Effects of irrigation with saline waters, at different concentrations, on soil physical and chemical characteristics

An irrigation experiment with saline water at different concentrations was carried out over a 7-year period on the same clay-silty soil in the Volturno Valley at Vitulazio to evaluate long-term effects of irrigation with saline water on crops and soil. The spatial distribution of the experimental treatments remained the same throughout the 7-year period in order to assess the effects of salt accumulation. Three saline concentrations of irrigation water (0.25-0.5 and 1% of NaCl) and two irrigation levels (100% and 40% restitution of evapotranspiration) were applied. The electrolytic concentration (ECe) was measured every year in spring before the irrigation season. Autumn-spring rainfall caused leaching of salts from 0 to 0.4 m layer and an accumulation of salt in the deeper layers. Accumulation was directly correlated to the quantity of NaCl applied with irrigation. This allowed us to calculate, for the 0.4-1.1 m layer, the mean annual increase in ECe in (dS m(-1) pert ha(-1) year(-1) of NaCl given). At the end of the experiment, it was observed that there was an increase in ECe at a depth of 3 m for the saltiest treatments. The percentage of exchangeable sodium (ESP), however, increased with the saline concentration of the irrigation water (quantity of NaCl) above all in the 0-0.4 m layer, and gradually decreased with depth. Irrigation with saline water led to an increase in ESP and a degradation of the soil physical properties that were estimated indirectly by measuring aggregate stability in water (IASW). The index of aggregate stability in water for the top layer (0-0.15 m) was inversely correlated to the ESP values, even after the leaching due to the autumn-spring rainfall. (c) 2005 Elsevier B.V. All rights reserved.