24 research outputs found
Use of Aerial Thermal Imaging to Assess Water Status Variability in Hedgerow Olive Orchards
Characterization of the spatial variability in tree water status is a prerequisite to conduct precise irrigation
management within an orchard. This study assessed the suitability of a crop water stress index (CWSI) derived from
high-resolution aerial thermal imagery to estimate tree water status variability in super high density (SHD) olive
orchards. The experiment was conducted at a commercial SHD olive orchard near Seville (southwestern Spain). The drip
irrigated trees were submitted to three irrigation regimes (four plots per treatment): a full irrigation treatment replacing
the crop water needs (ETc) and two regulated deficit irrigation treatments replacing ca. 45% of ETc. During the irrigation
season, meteorological variables, soil moisture content, leaf water potential and leaf gas exchange measurements were
performed. Infrared temperature sensors (IRTS) installed about 1 m above the canopies were used to derive the required
baselines for CWSI calculation. A thermal camera installed on a mini RPAS (Remote Piloted Aerial System) allowed
recording high-resolution thermal images at 5 representative dates of the olive tree growing season. CWSI values derived
from aerial thermal imagery were sensitive to the deliberately imposed variations in tree water status within the SHD
olive orchard. Maximum stomatal conductance and midday stem water potential showed tight correlations with CWSI.
We conclude that high resolution thermal imagery captured from a mini RPAS has proven to be a suitable tool to capture
tree water status variability within SHD olive orchards.Ministerio de Economía y Competitividad AGL2012- 34544/ECOLIMAJunta de Andalucía P12-AGR-122
Monitoring of emerging water stress situations by thermal and vegetation indices in different almond cultivars
In recent years, the area dedicated to modern irrigated almond plantations has increased significantly in Spain. However, the legal irrigation allocations are lower than the maximum water requirements of the crop in most cases. Therefore, almond growers are forced to implement regulated deficit irrigation strategies on their farms, applying water stress in certain resistant phenological periods and avoiding it in sensitive periods. Given the need to monitor the water status of the crop, especially in the most sensitive periods to water stress, the objective of this work was to evaluate the sensitivity of two UAV-based crop water status indicators to detect early water stress conditions in four almond cultivars. The field trial was conducted during 2020 in an experimental almond orchard, where two irrigation strategies were established: full irrigation (FI), which received 100% of irrigation requirements (IR), and regulated deficit irrigation (RDI), which received 70% of IR during the whole irrigation period except during the kernel-filling stage when received 40% IR. The UAV flights were performed on four selected dates of the irrigation season. The Crop Water Status Index (CWSI) and the Normalized Difference Vegetation Index (NDVI) were derived from thermal and multispectral images, respectively, and compared to classical water status indicators, i.e., stem water potential (Ψstem ), stomatal conductance (gs ), and photosynthetic rate (AN ). Of the four flights performed, three corresponded to mild water stress conditions and a single flight was performed under moderate water stress conditions. Under mild water stress, CWSI was not able to capture the differences between FI and RDI trees that were observed with Ψstem . Under moderate stress conditions, CWSI was sensitive to the water deficit reached in the trees and showed significant differences among both irrigation treatments. No differences were observed in the CWSI and NVDI response to water stress among cultivars. Although NDVI and CWSI were sensitive to water stress, the low signal intensity observed in NDVI makes this index less robust than CWSI to monitor crop water stress. It can be concluded that UAV-based CWSI measurements are reliable to monitor almond water status, although for early (mild) levels of water stress, Ψstem seems to be the preferred option.Junta de Andalucía AVA.AVA2019.05
Monitoring Crop Evapotranspiration and Crop Coefficients over an Almond and Pistachio Orchard Throughout Remote Sensing
In California, water is a perennial concern. As competition for water resources increases due to growth in population, California’s tree nut farmers are committed to improving the efficiency of water used for food production. There is an imminent need to have reliable methods that provide information about the temporal and spatial variability of crop water requirements, which allow farmers to make irrigation decisions at field scale. This study focuses on estimating the actual evapotranspiration and crop coefficients of an almond and pistachio orchard located in Central Valley (California) during an entire growing season by combining a simple crop evapotranspiration model with remote sensing data. A dataset of the vegetation index NDVI derived from Landsat-8 was used to facilitate the estimation of the basal crop coefficient (Kcb), or potential crop water use. The soil water evaporation coefficient (Ke) was measured from microlysimeters. The water stress coefficient (Ks) was derived from airborne remotely sensed canopy thermal-based methods, using seasonal regressions between the crop water stress index (CWSI) and stem water potential (Ψstem). These regressions were statistically-significant for both crops, indicating clear seasonal differences in pistachios, but not in almonds. In almonds, the estimated maximum Kcb values ranged between 1.05 to 0.90, while for pistachios, it ranged between 0.89 to 0.80. The model indicated a difference of 97 mm in transpiration over the season between both crops. Soil evaporation accounted for an average of 16% and 13% of the total actual evapotranspiration for almonds and pistachios, respectively. Verification of the model-based daily crop evapotranspiration estimates was done using eddy-covariance and surface renewal data collected in the same orchards, yielding an R2 ≥ 0.7 and average root mean square errors (RMSE) of 0.74 and 0.91 mm·day−1 for almond and pistachio, respectively. It is concluded that the combination of crop evapotranspiration models with remotely-sensed data is helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions
New strategies for row-crop management based on cost-effective remote sensors
Agricultural technology can be an excellent antidote to resource scarcity. Its growth has
led to the extensive study of spatial and temporal in-field variability. The challenge of
accurate management has been addressed in recent years through the use of accurate
high-cost measurement instruments by researchers. However, low rates of technological
adoption by farmers motivate the development of alternative technologies based on
affordable sensors, in order to improve the sustainability of agricultural biosystems.
This doctoral thesis has as main objective the development and evaluation of systems
based on affordable sensors, in order to address two of the main aspects affecting the
producers: the need of an accurate plant water status characterization to perform a
proper irrigation management and the precise weed control.
To address the first objective, two data acquisition methodologies based on aerial
platforms have been developed, seeking to compare the use of infrared thermometry
and thermal imaging to determine the water status of two most relevant row-crops in the
region, sugar beet and super high-density olive orchards. From the data obtained, the
use of an airborne low-cost infrared sensor to determine the canopy temperature has
been validated. Also the reliability of sugar beet canopy temperature as an indicator its
of water status has been confirmed. The empirical development of the Crop Water Stress
Index (CWSI) has also been carried out from aerial thermal imaging combined with
infrared temperature sensors and ground measurements of factors such as water
potential or stomatal conductance, validating its usefulness as an indicator of water
status in super high-density olive orchards.
To contribute to the development of precise weed control systems, a system for detecting
tomato plants and measuring the space between them has been developed, aiming to
perform intra-row treatments in a localized and precise way. To this end, low cost optical
sensors have been used and compared with a commercial LiDAR laser scanner. Correct
detection results close to 95% show that the implementation of these sensors can lead
to promising advances in the automation of weed control.
The micro-level field data collected from the evaluated affordable sensors can help
farmers to target operations precisely before plant stress sets in or weeds infestation
occurs, paving the path to increase the adoption of Precision Agriculture techniques
Remote Sensing Energy Balance Model for the Assessment of Crop Evapotranspiration and Water Status in an Almond Rootstock Collection
One of the objectives of many studies conducted by breeding programs is to characterize and select rootstocks well-adapted to drought conditions. In recent years, field high-throughput phenotyping methods have been developed to characterize plant traits and to identify the most water use efficient varieties and rootstocks. However, none of these studies have been able to quantify the behavior of crop evapotranspiration in almond rootstocks under different water regimes. In this study, remote sensing phenotyping methods were used to assess the evapotranspiration of almond cv. “Marinada” grafted onto a rootstock collection. In particular, the two-source energy balance and Shuttleworth and Wallace models were used to, respectively, estimate the actual and potential evapotranspiration of almonds grafted onto 10 rootstock under three different irrigation treatments. For this purpose, three flights were conducted during the 2018 and 2019 growing seasons with an aircraft equipped with a thermal and multispectral camera. Stem water potential (Ψstem) was also measured concomitant to image acquisition. Biophysical traits of the vegetation were firstly assessed through photogrammetry techniques, spectral vegetation indices and the radiative transfer model PROSAIL. The estimates of canopy height, leaf area index and daily fraction of intercepted radiation had root mean square errors of 0.57 m, 0.24 m m–1 and 0.07%, respectively. Findings of this study showed significant differences between rootstocks in all of the evaluated parameters. Cadaman® and Garnem® had the highest canopy vigor traits, evapotranspiration, Ψstem and kernel yield. In contrast, Rootpac® 20 and Rootpac® R had the lowest values of the same parameters, suggesting that this was due to an incompatibility between plum-almond species or to a lower water absorption capability of the rooting system. Among the rootstocks with medium canopy vigor, Adesoto and IRTA 1 had a lower evapotranspiration than Rootpac® 40 and Ishtara®. Water productivity (WP) (kg kernel/mm water evapotranspired) tended to decrease with Ψstem, mainly in 2018. Cadaman® and Garnem® had the highest WP, followed by INRA GF-677, IRTA 1, IRTA 2, and Rootpac® 40. Despite the low Ψstem of Rootpac® R, the WP of this rootstock was also high.info:eu-repo/semantics/publishedVersio
Monitoring crop evapotranspiration and crop coefficients over an almond and pistachio orchard throughout remote sensing
In California, water is a perennial concern. As competition for water resources increases due to growth in population, California’s tree nut farmers are committed to improving the efficiency of water used for food production. There is an imminent need to have reliable methods that provide information about the temporal and spatial variability of crop water requirements, which allow farmers to make irrigation decisions at field scale. This study focuses on estimating the actual evapotranspiration and crop coefficients of an almond and pistachio orchard located in Central Valley (California) during an entire growing season by combining a simple crop evapotranspiration model with remote sensing data. A dataset of the vegetation index NDVI derived from Landsat-8 was used to facilitate the estimation of the basal crop coefficient (Kcb), or potential crop water use. The soil water evaporation coefficient (Ke) was measured from microlysimeters. The water stress coefficient (Ks) was derived from airborne remotely sensed canopy thermal-based methods, using seasonal regressions between the crop water stress index (CWSI) and stem water potential (Ψstem). These regressions were statistically-significant for both crops, indicating clear seasonal differences in pistachios, but not in almonds. In almonds, the estimated maximum Kcb values ranged between 1.05 to 0.90, while for pistachios, it ranged between 0.89 to 0.80. The model indicated a difference of 97 mm in transpiration over the season between both crops. Soil evaporation accounted for an average of 16% and 13% of the total actual evapotranspiration for almonds and pistachios, respectively. Verification of the model-based daily crop evapotranspiration estimates was done using eddy-covariance and surface renewal data collected in the same orchards, yielding an R2 ≥ 0.7 and average root mean square errors (RMSE) of 0.74 and 0.91 mm·day−1 for almond and pistachio, respectively. It is concluded that the combination of crop evapotranspiration models with remotely-sensed data is helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions.info:eu-repo/semantics/publishedVersio
A review of current and potential applications of remote sensing to study the water status of horticultural crops
Published: 17 January 2020With increasingly advanced remote sensing systems, more accurate retrievals of crop water status are being made at the individual crop level to aid in precision irrigation. This paper summarises the use of remote sensing for the estimation of water status in horticultural crops. The remote measurements of the water potential, soil moisture, evapotranspiration, canopy 3D structure, and vigour for water status estimation are presented in this comprehensive review. These parameters directly or indirectly provide estimates of crop water status, which is critically important for irrigation management in farms. The review is organised into four main sections: (i) remote sensing platforms; (ii) the remote sensor suite; (iii) techniques adopted for horticultural applications and indicators of water status; and, (iv) case studies of the use of remote sensing in horticultural crops. Finally, the authors’ view is presented with regard to future prospects and research gaps in the estimation of the crop water status for precision irrigation.Deepak Gautam and Vinay Paga
Feasibility of Using the Two-Source Energy Balance Model (TSEB) with Sentinel-2 and Sentinel-3 Images to Analyze the Spatio-Temporal Variability of Vine Water Status in a Vineyard
In viticulture, detailed spatial information about actual evapotranspiration (ETa) and vine water status within a vineyard may be of particular utility when applying site-specific, precision irrigation management. Over recent decades, extensive research has been carried out in the use of remote sensing energy balance models to estimate and monitor ETa at the field level. However, one of the major limitations remains the coarse spatial resolution in the thermal infrared (TIR) domain. In this context, the recent advent of the Sentinel missions of the European Space Agency (ESA) has greatly improved the possibility of monitoring crop parameters and estimating ETa at higher temporal and spatial resolutions. In order to bridge the gap between the coarse-resolution Sentinel-3 thermal and the fine-resolution Sentinel-2 shortwave data, sharpening techniques have been used to downscale the Sentinel-3 land surface temperature (LST) from 1 km to 20 m. However, the accurate estimates of high-resolution LST through sharpening techniques are still unclear, particularly when intended to be used for detecting crop water stress. The goal of this study was to assess the feasibility of the two-source energy balance model (TSEB) using sharpened LST images from Sentinel-2 and Sentinel-3 (TSEB-PTS2+3) to estimate the spatio-temporal variability of actual transpiration (T) and water stress in a vineyard. T and crop water stress index (CWSI) estimates were evaluated against a vine water consumption model and regressed with in situ stem water potential (Ψstem). Two different TSEB approaches, using very high-resolution airborne thermal imagery, were also included in the analysis as benchmarks for TSEB-PTS2+3. One of them uses aggregated TIR data at the vine+inter-row level (TSEB-PTairb), while the other is based on a contextual method that directly, although separately, retrieves soil and canopy temperatures (TSEB-2T). The results obtained demonstrated that when comparing airborne Trad and sharpened S2+3 LST, the latter tend to be underestimated. This complicates the use of TSEB-PTS2+3 to detect crop water stress. TSEB-2T appeared to outperform all the other methods. This was shown by a higher R2 and slightly lower RMSD when compared with modelled T. In addition, regressions between T and CWSI-2T with Ψstem also produced the highest R2.info:eu-repo/semantics/publishedVersio
Precision irrigation in citrus with different water qualities
[SPA] Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones. El cambio climático hará que la temperatura de la Tierra aumente 2,2 ◦C de aquí a 2040. Se prevé que este aumento de la temperatura del aire vaya acompañado de una reducción de las precipitaciones, lo que aumentará la intensidad y la frecuencia de los episodios de sequía. Paralelamente, la población mundial es más de tres veces mayor que a mediados del siglo XX y seguirá aumentando en los próximos años, lo que incrementará la demanda de agua para la producción de alimentos. En la actualidad, la producción mundial de alimentos mediante regadío representa más del 40 % del total y sólo utiliza alrededor del 20 % de la superficie destinada a este fin. Los cítricos son una de las principales especies cultivadas en todo el mundo, repartidas en más de 140 países. Esta especie depende del riego y tiene una demanda de agua media-alta. Para hacer frente a la sequía, la agricultura de regadío se ve obligada a realizar los máximos esfuerzos para mejorar la eficiencia en el uso del agua. En este contexto, la presente tesis doctoral tiene como objetivo evaluar la sostenibilidad del riego de precisión de cultivos de cítricos (pomelo y lima), con especial atención al estudio de la evapotranspiración del cultivo (ETc) y al uso de indicadores del estado hídrico de suelo y planta. Para alcanzar estos objetivos se han llevado a cabo varios experimentos (Artículos del I al IV). Un buen conocimiento de la ETc es necesario para decidir "cuándo" regar y "cuánta" agua aplicar. En el Artículo I, se calculó la ETc de limeros jóvenes por el método del balance hídrico del suelo utilizando lisímetros de pesada. A lo largo del ciclo de cultivo, la ETc fue más alta en Julio (2,56 L planta-1día-1), debido al elevado consumo de agua durante la última fase de crecimiento del fruto. Cuando los cambios en la biomasa de la lima fueron insignificantes, las variaciones en el peso de las macetas servían para validar la ETc calculada por el método del balance hídrico (r2=0,92***). En este artículo, se propone un prototipo de lisímetro de pesada escalable, sencillo y robusto, para árboles jóvenes cultivados en maceta, que proporciona una forma práctica y rentable de medir la ETc durante todo el año. En limeros jóvenes cultivados al aire libre y bajo malla de sombreo se midieron indicadores discretos del estado hídrico de la planta, como el potencial hídrico del tallo (Ψstem), la conductancia estomática (gs) y la fotosíntesis neta (Pn), así como indicadores continuos como la temperatura de la copa (Tc) (Artículos II y III). En el Artículo II, el sombreado incrementó un 54 y 37 % la gs y la Pn diaria acumulada, respectivamente. Además, bajo malla se incrementó el Ψstem en 0,05 MPa y se redujeron los valores de la diferencia de temperatura entre la copa y el aire (Tc-Ta) en 1,7 ◦C según los Artículos II y III. Estos hechos apuntaron un mejor comportamiento fisiológico de los limeros en condiciones de sombreado. En el Artículo III, se evaluó el efecto combinado del sistema de cultivo y el riego deficitario en los indicadores de estado hídrico del suelo y de la planta. Los resultados indicaron que cuando el estrés hídrico del suelo fue moderado, las condiciones de sombreado amortiguaron el efecto negativo sobre el estado hídrico del suelo y de la planta, permitiendo posponer el déficit hídrico. Sin embargo, cuando el estrés hídrico del suelo fue severo, se observaron valores igualmente bajos de estos indicadores tanto en campo abierto como en condiciones de sombreado. Además, se proponen dos nuevos índices basados en la Tc, que mostraron una respuesta diferente según el sistema de cultivo y el tratamiento de riego considerado. La programación del riego basada en indicadores del estado hídrico del suelo y de la planta permite ajustar la dosis de riego a las necesidades hídricas del cultivo. En esta tesis, el riego de los limeros se gestionó automáticamente, en base a valores umbrales del contenido de agua del suelo medidos en la zona radicular activa. El uso de este protocolo de riego promovió un estado hídrico óptimo de la planta, como se observó en los limeros cultivados en maceta (Artículo I) y en el suelo (Artículos II y III). En cuanto a los indicadores del estado hídrico de la planta, la medida de la Tc a distancia y en tiempo real supone una gran ventaja para la gestión del riego. En este sentido, en el Artículo III, se propusieron valores umbrales de la Tc-Ta de 2,4 y 0,8 ◦C para limeros bien regados cultivados al aire libre y bajo malla de sombreo, respectivamente. En el Artículo IV, se evaluó la robustez de varios índices basados en la Tc para estimar la gs en pomelos adultos regados con diferentes cantidades (riego completo y deficitario) y calidades de agua (trasvase y agua regenerada) de riego durante dos estados fenológicos (floración-brotación y crecimiento del fruto). Además, se comprobó la capacidad de diferentes índices térmicos para determinar la gs en diferentes intervalos de datos térmicos y en diferentes condiciones de déficit de presión de vapor (VPD) y de radiación fotosintéticamente activa (PAR). Los resultados sugirieron que los índices térmicos y la gs tenían el mayor grado de correlación cuando los datos térmicos se promediaron a 60 min, a VPD entre 0 y 3,5 kPa, y a PAR 1200 μmol m-2 s-1. En estas condiciones, los árboles con riego deficitario y los regados con agua regenerada fueron los que mostraron las mejores correlaciones entre los índices térmicos y la gs. El índice de estrés hídrico del cultivo (CWSI) y la Tc-Ta estimaron mejor la gs durante la floración-brotación, y los valores absolutos de Tc durante el estado fenológico de crecimiento del fruto, independientemente de la calidad y cantidad de agua aplicada. Esto indicó que durante floración-brotación la Tc dependía principalmente de las condiciones climáticas más que del estado hídrico de la planta, mientras que durante el período de crecimiento del fruto la Tc estaba más influenciada por factores intrínsecos de la planta (apertura estomática). En general, los índices térmicos han demostrado ser buenos indicadores del estado hídrico de la planta para una gestión precisa del riego en cítricos. [ENG] This doctoral dissertation has been presented in the form of thesis by publication. In the coming years, climate change will cause the earth's temperature to rise 2.2 ◦C by 2040. This increase in air temperature is expected to be accompanied by a reduction in precipitation, which will increase the intensity and frequency of drought events. In parallel, the world’s population is more than three times larger than it was in the mid-twentieth century. It will continue increasing in the subsequent years, driving up water demand for food production. Currently, global food production from irrigation represents more than 40 % of the total and uses only about 20 % of the land area designated to this end. Citrus is one of the main species cultivated worldwide, spread in more than 140 countries. This species is irrigation-dependent, and it has a medium-high water demand. In order to cope with this water scarcity, irrigated agriculture is forced to make utmost efforts to improve water use efficiency. In this context, this thesis is aimed to assess the sustainability of precise irrigation of citrus crops (grapefruit and lime), with special attention to the study of crop evapotranspiration (ETc) and the use of soil and plant water status indicators. To achieve these objectives several experiments were carried out (Articles I to IV). A sound knowledge of ETc is necessary to decide ‘when’ to irrigate and ‘how much’ water to apply. In Article I, young lime’s ETc was calculated by soil water balance method using drainage-weighing pot-lysimeters. Along the crop cycle, ETc was the highest in July (2.56 L plant-1day-1), due to the elevated water consumption during the last fruit growth stage. When lime tree biomass changes were negligible, pot weight variations served for ETc-water balance validation (r2=0.92***). A prototype of a simple and robust scalable drainage-weighing lysimeter for young potted trees was proposed, which provided a practical and cost-effective way to measure ETc throughout the year. Discrete plant water status indicators, as stem water potential (Ψstem), stomatal conductance (gs) and net photosynthesis (Pn), as well as continuous ones like canopy temperature (Tc) were measured on lime trees grown in shaded and in open-field conditions (Articles II and III). In Article II, shading increased by 54 and 37 % daily accumulated leaf gs and Pn, respectively. Moreover, in shaded conditions Ψstem was increased by 0.05 MPa and canopy to air temperature difference (Tc-Ta) values were reduced by 1.7 ◦C according to Articles II and III. These facts pointed to a better physiological performance of lime trees under shading conditions. In Article III, the combined effect of cropping system and deficit irrigation on soil and plant water status indicators was evaluated. The results indicated that when soil water stress was moderate, shading conditions cushioned the negative effect on soil and plant water status, allowing to postpone water deficits. However, when soil water stress was severe, similar low values of these indicators were observed in open-field and in shaded conditions. Additionally, two new thermal-based indices were proposed, which showed a different response by cropping system-irrigation treatment considered. Irrigation scheduling based on soil and plant water status indicators allows adjusting the irrigation dose to crop water needs. In this thesis, irrigation of lime trees was automatically managed, based on soil water content threshold values measured in the active root zone. This irrigation protocol promoted an optimal plant water status, as proved in pot grown (Article I), and in field grown (Articles II y III) lime trees. Regarding plant water status indicators, remote and real-time Tc measurement supposes a great advantage for irrigation management purposes. In this sense, in Article III, Tc-Ta threshold values of 2.4 and 0.8 ◦C were proposed for full irrigated lime trees in open-field and shaded conditions, respectively. In Article IV, the robustness of several thermal-based indices to estimate gs for different irrigation strategies (full and deficit irrigation), water sources (transfer and reclaimed water) and phenological stages (flowering-sprouting and fruit growth) in grapefruit trees were evaluated. In addition, the ability of thermal indices to determine gs at different averaged thermal data intervals, vapour pressure deficit (VPD) and photosynthetically active radiation (PAR) conditions, was tested. The results suggested that thermal indices and gs had the highest degree of correlation at 60 min thermal average data, VPD between 0 and 3.5 kPa and PAR 1200 μmol m-2 s-1. In these conditions, trees under deficit irrigation and those irrigated with reclaimed water showed the best thermal indices-gs correlations. Crop water stress index (CWSI) and Tc-Ta estimated gs better during flowering-sprouting (FS), and Tc during fruit growth (FG), independently of quality of the irrigation source and the amount of water applied. This fact indicated that in FS stage Tc depended mainly on climatic conditions rather than on plant water status, whereas in FG stage it was more influenced by intrinsic plant factors (stomatal opening). Overall, thermal-based indices have demonstrated to be suitable plant water status indicators for precise irrigation management of citrus trees.Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones. Está formada por un total de cuatro artículos: Article I: Mira-García, A.B., Vera, J., Conejero, W., Conesa, M.R., Ruiz-Sánchez, M.C., 2021. Evapotranspiration in young lime trees with automated irrigation. Scientia Horticulturae 288, 110396. DOI: 10.1016/j.scienta.2021.110396 Article II Mira-García, A.B., Conejero, W., Vera, J., Ruiz-Sánchez, M.C., 2020. Leaf water relations in lime trees grown under shade netting and open-air. Plants 9(4), 510. DOI: 10.3390/plants9040510 Article III Mira-García, A.B., Conejero, W., Vera, J., Ruiz-Sánchez, M.C., 2022. Water status and thermal response of lime trees to irrigation and shade screen. Agricultural Water Management 272, 107843. DOI: 10.1016/j.agwat.2022.107843 Article IV Mira-García, A.B., Romero-Trigueros, C., Bayona-Gambín, J.M., Sánchez- Iglesias, M.P., Nortes-Tortosa, P.A., Nicolás-Nicolás, E., 2023. Estimation of stomatal conductance by infrared thermometry in citrus trees cultivated under regulated deficit irrigation and reclaimed water. Agricultural Water Management 276, 108057 DOI: 10.1016/j.agwat.2022.108057Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado en Técnicas Avanzadas en Investigación y Desarrollo Agrario y Alimentari
Tree extraction and estimation of walnut structure parameters using airborne LiDAR data
[EN] The development of new tools based on remote sensing data in agriculture contributes to cost reduction, increased production, and greater profitability. Airborne LiDAR (Light Detection and Ranging) data show a significant potential for geometrically characterizing tree plantations. This study aims to develop a methodology to extract walnut (Juglans regia L.) crowns under leafless conditions using airborne LiDAR data. An original approach based on the alpha-shape algorithm, identification of local maxima, and k-means algorithms is developed to extract the crowns of walnut trees in a plot located in Viver (Eastern Spain) with 192 trees. In addition, stem diameter and volume, crown diameter, total height, and crown height were estimated from cloud metrics and other 2D parameters such as crown area, and diameter derived from LiDAR data. A correct identification was made of 178 trees (92.7%). For structure parameters, the most accurate results were obtained for crown diameter, stem diameter, and stem volume with coefficient of determination values (R-2) equal to 0.95, 0.87 and 0.83; and RMSE values of 0.43 m (5.70%), 0.02 m (9.35%) and 0.016 m(3) (21.55%), respectively. The models that gave the lowest R-2 values were 0.69 for total height and 0.70 for crown height, with RMSE values of 0.84 m (12.4%) and 0.83 m (14.5%), respectively. A suitable definition of the central and lower parts of tree canopies was observed. Results of this study generate valuable information, which can be applied for improving the management of walnut plantations.Estornell Cremades, J.; Hadas, E.; Marti-Gavila, J.; López- Cortés, I. (2021). Tree extraction and estimation of walnut structure parameters using airborne LiDAR data. International Journal of Applied Earth Observation and Geoinformation. 96:1-9. https://doi.org/10.1016/j.jag.2020.102273S199