Special Issue on Trends and Challenges of Sustainable Irrigated Agriculture

In the twenty-first century, the shortage of freshwater is one of the most important environmental concerns facing several regions of the world because of the growing demand of increasing population, agricultural intensification, and economic growth. Global climate change will contribute to exacerbate the problem, generating new drought-prone areas and increasing those already characterized by severe aridity. Worldwide it is estimated that, on average, agriculture accounts for 70% of the total water consumption, compared with 10% for domestic consume and the remaining used by industry. Moreover, according to FAO estimates, by 2050 agricultural production has to increase by 60% to satisfy the demands for food and feed (FAO 2013). Within this context, it is necessary to think back and make effective policies and actions for enhancing rational land use planning and agricultural inputs for a better exploitation of the existing technologies, even to rise the farmers’ awareness on the consequences of water scarcity. Sustainable agriculture must therefore be prescribed as a policy approach to maximize production while maintaining environmental quality in a fragile and quite stressed environment (Provenzano et al. 2013; Cammalleri et al. 2013b). It requires the conversion of current agricultural practices toward systems more productive and resilient to climate variability, in which land, water, and other inputs would be more efficiently used, and crops yield would be less variable. Heading forward to achieve these goals, shortand long-term strategies across different and integrated pathways are required. These would have to keep in mind issues such as food security and agricultural development, and take into account the existing environmental constrains. According to FAO (2013), climate-smart agriculture (CSA) would be an integrated approach to achieve the goals of a sustainable development. It addresses the food security and climate challenges issues within the economic, social, and environmental dimensions of sustainable development. Considering that in irrigated agriculture, water resources (both quantity and quality) are one of the major environmental constrains, which will intensify in the future, there is a priority for water management agents and stakeholders to consider its use sustainable. Thus, it is required and no longer postponed to improve technologies and approaches to optimize water use at different scales (farm, field, district, and higher). On the one hand, it is necessary to increase the performance of irrigation systems, and on the other hand, it is crucial to adopt technologies for irrigation scheduling aimed to increase water use efficiency, avoiding wastes and losses. This special issue reports the results of some research presented in the session 11.3. Soil and Irrigation Sustainability Practices, at the European Geoscience Union general assembly, held in Vienna in 2012, related, as summarized below, to applications of on-farm control sensors aimed to increase effectiveness of irrigation, to methodologies for improving agrohydrological models predictions, as well as to practices of good management in different cropsystems. The contributions of the papers in this volume are not intended to get into an exhaustive detail of the above issues; nevertheless, they highlight some advice to implement actions toward a more sustainable management of irrigated agriculture. Playan et al. (2014) describe the importance of investment in water-efficient technologies aiming at maximizing economic return in on-farm irrigation systems. Then, present a list of existing opportunities that, under particular conditions, allows to maximize irrigation efficiency and water productivity overpassing the unsatisfactory water use efficiency, often recognized at farm level. In particular, agrohydrological models and soil sensors have been successfully used to control landscape irrigation, whereas intelligent and autonomous systems are effectively applied to monitor the climate and to drive the complex water and nutrient application in greenhouses. In addition, the development of affordable systems for drip irrigated orchards, for irrigation machines, and for solidsets sprinkler irrigation still remain in the domain of science and technology. In fact, according to the authors, in drip irrigated orchards with automated deficit irrigation, the need of a high number of sensors for the continuous and precise monitoring of soil and crop water status, as well as the required skills, often limit this methodology. Moreover, for self-propelled sprinkler irrigation machines, the main concern still remains in the difficulty of set input application to field variability despite the progress in automation and also in the possibility of adaption under different soil-crop systems. The paper finally presents an on-farm controller device driven by simulation models that can be used for a solid set sprinkler system, in order to reduce the effects of meteorological conditions on wind drift and evaporation losses. The opportunities and the limitation of their different alternatives, according to sitespecific conditions, are illustrated and discussed. A methodology to derive standardized reference evapotranspiration zone maps by daily climate data and GIS is proposed in the paper by Mancosu et al. (2014) that describes its application for Sardinia region (Italy). The characterization of irrigated zones by class of reference evapotranspiration open the window to evaluate crop water requirements on large areas and/or to investigate the impact of climate change. Reference evapotranspiration was estimated by means of the UN-FAO Penman Monteith equation (PM), as later modified by ASCE-EWRI, for the meteorological stations providing the full required dataset (solar radiation, air temperature, wind speed, relative humidity). Likewise, for meteorological stations providing only air temperature (partial data), it is shown that the PM equation generally provides better estimations of reference evapotranspiration than the Hargreaves-Samani equation, even