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 irri...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-07-01
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| Series: | Agronomy |
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| Online Access: | https://www.mdpi.com/2073-4395/11/7/1419 |
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| author | Saray Gutiérrez-Gordillo Javier de la Gala González-Santiago Emiliano Trigo-Córdoba Alfredo Emilio Rubio-Casal Iván Francisco García-Tejero Gregorio Egea |
| author_facet | Saray Gutiérrez-Gordillo Javier de la Gala González-Santiago Emiliano Trigo-Córdoba Alfredo Emilio Rubio-Casal Iván Francisco García-Tejero Gregorio Egea |
| author_sort | Saray Gutiérrez-Gordillo |
| collection | DOAJ |
| description | 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 (Ψ<sub>stem</sub>), stomatal conductance (g<sub>s</sub>), and photosynthetic rate (A<sub>N</sub>). 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 Ψ<sub>stem</sub>. 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, Ψ<sub>stem</sub> seems to be the preferred option. |
| first_indexed | 2024-03-10T09:48:48Z |
| format | Article |
| id | doaj.art-5b5007133e0f41e7a6c402e12ec78cec |
| institution | Directory Open Access Journal |
| issn | 2073-4395 |
| language | English |
| last_indexed | 2024-03-10T09:48:48Z |
| publishDate | 2021-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Agronomy |
| spelling | doaj.art-5b5007133e0f41e7a6c402e12ec78cec2023-11-22T02:58:55ZengMDPI AGAgronomy2073-43952021-07-01117141910.3390/agronomy11071419Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond CultivarsSaray Gutiérrez-Gordillo0Javier de la Gala González-Santiago1Emiliano Trigo-Córdoba2Alfredo Emilio Rubio-Casal3Iván Francisco García-Tejero4Gregorio Egea5Center “Las Torres”, Andalusian Institute of Agricultural and Fisheries Research and Training (IFAPA), Carretera Sevilla-Cazalla km 12.2, 41200 Sevilla, SpainArea of Agroforestry Engineering, Technical School of Agricultural Engineering (ETSIA), Universidad de Sevilla, Ctra. Utrera km 1, 41013 Sevilla, SpainCenter “Las Torres”, Andalusian Institute of Agricultural and Fisheries Research and Training (IFAPA), Carretera Sevilla-Cazalla km 12.2, 41200 Sevilla, SpainDepartment of Plant Biology and Ecology, University of Seville, Ap 1095, 41080 Sevilla, SpainCenter “Las Torres”, Andalusian Institute of Agricultural and Fisheries Research and Training (IFAPA), Carretera Sevilla-Cazalla km 12.2, 41200 Sevilla, SpainArea of Agroforestry Engineering, Technical School of Agricultural Engineering (ETSIA), Universidad de Sevilla, Ctra. Utrera km 1, 41013 Sevilla, SpainIn 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 (Ψ<sub>stem</sub>), stomatal conductance (g<sub>s</sub>), and photosynthetic rate (A<sub>N</sub>). 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 Ψ<sub>stem</sub>. 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, Ψ<sub>stem</sub> seems to be the preferred option.https://www.mdpi.com/2073-4395/11/7/1419CWSINDVIdeficit irrigationcrop water statusunmanned aerial systemsemerging water stress |
| spellingShingle | Saray Gutiérrez-Gordillo Javier de la Gala González-Santiago Emiliano Trigo-Córdoba Alfredo Emilio Rubio-Casal Iván Francisco García-Tejero Gregorio Egea Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars Agronomy CWSI NDVI deficit irrigation crop water status unmanned aerial systems emerging water stress |
| title | Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars |
| title_full | Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars |
| title_fullStr | Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars |
| title_full_unstemmed | Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars |
| title_short | Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars |
| title_sort | monitoring of emerging water stress situations by thermal and vegetation indices in different almond cultivars |
| topic | CWSI NDVI deficit irrigation crop water status unmanned aerial systems emerging water stress |
| url | https://www.mdpi.com/2073-4395/11/7/1419 |
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