Linking canopy temperature and trunk diameter fluctuations with other physiological water status tools for water stress management in citrus orchards

The continuous monitoring of crop water status is key to the sustainable management of water stress situations. Two deficit irrigation (DI) treatments were studied during the maximum evapotranspirative demand period in an orange orchard (Citrus sinensis (L.) Osb. cv. Navelina): sustained deficit irrigation irrigated at 55% crop evapotranspiration (ETC), and low-frequency deficit irrigation treatment, in which the plants were irrigated according to stem water potential at midday (Ψstem). Additionally, a control treatment irrigated at 100% of ETC was established. The daily canopy temperature (TC) was measured with an infrared thermometer camera together with measurements of trunk diameter fluctuations (TDF), Ψstem and stomatal conductance (gS). The time course of all physiological parameters and their relationships were analysed, confirming that canopy air temperature differential (TC – Ta) variations and TDF are suitable approaches for determining the water stress. In addition, the maximum daily shrinkage (MDS) and TC – Ta showed high sensitivity to water stress in comparison to Ψstem and gS. Significant relationships were found among MDS and TC – Ta with Ψstem and gS, for monitoring the crop water status by means of MDS vs Ψstem and TC – Ta vs Ψstem. Thus, the combination of these techniques would be useful for making scheduling decisions on irrigation in orchards with high variability in plant water stress.

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Monitoring of Emerging Water Stress Situations by Thermal and Vegetation Indices in Different Almond Cultivars

Agronomy ◽

10.3390/agronomy11071419 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1419

Author(s):

Saray Gutiérrez-Gordillo ◽

Javier de la Gala González-Santiago ◽

Emiliano Trigo-Córdoba ◽

Alfredo Emilio Rubio-Casal ◽

Iván Francisco García-Tejero ◽

...

Keyword(s):

Water Stress ◽

Deficit Irrigation ◽

Water Status ◽

Stress Conditions ◽

Irrigation Season ◽

Stem Water Potential ◽

Crop Water ◽

Regulated Deficit Irrigation ◽

Sensitive Periods ◽

Mild Water Stress

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.

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

Water ◽

10.3390/w12051298 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1298

Author(s):

Saray Gutiérrez-Gordillo ◽

Iván Francisco García-Tejero ◽

Víctor Hugo Durán Zuazo ◽

Amelia García Escalera ◽

Fernando Ferrera Gil ◽

...

Keyword(s):

Water Stress ◽

Thermal Imaging ◽

Water Status ◽

Irrigation Management ◽

Irrigation Treatment ◽

Canopy Temperature ◽

Irrigation Scheduling ◽

Stress Index ◽

Crop Water ◽

Crop Water Stress Index

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.

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Potential of UAS-Based Remote Sensing for Estimating Tree Water Status and Yield in Sweet Cherry Trees

Remote Sensing ◽

10.3390/rs12152359 ◽

2020 ◽

Vol 12 (15) ◽

pp. 2359

Author(s):

Víctor Blanco ◽

Pedro José Blaya-Ros ◽

Cristina Castillo ◽

Fulgencio Soto-Vallés ◽

Roque Torres-Sánchez ◽

...

Keyword(s):

Remote Sensing ◽

Deficit Irrigation ◽

Vegetation Index ◽

Sweet Cherry ◽

Prunus Avium ◽

Water Status ◽

Control Treatment ◽

Stem Water Potential ◽

Irrigation Treatments ◽

Cherry Trees

The present work aims to assess the usefulness of five vegetation indices (VI) derived from multispectral UAS imagery to capture the effects of deficit irrigation on the canopy structure of sweet cherry trees (Prunus avium L.) in southeastern Spain. Three irrigation treatments were assayed, a control treatment and two regulated deficit irrigation treatments. Four airborne flights were carried out during two consecutive seasons; to compare the results of the remote sensing VI, the conventional and continuous water status indicators commonly used to manage sweet cherry tree irrigation were measured, including midday stem water potential (Ψs) and maximum daily shrinkage (MDS). Simple regression between individual VIs and Ψs or MDS found stronger relationships in postharvest than in preharvest. Thus, the normalized difference vegetation index (NDVI), resulted in the strongest relationship with Ψs (r2 = 0.67) and MDS (r2 = 0.45), followed by the normalized difference red edge (NDRE). The sensitivity analysis identified the optimal soil adjusted vegetation index (OSAVI) as the VI with the highest coefficient of variation in postharvest and the difference vegetation index (DVI) in preharvest. A new index is proposed, the transformed red range vegetation index (TRRVI), which was the only VI able to statistically identify a slight water deficit applied in preharvest. The combination of the VIs studied was used in two machine learning models, decision tree and artificial neural networks, to estimate the extra labor needed for harvesting and the sweet cherry yield.

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Assessing canopy temperature-based water stress indices for soybeans under subhumid conditions

10.5194/egusphere-egu2020-16325 ◽

2020 ◽

Author(s):

Angela Morales Santos ◽

Reinhard Nolz

Keyword(s):

Water Stress ◽

Soil Water ◽

Water Status ◽

Canopy Temperature ◽

Irrigation Scheduling ◽

Stress Index ◽

Crop Water ◽

Stress Indices ◽

Soil Water Status ◽

Crop Water Stress

Sustainable irrigation water management is expected to accurately meet crop water requirements in order to avoid stress and, consequently, yield reduction, and at the same time avoid losses of water and nutrients due to deep percolation and leaching. Sensors to monitor soil water status and plant water status (in terms of canopy temperature) can help planning irrigation with respect to time and amounts accordingly. The presented study aimed at quantifying and comparing crop water stress of soybeans irrigated by means of different irrigation systems under subhumid conditions.The study site was located in Obersiebenbrunn, Lower Austria, about 30 km east of Vienna. The region is characterized by a mean temperature of 10.5&#176;C with increasing trend due to climate change and mean annual precipitation of 550 mm. The investigations covered the vegetation period of soybean in 2018, from planting in April to harvest in September. Measurement data included precipitation, air temperature, relative humidity and wind velocity. The experimental field of 120x120 m2 has been divided into four sub-areas: a plot of 14x120&#160;m2 with drip irrigation (DI), 14x120&#160;m2 without irrigation (NI), 36x120&#160;m2 with sprinkler irrigation (SI), and 56x120&#160;m2 irrigated with a hose reel boom with nozzles (BI). A total of 128, 187 and 114 mm of water were applied in three irrigation events in the plots DI, SI and BI, respectively. Soil water content was monitored in 10&#160;cm depth (HydraProbe, Stevens Water) and matric potential was monitored in 20, 40 and 60&#160;cm depth (Watermark, Irrometer). Canopy temperature was measured every 15&#160;minutes using infrared thermometers (IRT; SI-411, Apogee Instruments). The IRTs were installed with an inclination of 45&#176; at 1.8&#160;m height above ground. Canopy temperature-based water stress indices for irrigation scheduling have been successfully applied in arid environments, but their use is limited in humid areas due to low vapor pressure deficit (VPD). To quantify stress in our study, the Crop Water Stress Index (CWSI) was calculated for each plot and compared to the index resulting from the Degrees Above Canopy Threshold (DACT) method. Unlike the CWSI, the DACT method does not consider VPD to provide a stress index nor requires clear sky conditions. The purpose of the comparison was to revise an alternative method to the CWSI that can be applied in a humid environment.CWSI behaved similar for the four sub-areas. As expected, CWSI &#8805; 1 during dry periods (representing severe stress) and it decreased considerably after precipitation or irrigation (representing no stress). The plot with overall lower stress was BI, producing the highest yield of the four plots. Results show that DACT may be a more suitable index since all it requires is canopy temperature values and has strong relationship with soil water measurements. Nevertheless, attention must be paid when defining canopy temperature thresholds. Further investigations include the development and test of a decision support system for irrigation scheduling combining both, plant-based and soil water status indicators for water use efficiency analysis.

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Relationship of stem water potential and leaf conductance to vegetative growth of young olive trees in a hedgerow orchard

Australian Journal of Agricultural Research ◽

10.1071/ar07200 ◽

2008 ◽

Vol 59 (3) ◽

pp. 270 ◽

Cited By ~ 14

Author(s):

María Gómez-del-Campo ◽

A. Leal ◽

C. Pezuela

Keyword(s):

Water Stress ◽

Water Potential ◽

Soil Water ◽

Vegetative Growth ◽

Shoot Growth ◽

Irrigation Treatment ◽

Leaf Conductance ◽

Stem Water Potential ◽

Trunk Diameter ◽

Stem Water

In 2005, four irrigation treatments were applied to a 3-year-old cv. Cornicabra orchard. In T1, wetted soil volume was maintained close to field capacity by irrigating when soil sensors indicated that soil water potential in the root zone had fallen to –0.03 MPa and 0.06 MPa from spring until 15 August and from 15 August until September, respectively. On those days, 8, 6, 4, and 2 h of irrigation was applied to T1, T2, T3, and T4, so that over the season they received 106, 81, 76 and 31 mm of irrigation, respectively. The high value for T3 was the result of a valve failure on 13 June. Measurements were maintained throughout the experimental period of relative extractable water (REW) to 1 m depth at the wetted volume (0.30 m from a drip emitter), shoot length, trunk diameter, stem water potential (Ψstem) and leaf conductance (gl). The irrigation treatment significantly affected REW (P < 0.10), Ψstem, gl and vegetative growth (P < 0.05). Ψstem, and trunk diameter were the least variable parameters and Ψstem and shoot growth were the most sensitive to water stress. Although T1 received 24% more water than T2, no significant differences were detected in vegetative growth. T2 should be considered the optimum irrigation value. The mean monthly Kc for T2 was 0.086. The failure of the valve in T3 simulated a wet spring followed by limited irrigation. Irrigation applied was similar to T2 but shoot growth stopped one month earlier and lower values of Ψstem and gl were observed after mid August. REW was highly related to vegetative growth, 66% of maximum being achieved at REW 0.53 and 50% at 0.45. gl was independant of plant or soil water status and did not determine vegetative growth. A strong relationship established Ψstem as a good indicator of vegetative growth and hence of water stress. Shoot growth was 66% of maximum at Ψstem –1.5 MPa and 50% at –1.8 MPa.

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Simulating Canopy Temperature Using a Random Forest Model to Calculate the Crop Water Stress Index of Chinese Brassica

Agronomy ◽

10.3390/agronomy11112244 ◽

2021 ◽

Vol 11 (11) ◽

pp. 2244

Author(s):

Mingxin Yang ◽

Peng Gao ◽

Ping Zhou ◽

Jiaxing Xie ◽

Daozong Sun ◽

...

Keyword(s):

Water Stress ◽

Random Forest ◽

Water Status ◽

Canopy Temperature ◽

Random Forest Model ◽

Stress Index ◽

Crop Water ◽

Crop Water Stress Index ◽

Forest Model ◽

Water Stress Index

The determination of crop water status has positive effects on the Chinese Brassica industry and irrigation decisions. Drought can decrease the production of Chinese Brassica, whereas over-irrigation can waste water. It is desirable to schedule irrigation when the crop suffers from water stress. In this study, a random forest model was developed using sample data derived from meteorological measurements including air temperature (Ta), relative humidity (RH), wind speed (WS), and photosynthetic active radiation (Par) to predict the lower baseline (Twet) and upper baseline (Tdry) canopy temperatures for Chinese Brassica from 27 November to 31 December 2020 (E1) and from 25 May to 20 June 2021 (E2). Crop water stress index (CWSI) values were determined based on the predicted canopy temperature and used to assess the crop water status. The study demonstrated the viability of using a random forest model to forecast Twet and Tdry. The coefficients of determination (R2) in E1 were 0.90 and 0.88 for development and 0.80 and 0.77 for validation, respectively. The R2 values in E2 were 0.91 and 0.89 for development and 0.83 and 0.80 for validation, respectively. Our results reveal that the measured and predicted CWSI values had similar R2 values related to stomatal conductance (~0.5 in E1, ~0.6 in E2), whereas the CWSI showed a poor correlation with transpiration rate (~0.25 in E1, ~0.2 in E2). Finally, the methodology used to calculate the daily CWSI for Chinese Brassica in this study showed that both Twet and Tdry, which require frequent measuring and design experiment due to the trial site and condition changes, have the potential to simulate environmental parameters and can therefore be applied to conveniently calculate the CWSI.

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Plant Water Status as an Index of Irrigation Need in Deciduous Fruit Trees

HortTechnology ◽

10.21273/horttech.7.1.23 ◽

1997 ◽

Vol 7 (1) ◽

pp. 23-29 ◽

Cited By ~ 141

Author(s):

Kenneth A. Shackel ◽

H. Ahmadi ◽

W. Biasi ◽

R. Buchner ◽

D. Goldhamer ◽

...

Keyword(s):

Water Potential ◽

Deficit Irrigation ◽

Shoot Growth ◽

Water Status ◽

Plant Stress ◽

Irrigation Treatment ◽

Plant Water Status ◽

Plant Water ◽

Stem Water Potential ◽

Stem Water

To be useful for indicating plant water needs, any measure of plant stress should be closely related to some of the known short- and medium-term plant stress responses, such as stomatal closure and reduced rates of expansive growth. Midday stem water potential has proven to be a useful index of stress in a number of fruit tree species. Day-to-day fluctuations in stem water potential under well-irrigated conditions are well correlated with midday vapor-pressure deficit, and, hence, a nonstressed baseline can be predicted. Measuring stem water potential helped explain the results of a 3-year deficit irrigation study in mature prunes, which showed that deficit irrigation could have either positive or negative impacts on tree productivity, depending on soil conditions. Mild to moderate water stress was economically beneficial. In almond, stem water potential was closely related to overall tree growth as measured by increases in trunk cross-sectional area. In cherry, stem water potential was correlated with leaf stomatal conductance and rates of shoot growth, with shoot growth essentially stopping once stem water potential dropped to between −1.5 to −1.7 MPa. In pear, fruit size and other fruit quality attributes (soluble solids, color) were all closely associated with stem water potential. In many of these field studies, systematic tree-to-tree differences in water status were large enough to obscure irrigation treatment effects. Hence, in the absence of a plant-based measure of water stress, it may be difficult to determine whether the lack of an irrigation treatment effect indicates the lack of a physiological response to plant water status, or rather is due to treatment ineffectiveness in influencing plant water status. These data indicate that stem water potential can be used to quantify stress reliably and guide irrigation decisions on a site-specific basis.

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A New Low-Cost Device Based on Thermal Infrared Sensors for Olive Tree Canopy Temperature Measurement and Water Status Monitoring

Remote Sensing ◽

10.3390/rs12040723 ◽

2020 ◽

Vol 12 (4) ◽

pp. 723 ◽

Cited By ~ 3

Author(s):

Miguel Noguera ◽

Borja Millán ◽

Juan José Pérez-Paredes ◽

Juan Manuel Ponce ◽

Arturo Aquino ◽

...

Keyword(s):

Water Stress ◽

Water Status ◽

Low Cost ◽

Canopy Temperature ◽

Olive Tree ◽

Thermal Infrared ◽

Tree Canopy ◽

Coefficient Of Determination ◽

Crop Water ◽

Olive Orchard

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.

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Absence of Yield Reduction after Controlled Water Stress during Prehaverst Period in Table OliveTrees

Agronomy ◽

10.3390/agronomy10020258 ◽

2020 ◽

Vol 10 (2) ◽

pp. 258 ◽

Cited By ~ 1

Author(s):

María Martín-Palomo ◽

Mireia Corell ◽

Ignacio Girón ◽

Luis Andreu ◽

Alejandro Galindo ◽

...

Keyword(s):

Water Stress ◽

Deficit Irrigation ◽

Water Status ◽

Block Design ◽

Irrigation Scheduling ◽

Yield Reduction ◽

Irrigation Season ◽

Stem Water Potential ◽

Olive Trees ◽

Effect On Yield

Deficit irrigation scheduling is becoming increasingly important under commercial conditions. Water status measurement is a useful tool in these conditions. However, the information about water stress levels for olive trees is scarce. The aim of this experiment was to evaluate the effect on yield of a moderate controlled water stress level at the end of the irrigation season. The experiment was conducted in the experimental farm of La Hampa (Coria del Río, Seville, Spain) during three years. A completely randomized block design was performed using three different irrigation treatments. Deficit irrigation was applied several (4 or 2) weeks before harvest. Irrigation was controlled using the midday stem water potential, with a threshold value of −2 MPa and compared with a full irrigated treatment. This water stress did not reduced gas exchange during the deficit period. The effect on yield was not significant in any of the three seasons. In the high-fruit load season, fruit volume was slightly affected (around 10%), but this was not significant at harvest. Results suggest an early affection of fruit growth with water stress, but with a slow rate of decrease. Moderate water stress could be useful for the management of deficit irrigation in table olive trees.

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Improving Almond Productivity under Deficit Irrigation in Semiarid Zones

The Open Agriculture Journal ◽

10.2174/1874331501105010056 ◽

2011 ◽

Vol 5 (1) ◽

pp. 56-62 ◽

Cited By ~ 4

Author(s):

I.F. García-Tejero ◽

V.H. Durán-Zuazo ◽

L.M. Vélez ◽

A. Hernández ◽

A. Salguero ◽

...

Keyword(s):

Water Potential ◽

Water Use ◽

Deficit Irrigation ◽

Water Status ◽

Low Frequency ◽

Canopy Temperature ◽

Prunus Dulcis ◽

Stem Water Potential ◽

Irrigation Period ◽

Stem Water

Sustainable water use is one of the greatest challenges of irrigated agricultural systems. This study presents the results related to the agronomic and physiological response to the deficit irrigation of almond trees (Prunus dulcis DA Webb Mill cv. Guara) under semiarid Mediterranean conditions in the Guadalquivir river basin (SW Spain). Two deficitirrigation strategies were tested: i) regulated deficit irrigation (RDI), which was irrigated at 100% of crop evapotranspiration (ETC) throughout the irrigation period, except during the kernel-filling stage, when these trees where irrigated at 30% ETC, and ii) low-frequency deficit irrigation (LFDI), in which trees were subjected to different irrigationrestriction periods, defined in terms of stem water potential at midday (ΨStem). As control, a fully irrigated treatment (C-100) was used, which received irrigation covering the 100% of ETC. The stem water potential (ΨStem), the stomatal conductance (gS), the photosynthesis rate (Pn) and canopy temperature (TC) were monitored, revealing significant differences mainly in LFDI in comparison with C-100. Also, highly significant relationships were found among plant physiological parameters, showing that the water status is strongly related to the crop water availability. On other hand, in terms of nut yield, there was a notable improvement under LFDI compared with RDI, with increases of 16% in relation to C-100, and with water savings of close to 170 mm. Thus, these findings demonstrate that the LFDI is a sustainable strategy to improve almond productivity as well as water-use efficiency under limited water resources.

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