The effect of sub-irrigation with untreated and treated municipal wastewater on organic matter and nitrogen content in two different soils

The aim of this study is to investigate the effect of sub-irrigation with untreated and treated municipal wastewater on soil organic matter % and nitrogen %. Three treatments were used: untreated wastewater U, treated wastewater T and tap water W being the control treatment, in two soil types, Sandy loam SL and Loamy sand LS. A sub-irrigation system including pots filled with soil installed in one of the greenhouses of the Agricultural University of Athens. The wastewater used was applied in the soil in pots at a depth of 10cm and 20cm. In order to determine the changes of organic matter % and total N % at the point where the emitter was placed, the soil was divided into two zones according to depth: (zone I -upper) and (zone II-lower). The total N %, ammonia nitrogen (NH4-N), nitrogen nitrates (NO3-N) and organic matter % were determined in the soil samples. Statistically significant differences (p < 0.05) were observed in organic matter % and total N % only for LS soil. Between the two zones, sub-irrigation with T at a depth of 20 cm resulted in an increase in organic matter % in zone (I) for SL soil while for LS soil sub-irrigation with U at a depth of 20 cm led to an increase of total N% in zone (I) and nitrate and ammonium in zone (II) both statistically significant (p < 0.05).