Implications of agricultural production, policy and land use changes on water resource assessment

Una gestión más eficiente y equitativa del agua a escala de cuenca no se puede centrar exclusivamente en el recurso hídrico en sí, sino también en otras políticas y disciplinas científicas. Existe un consenso creciente de que, además de la consideración de las cambiantes condiciones climáticas, es necesaria una integración de ámbitos de investigación tales como la agronomía, planificación del territorio y ciencias políticas y económicas a fin de satisfacer de manera sostenible las demandas de agua por parte de la sociedad y del medio natural. La Política Agrícola Común (PAC) es el principal motor de cambio en las tendencias de paisajes rurales y sistemas agrícolas, pero el deterioro del medio ambiente es ahora una de las principales preocupaciones. Uno de los cambios más relevantes se ha producido con la expansión e intensificación del olivar en España, principalmente con nuevas zonas de regadío o la conversión de olivares de secano a sistemas en regadío. Por otra parte, el cambio de las condiciones climáticas podría ejercer un papel importante en las tendencias negativas de las aportaciones a los ríos, pero no queda claro el papel que podrían estar jugando los cambios de uso de suelo y cobertura vegetal sobre las tendencias negativas de caudal observadas. Esta tesis tiene como objetivo mejorar el conocimiento de los efectos de la producción agrícola, política agraria y cambios de uso de suelo y cobertura vegetal sobre las condiciones de calidad del agua, respuesta hidrológica y apropiación del agua por parte de la sociedad. En primer lugar, el estudio determina las tendencias existentes de nitratos y sólidos en suspensión en las aguas superficiales de la cuenca del río Guadalquivir durante el periodo de 1998 a 2009. Desde una perspectiva de política agraria, la investigación trata de evaluar mediante un análisis de datos de panel las principales variables, incluyendo la reforma de la PAC de 2003, que están teniendo una influencia en ambos indicadores de calidad. En segundo lugar, la apropiación del agua y el nivel de contaminación por nitratos debido a la producción del aceite de oliva en España se determinan con una evaluación de la huella hídrica (HH), teniendo en cuenta una variabilidad espacial y temporal a largo de las provincias españolas y entre 1997 y 2008. Por último, la tesis analiza los efectos de los cambios de uso de suelo y cobertura vegetal sobre las tendencias negativas observadas en la zona alta del Turia, cabecera de la cuenca del río Júcar, durante el periodo 1973-2008 mediante una modelización ecohidrológica. En la cuenca del Guadalquivir cerca del 20% de las estaciones de monitoreo muestran tendencias significativas, lineales o cuadráticas, para cada indicador de calidad de agua. La mayoría de las tendencias significativas en nitratos están aumentando, y la mayoría de tendencias cuadráticas muestran un patrón en forma de U. Los modelos de regresión de datos de panel muestran que las variables más importantes que empeoran ambos indicadores de calidad del agua son la intensificación de biomasa y las exportaciones de ambos indicadores de calidad procedentes de aguas arriba. En regiones en las que el abandono agrícola y/o desintensificación han tenido lugar han mejorado las condiciones de calidad del agua. Para los nitratos, el desacoplamiento de las subvenciones a la agricultura y la reducción de la cuantía de las subvenciones a tierras de regadío subyacen en la reducción observada de la concentración de nitratos. Las medidas de modernización de regadíos y el establecimiento de zonas vulnerables a nitratos reducen la concentración en subcuencas que muestran una tendencia creciente de nitratos. Sin embargo, el efecto de las exportaciones de nitratos procedente de aguas arriba, la intensificación de la biomasa y los precios de los cultivos presentan un mayor peso, explicando la tendencia creciente observada de nitratos. Para los sólidos en suspensión, no queda de forma evidente si el proceso de desacoplamiento ha influido negativa o positivamente. Sin embargo, los mayores valores de las ayudas agrarias aún ligadas a la producción, en particular en zonas de regadío, conllevan un aumento de las tasas de erosión. Aunque la cuenca del Guadalquivir ha aumentado la producción agrícola y la eficiencia del uso del agua, el problema de las altas tasas de erosión aún no ha sido mitigado adecuadamente. El estudio de la huella hídrica (HH) revela que en 1 L de aceite de oliva español más del 99,5% de la HH está relacionado con la producción de la aceituna, mientras que menos del 0,5% se debe a otros componentes, es decir, a la botella, tapón y etiqueta. Durante el período estudiado, la HH verde en secano y en regadío representa alrededor del 72% y 12%, respectivamente, del total de la HH. Las HHs azul y gris representan 6% y 10%, respectivamente. La producción de aceitunas se concentra en regiones con una HH menor por unidad de producto. La producción de aceite de oliva ha aumentado su productividad del agua durante 1997-2008, incentivado por los crecientes precios del aceite, como también lo ha hecho la cantidad de exportaciones de agua virtual. De hecho, las mayores zonas productoras presentan una eficiencia alta del uso y de productividad del agua, así como un menor potencial de contaminación por nitratos. Pero en estas zonas se ve a la vez reflejado un aumento de presión sobre los recursos hídricos locales. El aumento de extracciones de agua subterránea relacionadas con las exportaciones de aceite de oliva podría añadir una mayor presión a la ya estresada cuenca del Guadalquivir, mostrando la necesidad de equilibrar las fuerzas del mercado con los recursos locales disponibles. Los cambios de uso de suelo y cobertura vegetal juegan un papel importante en el balance del agua de la cuenca alta del Turia, pero no son el principal motor que sustenta la reducción observada de caudal. El aumento de la temperatura es el principal factor que explica las mayores tasas de evapotranspiración y la reducción de caudales. Sin embargo, los cambios de uso de suelo y el cambio climático han tenido un efecto compensatorio en la respuesta hidrológica. Por un lado, el caudal se ha visto afectado negativamente por el aumento de la temperatura, mientras que los cambios de uso de suelo y cobertura vegetal han compensado positivamente con una reducción de las tasas de evapotranspiración, gracias a los procesos de disminución de la densidad de matorral y de degradación forestal. El estudio proporciona una visión que fortalece la interdisciplinariedad entre la planificación hidrológica y territorial, destacando la necesidad de incluir las implicaciones de los cambios de uso de suelo y cobertura vegetal en futuros planes hidrológicos. Estos hallazgos son valiosos para la gestión de la cuenca del río Turia, y el enfoque empleado es útil para la determinación del peso de los cambios de uso de suelo y cobertura vegetal en la respuesta hidrológica en otras regiones. ABSTRACT Achieving a more efficient and equitable water management at catchment scale does not only rely on the water resource itself, but also on other policies and scientific knowledge. There is a growing consensus that, in addition to consideration of changing climate conditions, integration with research areas such as agronomy, land use planning and economics and political science is required to meet sustainably the societal and environmental water demands. The Common Agricultural Policy (CAP) is a main driver for trends in rural landscapes and agricultural systems, but environmental deterioration is now a principal concern. One of the most relevant changes has occurred with the expansion and intensification of olive orchards in Spain, taking place mainly with new irrigated areas or with the conversion from rainfed to irrigated systems. Moreover, changing climate conditions might exert a major role on water yield trends, but it remains unclear the role that ongoing land use and land cover changes (LULCC) might have on observed river flow trends. This thesis aims to improve the understanding of the effects of agricultural production, policies and LULCC on water quality conditions, hydrological response and human water appropriation. Firstly, the study determines the existing trends for nitrates and suspended solids in the Guadalquivir river basin’s surface waters (south Spain) during the period from 1998 to 2009. From a policy perspective, the research tries to assess with panel data analysis the main drivers, including the 2003 CAP reform, which are having an influence on both water quality indicators. Secondly, water appropriation and nitrate pollution level originating from the production of olive oil in Spain is determined with a water footprint (WF) assessment, considering a spatial temporal variability across the Spanish provinces and from 1997 to 2008 years. Finally, the thesis analyzes the effects of the LULCC on the observed negative trends over the period 1973-2008 in the Upper Turia basin, headwaters of the Júcar river demarcation (east Spain), with ecohydrological modeling. In the Guadalquivir river basin about 20% of monitoring stations show significant trends, linear or quadratic, for each water quality indicator. Most significant trends of nitrates are augmenting than decreasing, and most significant quadratic terms of both indicators exhibit U-shaped patterns. The panel data models show that the most important drivers that are worsening nitrates and suspended solids in the basin are biomass intensification and exports of both water quality indicators from upland regions. In regions that agricultural abandonment and/or de-intensification have taken place the water quality conditions have improved. For nitrates, the decoupling of agricultural subsidies and the reduction of the amount of subsidies to irrigated land underlie the observed reduction of nitrates concentration. Measures of irrigation modernization and establishment of vulnerable zones to nitrates ameliorate the concentration of nitrates in subbasins showing an increasing trend. However, the effect of nitrates load from upland areas, intensification of biomass and crop prices present a greater weight leading to the final increasing trend in this subbasins group, where annual crops dominate. For suspended solids, there is no clear evidence that decoupling process have influenced negatively or positively. Nevertheless, greater values of subsidies still linked to production, particularly in irrigated regions, lead to increasing erosion rates. Although agricultural production has augmented in the basin and water efficiency in the agricultural sector has improved, the issue of high erosion rates has not yet been properly faced. The water footprint (WF) assessment reveals that for 1 L Spanish olive oil more than 99.5% of the WF is related to the olive fruit production, whereas less than 0.5% is due to other components i.e. bottle, cap and label. Over the studied period, the green WF in rainfed and irrigated systems represents about 72% and 12%, respectively, of the total WF. Blue and grey WFs represent 6% and 10%, respectively. The olive production is concentrated in regions with the smallest WF per unit of product. The olive oil production has increased its apparent water productivity from 1997 to 2008 incentivized by growing trade prices, but also did the amount of virtual water exports. In fact, the largest producing areas present high water use efficiency per product and apparent water productivity as well as less nitrates pollution potential, but this enhances the pressure on the available water resources. Increasing groundwater abstractions related to olive oil exports may add further pressure to the already stressed Guadalquivir basin. This shows the need to balance the market forces with the available local resources. Concerning the effects of LULCC on the Upper Turia basin’s streamflow, LULCC play a significant role on the water balance, but it is not the main driver underpinning the observed reduction on Turia's streamflow. Increasing mean temperature is the main factor supporting larger evapotranspiration rates and streamflow reduction. In fact, LULCC and climate change have had an offsetting effect on the streamflow generation during the study period. While streamflow has been negatively affected by increasing temperature, ongoing LULCC have positively compensated with reduced evapotranspiration rates, thanks to mainly shrubland clearing and forest degradation processes. The research provides insight for strengthening the interdisciplinarity between hydrological and spatial planning, highlighting the need to include the implications of LULCC in future hydrological plans. These findings are valuable for the management of the Turia river basin, as well as a useful approach for the determination of the weight of LULCC on the hydrological response in other regions.

Afectación de los agrosistemas de la zona del Caño San Miguel por la salinización de los suelos

La degradación por salinización de los suelos regados con aguas salobres viene aumentando a escala mundial. El problema de la concentración de sales más solubles que el yeso depende principalmente del agua de riego, la aridez climática y la ausencia de drenaje. Estas condiciones se dan en el aluvium del río Limón, que es un tributario del lago Maracaibo, sito en el estado de Zulia de Venezuela. La regulación del río Limón mediante el cierre de los embalses de Manuelote y Tulé ha disminuido los aportes de aguas y sedimentos de las avenidas de inundación, que tienen carácter diluyente. Por otro lado, el balance de sales solubles en el suelo ha registrado una acumulación neta en los años de extrema aridez anteriores al año 2006, dado que la mayor dilución de las aguas ombrogénicas embalsadas procedentes de las lluvias no ha sido suficiente para compensar la concentración por evapotranspiración “in situ” de las aguas retenidas en la cuenca baja, sobre todo en ausencia de desagüe superficial y drenaje profundo. Las inundaciones posteriores a 2006 fueron suficientes para disminuir la salinidad superficial hasta los valores encontrados en 2010. El estudio experimental de esta problemática en el sector del caño San Miguel ha sido abordado mediante el establecimiento del perfil de salinidad acoplado con el perfil hipotético de humedad usado en la taxonomía de suelos. Este perfil define la disponibilidad del agua del suelo para la vegetación en función de tres potenciales: 1) el potencial físico-químico o matricial, que depende de la energía de adsorción a la superficie de las partículas; 2) el potencial gravitatorio, que depende de la profundidad; y 3) el potencial osmótico, que depende de la concentración de la solución del suelo; lo que supone un avance respecto a tener en cuenta sólo el perfil de humedad, que solamente considera el potencial gravi-químico integrado por el matricial y el gravitatorio. El perfil normalizado de 200 mm de de agua útil, retenida entre 33 y 1500 kPa de succión, incluye ocho fases gravi-químicas de 25 mm. La presente investigación incluye el potencial osmótico estimado por la conductividad eléctrica del extracto de pasta saturada. Los experimentos de lavado de sales en columnas de suelo, simulando la distribución de las lluvias en cinco años representativos de los cuartiles estadísticos de la serie disponible de 38 años completos, han determinado el comportamiento de las sales solubles en un suelo sometido a drenaje. Los resultados han evidenciado que el balance de sales unido al balance de agua controla la degradación de los agrosistemas por salinización. La alternativa frutícola puede ser aumentada en estas condiciones, porque el balance de sales favorece el establecimiento de cultivos permanentes a costa de otros usos del suelo de menor interés económico, como el cultivo de forrajes en regadío y el aprovechamiento de los pastizales en secano durante el barbecho de desalinización, cuya caracterización se ha completado con el estudio de la vegetación indicadora del grado de salinidad. ABSTRACT Saline degradation of soils irrigated with brackish water is increasing worldwide. The problem of salts concentration more soluble than gypsum depends on irrigation water quality, climatic aridity, and drainage limitations. These conditions meet in Limón River alluvium, which is tributary to Maracaibo´s Lake in Zulia State, Venezuela. Limón River regulation by closing Manuelote and Tulé reservoirs has diminished the input of water and sediments from inundations, which exerted dilutive effects. On the other hand, the soil balance of soluble salts has registered a net accumulation during those extremely dry years before 2006 because the greater dilution of ombrogenic dammed water coming from rain has not been enough to compensate salt concentration by “in situ” evapotranspiration in middle basin water, mainly in the absence of superficial runoff and deep drainage. Floods after 2006 were enough to reduce the high superficial salinity figures to those addressed in 2010. The experimental study of this trouble in San Miguel´s pipe area has been addressed through of the establishment of its salinity profile together to the hypothetic moisture profile typically used in soil taxonomy. This salinity profile describes soil water availability for vegetation according to three potentials: 1) physico-chemical or matrix potential, which depends on the adsorption energy of the soil solution to the surface of soil particles; 2) gravitational potential, which depends on soil depth; and 3) osmotic potential, which depends on the concentration of the soil solution. This represents an advance from just using moisture regime, which only considers the matrix and gravitational components of a gravi-chemical potential. The standardized moisture profile of 200 mm useful water being retained between 33 and 1500 kPa includes eight gravi-chemical stages of 25 mm. This research also includes the osmotic component, which is estimated by the electric conductivity of the saturated paste extract. Salts leaching trials in soil columns simulating rain distribution along five model years, representing the statistical quartiles of the available series of 38 complete years, have determined the behaviour of soluble salts in a soil being subjected to drainage. Results have evidenced that salt and water balances considered together are able to control the agrosystem’s degradation by salinization. The fruit production alternative could be improved under these conditions because the salts balance favours the establishment of permanent crops to the detriment of other soil uses of lower economical interest such as irrigated forage and non-irrigated pasture during desalinization fallow, which characterization has been completed through assessing the presence of salinity-indicator vegetation.

Estudio de la ecología de Ulmus laevis Pallas en la Península Ibérica

Esta tesis doctoral pretende profundizar en el conocimiento de la ecología de Ulmus laevis Pallas, especie autóctona en peligro de extinción en la Península Ibérica, con el fin de proponer medidas adecuadas para su conservación. Se ha estudiado la distribución natural de la especie atendiendo a aspectos edáficos. Los resultados muestran que U. laevis presenta menor capacidad de acidificación de la rizosfera, menor actividad de la reductasa férrica y menor homeostasis que U. minor Mill. cuando crecen en sustratos con una disponibilidad de hierro limitada. Estas diferencias ayudan a comprender la distribución de ambas especies en la Península Ibérica: U. laevis se ve restringido a suelos ácidos o moderadamente ácidos, mientras que U. minor es capaz de habitar tanto suelos ácidos como básicos. Se han analizado las propiedades hidráulicas y anatómicas de U. laevis, constatando que sus características son favorables en ambientes con gran disponibilidad hídrica y que se trata del olmo ibérico más vulnerable a la cavitación por estrés hídrico, por lo que la aridificación del clima y la pérdida de los freáticos supone un riesgo para sus poblaciones. Para evaluar la capacidad de recuperación de la especie se han estudiado la diversidad y estructura genética espacial de las dos mayores poblaciones españolas. Los resultados evidencian que estas poblaciones mantienen niveles de diversidad equiparables o ligeramente superiores a los europeos, pese a haber sufrido un cuello de botella prolongado durante las glaciaciones y a las reducciones poblacionales recientes. En la actualidad la endogamia no representa un riesgo para estas poblaciones. También se ha analizado la producción, dispersión y predación de semillas en Valdelatas (Madrid). Los resultados han mostrado que el viento dispersa las sámaras a corta distancia (<30 m) y que los años no veceros las probabilidades de establecimiento de regenerado son bajas. Además, la producción de sámaras vanas puede tratarse de un carácter adaptativo que aumenta la eficiencia biológica de la especie, ya que favorece la supervivencia de las semillas embrionadas disminuyendo sus tasas de predación pre- y post-dispersión. La modificación del hábitat de esta especie como consecuencia de las actividades humanas afecta de manera negativa al establecimiento del regenerado. La conservación de esta especie a largo plazo requiere la recuperación de los niveles freáticos y de regímenes hidrológicos que permitan avenidas, ya que estas crean las condiciones adecuadas para el establecimiento de regenerado al eliminar la vegetación preexistente y depositar barro. ABSTRACT Ulmus laevis Pallas is an endangered species in the Iberian Peninsula. Therefore, in order to be able to propose adequate management guidelines for its conservation, this PhD Thesis intends to advance the knowledge on the species ecology in the region. Firstly, the species natural distribution was studied in relation to soil nature. Results show that U. minor Mill. had a higher root ferric reductase activity and proton extrusion capability than U. laevis, and maintained a better nutrient homeostasis when grown under iron limiting conditions. These differences in root Fe acquisition efficiencies proved helpful to understand the distribution of these species in the Iberian Peninsula, where U. laevis is restricted to acid or moderately acid soils, whereas U. minor can grow both in acid and basic soils. Secondly, we studied Ulmus laevis’ xylem anatomy and hydraulic traits. These proved favourable for growing under high water availability, but highly susceptible to drought-stress cavitation. Therefore, this species is vulnerable to the Iberian Peninsula’s aridification. Spatial genetic structure and diversity were evaluated in two of the biggest U. laevis populations in Spain in order to evaluate their recovery capabilities. These populations maintain similar or slightly higher diversity levels than European populations, despite having undergone an ancestral genetic bottleneck and having suffered recent population size reductions. No inbreeding problems have been detected in these populations. Seed production, dispersal and predation were assessed in Valdelatas’ elm grove (Madrid). Despite U. laevis samaras being winged nuts, wind dispersed them short distances from the mother tree (<30 m). The seed shadow models show that non-mast years provide very few chances for the stand to regenerate due to their low full seed flux. Empty samaras deceive pre- and post-dispersal predators increasing full seed survival probabilities. Therefore, empty fruit production might be an adaptive trait that increases plant fitness. Finally, human-induced changes in water-table levels and river regulation may affect U. laevis seed dispersal and regeneration establishment negatively. The long-term conservation and expansion of this species in the Iberian Peninsula requires the recovery of water-tables and of natural hydrological regimes, as flooding eliminates vegetation, creating open microhabitats and deposits mud, creating the ideal conditions for seedling establishment.

Canopy fruit location can affect olive oil quality in Arbequina hedgerow orchards

The effect of location of fruit in canopies of hedgerow olive trees (Olea europaea L., cv. ‘Arbequina’) on quality of virgin oil was tested by analyzing oils extracted from different height layers and faces of 9 olive hedgerows (6 North-South oriented and 3 East-West). Although sensory attributes were not different other oil quality parameters may be significantly modified by fruit position. In some hedgerows, oils extracted from fruits harvested from higher layers exhibited significantly higher stability against oxidation, along with higher palmitic acid, linoleic acid and phenol contents, but lower oleic acid content. Oils extracted from fruits harvested from East and North facing hedgerows oriented North-South and East-West, respectively, exhibited higher oleic contents and lower saturated and polyunsaturated fatty acid contents. The mean phenol content of oils extracted from fruits from a North-South oriented hedgerow was significantly greater from one of the East-West oriented hedgerows. These findings may be relevant for the design of future olive hedgerows destined for olive oil production.

Summer deficit irrigation strategies in hedgerow olive orchard cv. ‘Arbequina’: Effect on fruit characteristics and yield.

Maximum production in hedgerow olive orchards is likely not achieved with maximum evapotranspiration over the long-term. Thus, regulated deficit irrigation (RDI) should be considered as a management option. Four irrigation treatments were evaluated during the summer when olive is most drought resistant. Control (CON) was irrigated to maintain the rootzone close to field capacity. Severe water deficit was applied by irrigating 30% CON from end of fruit drop to end July (DI-J) and from end July until beginning of oil synthesis (DI-A). Less severe water deficit was applied during July and August (DI-JA) by irrigating 50% CON. Flowering, fruiting, abscission, fruit development, fresh and dry weight of fruits, and oil production were evaluated. There were not significant differences in number of buds initiated, number of fruits per inflorescence and fruit drop. Oil production was significantly different between irrigation treatments in all experimental years. CON produced more oil and fruit with higher oil% than DI-A and DI-JA. Oil production of DI-J was not significantly reduced compared to CON and oil% was greater. DI-J was the most effective RDI strategy; with 16% less applied water relative to CON average loss in oil production of 8% was not significantly different to CON. While DI-JA saved most water (27%), oil production was reduced by 15%. Greatest loss in oil production (21%) was observed in DI-A with water saving of 22%.

Fruit quality sensing:Post-harvest ripeness

Firmness sensing of selected varieties of apples, pears and avocado fruits has been developed using a nondestructive impact technique. In addition to firmness measurements, postharvest ripeness of apples and pears was monitored by spectrophotometric reflectance measurements, and that of avocadoes by Hunter colour measurements. The data obtained from firmness sensing were analyzed by three analytical procedures: principal component, correlation and regression, and stepwise discriminant analysis. A new software was developed to control the impact test, analyse the data, and sort the fruit into specified classes, based on the criteria obtained from a training procedure. Similar procedures were used to analyse the reflectance and colour data. Both sensing systems were able to classify fruits w i th good accuracy.

Influence of climate change on the flowering of temperate fruit trees

It is well known that winter chilling is necessary for the flowering of temperate trees. The chilling requirement is a criterion for choosing a species or variety at a given location. Also chemistry products can be used for reducing the chilling-hours needs but make our production more expensive. This study first analysed the observed values of chilling hours for some representative agricultural locations in Spain for the last three decades and their projected changes under climate change scenarios. Usually the chilling is measured and calculated as chilling-hours, and different methods have been used to calculate them (e.g. Richarson et al., 1974 among others) according to the species considered. For our objective North Carolina method (Shaltout and Unrath, 1983) was applied for apples, Utah method (Richardson et al. 1974) for peach and grapevine and the approach used by De Melo-Abreu et al. (2004) for olive trees. The influence of climate change in temperate trees was studied by calculating projections of chilling-hours with climate data from Regional Climate Models (RCMs) at high resolution (25 km) from the European Project ENSEMBLES (http://www.ensembles-eu.org/). These projections will allow for analysing the modelled variations of chill-hours between 2nd half of 20C and 1st half of 21C at the study locations.

Canopy fruit location can affect olive oil quality in Arbequina hedgerow orchards.

The effect of location of fruit in canopies of hedgerow olive trees (Olea europaea L., cv. ‘Arbequina’) on quality of virgin oil was tested by analyzing oils extracted from different height layers and faces of nine olive hedgerows (6 North–South oriented and 3 East– West). Although sensory attributes were not different, other oil quality parameters may be significantly modified by fruit position. Oils extracted from fruits harvested from higher layers exhibited significantly higher stability against oxidation, along with higher palmitic acid, linoleic acid and phenol contents, but lower oleic acid content. Oils extracted from fruits harvested from East and North facing hedgerows oriented North–South and East–West, respectively, exhibited higher oleic contents and lower saturated and polyunsaturated fatty acid contents. The mean phenol content of oils extracted from fruits from a North–South oriented hedgerow was significantly greater from one of the East–West oriented hedgerows. These findings may be relevant for the design of future olive hedgerows destined for olive oil production.

Fruit firmness and skin resistance of processing tomato varieties tested in Badajoz (Spain), related to mechanical harvesting.

Determinations of resistance to damage were carried out in a total of 31 tomato varieties for processing, with the purpose of choosing the most suitable ones for mechanical harvesting. The characteristics studied include: puncture, deformation and rupture of the fruits, the ease of detachment of the fruits also being determined. Seventeen varieties were chosen, for further tests, with values 0.76 to 1.7 2 N of resistance to puncture; 3 to 9 N/mm of resistance to compression and 2.16 to 29.40 N resistance to detachment.

Quality assurance systems in the production and marketing of fresh peaches.

Due to the fast rate of peach post-harvest ripening, damage due to mechanical handling, externally appreciated as bruises and soft areas, is a real problem that leads to an early harvesting and poor quality of the fruits, as perceived by the consumers. More and more, the European consumer asks for good taste and freshness of fruits and vegetables, and these quality factors are not included in standards, nor in most of the producers' practices. Fruit processing and marketing centres (co-operatives) are increasingly interested in adopting quality controls in their processes. ISO 9000 procedures are being applied in some food areas, primarily milk and meat processors, but no generalised procedures have been developed until the present time to be applied to fresh product processes. All different peach and nectarine varieties that are harvested and handled in Murcia cooperatives and sold in a large supermarket in Madrid were analysed during the whole 1997 season (early May to late August). A total number of 78 samples of 25 fruits (co-operative) or 10 fruits (market), were tested in the laboratory for mechanical, optical, chemical and tasting quality. The variability and relationships between all these quality parameters are presented and discussed, and sampling unit sizes which would be advisable for quality control are calculated.

Determination of firmness in a fruit packing line using a non destructive impact sensor.

The increasing of quality fruit demanded by the consumers is originating an advance in the development and application of sensors capable of measuring parameters of quality (sugar, acids, firmness, etc) on a non destructive way. Some of these sensors are already operative for their use in laboratory and even in lines. The Physical Properties laboratory of the Polytechnic University of Madrid, is developing different sensors for their implementation in lines. One of them is a non destructive impact sensor to measure fruit firmness.