Workpackage number 2: Efects on crop physiology Start date or start event: 0
Activity Type: RTD/Innovation
Participant ID

CSIC

UPCT

INRA

UTH 

LRA

SAPIAMA

Person-month per participant

18 

12 

6

12

12

12


Objectives

  1. Acquisition of complementary knowledge on crop physiological response under different orchard irrigation, locations and species.
  2. Elaboration and validation of agro-physiological criteria (indicators) that could be used in monitoring the water status of the crop.

Description of work

(Task 2.1)Acquisition of knowledge on crop physiological response and water use efficienty under different irrigation scenarios (months: 1-36).

The knowledge of the physiological response of a species to water stress induced by a given environmental situation and irrigation practices, is a primary and necessary step in order to evaluate the agronomic performances of a given irrigation strategy. To this aim, in each experimental site, research groups will study the physiological behaviour of each species under different water management, especially through:

  • morphometric measurements (stem and trunk diameter, tree height, leaf area index, crow diameter, canopy architecture)
  • monitoring of plant water status (leaf water potential, leaf turgor potential, leaf osmotic potential)
  • gas exchange measurements (photosynthesis,transpiration and stomatal conductance at the leaf and shoot scale, whole tree transpiration by means of weighing lysimeters, electronic balance and sap flow meter, etc)

These physiological studies will be carried out by CSIC (olive, citrus, peach) and UPCT (almond) in Spain, INRA (peach) in France, UTH (peach, olive) in Greece, SAPIAMA (citrus) in Marroco, and LRA (citrus, peach) in Lebanon.

(Task 2.2) Analysis and interpretation of new soil and plant based indicators of water stress (months: 1-18).

Task 2.2 is aimed to prove the practical feasibility of irrigation scheduling based on sensing plant and soil water status. In these methods, the information supplied by the sensors is recorded and treated in order to compute plant stress indicators, whose value will be compared to threshold values (irrigation criteria) in order to decide about the timing and amount of water supply. Some examples of indicators proposed in the literature are the Stem Maximum Daily Shrinkage/ETc, Stem Water Potential/VPD, Daily Sap flow/ETc, Daily changes in Soil Humidity, etc.

The micrometric trunk diameter fluctuations (TDF) will be measured using sets of linear variable displacement transducers (LVDT) (model DF ± 2.5 mm, accuracy ± 10 µm, Solartron Metrology, Bognor Regis, UK) attached to the trunk, with a special bracket made of Invar, an alloy of Ni and Fe with a thermal expansion coefficient close to zero, and aluminium.

Sap flow will be measured using the compensation heat-pulse technique [Green and Clothier, 1988). One set of heat-pulse probes will be located above the LVDT sensors on each tree. Each set consists of a heater needle of 1.8 mm diameter and two temperature probes also of 1.8 mm diameter installed in parallel holes drilled radially in the trunks. Each heat-pulse probe has four thermocouple sensors to monitor the sap velocity profile over a radial depth.

The daily changes in soil humidity will be measured using capacitance probes.The capacitance sensor consist of two brass rings (50.5 mm o.d. and 25 mm high), mounted on a plastic sensor body separated by a 12-mm plastic ring. Measuring of the capacitance gives the dielectric constant, hence the water content of the soil. The variation of the dielectric constant of the medium soil-water-air depends mainly on the soil water content.

These methods are particularly adequate in the case of RDI scheduling, as they allow to estimate the actual plant stress intensity during the different phenological stages, and therefore to optimally modulate the water supply according to a given soil-plant-based criteria. In the field experiments of WP2, the pertinence and efficiency of the above-mentioned soil-plant indicators and irrigation criteria will be testedunder real orchard conditions, evaluating water savings, plant water status, and the resulting crop yield and quality.

The results obtained in WP2 (First, Second and Third Reports on “Crop physiological responses to water scarcity, irrigation water quality and fertigation”, Months 12, 24 and 36 respectively) will be the scientific basis and the necessary milestones for: a) Development of fruit models at the tree scale, b) development of new sensors for monitoring soil and plant water status, c) development of irrigation control algorithms.

Deliverables:

D6, D18: Identification of different irrigation practices effects on crop physiology (Fist year), and First Report on “Crop physiological responses to water scarcity, irrigation water quality and fertigation” (month 12)

D24, D38: Identification of different irrigation practices effects on crop physiology (Second year), and Second Report on “Crop physiological responses to water scarcity, irrigation water quality and fertigation”. It will include the analysis of the relations between environmental conditions (radiation, VPD, soil water status) and the selected stress indicators (stem water potential, stomatal conductance, transpiration, fluorescence, trunk diameter, sap flow, transpiration, etc.). (month 24)

D36: Preliminary recommendations to technological partners about the best agro-physiological indicator/s for irrigation scheduling and management. First guidelines for optimal use of stress indicators based on trunk diameter and sap flow data (calibration, installation, energy supply, data management, etc.) (months 18)

D46, D60: Identification of different irrigation practices effects on crop physiology (Third year), and Third Report on “Crop physiological responses to water scarcity, irrigation water quality and fertigation” . Synthesis of the results of WP2. (month 36)


Milestonesand expected result:

Milestones:

M2.1 Month 12.

The 1st report on crop response should give enough information for the selection of the stress indicators.

M2.2 Month 24.

The 2nd report should contain the elements for designing the definitive hardware and software (WP9).

Results:

The results obtained in WP2 will be compiled in a database. The latter will be used by the modelling activities and also to perform a meta-analysis in order to test under different scenarios the stability of each indicator of irrigation scheduling, as well as to identify the most robust sensors.