Papers by Samuel Ortega-Farias
VII International Symposium on Olive Growing, 2014
VII International Symposium on Irrigation of Horticultural Crops, 2014
Keywords: Merlot, eddy covariance system, latent heat flux, sensible heat flux.
IV International Symposium on Irrigation of Horticultural Crops, 2004
An experiment was carried out to evaluate the effects of different levels of water application du... more An experiment was carried out to evaluate the effects of different levels of water application during postsetting and post-veraison on wine quality of cv. Cabernet Sauvignon (Vitis vinifera L.) during the 2000-2001 and 2001-2002 growing seasons. The vineyard is located in the Pencahue Valley, VII Region of Chile (35º22' S lat; 71º47' W long). The 7 yearold vineyard was drip irrigated and trained in a vertical shoot positional system. Irrigation treatments were the application of 40, 70 and 100% of the real evapotranspiration (ETreal) during post-setting and postveraison. The results showed that the best combination for wine quality was obtained by restricting water applications to 40% ETreal during post-setting and 70% ETreal during post-veraison, with significant increments in the global quality and wine sensory attributes. On the contrary, the worst wine quality (higher titratable acidity and low total concentrations of phenols and anthocyanins) was obtained with a water application of 100% of the ETreal during the whole growing period.
Durante tres temporadas agrícolas (2007-2008, 2008-2009 y 2009-2010), se llevó a cabo un estudio ... more Durante tres temporadas agrícolas (2007-2008, 2008-2009 y 2009-2010), se llevó a cabo un estudio para cuantificar evapotranspiración real (ETa) de un viñedo, regado por goteo, para diferentes cultivares de vides tintas (Vitis vinífera L.): Carménère, Merlot y Cabernet Sauvignon, mediante el uso de imágenes satelitales Landsat 5 (TM), 7 (ETM+) y datos meteorológicos, a través del modelo residual del balance de energía superficial METRIC (Allen et al. 2007). Lo anterior permitió realizar cartografías de la evolución de la ETa promedio del viñedo, para las tres temporadas evaluadas. Para analizar el desempeño del modelo, los datos estimados de evapotranspiración real diaria (ETaM), fueron comparados con los medidos por un sistema de flujos turbulentos instalado en una parcela experimental (4,25 ha), dentro de un cuartel plantado con cv. Merlot. El análisis estadístico consideró la comparación de los datos observados versus los estimados, evaluando la pendiente (b), el coeficiente de de...
VII International Symposium on Olive Growing, 2014
Irrigation scheduling is critical for olive orchards, since it affects both fruit yield and olive... more Irrigation scheduling is critical for olive orchards, since it affects both fruit yield and olives composition. Regulated deficit irrigation (RDI) strategies have been applied with positive results in the past. However, to successfully regulate stress levels, it is necessary to have accurate measurements of plant water status, which is usually done using a pressure chamber. Canopy temperature (T c ) is another potential accurate indicator of water stress. Therefore, the objective of this study was to evaluate three methods to obtain T c values from infrared thermal images to calculate the crop water stress index (CWSI). Furthermore, the relation between CWSI and midday stem water potential (MSWP) was also studied. The methods used to obtain T c were: i) T c1 obtained from a region of interest within the image; ii) T c2 obtained from whole image; iii) T c3 obtained from a filtered image using an interactive filtering process to exclude non-leaf material (low and high temperature values). The infrared thermal images were obtained using an infrared camera (Model i40, FLIR Instruments) in parallel with MSWP measurements from trees under different RDI strategies in a drip irrigated olive orchard (Olea europaea L. 'Arbequina') located in Pencahue valley, Maule Region, Chile (35°23'L.S; 71°44'L.W; 96 m a.s.l.) during the 2011-2012 season. Results obtained in this study showed that CSWI 3 calculated using T c3 had a better correlation with MSWP compared to the two other methods studied. The interactive filter process to obtain T c values could be used in olive orchards as a fast and cheap indicator of water stress. Further studies are required to automate the analysis process.
VIII International Symposium on Sap Flow, 2012
A study was carrying out to develop a dual crop coefficient (soil evaporation (Ke) plus canopy tr... more A study was carrying out to develop a dual crop coefficient (soil evaporation (Ke) plus canopy transpiration (Kcb) coefficients) for a drip-irrigated Merlot vineyard located in the Talca valley. In this study, the transpiration (Tsap) and actual evapotranspiration (ETa) were measured using compensation heat-pulse sap flow sensors (SF) and Eddy covariance system (EC), respectively. Soil evaporation (Es) was estimated as a residual of the actual evapotranspiration (Es = ETa -Tsap), and reference evapotranspiration (ETo) was calculated using FAO-56 standardized Penman-Monteith. Using these information, basal (ratio of Tsap to ETo) and soil (ration of Es to ETo) coefficients were estimated for key phenological stages. Results indicate that the ratios of Tsap to ETo were about 0.38 for initial conditions, 0.60 for middle season and 0.54 for the end of vine growing season. Also, the ratios of Es to ETo under the conditions of this study were very similar for the three periods with average values around to 0.12.
VII International Symposium on Olive Growing, 2014
Plant water status is an important factor to be quickly and accurately assessed temporally and sp... more Plant water status is an important factor to be quickly and accurately assessed temporally and spatially to maintain yield and quality standards in a changing environment. The pressure chamber is the most common method to measure midday stem water potential (MSWP), which is used as an accurate indicator of plants water status. However, the use of the latter method has the disadvantages of being manual, destructive, slow and impractical to have a good spatial representation of plant water status of a whole olive orchard. The objective of this research was to test an indirect method to estimate MSWP using visible and near infrared (NIR) spectroscopy analysis. This method is non-destructive and quick to implement in the field having the extra advantage of assessing the whole tree with a single measurement using short-range remote sensing. In this study, MSWP was measured using a pressure chamber (PMS Instrument Co. USA) to characterize water status of olive trees in a commercial drip-irrigated 'Arbequina' orchard (Pencahue, Region del Maule, Chile). Canopy reflectance was measured between 350 and 2500 nm wavelength region with a spectrometer FieldSpect3 (Analytical Spectral Device, ASD Co., USA) from 2.5 m distance. The spectroscopy analysis was done using partial least squares (PLS) regression by the Unscramble software. The validation process showed a root mean square error (RMSE) equal to 0.88 MPa and coefficient of determination (R 2 ) equal to 0.75. These results showed that the noninvasive method, using spectral reflectance data, could obtain a surrogate of stem water potential of olive trees, providing the possibility to screen more samples under field conditions and to automate the data gathering and analysis once a calibration curve is developed.
VIII International Symposium on Sap Flow, 2012
The two-layer model of Shuttleworth and Wallace (SW) was evaluated to estimate transpiration (T s... more The two-layer model of Shuttleworth and Wallace (SW) was evaluated to estimate transpiration (T sw ) from a drip-irrigated olive (Olea europaea L. 'Arbequina') orchard, located in Pencahue Valley, Maule Region of Chile (35º 23' LS; 71º 44' LW). An automatic weather station was installed in the center of the orchard to measure air temperature, relative humidity, wind speed, latent heat flux, net radiation and soil heat flux from October to December 2010. Values of T sw were compared with sap flow measurements on 30-minute time interval. Results indicated that model was able to predict olive transpiration with a root mean square error (RMSE) of 22 W m -2 and a mean absolute error (MAE) of 18 W m -2 . On a daily basis, the model was able to predict the olive transpiration with RMSE and MAE values of 0.51 and 0.41 mm d -1 , respectively. In general, the model tended to underestimate transpiration with errors less than 12 and 17% on 30-minute and daily basis, respectively.
VI International Symposium on Irrigation of Horticultural Crops, 2011
The goal of this study was to test the feasibility of extrapolating a single vine water status me... more The goal of this study was to test the feasibility of extrapolating a single vine water status measurement to several locations using ancillary information with a high-spatial resolution. An experiment to identify and test the model was carried out over a commercial 'Syrah' field located in the Languedoc-Roussillon Region, France, during the 2003 and 2004 growing seasons. A regular grid of 49 measurement sites was distributed over the field. For each grid point, measurements were conducted to assess: (i) predawn leaf water potential (PLWP) at seven dates in 2003 and six dates in 2004, and (ii) vine vegetative expression (vine trunk circumference, expose leaf area and pruning weight). Results showed that most of the variables of plant (water status and vegetative growth) were highly correlated among them and with NDVI and ER a . Also, the proposed model was able to predict spatial variability of PLWP with a spatial and temporal mean error of 0.09 and 0.10 MPa, respectively. This result shows the ability of this approach to extrapolate the plant water status from one reference site by taking into account spatial variability characterised by ancillary information. Further studies will aim to confirm the relevancy of this approach for different seasons, locations and cultivars.
Resumo En general, la disponibilidad de agua para el riego se ha reducido significativamente en l... more Resumo En general, la disponibilidad de agua para el riego se ha reducido significativamente en los últimos años debido a las frecuentes sequías y a la fuerte competencia por el recurso hídrico entre la agricultura, la industria y las áreas urbana. Debido a lo anterior, el Centro de Investigación y Transferencia en Riego y Agroclimatología (CITRA) de la Universidad de Talca, implementó un Sistema Integral para la Gestión Hídrica con el objeto de asesorar a los agricultores (VI y VII Regiones, Chile) en la programación del riego en cultivos, frutales y viñas. Este sistema entrega a los agricultores información climática básica (temperatura, humedad relativa, velocidad del viento, radiación solar y precipitaciones) y procesada (evapotranspiración de referencia, tiempos de riego y frecuencias de riego), la cual permite optimizar el uso del agua en cultivos, frutales y viñas. Entre los principales resultados obtenidos por este servicio durante los años 1997 y 2005, se pueden mencionar: ...
The Priestley-Taylor (PT) model was evaluated for estimating the real evapotranspiration (ETreal)... more The Priestley-Taylor (PT) model was evaluated for estimating the real evapotranspiration (ETreal) of a drip-irrigated greenhouse tomato ( Lycopersicon esculentum Mill.) crop. The net radiation incorporated in the PT model was estimated using meteorological variables. For this experiment, an automatic weather station (AWS) was installed inside the greenhouse to measure solar radiation (Rgi), net radiation (Rn), air temperature (Ta) and relative humidity (RH). Another AWS was installed over a grass cover to measure atmospheric conditions outside the greenhouse. The experiment was carried out at the Panguilemo experimental station (35°23' S, 71°40' W, 110 m.a.s.l.) from August to December 2000. The PT model was evaluated using the ETreal obtained from the water balance (WB) method. In this case, values of ETreal by PT model were calculated using: a) Rgi and soil heat flux (G) = 0; b) Rgi and G ≠ 0; c) solar radiation measured outside the greenhouse (Rge) and G = 0; and d) Rge a...
La deshidratación prematura de bayas en el cv. Merlot consiste en una rápida pérdida de agua desd... more La deshidratación prematura de bayas en el cv. Merlot consiste en una rápida pérdida de agua desde la pinta en adelante, cuando la fruta no ha alcanzado aún la concentración de azucares mínimas para ser cosechas. En Australia, la deshidratación prematura de bayas se ha descrito en el cv. Syrah presentándose muy cerca de la cosecha, donde las pérdidas de rendimiento pueden alcanzar hasta un 25%. En Chile, el deshidratado de bayas en el cv. Merlot comenzaría a manifestarse a partir de la pinta, estimándose reducciones del rendimiento que pueden varias entre un 20 % y 80 % . En este caso, bayas deshidratadas tienen una alta acidez, no toman color y permanecen rosadas hasta cosecha. Además, este problema puede producir perdidas importantes en la calidad del vino debido a la generación de aromas y sabores extraños en el mosto.
IV International Symposium on Irrigation of Horticultural Crops, 2004
Non-uniform Soil Wetting Patterns are commonly found in the field and numerical or empirical mode... more Non-uniform Soil Wetting Patterns are commonly found in the field and numerical or empirical models developed to characterise them may or may not be accurate. Quantitative assessment of non-uniform wetted zones is essential for optimal irrigation management of crops under precision irrigation techniques such as Regulated Deficit Irrigation (RDI) or Partial Root-zone Drying (PRD). A field study was carried out to visualise the wetting pattern in situ on Grapevines (Vitis vinifera var. Cabernet Sauvignon) at Pencahue VII Region, Chile (University of Talca) and (Vitis vinifera var. Shiraz) at Richmond NSW, Australia (University of Western Sydney). In Chile, soil moisture and soil wetting pattern volumes were correlated with plant water status, measured as stem water potential (Ψ stem ) on RDI treatments. In Australia soil moisture data were collected using an array of capacitance probes (Sentek Pty. Ltd.) and used to generate 3D real time animations of soil wetting patterns at different irrigation systems (drip and sub-surface drip) using WPA© (Wetting Pattern Analyser), which is a novel software tool for visualisation and animation of field soil wetting patterns. Preliminary results have shown the critical importance of the location of soil moisture probes to schedule irrigation and a strong correlation of total available water in the wetted zone, (r 2 = 0.77) and normalised soil moisture (r 2 = 0.84) with Ψ stem .
Irrigation Science, 2009
A study was performed in order to evaluate the three-source model (Clumped model) for direct esti... more A study was performed in order to evaluate the three-source model (Clumped model) for direct estimation of actual evapotranspiration (ET a ) and latent heat flux (LE) over a drip-irrigated Merlot vineyard trained on a vertical shoot positioned system (VSP) under semi-arid conditions. The vineyard, with an average fractional cover of 30%, is located in the Talca Valley, Region del Maule, Chile. The performance of the Clumped model was evaluated using an eddy covariance system during the 2006/2007 and 2007/ 2008 growing seasons. Results indicate that the Clumped model was able to predict ET a with a root mean square error (RMSE), mean bias error (MBE), and model efficiency (EF) of 0.33, -0.15 mm day -1 and 74%, respectively. Also, the Clumped model simulated the daytime variation of LE with a RMSE of 36 W m -2 , MBE of -8 W m -2 , and EF of 83%. Major disagreement (underestimated values) between observed and estimated values of ET a was found for clear days after rainfall or foggy days, but underestimated values were less than 10% of the data analysis. The results obtained in this study indicate that the Clumped model could be used to directly estimate vine water requirements for a drip-irrigated vineyard trained on a VSP. However, application of the Clumped model requires a good characterization of the drip-irrigated vineyard architecture.
Ciencia e investigación agraria
Un estudio fue desarrollado para evaluar un modelo de radiacion neta en las unidades agroclimatic... more Un estudio fue desarrollado para evaluar un modelo de radiacion neta en las unidades agroclimaticas de Panguilemo (UAP) localizadas en Talca (Chile) y Oregon (USA), respectivamente. En ambas localidades, una estacion meteorologica automatica fue ubicada sobre una cubierta vegetal de festuca en condiciones de referencia para medir la radiacion neta, radiacion global, temperatura de aire y presion de vapor en intervalos de una hora. Los resultados indicaron que existio una alta correlacion entre los valores de radiacion neta observados (Rno) y estimados (Rne), con un r2 de 0,97 y r2 de 0,98 para la UAP y UAC, respectivamente. Las mayores dispersiones entre Rno y Rne fueron encontradas durante la noche, pero no afectaron significativamente el calculo final de la radiacion neta. Estos resultados sugieren el modelo de Rn estudiado puede ser utilizado en la formula de Penman-Monteith para determinar los requerimientos hidricos de los cultivos en las localidades de Talca y Oregon
This paper describes an application of real time data capture and wireless transmission of meteor... more This paper describes an application of real time data capture and wireless transmission of meteorological data used by agricultural administrators to support operational decisions such as irrigation scheduling and pesticide application. Forestry companies need such information for managing operations during the fire season. The system architecture based on distributed wireless data communication using cell phone components is selected as the required interface and software drivers are implemented to connect different brands of meteorological data stations with a GSM cell phone and thereby insulate the variations in technology, transmission and storage schemes from the overlying database and application software layers.
Uploads
Papers by Samuel Ortega-Farias