Definición de la etapa de desarrollo de los cultivos para estimar evapotranspiración usando la metodología FAO-56 y sensores remotos

Se analizan los patrones temporales de variables biofísicas y espectrales: índicede área foliar (IAF), cobertura aérea (fv), e índice de vegetación cinemáticamentemodificado y ajustado por suelo (IV_CIMAS), en cultivos con densidad foliar alta(sorgo) y densidad foliar media (algodón y maíz). En el caso del sorgo, se analiza larelación de estos patrones temporales con el coeficiente basal de cultivo (Kcb). Lasvariables fv, IAF e IV_CIMAS fueron modeladas con un modelo expo-lineal truncado(ELT) y uno expo-lineal asimétrico (ELA). Ambos presentaron un buen ajusteestadístico en los tres cultivos; sin embargo, el modelo ELT resulta más adecuado,porque no requiere el valor máximo de la variable. De las tres variables modeladas,el IV_CIMAS representa mejor la cantidad y calidad de la vegetación en un píxel oparcela, ya que es función de la cantidad de área foliar, de su distribución espacial,de las propiedades ópticas de las hojas y del suelo de fondo de la vegetación. Con elobjeto de estimar evapotranspiración, según lo establecido en FAO-56, se analizarontres métodos distintos para caracterizar la etapa de desarrollo del cultivo de sorgo.Los métodos definen la duración de la etapa con base en la cobertura del suelo, laetapa de floración y mediante la información espectral (IV_CIMAS). Se analizaronlos errores (RECM y ERM) de las estimaciones de Kcb de la etapa de desarrollovegetativo mediante los tres métodos, en relación con las estimaciones de Kcb de unlisímetro de pesada, obteniendo los mejores resultados para el método IV_CIMAS ylos peores para el método FAO-56-Floración

Monitoring 10-m LST from the Combination MODIS/Sentinel-2, Validation in a High Contrast Semi-Arid Agroecosystem

Downscaling techniques offer a solution to the lack of high-resolution satellite Thermal InfraRed (TIR) data and can bridge the gap until operational TIR missions accomplishing spatio-temporal requirements are available. These techniques are generally based on the Visible Near InfraRed (VNIR)-TIR variable relations at a coarse spatial resolution, and the assumption that the relationship between spectral bands is independent of the spatial resolution. In this work, we adopted a previous downscaling method and introduced some adjustments to the original formulation to improve the model performance. Maps of Land Surface Temperature (LST) with 10-m spatial resolution were obtained as output from the combination of MODIS/Sentinel-2 images. An experiment was conducted in an agricultural area located in the Barrax test site, Spain (39°03′35″ N, 2°06′ W), for the summer of 2018. Ground measurements of LST transects collocated with the MODIS overpasses were used for a robust local validation of the downscaling approach. Data from 6 different dates were available, covering a variety of croplands and surface conditions, with LST values ranging 300-325 K. Differences within ±4.0 K were observed between measured and modeled temperatures, with an average estimation error of ±2.2 K and a systematic deviation of 0.2 K for the full ground dataset. A further cross-validation of the disaggregated 10-m LST products was conducted using an additional set of Landsat-7/ETM+ images. A similar uncertainty of ±2.0 K was obtained as an average. These results are encouraging for the adaptation of this methodology to the tandem Sentinel-3/Sentinel-2, and are promising since the 10-m pixel size, together with the 3-5 days revisit frequency of Sentinel-2 satellites can fulfill the LST input requirements of the surface energy balance methods for a variety of hydrological, climatological or agricultural applications. However, certain limitations to capture the variability of extreme LST, or in recently sprinkler irrigated fields, claim the necessity to explore the implementation of soil moisture or vegetation indices sensitive to soil water content as inputs in the downscaling approach. The ground LST dataset introduced in this paper will be of great value for further refinements and assessments

Quantitative analysis of almond yield response to irrigation regimes in Mediterranean Spain

Almond plantations are expanding worldwide, specifically in Spain; the new orchards are often designed under more intensive systems in comparison to the traditional rainfed orchards frequently found in the Mediterranean Sea basin. In these new areas, water is the main limiting factor, and therefore, the present research is aimed at quantitatively analyzing previous findings obtained in irrigation field trials carried out in Spain with mature almond trees. The goal was to derive applied water-production functions and compare sustained and regulated deficit irrigation strategies to provide robust information on the marginal water productivity and the preferred irrigation option to be applied under water scarcity conditions. This quantitative analysis reported a yield increase as water application increased, with the highest potential yield of about 2500 kg/ha achieved with around 1000 mm of irrigation water applied. Under severe water restrictions, similar responses were observed regardless of the deficit irrigation technique employed. In contrast, under moderate water stress, it seems more advantageous to apply a regulated deficit irrigation strategy rather than a sustained deficit strategy. The reported results are useful for deriving more sustainable irrigation protocols and highlight the need to optimize other inputs in addition to water to take full advantage of the irrigation intensification to be carried out in the new almond plantations.Publishe

Sin / Sense

Sexto desafío por la erradicación de la violencia contra las mujeres del Institut Universitari d’Estudis Feministes i de Gènere «Purificación Escribano» de la Universitat Jaume

Is the Subsurface Drip the Most Sustainable Irrigation System for Almond Orchards in Water-Scarce Areas?

The expansion of irrigated almond orchards in arid and semi-arid areas with scarce water available raises key issues related to the sustainability of the water resources. A 3-year field experiment was conducted on a commercial young almond orchard located in the southeast of Spain to study the effect of two drip irrigation systems (surface, DI and subsurface, SDI) on almond crop growth and their physiological responses under fully-irrigated conditions. Crop evapotranspiration (ETc) and its components (crop transpiration, Tc and soil evaporation, Es) were monitored as well as the irrigation water and nitrogen productivities. To estimate ETc, a simplified two-source energy balance (STSEB) approach was used. Although a lower irrigation water amount was applied in SDI compared to DI (differences between 10% and 13.8%), the almond crop growth and physiological responses as well as the yield components and kernel yield showed no significant differences. The ETc estimates resulted in small differences for spring and fall periods (0.1–0.2 mm day−1) for both treatments, while differences were significant during higher ETo periods (May–August), being 1.0–1.3 mm day−1 higher for the DI treatment than for the SDI treatment. The irrigation water productivity (IWP) was significantly higher in the SDI treatment than in the DI treatment. However, no significant differences between the two treatments were observed for nitrogen productivity. It can be concluded that the SDI system is a suitable strategy for irrigating almond crops, reducing consumptive water use and increasing IWP

Is the Subsurface Drip the Most Sustainable Irrigation System for Almond Orchards in Water-Scarce Areas?

The expansion of irrigated almond orchards in arid and semi-arid areas with scarce water available raises key issues related to the sustainability of the water resources. A 3-year field experiment was conducted on a commercial young almond orchard located in the southeast of Spain to study the effect of two drip irrigation systems (surface, DI and subsurface, SDI) on almond crop growth and their physiological responses under fully-irrigated conditions. Crop evapotranspiration (ETc) and its components (crop transpiration, Tc and soil evaporation, Es) were monitored as well as the irrigation water and nitrogen productivities. To estimate ETc, a simplified two-source energy balance (STSEB) approach was used. Although a lower irrigation water amount was applied in SDI compared to DI (differences between 10% and 13.8%), the almond crop growth and physiological responses as well as the yield components and kernel yield showed no significant differences. The ETc estimates resulted in small differences for spring and fall periods (0.1–0.2 mm day−1) for both treatments, while differences were significant during higher ETo periods (May–August), being 1.0–1.3 mm day−1 higher for the DI treatment than for the SDI treatment. The irrigation water productivity (IWP) was significantly higher in the SDI treatment than in the DI treatment. However, no significant differences between the two treatments were observed for nitrogen productivity. It can be concluded that the SDI system is a suitable strategy for irrigating almond crops, reducing consumptive water use and increasing IWP

Monitoring Crop Evapotranspiration and Transpiration/Evaporation Partitioning in a Drip-Irrigated Young Almond Orchard Applying a Two-Source Surface Energy Balance Model

Encouraged by the necessity to better understand the water use in this woody crop, a study was carried out in a commercial drip-irrigated young almond orchard to quantify and monitor the crop evapotranspiration (ETc) and its partitioning into tree canopy transpiration (T) and soil evaporation (E), to list and analyze single and dual crop coefficients, and to extract relationships between them and the vegetation fractional cover (fc) and remote-sensing-derived vegetation indices (VIs). A Simplified Two-Source Energy Balance (STSEB) model was applied, and the results were compared to ground measurements from a flux tower. This study comprises three consecutive growing seasons from 2017 to 2019, corresponding to Years 2 to 4 after planting. Uncertainties lower than 50 W m−2 were obtained for all terms of the energy balance equation on an instantaneous scale, with average estimation errors of 0.06 mm h−1 and 0.6 mm d−1, for hourly and daily ETc, respectively. Water use for our young almond orchard resulted in average mid-season crop coefficient (Kc mid) values of 0.30, 0.33, and 0.45 for the 2017, 2018, and 2019 growing seasons, corresponding to fc mean values of 0.21, 0.35, and 0.39, respectively. Average daily evapotranspiration for the same periods resulted in 1.7, 2.1, and 3.2 mm d−1. The results entail the possibility of predicting the water use of any age almond orchards by monitoring its biophysical parameters

Sustainable Production of Barley in a Water-Scarce Mediterranean Agroecosystem

Scarcity of water resources is one of the main constraints on agricultural activity in arid and semi-arid areas. Despite the great technological development over recent decades, farmers are demanding methodologies and tools adapted to their training, management restrictions, and economic capacity. To tackle these challenges, the sustainable production in water-limited environments of Mediterranean agroecosystems (SUPROMED) project combines, in an online platform, a set of models and methodologies for more efficient management of water, energy, and fertilizers. A two-year trial (2020–2021) was conducted in the Castilla-La Mancha region (Spain) to demonstrate, for a barley crop, the effectiveness of SUPROMED as a farm management support tool. The impact of transferring the model for the economic optimization of irrigation water use at farm level (MOPECO model) irrigation scheduling among other methods and tools, integrated in the SUPROMED platform, to farmers was determined by analyzing a set of productive, economic, and environmental key performance indicators (KPIs). The KPIs were selected to show farmers how the efficient use of productive factors could improve the profitability of their farms, thus reducing the impact of agriculture on the environment. In 2020, the management plan proposed by SUPROMED achieved the same yield as traditional management using 32% less water and resulting in a 13% and 66% improvement in gross margin and gross economic irrigation water productivity, respectively. In 2021, the management implemented by a farmer trained in the use of the tools and methodologies in the SUPROMED platform showed improvements in most of the KPIs analyzed, achieving similar results to those obtained by SUPROMED during 2020. The results are promising, indicating that the tools and models proposed in SUPROMED can be easily used by farmers and can improve the economic and environmental sustainability of Mediterranean agroecosystems. The involvement of public administrations, together with local researchers and technicians, is required for the effective promotion and use of these methodologies by the productive sector

Modeling reference evapotranspiration with calculated targets.Assessment and implications

[EN] Due to the absence of experimental reference evapotranspiration (ETo) records, data-driven models con-sider in most cases calculated ETotargets to train and test the models, usually according to the standardFAO56 Penman Monteith equation (FAO56-PM). This procedure is also adopted for calibrating moreconventional empirical approaches like the well-known Hargreaves (HG) equation. This study aims atassessing the performance implications derived from using calculated targets instead of experimentalmeasurements for training and testing data-driven models or calibrating empirical methods. Thereforean application of a gene expression programming (GEP) based approach for estimating ETois presentedconsidering calculated and lysimetric targets fed with two different input combinations and assessedthrough k-fold testing. The same procedure is adopted to evaluate the calibration of the HG equation.Finally, the FAO56-PM and the HG equations are compared with their corresponding GEP models bearingin mind the type of targets used. The locally trained GEP4 and GEP6 models trained using the experimen-tal lysimetric targets are more accurate than the corresponding HG and FAO56-PM equations, assessedusing lysimetric benchmarks. The external performance accuracy of GEP4 and GEP6 models decreasesconsiderably in the cross-station approach using experimental targets. In this case, the FAO56-PM andthe HG equations might be preferable. The accuracy of the GEP models trained with calculated targetsdecreases considerably when the performance is assessed using experimental benchmarks. The conclu-sions drawn when only calculated benchmarks are used might be not sound or even false. The sameapplies for empirical equations calibrated with calculated targets. Four new GEP-based equations (oneper input combination and station) are provided to estimate ETo.P. Marti acknowledges the financial support of the research grant Juan de la Cierva JCI-2012-13513 (Spanish Ministry of Economy and Competitiveness).Martí Pérez, PC.; González Altozano, P.; López-Urrea, R.; Mancha, LA.; Shiri, J. (2015). Modeling reference evapotranspiration with calculated targets.Assessment and implications. Agricultural Water Management. 149:81-90. https://doi.org/10.1016/j.agwat.2014.10.028S819014

Modelling evapotranspiration in a spring 1 wheat from thermal radiometry: Crop coefficients and E/T partitioning

Wheat is one of the crops occupying the largest areas in the world (218 million ha in 2013). Understanding the land-atmosphere energy exchanges over these croplands becomes important not only for agronomy but also for climatic and meteorological aspects. This study continues previous work on the estimation of actual evapotranspiration and the assessment of crop coefficients of sorghum, sunflower, or canola. Two variations of a simple two-source energy balance (STSEB) approach were used in combination with land surface temperature measurements to calculate hourly and daily values of surface fluxes and actual evapotranspiration (ET). An experiment was carried out during the spring season of 2014 in Las Tiesas experimental farm in Barrax, Spain. Soil and canopy temperature components together with meteorological variables and biophysical parameters were measured from planting to senescence. Comparison to lysimeter measurements showed calculation errors of ±0.11 mm h-1 and ±0.8 mm d-1 for hourly and daily ET values, respectively, whereas an underestimation no greater than 4% resulted from the entire campaign. Partition between soil and canopy components yielded a ratio of evaporation (E) to transpiration (T) of 36% to 64%, respectively, for the total growing season. Dual crop coefficients were also calculated and compared to those proposed by FAO56. Although separate E and T measurements were not available, similar results between the STSEB and FAO 56 models demonstrate the utility of the STSEB for investigating management strategies aimed at increasing crop water use efficiency