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Because of the high costs and environmental impacts of peat and chemical fertilizers, the search for sustainable alternatives is increasing. Posidonia-based compost (C) has been widely tested as a growing media, while the combination with decontaminated dredged sediments (S) has only recently been studied. Moreover, little information is available on the relationship between plants and growing media. In this work, the suitability of growing media (CS) composed of 100% C, 70% C + 30% S and 30% C + 70% S were investigated compared to peat, for ornamental plants (Elaeagnus macrophylla, Photinia × fraseri and Viburnum tinus). Plant growth, physiological, nutritional and antioxidant responses were also investigated. The CS were compliant with current legislation on growing media. The Cu (+60%; +70%), Mg (+11%; +23%) and Ca (+66%; +72%) concentrations were higher in CS with 30% and 70% of S, respectively, than peat. The plants growing in CS had lower antioxidant activities than those on peat, suggesting a better plant tolerance to abiotic stress. In conclusion, the use of CS growing media, especially those with 30% and 70% of S, can be a valuable strategy to replace peat and reduce the application of fertilizers.

Solos afetados por sais são característicos de zonas áridas/semi-áridas. Este trabalho foi desenvolvido no vale do Açu (RN), no período abril/90 a janeiro/91, objetivando avaliar o efeito do preparo do solo (convencional e convencional + subsolagem) e da aplicação de condicionadores ( gesso, esterco de curral e palha de carnaúba) nas propriedades químicas de um solo aluvial salino sódico. A subsolagem proporcionou efeito eficaz na redução da porcentagem de sódio trocável (PST) e no abaixamento do pH do solo. Nos tratamentos com gesso, foram detectados os maiores valores de cálcio trocável, redução na PST para menos de 15% na camada de 0-0,15 m e aumento na salinidade do solo. O esterco de curral foi benéfico na redução da PST, principalmente quando associado à subsolagem e à gessagem. Existe um desbalanço natural nas relações K:Ca:Mg trocáveis no solo, que se acentua com a gessagem, necessitando de correção potássica para que se atinja o equilíbrio. A proporção entre cátions trocáveis e solúveis no solo ficou entre 13 e 16:1, para cálcio e magnésio, e entre 0,3 e 3,9:1, para o sódio, sendo este o único cátion solúvel que diminuiu com a subsolagem. Salt-affected soils are characteristics of arid and semi-arid zones of the world. This study was undertaken at Açu valley region of Rio Grande do Norte State, Brazil, by means of a field experiment conducted from April/90 to January/91. The objective of this study was to evaluate the effects of subsoiling and amendment additions (gypsum, farmyard manure and Copernica cerifera straw), on chemical properties of saline sodic soil. Subsoiling treatment provided beneficial effects decreasing soil exchangeable sodium percentage (ESP) and pH levels. Gypsum treatments increased soil exchangeable-Ca and salinity levels and decreased ESP to levels lower than 15% in soil layer depth to 0-0.15 m. Farmyard manure treatment decreased ESP levels, especially when associated with subsoiling and gypsum treatment. There is a natural imbalance in K:Ca:Mg ratios that increases with gypsum treatments requiring soil potassium correction in order to reach the equilibrium. The ratios between exchangeable and soluble cations ranged from 13 to 16:1 for calcium and magnesium and from 0.3 and 3.9:1 for sodium. Among the soluble cations, sodium was the only one decreased by subsoiling.