Effect of irrigation water quality on soil properties and infrared spectroscopic signatures

Aim of study: To study the effect of irrigation with medium-to-low-quality water on an olive farm that seems to be causing salinity and/or sodicity problems in soils, and the ability of infrared spectroscopy to detect this problem. Area of study: The study was conducted in an olive (Olea europaea L.) grove located in Guarroman (Jaen, Spain), on the boundary of the Sierra Morena Mountains and the Guadalquivir Depression. Material and methods: The olive farm is cultivated over two soil typologies, a calcareous area (carbonated) dominated by Regosols and a siliceous area with Leptosols. Typical soil physical and chemical parameters were determined, as well as near and mid infrared spectra were collected for analysis. Main results: Soil physical properties were affected by irrigation, with low infiltration rates and symptoms of structural degradation. Chemical properties were also altered, showing high pH, low amounts of organic carbon and N, and high sodium concentrations. These effects were stronger in the samples directly affected by the irrigation bulb, with the siliceous soils more affected than carbonated, probably due to the positive effect of the higher amounts of calcium in the latter. Using infrared spectroscopy, it was possible to discriminate the samples of this farm affected by sodicity from similar soil samples in Jaen province not affected. Research highlights: the use of medium-to-low quality irrigation water affected soil physical and chemical properties. Infrared spectroscopy could be useful for quick assessment of soil quality and soil degradation from salinity and sodicity.