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[SPA] El potencial hídrico de tallo es el indicador más comúnmente utilizado para evaluar el estado hídrico de las plantas debido a su elevada sensibilidad a la demanda climática y al régimen de riego, a pesar de su baja escala espacial y temporal. El objetivo de nuestro trabajo fue evaluar otros indicadores, como la firma espectral a nivel foliar emitida por mandarinos adultos sometidos a distintas intensidades de estrés hídrico, que nos permitan estimar el estado hídrico del cultivo a una mayor escala. La emisión de radiaciones de longitud de onda de 1000 nm, y el rango entre 1540-1740 nm (SWIR) permitieron diferenciar los niveles de estrés de manera significativa. A través de la combinación de distintas longitudes de onda y estructuras de índice identificamos un nuevo indicador altamente sensible al estado hídrico, denominado Índice de Relación Infrarrojo Visible (VIRI), muy bien correlacionado con el potencial hídrico de tallo. Este índice podría ser un complemento válido para la programación del riego a una escala mayor de parcela. [ENG] Stem water potential is the most used indicator to assess plant water status due to its high sensitivity to climatic demand and irrigation regime, despite its low spatial and temporal scale. The aim of our work was to evaluate other indicators, such as the leaf-scale spectrum emitted by adult mandarin trees subjected to different water stress intensities, which allow us to estimate the plant water status at a larger scale. The emission of radiation at a wavelength of 1000 nm, and the range between 1540-1740 nm (SWIR) allowed us to differentiate the levels of stress in a significant way. Through the combination of different wavelengths and index structures we identified a new indicator highly sensitive to water status, called Visible Infrared Ratio Index (VIRI), which correlates very well with stem water potential. This index could be a valid complement for irrigation scheduling at a larger plot scale.

[SPA] Debido a los escasos recursos hídricos presentes en la actualidad, se hace necesario explorar otras fuentes de agua para el riego. La salinidad es uno de los mayores problemas a los que se deben enfrentar los cultivos que utilicen un recurso hídrico de escasa calidad, mermando principalmente el rendimiento del cultivo, y a su vez, pudiendo afectar al suelo. Con el fin de atenuar ambos, en este estudio se ha realizado la aplicación de Accudo®, un bioestimulante compuesto por microorganismos. A pesar de observar un incremento significativo en la conductividad eléctrica del suelo, que causó una reducción de la actividad ureasa, la bioestimulación incrementó esta actividad enzimática, mitigando los efectos que la salinidad causó sobre el suelo y permitiendo llevar a cabo cultivos con aguas no convencionales de una forma más sostenible. [ENG] Due to the scarce water resources present at the moment, other water resources need to be explored for irrigation. Salinity is one of the major problems that crops using this type of resources must face, mainly affecting yields, but also having an effect on soil quality. In order to mitigate both, Accudo®, a biostimulant composed of microorganisms, was applied in this study. Despite observing a significant increase in soil electrical conductivity, which caused a reduction in urease activity, biostimulation increased this enzyme activity, mitigating the effects that salinity caused on the soil and allowing crops to be grown with non-conventional water resources, in a more sustainable way.

[SPA] Esta tesis doctoral se presenta bajo la modalidad de compendio de publicaciones. La agricultura de regadío en zonas de clima mediterráneo semiárido como el sudeste de España se enfrenta a un complejo desafío. Por un lado, la disponibilidad hídrica actual ha inducido a que la producción de cultivos leñosos, como el mandarino, generalmente se realice bajo condiciones de infradotación hídrica. Por otro lado, las proyecciones indican que, por efecto del cambio climático, la escasez de agua se acentuará al menos en un 30% para finales de este siglo. Sumado a esto, diversas investigaciones señalan que la agricultura tradicional intensiva como los monocultivos leñosos, puede tener diversas implicaciones negativas sobre el medioambiente, como la degradación del suelo, emisión de gases de efecto invernadero, contaminación de acuíferos, disminución del hábitat de diversas especies, y disminuir la sensibilidad de plagas y enfermedades a métodos de control químicos. Considerando que la escasez hídrica es uno de los principales factores que limitan el desarrollo de una agricultura sostenible, se planteó el objetivo de incrementar la productividad del agua y sostenibilidad basándose en tres ejes principales: (i) la delimitación más precisa de los períodos en los que el cultivo del mandarino es menos sensible al déficit hídrico; (ii) la exploración de nuevos indicadores para incrementar la eficiencia en la programación del riego; y (iii) la evaluación del efecto del acolchado geotextil y la implementación de sistemas de cultivo diversificados sobre el estado hídrico del cultivo, como alternativa para incrementar la sostenibilidad medioambiental, bajo distintos escenarios de disponibilidad de agua. Para responder a estos objetivos, se realizaron tres ensayos independientes en una finca comercial de mandarinos adultos ‘Clemenvilla’ ubicada en la Región de Murcia (España) durante tres temporadas consecutivas. En el artículo 1 del presente compendio, se evalúo la respuesta del c

[ESP] El uso de bioestimulantes en la agricultura se ha visto incrementado en la última década con el fin de promover la sostenibilidad de la producción agrícola, ya que incrementan la producción obtenida. El objetivo de este trabajo fue analizar de forma conjunta la respuesta agronómica, fisiológica y microbiológica de un cultivo de pimiento bajo invernadero, tras la aplicación de un bioestimulante compuesto por extractos de algas. Las plantas bioestimuladas mostraron un mayor número de frutos comerciales, junto a un índice de área foliar más elevado con respecto al control no bioestimulado. Asimismo, es de destacar la mayor colonización de sus raíces, debida a la acción de hongos micorrícicos endémicos del suelo, que dio lugar a una mayor respiración de suelo en este tratamiento. [ENG] Recent studies show that biostimulants can enhance crop yield and therefore their sustainability. That could be the reason why their use has increased among farmers. The aim of this work has been to analyze the agronomical, physiological, and microbiological responses of a pepper crop after biostimulation with seaweed extract. The biostimulated plants showed a higher number of commercial fruits, and an enhanced leaf area index than non-treated plants. The roots of the treated plants were colonized in greater proportion by endemic mycorrhizal fungi, and as a consequence, the soil respiration increased.

[ESP] Las técnicas de cultivo suelen influir sobre la calidad de la uva. Una de ellas es la aplicación de estrategias de riego deficitario, que permitiría, además, incrementar la eficiencia de uso del agua de riego, cuestión fundamental en zonas semiáridas. No obstante, estas requieren de una adecuada planificación para que la producción y la calidad de la uva no se vean afectadas negativamente. El objetivo de este trabajo fue determinar la intensidad de estrés hídrico que permita maximizar el rendimiento y la calidad de la baya en el momento de la cosecha. Así, se establecieron distintas relaciones entre la integral de estrés hídrico, el rendimiento, la firmeza y el color de la baya, a partir de los resultados obtenidos en dos parcelas comerciales, en los que se aplicaron distintas estrategias de riego deficitario entre los años 2011 y 2017. [ENG] Cultivation techniques often influence the quality of the grape. One of them is the application of deficit irrigation strategies, which would also allow increasing the irrigation water use efficiency, a fundamental issue in semi-arid areas. However, these require proper planning so that the production and quality of the grapes are not negatively affected. The objective of this work was to determine the intensity of water stress that allows maximizing the yield and quality of the berry at harvest time. Thus, different relationships were established between the water stress integral, yield, firmness, and berry color, based on the results obtained in two commercial plots, in which different deficit irrigation strategies were applied between the years 2011 and 2017.

En este trabajo se presentan los resultados más importantes descritos en dos Tesis Doctorales, que bajo mi dirección presentaron los Dres. Elisa Pagán Rubio, y José María de la Rosa Sánchez en la Universidad Politécnica de Cartagena, relativas a la respuesta al déficit hídrico de tres cultivos de elevada importancia en la agricultura española, mandarino, almendro y nectarino. Se describen para estos tres cultivos los valores umbrales del estado hídrico de la planta que deben de respetarse para su ciclo completo, tanto para los denominados períodos críticos como para los no críticos, de cara a la aplicación de estrategias de riego deficitario controlado. Mientras que para el mandarino la segunda fase del crecimiento del fruto puede considerarse no crítica hasta el inicio de la ralentización del tronco, en el almendro es la denominada fase IV, o de crecimiento del tamaño del grano, y en el nectarino extratemprano, la fase postcosecha final, coincidente con los meses de mayor demanda evaporativa del año.

The implementation of alley cropping in orchards has been suggested as a sustainable strategy to increase farmer revenues by crop diversification, enhance soil organic matter (SOM) and fertility, water retention, overall biodiversity, and contribute to climate change mitigation. Thus, the objective of this study was to assess if alley cropping with annual crops can contribute to i) mitigate soil greenhouse gas (GHG) emissions, ii) enhance C sequestration in a semiarid Mediterranean irrigated citrus orchard, and iii) increase land productivity. For this, two different treatments were established: i) conventional mandarin monoculture (MC) with no alley cropping; and ii) mandarin diversified with alley cropping of barley/vetch and fava bean (DIV). Measurements of soil CO2 and N2O emissions were periodically performed (every 7–20 days) during two years. Soil CO2 emission rates followed the soil moisture trend, and showed no significant differences between treatments. As an average, soil CO2 emission rates were 147 mg m-2 h-1 in MC and 196 mg m-2 h-1 in DIV. Soil N2O emission rates were not correlated to soil moisture nor temperature, and showed average values of 0.026 mg m-2 h-1 in MC and − 0.002 mg m-2 h-1 in DIV. Alley cropping did not contribute to significantly increase soil organic C and total nitrogen in two years’ time. With regard to production, mandarin yield showed no significant differences between treatments, but alley crops contributed to complementary commodities to the main cash crop, increasing overall land productivity. Thus, alley cropping in irrigated Mediterranean orchards has no significant effect on soil C sequestration and GHG emissions at short-term, with increased land productivity owing to new commodities grown in the alleys. These results confirm that under semiarid Mediterranean climate, long periods are needed to efficiently assess soil C sequestration potential of sustainable practices in orchards.

The implementation of alley cropping in orchards has been suggested as a sustainable strategy to increase farmer revenues by crop diversification, enhance soil organic matter (SOM) and fertility, water retention, overall biodiversity, and contribute to climate change mitigation. Thus, the objective of this study was to assess if alley cropping with annual crops can contribute to i) mitigate soil greenhouse gas (GHG) emissions, ii) enhance C sequestration in a semiarid Mediterranean irrigated citrus orchard, and iii) increase land productivity. For this, two different treatments were established: i) conventional mandarin monoculture (MC) with no alley cropping; and ii) mandarin diversified with alley cropping of barley/vetch and fava bean (DIV). Measurements of soil CO2 and N2O emissions were periodically performed (every 7–20 days) during two years. Soil CO2 emission rates followed the soil moisture trend, and showed no significant differences between treatments. As an average, soil CO2 emission rates were 147 mg m-2 h-1 in MC and 196 mg m-2 h-1 in DIV. Soil N2O emission rates were not correlated to soil moisture nor temperature, and showed average values of 0.026 mg m-2 h-1 in MC and − 0.002 mg m-2 h-1 in DIV. Alley cropping did not contribute to significantly increase soil organic C and total nitrogen in two years’ time. With regard to production, mandarin yield showed no significant differences between treatments, but alley crops contributed to complementary commodities to the main cash crop, increasing overall land productivity. Thus, alley cropping in irrigated Mediterranean orchards has no significant effect on soil C sequestration and GHG emissions at short-term, with increased land productivity owing to new commodities grown in the alleys. These results confirm that under semiarid Mediterranean climate, long periods are needed to efficiently assess soil C sequestration potential of sustainable practices in orchards.

Water scarcity in arid and semiarid regions poses problems for agricultural systems, awakening special interest in the development of deficit irrigation strategies to improve water conservation. Toward this purpose, farmers and technicians must monitor soil water and soluble nutrient contents in real time using simple, rapid and economical techniques through time and space. Thus, this study aimed to achieve the following: (i) create a model that predicts water and soluble nutrient contents in soil profiles using electrical resistivity tomography (ERT); and (ii) apply the model to different woody crops under different irrigation regimes (full irrigation and regulated deficit irrigation (RDI)) to assess the efficiency of the model. Simple nonlinear regression analysis was carried out on water content and on different ion contents using electrical resistivity data as the dependent variable. A predictive model for soil water content was calibrated and validated with the datasets based on exponential decay of a three-parameter equation. Nonetheless, no accurate model was achieved to predict any soluble nutrient. Electrical resistivity images were replaced by soil water images after application of the predictive model for all studied crops. They showed that under RDI situations, soil profiles became drier at depth while plant roots seemed to uptake more water, contributing to reductions in soil water content by the creation of desiccation bulbs. Therefore, the use of ERT combined with application of the validated predictive model could be a sustainable strategy to monitor soil water evolution in soil profiles under irrigated fields, facilitating land irrigation management.

[SPA] Las denominadas estrategias de Riego Deficitario Controlado (RDC) en un cultivo dado, se basan en la reducción de los aportes hídricos en determinados periodos fenológicos denominados no críticos, sin afectar negativamente ni a la producción ni a la calidad de la cosecha, incrementando significativamente la eficiencia en el uso del agua de riego. Por ello, es una estrategia muy útil para que el agricultor pueda mitigar la grave escasez de recursos hídricos que sufre la agricultura, modulando el riego aplicado a la disponibilidad de agua de riego y a la fenología del cultivo. Bajo esta premisa se realizó un estudio en el cultivo del paraguayo Carioca durante 3 años consecutivos, con el fin de establecer protocolos de riego que se ajustaran a la disponibilidad de agua de riego. Asimismo, se estableció el potencial hídrico de tallo a mediodía como el indicador del estado hídrico de planta más sensible al déficit hídrico, considerando un valor umbral de -1,5 MPa para optimizar la programación del riego deficitario. [ENG] The so-called Regulated Deficit Irrigation (RDC) strategies in a given crop are based on the reduction of water inputs in certain non-critical phenological periods, without negatively affecting either the production or the quality of the harvest, significantly increasing the efficiency in the use of irrigation water. Therefore, it is a very useful strategy for the farmer to mitigate the serious shortage of water resources suffered by agriculture, modulating the irrigation applied to the availability of irrigation water and the phenology of the crop. Under this premise, a study was carried out in Carioca platerine crop for 3 consecutive years, to establish irrigation protocols that adjusted to the availability of irrigation water. Likewise, the stem water potential at midday was established as the indicator of the plant water status most sensitive to water deficit, considering a threshold value of -1.5 MPa to optimize deficit irrigation scheduling.

[SPA] El brócoli es considerado un cultivo que requiere altas cantidades de nitrógeno (N) para alcanzar su potencial productivo, puesto que el N es el macronutriente más determinante para el desarrollo y rendimiento de la producción agrícola. Asimismo, el uso del N puede presentar un impacto negativo sobre el medioambiente, incluso bajo estrategias eficientes de fertirrigación. Por ello, el objetivo principal de este trabajo fue determinar la dosis más adecuada de N para maximizar el uso eficiente del N por el cultivo, con el menor impacto posible en el medioambiente. Se establecieron 3 tratamientos basados en diferentes coeficientes de extracción de N por el cultivo: 9,0, 7,3 y 5,7 kg de N por t recolectada y se determinó el efecto sobre el intercambio gaseoso foliar y rendimiento. El coeficiente de extracción más restrictivo no afectó significativamente la actividad fisiológica de las plantas, producción ni características físicas de las pellas recolectadas. [ENG] Broccoli is considered a crop that requires high amounts of nitrogen (N) to reach its productive potential, since N is the most determining macronutrient for the development and performance of agricultural production. Moreover, N use can have a negative impact on the environment, even under efficient fertigation strategies. Therefore, the main objective of this work was to determine the most adequate N dose to maximize the efficient use of N by the crop, with the least possible impact on the environment. Three treatments were established based on different N extraction coefficients for the crop: 9.0, 7.3, and 5.7 kg of N per t harvested, and the effect on leaf gas exchange and yield was determined. The most restrictive extraction coefficient did not significantly affect plant physiological activity, yield or physical characteristics of the harvested heads.

In citrus fruits, phases I and II of fruit growth are sensitive to water deficit, and for this reason, deficit irrigation (DI) has been usually restricted to the final ripening phase. However, the optimal timing and intensity of stress during sensitive phases have not been clearly defined. The main objective was to determine the sensitivity of the second stage of fruit growth to water deficit in adult mandarin trees, and to explore the suitability of different soil and plant water status indicators, including the leaf-scale spectrum, according to the water stress level. Four irrigation treatments were tested: a control (CTL) irrigated at ~ 80% of ETc during the entire crop cycle, and three irrigation suppression treatments, in which no water was applied during the end of phase I and the beginning of phase II (DI1), the second half of phase II (DI2), and phase III of fruit growth (DI3), respectively. Phase II of fruit growth can be considered as a non-critical phenological period until the fruit reaches approximately 60% of its final size, with the application of a water deficit using an irrigation threshold of midday stem water potential of − 1.8 MPa, and a cumulative water stress integral close to 28 MPa day. The novel visible infrared ratio index (VIRI) showed a high sensitivity for trees subjected to moderate and severe water stress and can be complementarily used to estimate on a larger temporal and spatial scale the plant water status. Wavelengths in the short-wave infrared (SWIR) region allowed differentiation between non-stressed, moderately, and severely water-stressed trees, and can be considered as an initial basis for determining the water status of mandarin trees at various stress intensities by remote sensing.

Data and metadata of crop yield and quality from different cases studies and long terms from WP3 "Crop production and quality", derived from H2020 Diverfarming project. This workpackage provides robust and sound data about how diversified cropping systems with low-input practices and efficient use of resources have positive effects on crop production and quality, and so, farm yields and economic revenues for farmers is increased. This can increase trading productivity with high quality outputs, so improving the competitiveness of European agriculture in the global market. http://www.diverfarming.eu.