| The great challenge in agriculture for the near future, will be, on the one hand, the task of increasing food production with less water, particularly in countries with limited water and land resources, and on the other hand the safe use of non conventional water resources, such as treated wastewater, for irrigation. In this sense, almost all types of treated effluents remain moderately to highly saline and consequently their long term use in irrigation may significantly affect the physical and chemical properties of the soil especially under modern and intensive agricultural system in arid and semi-arid areas, therefore appropriate strategies for managing soil, water and crops may also be needed when these non conventional resources are used for irrigation.;In this thesis, the first investigation approximation into reclaimed water was on lemon trees (Chapter II). The aim of this work was to study the effects of reclaimed water on lemon tree performance. In particular, this research was to compare two sources of treated wastewater, one obtained with a secondary treatment (Cartagena) and the other with a tertiary treatment blending with well water (Campotejar), and to study their effects on soil chemical properties, on the leaf mineral status, crop production and fruit quality and safety. The main results obtained shown that the possibility of blending reclaimed water with well water is a good solution to avoid the problems associated with wastewater use in agriculture. The high salinity, Cl and B concentration were the main restrictions associated with treated wastewater used in the experiment. The use of reclaimed water as irrigation water for lemon trees did not represent a microbial risk for lemon fruit.;Little is known about the interaction between deficit irrigation and saline water. For this reason, the main objectives of the second study were to evaluate the combined effects of different irrigation water qualities (Tajo Segura water transfer canal, irrigators association and reclaimed water) and the regulated deficit irrigation strategies on mandarin tree crop performance under Mediterranean climate conditions and their effects on plant physiology and leaf mineral status, soil chemical properties and water content, yield and fruit quality (Chapter III). Yield reductions were not significant between treatments, although a tendency to reduced number of fruit was detected in the reclaimed water treatments. This reduction was more pronounced under combined conditions of reduced irrigation quality water and regulated deficit irrigation. The combined effects of RDI strategies and of using reclaimed water can increase some fruit quality parameters such as vitamine C on mandarin trees. Plant water relations and vegetative growth were not significantly affected by the use of reclaimed water. However, water stress in the RDI treatments induced some reductions in the stem water potential that inmediatly were recovered when deficit period disappeared.;Although no leaf toxic visual symptoms were seen during the experiment,a tendency was identified in terms of salts accumulation in the soil during last season in RW-RDI treatment. In this sense, it is important to remark that in arid and semi-arid areas, the combination of RDI strategies and reclaimed water-use can be affected in the long-term because of the salts and boron accumulation.;The last work was based in the use of Geographical Information Systems (GIS) as a tool in the planning and management of water reuse projects (Chapter IV). A work in the Beira Interior region (Portugal) was developed with the aims at identifying potential sites for reclaimed water use, using a GIS-based multi-criteria analysis. A constructed wetland (CW) system located in the northwest part of the Beira Interior region was used as the source of reclaimed water. The work also intended to show that small wastewater treatment facilities may be used for aquifer recharge in areas of water scarcity, reducing the discharge of residuals loads to the environment and benefiting economic and tourist activities. (Abstract shortened by UMI.)... |
