Assessing the Water-Stress Baselines by Thermal Imaging for Irrigation Management in Almond Plantations under Water Scarcity Conditions

Saray Gutiérrez-Gordillo,Virginia Hernández-Santana,Belén Cárceles Rodríguez,José Juan Amores-Agüera,Fernando Ferrera Gil,Víctor Hugo Durán Zuazo,Iván Francisco García-Tejero,Amelia García Escalera

doi:10.3390/w12051298

Abstract

This work examines the use of thermal imaging to determine the crop water status in young almond trees under sustained deficit irrigation strategies (SDIs). The research was carried out during two seasons (2018–2019) in three cultivars (Prunus dulcis Mill., cvs. Guara, Lauranne, and Marta) subjected to three irrigation treatments: a full irrigation treatment (FI) at 100% of irrigation requirements (IR), and two SDIs that received 75% and 65% of the IR, respectively. Crop water monitoring was done by measurements of canopy temperature, leaf water potential (Ψleaf), and stomatal conductance. Thermal readings were used to define the non-water-stress baselines (NWSB) and water-stress baselines (WSB) for each treatment and cultivar. According to our findings, Ψleaf was the most responsive parameter to reflect differences in almond water status. In addition, NWSB and WSB allowed the determination of the crop water-stress index (CWSI) and the increment of canopy temperature (ITC) for each SDI treatment, obtaining threshold values of CWSI (0.12–0.15) and ITC (~1 °C) that would ensure maximum water savings by minimizing the effects on yield. The findings highlight the importance of determining the different NWSB and WSB for different almond cultivars and its potential use for proper irrigation scheduling.

Highlights

Irrigation performs an essential role in agriculture
Canopy volumes were very similar within each cultivar, without differences between irrigation treatments
In relation to ETC, similar values for 2018 and 2019 (~880 and 840 mm respectively) were registered. This fact, together with the high differences in terms of rainfall, promoted that the irrigation doses applied in the studied treatments were much greater in the second experimental season

Summary

Introduction

Irrigation performs an essential role in agriculture. The increase in total irrigated area, coupled with scarce water resources, has encouraged the implementation of irrigation strategies that optimize the water-use efficiency. In areas such as southern Spain, this supply is crucial for the proper development of woody crops, when the maximum evapotranspiration rates coincide with the rainfall absence. Considering the current scenarios of climatic change and water scarcity, the adaptation and sustainable strategies to boost the proper water management in irrigated crops is vital [1]. Deficit irrigation (DI) has been implemented to enhance the yield, reducing the irrigation supplies and maximizing the crop productivity [2].

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