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Title: Isolated and combined effects of soil salinity and waterlogging in seedlings of 'Green Dwarf' coconut

Author
item MEDEIROS, WILIANA - Universidade Federal Do Ceara (UFC)
item OLIVEIRA, FRANCISCO - Universidade Federal Do Ceara (UFC)
item LACERDA, CLAUDIVAN - Universidade Federal Do Ceara (UFC)
item SOUSA, CARLOS - Universidade Federal Do Ceara (UFC)
item CAVALACANTE, LOURIVAL - Universidade Federal Da Paraiba (UFPB)
item SILVA, ALEXANDRE - Instituto Federal De Educação Ciência E Tecnologia
item Ferreira, Jorge

Submitted to: Semina Agricultural Sciences (Semina: Ciências Agrárias)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2018
Publication Date: 8/2/2018
Citation: Medeiros, W.J., Oliveira, F.I., Lacerda, C.F., Sousa, C.H., Cavalacante, L.F., Silva, A.R., Ferreira, J.F. 2018. Isolated and combined effects of soil salinity and waterlogging in seedlings of 'Green Dwarf' coconut. Semina Agricultural Sciences (Semina: Ciências Agrárias). 39(4):1459-1468. http://dx.doi.org/10.5433/1679-0359.2018v39n4p1459.
DOI: https://doi.org/10.5433/1679-0359.2018v39n4p1459

Interpretive Summary: Degraded soils with excess salinity are unproductive unless utilized to grow plant species that are tolerant to salinity. In addition, in clayey soils, the problem of salinity is aggravated when accompanied by cycles of waterlogging during the the rainy season or when excess irrigation is applied. The aim of this work was to evaluate the effects of soil salinity and waterlogging, isolated and combined, on the responses of young plants of green dwarf coconut. The experiment was conducted under controlled environment and the treatments comprised of five waterlogging cycles (0, 1, 2, 3 and 4), each with a duration of four days, applied at 30, 60, 90 and 120 days into the experimental period, with five levels of soil salinity, expressed as electrical conductivity or EC, and with the following values: 1.70, 11.07, 16.44, 22.14 and 25.20 dS m-1. Both leaf expansion and biomass accumulation were inhibited in coconut seedlings. This stunting effect was associated more with soil salinity than with waterlogging cycles so that the effects of excess water were seen only at the lower levels of salinity. Leaf gas exchange was reduced mainly due to soil salinity, and this response was related to stomatal and non-stomatal effects. The green dwarf coconut seedlings were classified as moderately-tolerant to salinity when grown in soils with an EC up to 11.07 dS m-1, having the potential to be used in revegetation programs of salt-affected areas, provided that these areas are not exposed to frequent waterlogging cycles. The information contained in this work is important for farmers involved in the continuous expansion of the coconut water industry in the Brazilian semiarid and other regions afflicted by saline soils. It also indicates to green dwarf coconut farmers that they should not try to establish the crop in soils of moderate salinity when the area is subjected to waterlogging.

Technical Abstract: Soil salinization is a problem commonly found in semi-arid regions. In addition, the problem of salinity is aggravated in clayey soils when accompanied by cycles of waterlogging in the rainy season or when excess irrigation is applied. In this work we evaluated the isolated and combined effects of soil salinity and waterlogging on the responses of young plants of ‘Green Dwarf’ coconut. The experiment was conducted under controlled environment in a complete randomized block design, arranged in split plots with five replications. The plots comprised five waterlogging cycles (0, 1, 2, 3 and 4), each with a duration of four days, and applied at 30, 60, 90 and 120 days into the experimental period, with the sub-plots consisting of five levels of soil salinity (1.70, 11.07, 16.44, 22.14 and 25.20 dS m-1). Response of coconut seedlings to waterlogging was dependent on the level of soil salinity, with waterlogging significantly impairing biomass accumulation and leaf expansion at low soil salinity levels, but causing no additional harm at elevated salinity. Leaf gas exchange was reduced mainly due to soil salinity, and this response was related to stomatal and non-stomatal effects. Seedlings of ‘Green Dwarf’ coconut used in this study were classified as moderately-tolerant to salinity when grown in soils with an electrical conductivity up to 11.07 dS m-1, having the potential to be used in revegetation programs of salt-affected areas, provided that these areas are not exposed to frequent waterlogging cycles.