Samuel Ortega-Farias

Universidad de Talca · Center for Irrigation and Agroclimatology Research (CITRA)

This work aimed to assess the performance of different thermal-infrared (TIR)-based physiological indicators (PI) as an alternative to the stem water potential (Ψs) and stomatal conductance (gs) for monitor the water status of grafted drip-irrigated 'Regina' cherry trees. In addition, we evaluated the usefulness of piecewise linear regression for f...

Atmospheric longwave downward radiation (Ld) is one of the significant components of net radiation (Rn), and it drives several essential ecosystem processes. Ld can be estimated with simple empirical methods using atmospheric emissivity (εa) submodels. In this study, eight global models for εa were evaluated, and the best-performing model was calib...

Evapotranspiration (ET) is an essential part of energy flow between the surface of the earth and the atmosphere, simultaneously involving the water, carbon, and energy cycles. It is mainly determined by climate change, land use, and land cover changes. Climate change is expected to intensify the hydrological cycle and alter ET. Land use affects ET...

Response of fruit yield, fruit quality, and water productivity to different irrigation levels for a microsprinkler-irrigated apple orchard (cv. Fuji) growing under Mediterranean conditions

The culture of açaí (Euterpe oleraceae M.), originating from floodplain areas, was planted on dry land in many properties in Pará, Brazil, making necessary the use of irrigation. To irrigate adequately with less waste, it is necessary that studies aim at increasing efficiency in the use of water in this sector, and one of the ways to do so is to es...

Water relations in vineyards have been largely studied; giving insides regarding the way grapevine interacts with its environment according to water availability, providing us terminologies like Isohydric and Anisohydric, which have been applied to categorize cultivars and rootstocks. Recently, the use of this terminology has been subjected to disc...

Tahiti lime is a species of great economic importance worldwide. In Brazil, production is concentrated in the states of São Paulo and Pará, where it is usually grafted onto the Rangpur lime. This study aimed to analyze the effects of different irrigation depths on the fruit yield, phenology, and gas exchange of Tahiti lime trees grafted onto Swingl...

We investigate the balance of radiation and energy over a lime orchard in Eastern Amazon and how it relates to environmental conditions. We found that lime trees aged between 6 and 7 years old reflect 11.0% to 14.5% of incoming shortwave radiation, and the latent heat flux corresponds to 57.6% and 66.6% of the daily net radiation in the dry season...

Atmospheric longwave downward radiation (Ld) is one of the significant components of net radiation (Rn), and it drives several essential ecosystem processes. Ld can be estimated with simple empirical methods using atmospheric emissivity (εa) submodels. In this study, eight εa global models were evaluated, and the one with the best performance was c...

Due to drought intensification in Mediterranean-type climates, raspberry growers need to implement irrigation scheduling to save water without decreases in yield and fruit quality. A study was performed to evaluate the effects of four irrigation levels on yield (Y), fruit number (FM²), fruit weight (FW), water productivity (WP), fruit quality (titr...

The population growth and climatic factors nega- tively impact the current scenario of reduced water availability. In particular, agriculture has become one of the most severely affected economic areas since it uses a significant amount of freshwater. Therefore, it has become necessary to implement strategies to accurately determine water demand at...

Chile's main agricultural areas will significantly reduce rainfall (between 20-40%) due to global climate change. Also, Chile is periodically affected by the climatic phenomenon of “La Niña” (ENSO) and the Pacific Decadal Oscillation (PDO), which have produced important droughts and economic losses in most of the agricultural areas. Under these con...

Climate change has an impact on agricultural sys- tems, affecting control and management practices. Field knowl- edge provided by the farmer and theoretical knowledge lack a useful articulation for decision making and the generation of adaptation strategies. Therefore, in our work we created a technological tool, hosted on a web page with the objec...

Mediterranean areas “such as the central zone of Chile” have faced severe limitations in water availability for irrigation due to a combination of various factors such as unsustainable industry use and climate change. Several strategies have been developed to overcome this problem, such as using physiological measurements to estimate plant water st...

Yield and oil quality responses to different degrees of water stress have often reported for olive trees, but few studies have addressed how midday stem water potential (Ψstem), stomatal conductance (gs), net assimilation (An), and oil yield respond to rewatering after experiencing water deficit. The objective of this study was to evaluate the resp...

Due to the proliferation of precision agriculture, the obstacle of estimating evapotranspiration (ET) and its components from shadow pixels acquired from remote sensing technology should not be neglected. To accurately detect shaded soil and leaf pixels and quantify the implications of shadow pixels on ET inversion, a two-year field-scale observati...

A field experiment was carried out to implement the Shuttleworth and Wallace (SW) model to estimate vineyard actual evapotranspiration (ETa) using thermal images from an unmanned aerial vehicle (UAV) and meteorological data. The vineyard (‘Cabernet Sauvignon’) was located in Pencahue Valley, Maule Region, Chile (35°20’33”S, 71°46’41”W, 86 m a.s.l.)...

Water scarcity and the new production objectives put pressure on agriculture to make efficient use of water. For this, constant monitoring of physiological variables is required, which is commonly done using midday stem water potential (MSWP). However, this measurement in large areas is limited by the inability of performing a large number of measu...

Chile's main agricultural areas will significantly reduce rainfall (between 20-40%) due to global climate change. Also, Chile is periodically affected by the climatic phenomenon of “La Niña” (ENSO) and the Pacific Decadal Oscillation (PDO), which have produced important droughts and economic losses in most of the agricultural areas. Under these con...

The increase of vineyard's water consumption due to the Global Warming Phenomenon (GWP) has forced the winegrowers to strengthen their irrigation and water stewardship efforts, intended for maintaining this resource's long-term sustainable use. Due to water being a limited resource, implementing the Water Footprint (WF) concept in winegrapes produc...

Near-surface air (Ta) and land surface (Ts) temperatures are essential parameters for research in the fields of agriculture, hydrology, and ecological changes, which require accurate datasets with different temporal and spatial resolutions. However, the sparse spatial distribution of meteorological stations in Northwest China may not effectively pr...

Accurate monitoring of crop transpiration (T) is essential for saving and managing irrigation water resources. Ground and UAV (Unmanned Aerial Vehicle) thermal infrared (TIR) images have high enough resolution to meet the needs of precision agriculture. At present, they are mostly used to assess crop water stress instead of to monitor T, especially...

La uva de mesa (Vitis vinífera) es uno de los cultivos de mayor relevancia económica y social en Sonora, México. Debido a la precipitación escasa y la demanda evaporativa elevada de la zona, es un cultivo con un requerimiento alto de agua. Por ello su producción depende de la aplicación de riego y es importante estimar con precisión y de manera ext...

Monitoring grapevine phenology during the agricultural season is one of the most important tasks within the vine field since this is a key input for the proper planning of agricultural labor management. Traditionally, vine growers make very few phenological observations at the field level, which are extrapolated to an entire production unit, withou...

The AquaCrop model was evaluated considering a data set from a cowpea (BR3-Tracuateua cultivar) cultivation in Castanhal/Brazil under different irrigations during the reproductive phase, which is sensitive to water deficit. Data on leaf area index (LAI), soil water content (SWC), biomass, and final yield of two harvests were used for model calibrat...

A field experiment was performed to evaluate the Mapping Evapotranspiration at High Resolution using Internalized Calibration (METRIC) model that was used for mapping surface energy balance (SEB) components (net radiation (Rni), soil heat flux (Gi), sensible heat flux (Hi), and latent heat flux (LEi)) at times of Landsat satellite overpasses in con...

The use of unmanned aerial vehicles (UAVs) equipped with high-resolution thermal infrared (TIR) cameras can provide the necessary spatial variability for estimating energy balance (EB) components over heterogeneous canopies, such as those of vineyards. An experiment was carried out to evaluate a two-source patch energy balance (TSPEB) model for com...

As blueberries are susceptible to water stress and their future cultivation in semiarid Mediterranean areas will be challenged by drought, irrigation management strategies will be needed to optimize water productivity and maintain sufficient levels of fruit yield and quality. This study aim was to evaluate the effect of different irrigation levels...

The acai palm (Euterpe oleracea Mart.) is a fruit from the Amazon that is originally found in flooded areas. Over recent years, its marketability has gained significant interest in Brazil and abroad because of its agronomic, nutritional and economic potential. However, there is a lack of technical-scientific information about crop water requirement...

A study was performed to evaluate the clumped model in estimating olive orchard evapotranspiration (ETa) using meteorological data and high-resolution thermal infrared (TIR) imagery obtained from a camera onboard an unmanned aerial vehicle (UAV). An experimental site was established within a superintensive drip-irrigated olive (cv. Arbequina) orcha...

The Leaf Area Index (LAI) is one of the most important structural and functional attributes of forests. This is determined by indirect methods such as digital hemispheric photography (DHP), because is simple to use at the field level, but it does not reflect the spatial variability of forest stands at a larger scale. Therefore, there is increasing...

The midday stem water potential (Ψs) and stomatal conductance (gs) have been traditionally used to monitor water status of cherry trees (Prunus avium L.). Due to complexity of direct measurement, the use of infrared thermography has been proposed as an alternative. This study compares Ψs and gs against crop water stress indexes (CWSI) calculated fr...

An experiment was conducted to evaluate the effect of irrigation cut-off (ICO) strategies on yield components, water productivity (WP), and gas exchange in drip-irrigated hazelnut (Corylus avellana L., cv. Tonda di Giffoni) trees during two consecutive growing seasons. The experimental design was completely randomized, with four ICO treatments and...

We evaluated the effects of different post-harvest irrigation strategies on yield, fruit quality and quantity, and water productivity (WP) of sweet cherry trees, over a two-growing season experiment. The fruits were evaluated at harvest and after cold storage. The irrigation treatments were T0 = control (received 100% of the fruit grower irrigation...

The use of empirical agrometeorological models that can be adjusted to the climatic conditions of different regions has become increasingly necessary to improve water management in grain-producing municipalities. The aim of this work is to examine the correlation between various reference evapotranspiration (ETo) estimation methods and the standard...

En el presente trabajo se evaluó la correlación entre el índice de estrés hídrico (CWSI por sus siglas en inglés), calculado a partir del promedio de los pixeles de imágenes térmicas provenientes de una cámara infrarroja térmica (IRT) de bajo costo (≈ USD200) (CAT S60, Catphones Mobile Ltd., EEUU) y las variables fisiológicas potencial xilemático a...

Many irrigation strategies have been proposed in olive orchards to overcome both increasing water scarcity and competition for water with other sectors of society. However, threshold values of stomatal conductance (gs) and stem water potential (Ψstem) for use in designing deficit irrigation strategies have not yet been adequately defined. Thus, an...

A study was conducted in a drip-irrigated vineyard (cv. Cabernet Sauvignon) located in the Pencahue Valley of Chile during 2018/19 growing season. The 5 year-old vines were trained on a vertical shoot positioned system. A completely randomized design with four irrigation treatments with four replications was established to develop relationships bet...

The world’s five Mediterranean-climate regions (MCRs) share unique climatic regimes of mild, wet winters and warm and dry summers. Agriculture in these regions is threatened by increases in the occurrence of drought and high temperature events associated with climate change (CC). In this review we analyze what would be the effects of CC on crops (i...

The aim of this research was to evaluate the clumped model for estimating latent heat flux (LE) and actual evapotranspiration (ETa) over a non-water-stressed olive orchard. Additionally, submodels to compute the net radiation Rn, soil heat flux G, and canopy resistance rcs were also included. For this objective, a database was used from an experime...

A study was carried out to develop and validate models that simulate grapevine phenology of the cultivars Cabernet Sauvignon, Merlot, Chardonnay and Sauvignon Blanc growing under Mediterranean climate conditions. In this study, phenology models were developed using a monomolecular equation, where the dependent and independent variables were the Eic...

This article describes the implementation of two segmentation algorithms in combination with the Triangular Greenness Index (TGI) derived from images obtained from an unmanned aerial vehicle (UAV), with the objective of segmenting shadow, soil and vegetation data obtained from a commercial vineyard cv. Cabernet Sauvignon. The importance of this seg...

This manuscript presents a comparison of Normalized Difference Vegetation Index (NDVI) obtained with multispectral cameras versus four indices obtained from RGB sensors for the identification of soil and vegetation in images captured with an unmanned aerial vehicle. This comparison was made using the NDVI as ground truth, obtaining 2 classes of dat...

A remote sensing energy balance (RSEB) algorithm was used to estimate transpiration (TRSEB) from a high density and drip-irrigated olive (Olea europaea L. ‘Arbequina’) orchard, located in Pencahue Valley, Maule Region of Chile (35°23’S; 71°44’W). Meteorological variables over the orchard such as solar radiation, air temperature, relative humidity,...

In the Chilean viticultural industry, Carménère is considered an emblematic cultivar that is cultivated mainly in arid and semi-arid zones. For this reason, it is necessary to use precise irrigation scheduling for improving water use efficiency (WUE), water productivity (WP), yield and wine quality. This study evaluated the effects of three deficit...

An increase in olive oil consumption has occurred worldwide in the last decades and has resulted in more land area being dedicated to olive orchards in several southern hemisphere countries. In order to achieve sustainable productivity under the increasing water scarcity, optimal water use is essential. Thus, a field experiment was conducted during...

A study was carried out to evaluate the potential use of the two-source Shuttleworth and Wallace (SW) model to compute the intra-orchard spatial variability of actual evapotranspiration (ET) of olive trees using satellite images and ground-based climate data. The study was conducted in a drip-irrigated olive orchard using satellite images (Landsat...

Water stress caused by water scarcity has a negative impact on the wine industry. Several strategies have been implemented for optimizing water application in vineyards. In this regard, midday stem water potential (SWP) and thermal infrared (TIR) imaging for crop water stress index (CWSI) have been used to assess plant water stress on a vine-by-vin...

Highbush blueberries require sufficient water throughout the growing season, especially during fruit development. Regulated deficit irrigation (RDI) has been used in many fruit crops to save water and potentially increase fruit quality without reducing yield. Our aim was to determine the effects of RDI on yield, plant–water relations, and fruit qua...

Water stress which affects yield and wine quality is often evaluated using the midday stem water potential (Ψstem). However, this measurement is acquired on a per plant basis and does not account for the assessment of vine water status spatial variability. The use of multispectral cameras mounted on an unmanned aerial vehicle (UAV) is capable to ca...

Water stress, which affects yield and wine quality, is often evaluated using the midday stem water potential (Ψstem). However, this measurement is acquired on a per plant basis and does not account for the assessment of vine water status spatial variability. The use of multispectral cameras mounted on unmanned aerial vehicle (UAV) is capable to cap...

Traditionally, irrigation labor considers the value of reference evapotranspiration (ETo) and crop coefficient to estimate actual evapotranspiration (ETa). This methodology presents significant errors in the obtention of Kc. To avoid using empirical values of Kc, some authors suggest using two layer models to estimate ETa over sparse canopies such...

p style="text-align: justify;">Phenological models have been made mainly for winegrape cultivars, despite the economic importance of table grapes. The aim of this work was to develop and validate models for predicting phenological scales of table grapes (cvs. Thompson, Crimson and Superior Seedless and Red Globe) grown under semi-arid conditions. M...

An increase in the land area dedicated to super-high density olive orchards has occurred in Chile in recent years. Such modern orchards have high irrigation requirements, and optimizing water use is a priority. Moreover, this region presents low water availability, which makes necessary to establish irrigation strategies to improve water productivi...

A field experiment was carried out to calibrate and evaluate the METRIC (Mapping EvapoTranspiration at high Resolution Internalized with Calibration) model for estimating the spatial and temporal variability of instantaneous net radiation (Rni), soil heat flux (Gi), sensible heat flux (Hi), and latent heat flux (LEi) over a drip-irrigated apple (Ma...

A field experiment was carried out to implement a remote sensing energy balance (RSEB) algorithm to estimate spatial variability of vine water requirements or evapotranspiration (ET) over a drip-irrigated Cabernet Sauvignon vineyard located in the Pencahue Valley in the Maule Region, Chile (35°25´ LS; 71°44´ LW; 90 m asl). For this study, a helicop...