Partial drying of the root in the olive grove - Success story

We are going to present a successful case of partial desiccation of the roots of an olive grove, with comparative graphs of soil moisture.

Evaluation of the olive grove plot

An intensive olive grove needs to increase water contributions. To determine the water needs of a crop, a water balance can be made on the plot, in which the unknown is the amount of water consumed by the crop, or surface evapotranspiration, (ETo, mm).

The ETc, real evapotranspiration of the crop, consists of:

  • Evaporation from the soil and from the surface covered by plants.
  • Transpiration from plant leaves.
Propagación del riego

The olive tree needs water supply especially in flowering, setting and the first phases of fruit growth, and in the last stage of the fruit growth phase.
During most of the fruit growth period, the olive tree is less sensitive to lack of water.

With a Controlled Deficit Irrigation strategy, even suppressing irrigation when less input is needed, you can save up to 50% of the amount of irrigation water necessary to replenish the real root evapotranspiration, (ET C), without notable harvest reductions.

Its difficulty lies in knowing which are the moments of greatest sensitivity to water stress. For this, humidity and temperature sensors are essential.

Partial Rootzone Drying (PRD) in the olive grove

Partial root desiccation is a technique that can be used in agriculture and horticulture to save water without significantly compromising plant health and performance.

In this case, it is irrigated with less water than required to replace the real evapotranspiration of the root, ETC and, in addition, alternately in half of the rhizosphere, making the change to the other half every 2 or 3 weeks.

A double drip is advisable, to alternate irrigations. This will make the roots develop more when watering is suppressed.

Basically, it is considered that if irrigation water is applied to one half of the root system, signals are generated in the roots of the other half in response to the decreasing level of water in the soil, signals that travel to the aerial part of the plant. plant and induce greater stomatal closure, therefore reducing transpiration and increasing water use efficiency.

The signals stop being generated when the soil dries out too much, hence it is necessary to water again after a certain time, which is considered to be about two weeks, or three in the case of trees and plants whose root system explores a large volume of floor.

This technique is suitable for olive groves, because they have extensive root systems.

Well-drained soils with good water retention are ideal for this technique. Sandy soils may require adjustments in watering frequency.

We must divide the root area into at least two zones. One area will receive regular watering while the other will have reduced watering or be left to dry out. Frequency is based on plant response, adjust the amount of watering in each zone to optimize water use and maintain plant health.

Applying partial root desiccation carefully and systematically can be an effective strategy for saving water in agriculture and horticulture, especially in areas where water resources are limited.

Success story with partial root desiccation in the olive grove

470 / 5.000 We are on a plot with 1400 olive trees. Each olive tree has 2 drippers placed with a nominal flow rate of 4 liters per hour. Each dripper line has a length equivalent to about 25 olive trees, which is equivalent to 50 drippers per line, with a transported flow rate of 200 liters. hour.
A 20 mm diameter pipe is installed as a secondary pipe, and a 40 mm diameter pipe is installed as a general supply line to the sector.

In this graph we see how a stress episode occurred in the month of April, and another in the month of October, while we had excess humidity in the middle of summer.
This is an ideal example of a sector that could have benefited from that Possible diversion of irrigation, to avoid those two peaks of water stress that occurred at two key moments in the olive grove.

Proposed alternative

Reposition the drippers currently installed, until they are placed at a distance of 50 cm from each other.
Place a new dripper holder line on the opposite side, with another 2 drippers 50 cm apart.
With this proposal we assume all the pressure losses that the installation already has, but we make sure to wet 100% more surface and we do it, at least, with the same conditions as the current irrigation

We observed that the soil moisture content, in this sector, has been adequate in the irrigated area, even high, in the middle of summer. This tells us that we can divert water to irrigate the opposite side of the olive trees. With the same water expenditure as in this campaign, we will moisten twice the surface area with the adoption of the Partial Rootzone Drying (PRD) technique.

All calculations and graphs are carried out by our agronomic team, by placing humidity and temperature sensors.

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