Άρδευση με επεξεργασμένα αστικά λύματα. Πειραματικές μετρήσεις, προσομοιώσεις και επιπτώσεις στο έδαφος, τα φυτά και το περιβάλλον

Abstract

The aim of this study was to investigate the impacts of irrigation with treated wastewater through trickle irrigation, plus inorganic nitrogen fertilizer application, on plant growth, soil and groundwater pollution. In addition, this study was also aimed to investigate the reliability of a one-dimensional simulation model for describing soil water distribution bellow trickle irrigation, as well as, to investigate the influence of transient combined soil water and salinity stress on plant root water uptake. Regarding this, and for achieving these aims, the study was basically depends on a field experimental measurements and a simulation model named WANISIM, to evaluate the experimental results. The field experiment was conducted on the experimental farm of Land Reclamation Institute of Thessaloniki, located in Northern part of Greece, on a loamytextured soil. Sunflower and corn crops were grown in different growing seasons and irrigated with treated wastewater. Experimental measurements concerning soil, plants and irrigation wastewater were collected during the growing seasons and following the non-cultivated periods from April 2003 to April 2005. Soil hydraulic parameters concerning soil water retention characteristics, ,(h) and Saturated hydraulic conductivity, Ksat were measured in the field. ,(h) data were measured in different soil profiles (25, 55, 85 and 105 cm) in undisturbed soil core samples, and the measured data were fitted to the Van Genuchten (1980) equation. Ksat was measured in four different soil profiles mentioned above, using both Guelph permeameter and undisturbed soil core samples. Soil profiles were monitored every 15 days during the growing seasons and monthly during the following non-cultivated periods. Soil monitoring concerns soil moisture content, mineral nitrogen (NH4-N and NO3-N), total nitrogen, organic matter, electrical conductivity and soil pH. Soil samples were colleted in between plant rows and irrigation lines. Furthermore, irrigation wastewater samples were collected each irrigation time and analyzed for mineral nitrogen concentrations, electrical conductivity and pH. Moreover, for evaluating the performance of plant growth, Leaf area index (LAI), root depth-distribution, plant dry matter, plant height and nitrogen content of plant tissues, were measured at two weekly basics. Regarding the reliability of WANISIM model for describing soil water and nitrogen dynamics, the model was tested against experimental measurements of soil water content and mineral nitrogen concentrations (NH4-N and NO3-N). Comparison between simulated and measured results indicate that the model proposed can describes the reaction of continuum soil-plant-atmosphere, further to mineral nitrogen applied by wastewater and fertilizers in the field. However over-estimation of measured soil water contents was observed in some months, particularly during the sunflower season. This study also indicates that monitoring of soil moisture content in one place, in between plant rows and irrigation lines, is not representative for describing soil water dynamics bellow trickle emitters.