Estimation of vineyard water requirements using satellite-based surface energy balance

115 p.Since the 90's as a consequence of the Global Warming and the “La Niña” (ENSO) phenomena, the Chilean wine industry has been forced to increase irrigation systems investments, adopting new strategies of irrigation scheduling to improve the vineyard water use efficiency without affecting the grapes yield and quality. To develop an adequate irrigation strategy, the first step has been to estimate the vineyard water uptake or actual evapotranspiration ETa).Traditionally, vineyard ETa has been estimated by multiplying the reference evapotranspiration (ETo) by a single crop coefficient (Kc). Unfortunately, a major uncertainty in this approach is that many Kc values reported in literature are empirically determined from point-based measurements, and they are unable to describe the spatial variability of vineyard Kc, for each phenological stage. Recent advancements in using satellite remote sensing to determine ETa over space and time have made it possible to assess the variation in crop ETa at low-cost. One of the most cited remote sensing-based algorithms is METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) which is a onedimensional surface energy based residual model that has been extensively customized for application in full covered crops. For sparse crops such vineyards, as far as we know the application of METRIC to estimate ETa and Kc is still unexplored. In this way, this thesis was developed with the aim of critically study the applicability of METRIC over a drip-irrigated Merlot vineyard. To meet this, a study was carried out during the 2006-2007, 2007-2008 and 2008-2009 growing seasons. METRIC-based estimations were compared against ground measurements of vegetation indexes, surface energy balance components and vineyard ETa. Results indicated that METRIC’s semi-empirical sub-models for estimate vegetation indexes should be calibrated before its direct application to vineyards (Chapter 2). On the other hand, in the evaluation of METRIC to estimate the different components of the vineyard surface energy balance, results indicated that the compensation between the instantaneous fluxes of net radiation, soil heat fluxes and latent heath fluxes produced acceptable estimations of latent heat luxes (error less than 10%) to extrapolate them to daily (24 h) evapotranspiration (ETa) (Chapter 3). Finally for the main phenological stages of the Merlot vineyard, METRIC overestimated the Kc by about 10% in relation to ground measurements. However, those errors did not significantly affect the overall performance of METRIC during the study period into the estimation of daily (24 h) ETa and Kc (Chapter 4). Results exposed from Chapters two to four suggest that it is possible to confirm that the METRIC model can be used for obtain relatively good estimations of the vineyard ETa during the complete growing season

A soil water indicator for a dynamic model of crop and soil water interaction

Water scarcity is a critical issue in agriculture, and the development of reliable methods for determining soil water content is crucial for effective water management. This study proposes a novel, theoretical, non-physiological indicator of soil water content obtained by applying the next-generation matrix method, which reflects the water-soil-crop dynamics and identifies the minimum viable value of soil water content for crop growth. The development of this indicator is based on a two-dimensional, nonlinear dynamic that considers two different irrigation scenarios: the first scenario involves constant irrigation, and the second scenario irrigates in regular periods by assuming each irrigation as an impulse in the system. The analysis considers the study of the local stability of the system by incorporating parameters involved in the water-soil-crop dynamics. We established a criterion for identifying the minimum viable value of soil water content for crop growth over time. Finally, the model was calibrated and validated using data from an independent field study on apple orchards and a tomato crop obtained from a previous field study. Our results suggest the advantages of using this theoretical approach in modeling the plants' conditions under water scarcity as the first step before an empirical model. The proposed indicator has some limitations, suggesting the need for future studies that consider other factors that affect soil water content

Comparación del índice de vegetación de la diferencia normalizada (NDVI) obtenido desde imágenes satelitales y radiometría de campo en un huerto de olivos cv. arbequina

48 p.El presente trabajo consistió en la comparación entre valores del índice de vegetación de diferencia normalizada (NDVI) obtenidos a partir del satelite Landsat 7 (NDVISAT) y un radiómetro multiespectral portátil en terreno (NDVIPOND). Este estudio se realizó durante las temporadas 2008/2009, 2009/2010 y 2010/2011 en un huerto de Olivos (Olea europaea cv. Arbequina) ubicado en el valle de Pencahue, Región del Maule, Chile (35º23´ lat. Sur; 71º44´ long. Oeste; 90 m.s.n.m). Para realizar la comparación, los valores de NDVI obtenidos con radiometría de campo fueron ponderados de acuerdo a la fracción de cobertura vegetal (fc), la cual alcanzó aproximadamente un 30% de la superficie. Los resultados obtenidos indican que la relación entre los índices, presenta una pendiente significativamente igual a 1, con un nivel de confianza del 95% (α de 0,05). El análisis estadístico además indica que el error cuadrático medio (RMSE), el error absoluto medio (MAE) y el índice de acuerdo fueron 0,019, 0,014 y 0,98, respectivamente. La mejor comparación entre NDVIPOND y el NDVISAT presento una diferencia igual a cero (en 4 fechas de medidas) y en contraste la peor comparación presentó una diferencia de un 11,2%. Las diferencias observadas entre los NDVI obtenidos a ambas escalas pueden estar asociadas a que no se eliminaron los efectos atmosféricos (corrección atmosférica) en los valores de reflectancia a nivel de satélite o a errores inducidos por la dificultad en la obtención de valores puros de NDVI en la radiometría de campo sobre Olivos, dada la alta porosidad presente en el dosel del cultivo. Finalmente en cuanto a la relación entre el Kc y el NDVI está presento un R2 de 0,71 para valores correspondientes a la temporada 2009-2010 en donde estos coincidieron con lo reportado por la literatura. Palabras clave: Coeficiente de cultivo, METRIC, Landsat, Fracción de cobertura, Índice de vegetación./ ABSTRACT: A comparison between normalized difference vegetation index (NDVI) derived from satellite data (NDVIPOND) and a portable multispectral radiometer (NDVISAT) field was carried out. This study was performed in the 2008/2009, 2009/2010 and 2010/2011 seasons, in an olive trees orchard (Olea europaea cv. Arbequina) located in the valley of Pencahue, Maule Region, Chile (35 ° 23' Lat. South, 71; 44' Long W, 90 m.a.s.l.). Before making comparisons, the NDVI values from field radiometry were weighted according to the fraction of vegetation cover (fc), which reached about 30% of the surface. The results indicate that the linear fit between indices (NDVI weighted and NDVI satellite) have a significantly slope equal to 1, with a confidence level of 95% (α of 0.05). Statistical analysis also indicates that the mean square error (RMSE), mean absolute error (MAE) and the index of agreement were 0.019, 0.014 and 0.98, respectively. The best comparison between both NDVIs show differences equal to zero (in 4 dates) and the worst comparison showed a difference of 11,2%. The differences observed between NDVIs obtained in both scales can be associated with atmospheric effects (not atmospheric correction) in the reflectance values at satellite level or errors induced by the difficulty to obtain pure values of NDVI in olives plant using radiometry, given the high porosity present in the canopy. Finally regarding the relationship between Kc and NDVI is presented an R2 of 0.71 for values for the 2009-2010 agricultural season where these coincided with that reported in the literature. Keywords: Crop coefficient, METRIC, Landsat, Fractional cover, Vegetation inde

Calibration and validation of an aerodynamic method to estimate the spatial variability of sensible and latent heat fluxes over a drip irrigated Merlot vineyard

A study was carried out to calibrate and validate the aerodynamic temperature method for estimating the spatial variability of the sensible (H) and latent (LE) heat fluxes over a drip-irrigated merlot vineyard located in the Maule Region, in Chile. For this study, measurement of energy balance components and meteorological data were collected from the 2006 to 2010 growing seasons. The experimental plot was composed of a 4.25 ha of ‘Merlot’ vineyard, which was equipped with an Eddy- Covariance system and an automatic weather station. The k-fold cross-validation method was utilized to tune and validate a vineyard surface aerodynamic temperature (Taero) model, considering all of the days when Landsat scenes and ground measurements of meteorological data and surface energy balance (SEB) were available. Then, the satellite-based estimations of Taero were utilized to calculate the surface aerodynamic resistance (rah) and, subsequently, heat fluxes of H and LE. Results indicated that the estimated H and rah values were not significantly different to those measured in the vineyard (95% significance level) showing a root mean square (RMSE) and mean absolute error (MAE) between 34–29 W m−2 and 1.01–0.78 s m−1, respectively. Satellite-based computations of LE were somewhat higher than those measured at the time of satellite overpass (RMSE = 63 W m−2; MAE = 56 W m−2), presumably due to the biases embedded in the net radiation (Rn) and soil heat flux (G) computations. The proposed SEB method based on Taero is very simple to implement, presenting similar accuracies on ET mapping to those computed by complex satellitebased models.Sociedad Argentina de Informática e Investigación Operativ

Parameterization of the Satellite-Based Model (METRIC) for the Estimation of Instantaneous Surface Energy Balance Components over a Drip-Irrigated Vineyard

A study was carried out to parameterize the METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) model for estimating instantaneous values of albedo (shortwave albedo) (αi), net radiation (Rni) and soil heat flux (Gi), sensible (Hi) and latent heat (LEi) over a drip-irrigated Merlot vineyard (location: 35°25′ LS; 71°32′ LW; 125 m.a.s. (l). The experiment was carried out in a plot of 4.25 ha, processing 15 Landsat images, which were acquired from 2006 to 2009. An automatic weather station was placed inside the experimental plot to measure αi, Rni and Gi. In the same tower an Eddy Covariance (EC) system was mounted to measure Hi and LEi. Specific sub-models to estimate Gi, leaf area index (LAI) and aerodynamic roughness length for momentum transfer (zom) were calibrated for the Merlot vineyard as an improvement to the original METRIC model. Results indicated that LAI, zom and Gi were estimated using the calibrated functions with errors of 4%, 2% and 17%, while those were computed using the original functions with errors of 58%, 81%, and 5%, respectively. At the time of satellite overpass, comparisons between measured and estimated values indicated that METRIC overestimated αi in 21% and Rni in 11%. Also, METRIC using the calibrated functions overestimated Hi and LEi with errors of 16% and 17%, respectively while it using the original functions overestimated Hi and LEi with errors of 13% and 15%, respectively. Finally, LEi was estimated with root mean square error (RMSE) between 43 and 60 W·m−2 and mean absolute error (MAE) between 35 and 48 W·m−2 for both calibrated and original functions, respectively. These results suggested that biases observed for instantaneous pixel-by-pixel values of Rni, Gi and other intermediate components of the algorithm were presumably absorbed into the computation of sensible heat flux as a result of the internal self-calibration of METRIC

Análisis comparativo de estimación del NDVI mediante utilización de imágenes satelitales y espectroradiómetro portátil en un viñedo cv. merlot.

44 p.Esta investigación se desarrolló con el objetivo de analizar la variabilidad espacial del Índice de vegetación de la diferencia normalizada (NDVI) del viñedo, usando dos escalas de medición: satélite y mediciones de terreno, a lo largo de la temporada de crecimiento. Para ello se llevó a cabo un estudio en una parcela experimental de 4,25 ha de vid (Vitis vinífera L.) cv. Merlot, conducido en espaldera vertical simple y regada por goteo, para el período comprendido entre las temporadas 2007-2008 a la 2009-2010. Las mediciones en terreno se realizaron periódicamente usando un espectroradiómetro portátil, para una grilla de 64 puntos. Los datos obtenidos de NDVI para vid (NDVIp) y suelo (NDVIs) fueron escalados a nivel de viñedo usando la fracción de cobertura (Fc). Estos datos fueron comparados con los estimados a partir de imágenes satelitales del programa Landsat (NDVIsat), para los días donde hubo imágenes disponibles. Los resultados donde se obtuvieron valores del error absoluto medio (MAE) y cuadrado medio del error (RMSE) de 0,04 y 0,05, respectivamente. El análisis de regresión indica que el coeficiente de determinación (R2) y pendiente (b) presentaron valores de 98% y 0,98, respectivamente. El test-t indicó que la pendiente fue significativamente similar a la unidad, con un 95% de certeza. Estos resultados indican que el NDVI medido en terreno por un espectroradiómetro portátil y estimado por imágenes Landsat fueron similares para el período de estudio. Palabras claves: Viticultura de precisión, Teledetección, Reflectividad, Expresión vegetativa, Bandas espectrales./ABSTRACT:This research was developed with the aim of analyzing the spatial variability of the Normalized Difference Vegetation Index (NDVI) of the vineyard, using two measurement scales: satellite and field measurements throughout the growing season. For this purposes a study was carried out in an experimental plot (4.25 ha) of a drip-irrigated vineyard (Vitis vinifera L.) cv. Merlot, trained on a vertical shoot positioned system from 2007-2008 to 2009-2010 growing seasons. Ground measurements were regularly done using a hand-held multispectral radiometer for a grid of 64 points. Values of NDVI measured from vines (NDVIp) and soil (NDVIs) were scaled to vineyard using the fractional cover (Fc). These data were compared with NDVI-satellite based (NDVIsat) acquired from the Landsat program, for days when satellite images were available. The results indicate that the mean absolute error (MAE) and root mean square of error (RMSE) were 0.04 and 0.05, respectively. Regression analysis indicates that the coefficient of determination (R2) and slope (b) were 98% and 0.98, respectively. The t-test indicates that the slope was significantly similar to the unit, with a 95% of confidence. These results indicated that the NDVI measured from the hand-held multispectral radiometer and obtained from Landsat imagery were similar for the study periods Key words: Precision viticulture, Remote sensing, Reflectivity, Vegetative expression, Spectral bands

Estimación de la evapotranspiración de un huerto de manzanos cv. Pink Lady utilizando imágenes satelitales Landsat 7

47 p.Se realizó una investigación para validar el modelo METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) en la estimación del consumo de agua o evapotranspiración real (ETa) de un huerto de Manzanos (Malus domestica cv. Pink Lady) ubicado en el valle de Pelarco, Región del Maule, Chile (Lat. 35º25´ S; Long 71º23´ O; 189 m.s.n.m). Para estimar ETa usando el modelo METRIC se utilizaron seis imágenes satelitales (Landsat 7 ETM+) adquiridas durante días con cielo despejado en la temporada 2012-2013. El desempeño del modelo METRIC se evaluó usando mediciones de ETa desde un sistema de Flujos Turbulentos (EC) a la hora del paso del satélite (11:30 h). El análisis estadístico indicó que el modelo METRIC sobrestimó la ETa en alrededor de un 17 % con un error cuadrático medio (RMSE) de 1,03 mm d-1, un error absoluto (MAE) de 0,96 mm d-1 y una eficiencia del 0,48. Los mayores errores del modelo METRIC fueron asociados a la selección de pixeles fríos (sectores con menor temperatura en la imagen), los que fueron difíciles de obtener para algunas imágenes satelitales. Palabras clave: percepción remota, METRIC,evapotranspiración, Pink Lady, Eddy covariance, balance de energía./ABSTRACT: A study was carried out to validate the METRIC (Mapping EvapoTranspiration at high Resolution with Internalized Calibration) model to estimate the water requirements or real evapotranspiration (ETa) for a drip-irrigated apple orchard which is located at Pelarco Valley, Maule Region, Chile (Lat. 35º25´ S; Long 71º23´ W; 189 m above mean sea level). For estimating ETa using the METRIC model, six satellite images (Landsat 7 ETM+) acquired during clear sky days were used for the 2012-2013 growing season. The performance of METRIC was evaluated using measurements of ETa from an eddy covariance system (EC) at the time of satellite overpass (11:30 h). The statistical analysis indicated that the METRIC model overestimated ETa values by about 17 % with a root mean square error (RMSE), mean absolute error (MAE) and index of agreement (d) of 1.03 mm d-1, 0.96 mm d-1 y 0.48, respectively. Main errors of the METRIC model were associated with the selection of the cold pixels (coldest spots in the image), which were difficult to obtain for some satellite images. Keywords: Remote sensing, METRIC, Evapotranspiration, Pink Lady, eddy covariance, energy balance

Resultados preliminares de la determinación del Crop Water Stress Index (CWSI) en cerezos, usando una cámara termográfica de bajo costo

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 al mediodía (Ψx), obtenido mediante cámara de presión (modelo 600, PMS instruments, EEUU) y conductancia estomática (gs), obtenida mediante porómetro (SC-1, METER Group, Inc., EEUU).Sociedad Argentina de Informática e Investigación Operativ

Resultados preliminares de la determinación del Crop Water Stress Index (CWSI) en cerezos, usando una cámara termográfica de bajo costo

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 al mediodía (Ψx), obtenido mediante cámara de presión (modelo 600, PMS instruments, EEUU) y conductancia estomática (gs), obtenida mediante porómetro (SC-1, METER Group, Inc., EEUU).Sociedad Argentina de Informática e Investigación Operativ

Resultados preliminares de la determinación del Crop Water Stress Index (CWSI) en cerezos, usando una cámara termográfica de bajo costo

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 al mediodía (Ψx), obtenido mediante cámara de presión (modelo 600, PMS instruments, EEUU) y conductancia estomática (gs), obtenida mediante porómetro (SC-1, METER Group, Inc., EEUU).Sociedad Argentina de Informática e Investigación Operativ