5.0 x 3.0 m planting section), is achieved by laying a double drip line at the sides of the row (about 4,000 linear metres of line per hectare) at the time of planting.

In fact, this immediately leads to greater expansion of the root system, with positive repercussions on vegetative development and early onset of production. Irritec recommends drip point spacing of 50-60 cm and hourly flow rates of 2.1 or 4.0 l/h, but these vary according to different business situations. It is recommended to use standard Junior or Tandem type drip lines for topographically regular plots with rows that are not excessively long, or self-compensating Multibar F or Multibar C type drip lines, which ensure high dispensing uniformity even in cases of excessive slopes and long rows.

In mechanised plants where these drip lines may be an obstacle to agronomic operations carried out on the orange grove (e.g. soil processing, plant protection treatments, harvesting, etc.), the technique of subirrigation, i.e. the burying of the two drip lines (Multibar C Rootguard model) may be used at a depth of between 20 and 30 cm and a distance of 80 100 cm from the trunk. This (now proven) technique increases the performance of drip irrigation by minimising water and fertiliser waste.

Sub-irrigation (on new plantings) should be used with the aid of surface relief irrigation for the first two years of the orange grove’s life, allowing the young roots to develop properly in the first two years of life.