Suchergebnisse

To study the effects of water deficits on water use efficiency (WUE) of citrus trees, whole tree transpiration and CO2 assimilation were measured in a semi-arid environment during the summer of 2012. Young orange trees >Valencia Late>, either water stressed (DI) and well-irrigated (C), were monitored in selected days using a gas exchange chamber. Tree transpiration was also measured on a continuous basis with sap flow sensors. The water restriction reduced the transpiration of the DI treatment down to 60% of the maximum potential (treatment C) during the peak of water stress. The instantaneous WUE ranged between 1.7 and 79gCO2L-1H2O and was tightly related to the vapour pressure deficit. Differences in instantaneous WUE due to water stress were insignificant. On a daily basis, WUE ranged between 4.9 (7 August) and 8.8 (7 June) gL-1 for the daytime period; and between 4.0 and 8.2gL-1 for the 24h period. As water stress was imposed on the DI treatment, a trend of increasing WUE in DI relative to C was observed, reaching, in the maximum stress period, a difference, of 13-15% (daytime) and 20-22% (24h) although not statistically significant. Partial rewatering returned the WUE to similar values in both treatments. An analysis of the differences in the diurnal patterns of transpiration suggests that the increase in WUE due to water stress in citrus is achieved indirectly by shifting the overall carbon assimilation towards the morning hours of lower evaporative demand. © 2014 Elsevier B.V. ; This work was financially supported by the projects CONSOLIDER-RIDECO CSD2006-00067 and AGL2009-13105 of the Spanish Ministry of Science and Education, partly through European Union ERDF funds. ; Peer Reviewed

Spatial variations of crop yields are commonly observed in typical rainfed systems worldwide. It is accepted that such variations are likely to be associated, among other factors, with water spatial variations due to lateral water flows occurring in fields with undulating topography. However, some of the main processes governing water spatial distribution such as lateral flow are not entirely considered by the most commonly adopted crop simulation models. This brings uncertainty to the process of yield simulation at field-scale, especially under water-limited conditions. Although it is expected that lateral water movement determines spatial variations of crop yields, it is still unclear what is the net contribution of lateral water inflows (LIF) to spatial variations of rainfed yields in fields of undulating topography. In this sense, by combining field experimentation, simulation models (HYDRUS-1D and AquaCrop), and the use of artificial neural networks, we assessed the occurrence and magnitude of LIF, and their impact on wheat yields in Cordoba, Spain, over a 30-year period. Seasonal precipitation varied over 30 years from 212.8 to 759.5 mm, and cumulative LIF ranged from 30 to 125 mm. The ratio of seasonal cumulative LIF divided by seasonal precipitation varied from 10.7% to 38.9% over the 30 years. The net contribution of LIF to spatial variations of rainfed potential yields showed to be relevant but highly irregular among years. Despite the inter-annual variability, typical of Mediterranean conditions, the occurrence of LIF caused simulated wheat yields to vary + 16% from up to downslope areas of the field. The net yield responses to LIF, in downslope areas were on average 383 kg grain yield (GY) ha−1, and the LIF marginal water productivity reached 24.6 ( ± 13.2) kg GY ha−1 mm−1 in years of maximum responsiveness. Decision makers are encouraged to take water spatial variations into account when adjusting management to different potential yielding zones within the same field. However, this process is expected to benefit from further advances in in-season weather forecasting that should be coupled with a methodological approach such as the one presented here. ; This research received funding from the European Commission under project SHui - Grant agreement ID 773903 and also from the Spanish Government under Grant PID2019-105793RB-I00. ; Peer reviewed

This article outlines the major scientific objectives of the SHui project that seeks to optimize soil and water use in agricultural systems in the EU and China, by considering major current scientific challenges in this area. SHui (for Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems) is large cooperative project that aims to provide significant advances through transdisciplinary research at multiple scales (plot, field, catchment and region). This paper explains our research platform of long-term experiments established at plot scale, approaches taken to integrate crop and hydrological models at field scale; coupled crop models and satellite-based observations at regional scales; decision support systems for specific farming situations; and the integration of these technologies to provide policy recommendations through socio-economic analysis of the impact of soil and water saving technologies. It also outlines the training of stakeholders to develop a basic common curriculum despite the subject being distributed across different disciplines and professions. As such, this article provides a review of major challenges for improving soil and water use in EU and China as well as information about the potential to access information made available by SHui, and to allow others to engage with the project. ; This work has been supported by Project SHui which is co-funded by the European Union Project GA 773903 and the Chinese MOST. This work has been supported by P12-AGR-0931 (Andalusian Government), RTA2014-00063- C04-03 (Spanish government), SHui (European Commission Grant Agreement number: 773903) and EU‒FEDER funds ; Peer reviewed