ABSTRACT OF THE STUDY
      
      We intend to study with this research the possible consequences that the use of urban sewage may have in a certain crop, rice in this case, and in the environment. Thus, we try to analyses the effect which the irrigation mater has on soil properties and, in particular, if it affects, somehow, to the crop and the environment, represented here by the Albufera’s Natural Reserve. We will take into account the soil-water-plant interaction as well as the crop and soil abilities as water depurating elements in relation to the Lake where they flow into. This may represent that the water flowing into the Lake may have less polluant elements if it has had agricultural reuse.
      
      The originality of this study among the previous ones related with urban sewage reuse and its effects on soil, water, crops and the environment, from which the research has been borned, is precisely to see the linear evolution of various chemical parameters on flooded soils for rice crop.
      
      We’ve analysed nine plots alongside an irrigation line. The first one is irrigated only with urban sewage, but half way the irrigation line, the irrigation water come also from other origins with poor quality, and at the same time, the plots al the end of the line are affected by the “perellonŕ” which means that plots are flooded even if there is no crop.
      
      The essay refers mainly to soils, but considers also water and plant, taking into account the draw or nutrient accumulation like trace elements in the balance between fractions of soluble, absorbable and non absorbable elements by plants from soil solution which is the compulsory way for most of these elements.
      
      At the same tim in the analysis we consider not only the spatial but also the temporal evolution, comparing the results obtained in this study with sampling made before and after the harvest of rice during various crops campaigns.
      
      Water reuse for plot irrigation can cause a progresive accumulation of elements disolved in it or draw of these elements, which would carry its deposition in a place of such environmental importance as the Lake. Un increase on the nutrient contents of water, like nitrogen and phosphorus, mineral salts and trace metals alonside the irrigation line could lead us to think that the elements acumulate on the plot soils. On the contrary, if the results obtained in all plots were quite similar, that would mean that the elements drawn by irrigation water instead of acumulate in the irrigated plots would deposit finally in the bottom of the Lake.
      
      That’s why we analyses the agricultural soils irrigated with urban sewage in order to know to which extent all the concepts mentioned above take place in the soil-water-plants system and the environment, trying not to forget rice crop, water and all the sorrounding environment.