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A positive growth response to NaCl applications in Eucalyptus plantations established on K-deficient soils

Raposo Almeida J.C., Laclau J.P., De Moraes Gonçalves J.L., Ranger J., Saint André L.. 2010. Forest Ecology and Management, 259 (9) : p. 1786-1795.

DOI: 10.1016/j.foreco.2009.08.032

Contrasting responses of Eucalyptus trees to K fertilizer applications have been reported on soils with low K contents. A complete randomized block experiment was set up in Brazil to test the hypothesis that large atmospheric deposits of NaCl in coastal regions might lead to a partial substitution of K by Na in Eucalyptus physiology and enhance tree growth. Treatments with application of 1.5, 3.0, 4.5 kmol K ha_1 (K1.5, K3.0, K4.5, respectively) as KCl, 3.0 kmol K ha_1 applied as K2SO4, 3.0 kmol Na ha_1 (Na3.0) as NaCl commercialized for cattle feeding, and a mixture of 1.5 kmol K + 1.5 kmol Na ha_1 (K1.5 + Na1.5) were compared to a control treatment (C) with no K and Na applications. All the plots were fertilized with large amounts of the other nutrients. A positive effect of NaCl applications on the growth of E. grandis trees was observed. NaCl and KCl additions in treatments Na3.0 and K3.0 increased above-ground biomass by 56% and 130% three years after planting, respectively, in comparison with the C treatment. By contrast, accumulated litterfall up to age 3 years was not significantly modified. NaCl applications in the Na3.0 treatment significantly increased Na accumulation in above-ground tree components but did not modify K accumulation, whatever the sampling age. A partial substitution of K by Na in tree physiology, as observed for various agricultural crops, might explain this behaviour. Our results suggest the possibility of applying inexpensive K fertilizers, which are less purified in Na, and explain why high yields are achieved without K fertilizer applications in areas with large dry depositions ofmarine aerosols. Further investigations are necessary to identify the processes involving Na in Eucalyptus tree physiology.

Mots-clés : eucalyptus; plantations; fertilisation; croissance; chlorure de sodium; engrais minéral; potassium; sodium; physiologie végétale; carence minérale; brésil

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