Contribution of soil properties to the assessment of a seawater irrigation programme as a management strategy for abandoned solar saltworks M.N. González-Alcaraz a, ⁎, B. Aránega a , H.M. Conesa a , M.J. Delgado b , J. Álvarez-Rogel a a Departamento de Ciencia y Tecnología Agraria, Área de Edafología y Química Agrícola, E.T.S. de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, Cartagena, 30203 Murcia, Spain b Departamento de Química Agrícola, Geología y Edafología, Facultad de Química, Universidad de Murcia, Campus de Espinardo, Espinardo, 3100 Murcia, Spain abstract article info Article history: Received 22 July 2014 Received in revised form 21 October 2014 Accepted 19 November 2014 Available online xxxx Keywords: Ecosystem restoration Redoximorphic features Salt marsh Wetlands Halophytes The installation of desalination plants close to ecosystems of interest may have environmental impacts that make corrective measures necessary. Especially, wetlands (which are water-dependent ecosystems) are prone to degradation. This is the case for the Agua Amarga salt marsh (SE Spain), that includes an abandoned solar saltworks and surrounding, topographically higher zones, in which the groundwater withdrawal to supply two de- salination plants has led to a drop of the piezometric levels and the desiccation of the ecosystem. To overcome these problems, a programme to irrigate the marsh with seawater was established. This paper reports some soil charac- teristics of the marsh in relation to the different types of vegetation/environment identified and the seawater irri- gation programme, with the objective being to propose some guidelines to improve the management of the site. Surface and subsurface samples were taken from 63 plots and the depth of the water level and the soil redox poten- tial (Eh), moisture, electrical conductivity (EC), CaCO 3 , organic carbon, nitrogen and bulk density were determined. Also, the soil texture, structure, consistence, accumulation of salt crystals and redoximorphic features – indicative of reduction-oxidation processes – were described. The poor structure (weak, granular, subangular and angular blocks, very fine and fine) showed that the soils were hardly developed. The periphery (mainly colonised by Suaeda vera, Lygeum spartum and Limonium spp.) was less saline (EC 1:5 in the upper layers ~0.4 to ~4 dS m -1 ) and drier (water level N -1.5 m depth) than the abandoned saline ponds (EC 1:5 in the upper layers ~2 to ~9 dS m -1 and water level between -1 m depth and +0.2 m above the soil surface), mainly colonised by Sarcocornia fruticosa, Arthrocnemum macrostachyum, Salicornia patula, Phragmites australis and Ruppia maritima in the flooded ponds. The soils of the periphery were always oxic (Eh N + 500 mV), but most of the abandoned saline ponds had suboxic (~ + 100 mV b Eh b ~ + 350 mV) and even anoxic conditions (Eh b ~ + 100 mV), as shown by the existence of gley colours and redoximorphic features. The soil bulk density of the surface and subsurface layers showed that the most impermeable ponds were located in the centre of the marsh, where it is possible to maintain a surface water sheet during prolonged periods, suitable for the development of submerged plant species such as R. maritima and for wa- terbirds. Part of the seawater poured into more permeable ponds, such as those located in the southern and north- ern zones of the marsh, is lost by infiltration due to the lower bulk density of these soils. The latter facilitates the recovery of the piezometric levels and the growth of terrestrial plant species. Monitoring of redoximorphic features in the upper soil layers, in combination with symptoms of damage in the plants, could be used as a visual indicator of oxygen limitation due to excessive soil moisture. This would permit the regulation of the irrigation programme, hence optimising the energy and economic resources applied to maintain the ecosystem. © 2014 Elsevier B.V. All rights reserved. 1. Introduction For centuries, the salt extraction industry was an important economic activity in the Mediterranean basin. The general term “solar saltworks” has been used to describe the site and/or the installation where the salt making process takes place. It consists of a series of interconnected ponds through which seawater flows and, as the water is evaporated by solar energy, it becomes increasingly salty in successive ponds (Davis, 2000). The high chemical quality and yield of the salt produced made the solar saltworks profitable. However, since the mid-20th centu- ry, the salt industry has faced a deep crisis in the form of territorial pres- sures, changes in hydric systems, development of cold storage techniques and competition from lower priced, industrial salt. The resulting low prof- itability led to increasing desertion of small solar saltworks (Crisman et al., 2009). The abandonment of salt extraction and further activities may lead to the degradation and irreversible loss of these types of Catena 126 (2015) 189–200 ⁎ Corresponding author at: Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands. Tel.: +31 20 5987079; fax: +31 20 5987123. E-mail addresses: m.n.gonzalezalcaraz@vu.nl, nazaret.gonzalez@upct.es (M.N. González-Alcaraz). http://dx.doi.org/10.1016/j.catena.2014.11.012 0341-8162/© 2014 Elsevier B.V. All rights reserved. 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