|Author:||Cucci, G. ; Rubino, P. ; Caliandro, A.|
|Book Group Author:||NA|
Background. Most soils irrigated with brackish water are subject to salinization or alkalization, which cause a reduction in soil fertility and the formation of saline-alkaline soils in the medium or long term. To further contribute to the knowledge on these topics, a study was undertaken in Italy on the salinization and sodification of soils irrigated by waters with different salt concentrations and sodic levels, within a collaborative research project dealing with the effect of irrigation with saline-sodic waters on the chemical, hydrological, mechanical and agronomic aspects, under laboratory and field conditions. Methods. Two types of clay loam soils were tested for two consecutive years. They were packed in cylindrical pots and placed under a shed, and bean (1999) and capsicum (2000) were grown in succession. Both crops were irrigated with nine types of water obtained by mixing NaCl and CaCl2, from the factorial combination of three salt concentrations (0.001-0.01-0.1 M in the first year and 0.01-0.032-0.1 M in the second) with three SAR values (5-15-45). Both crops were irrigated whenever the bulk of soil in the pot had lost 30% of the available moisture by evapotranspiration, monitored by weighing the pots. Watering volumes corresponded to the volume required to restore field capacity to the entire soil profile plus the compared leaching requirement (10-20%). Throughout the cycles of both crops, drainage water was collected and analysed. At the end of the irrigation season in both years, soil samples were taken from the 0.30 m top layer of each pot and tested for electrical conductivity, pH, soluble Na-K-Ca-Mg on the saturation extract, plus exchangeable cations and exchangeable sodium percentage (ESP). Results. The amount of drainage water differed from the applied leaching requirement (LR). The amounts of leached solutes varied as a function of the amount of drainage water and its salt concentration. The percentages of leached solutes, as compared to those applied, decreased considerably as the irrigation water salinity increased. Salt build-up in the soil increased proportionately with the salt concentration of the irrigation water, while it varied slightly with LR and soil type. As a result of the balance between applied and leached solutes, at the end of the irrigation season of both years, the ECe values of the top soil layer (0.30 m) were 1 and 2.2 dS m-1 and 13.9 and 19.5 dS m-1, against a value of 0.71 dS m-1 observed prior to the research, using the lowest and highest water salinity, respectively. The exchangeable sodium percentages increased gradually, while those of Ca decreased gradually as the salinity and SAR of irrigation water increased; exchangeable potassium percentages did not vary considerably as a function of irrigation water quality. The exchangeable magnesium percentages increased proportionately with the SAR of irrigation water. Conclusions. The leaching requirement efficiency decreased considerably as irrigation water salinity increased. The results obtained show that in areas where the long term average yearly rainfall is not below 450-500 mm, winter rainfall could be more effective than LR to leach the solutes applied with brackish water, decreasing the seasonal irrigation volumes and amounts of applied solutes. A progressive sodification was observed in the top soil layer, as the salinity and SAR of the irrigation water increased.
|Pages:||41 - 48|
|Journal:||Italian Journal of Agronomy|
calcium, calcium chloride, clay loam soils, drainage water,electrical conductivity, evapotranspiration, exchangeable cations,irrigation, irrigation water, leaching, leaching requirement, magnesium,potassium, saline soils, saline water, salinity, salinization, sodicsoils, sodic water, sodium, sodium chloride, soil pH, soil types, soilwater content, solutes, Italy, Southern Europe, Europe, MediterraneanRegion, Developed Countries, European Union Countries, OECD Countries,salt water, watering, Soil Chemistry and Mineralogy (JJ200), Soil WaterManagement (Irrigation and Drainage) (JJ800) (Revised June 2002)[formerly Soil Water Management], Water Resources (PP200)