Abstract
In recent years, many olive orchards, which are a major crop in the Mediterranean basin, have been converted into intensive or super high-density hedgerow systems. This configuration is more efficient in terms of yield per hectare, but at the same time the water requirements are higher than in traditional grove arrangements. Moreover, irrigation regulations have a high environmental (through water use optimization) impact and influence on crop quality and yield. The mapping of (spatio-temporal) variability with conventional water stress assessment methods is impractical due to time and labor constraints, which often involve staff training. To address this problem, this work presents the development of a new low-cost device based on a thermal infrared (IR) sensor for the measurement of olive tree canopy temperature and monitoring of water status. The performance of the developed device was compared to a commercial thermal camera. Furthermore, the proposed device was evaluated in a commercially managed olive orchard, where two different irrigation treatments were established: a full irrigation treatment (FI) and a regulated deficit irrigation (RDC), aimed at covering 100% and 50% of crop evapotranspiration (ETc), respectively. Predawn leaf water potential (ΨPD) and stomatal conductance (gs), two widely accepted indicators for crop water status, were regressed to the measured canopy temperature. The results were promising, reaching a coefficient of determination R2 ≥ 0.80. On the other hand, the crop water stress index (CWSI) was also calculated, resulting in a coefficient of determination R2 ≥ 0.79. The outcomes provided by the developed device support its suitability for fast, low-cost, and reliable estimation of an olive orchard’s water status, even suppressing the need for supervised acquisition of reference temperatures. The newly developed device can be used for water management, reducing water usage, and for overall improvements to olive orchard management.
Highlights
Water management has become a key factor in sustainable agriculture, especially in regions such as the Mediterranean, where water scarcity problems are rising [1]
In order to check the differences in water status, two physiological variables related to water stress were assessed for each treatment: gs and ΨPD
A new low-cost device based on thermal infrared sensors was presented to measure, in a non-destructive way, the olive tree canopy temperature and to monitor its water status
Summary
Water management has become a key factor in sustainable agriculture, especially in regions such as the Mediterranean, where water scarcity problems are rising [1]. Traditional olive orchard cultivation is the most widespread method [2] This approach is based on having rain-fed trees at a density of 100–300 trees ha−1, where irrigation is controlled through cultural practices, such as pruning, which reduces water requirements [3]. Many traditional orchards have been converted into intensive and super high-density (SHD) hedgerow systems, with higher yields per ha and reduced managing costs due to augmented mechanization and automatization. Most of these new orchards are under irrigation scheduling, requiring 5000 m3 ha−1 to replace maximum crop evapotranspiration in semi-arid regions, such as the south of Spain and Portugal [4]. The reliability of the information provided by a pressure chamber decreases when the species display isohydric behaviour, characterized by strong stomatal regulation, reducing the sensitivity of leaf water potential measurements under conditions of low soil water content and high evaporative demand [6]
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