1150 AJCS 12(07):1150-1158 (2018) ISSN:1835-2707 doi: 10.21475/ajcs.18.12.07.PNE1122 Physiology and growth of cashew ‘anão precoce’ (Anacardium occidentale L.) subjected to salt stress and organic fertilization Elysson Marcks Gonçalves Andrade 1 , Geovani Soares de Lima 1* , Vera Lúcia Antunes de Lima 1 , Hans Raj Gheyi 2 , André Alisson Rodrigues da Silva 1 , Pedro Dantas Fernandes 1 , Leandro de Pádua Souza 1 , Saulo Soares da Silva 1 1 Federal University of Campina Grande, Academic Unit of Agricultural Engineering, Campina Grande, 58.109-970, Paraíba, Brazil 2 Federal University of Recôncavo of Bahia, Nucleus of Soil and Water Engineering, Cruz das Almas, 44.380-000, Bahia, Brazil *Corresponding author: geovanisoareslima@gmail.com Abstract Cultivation of cashew in the semi-arid region of Northeast Brazil is pivotal for the generation of jobs and income. However, agricultural production in this region has been compromised by water and soil salinity. Therefore, it is necessary to look for alternatives that minimize the effects of salt stress on cashew cultivation in this region. In this context, this study aimed to evaluate gas exchanges, photochemical efficiency and growth of cashew ‘anão precoce’ cv. BRS 226 Planalto’ irrigated with water containing different salinity levels and under organic fertilizer doses. The experiment was carried out in drainage lysimeters in a greenhouse, using a randomized block design in 5 x 4 factorial scheme with three replicates. Treatments corresponded to five levels of irrigation water electrical conductivity – ECw (0.7, 1.4, 2.1, 2.8 and 3.5 dS m -1 ) and four doses of organic fertilization (2.5, 3.5, 4.5 and 5.5%). Organic fertilizer doses were determined on the basis of soil volume. Bovine manure was used as source of organic fertilizer. The fertilizer was decomposed and applied in the soil before planting. Irrigation water salinity from 0.7 dS m -1 caused increase in the internal CO 2 concentration and reduction in CO 2 assimilation rate, transpiration and stomatal conductance of cashew ‘anão precoce’ plants, 126 days after transplantation. The results showed that chlorophyll a fluorescence and the absolute and relative growth rates were influenced by the increase of salinity in irrigation water. Organic fertilization had negative influence on gas exchanges, chlorophyll a fluorescence and growth of cashew ‘anão precoce’ in the post-grafting stage. Keywords: Anacardium occidentale L., salt stress, bovine manure. Abbreviations: gs_stomatal conductance; E_transpiration; A_CO 2 assimilation rate, Ci_internal CO 2 concentration; EICI_ instantaneous carboxylation efficiency; WUE_instantaneous water use efficiency; Fo_initial fluorescence; Fm_maximum fluorescence; Fv_ variable fluorescence; Fv/Fm_maximum quantum efficiency of photosystem II; ECw_electrical conductivity of the irrigation water. Introduction Cashew (Anacardium occidentale L.) is considered as one of the most important cultivated species of the tropical regions, occupying an estimated area of 3.39 million hectares in the world. Its main products of economic importance are the edible nut and liquid from the nutshell (Oliveira, 2008). In this context, global cashew nut production is approximately 3.7 million tons and the main producers are: Vietnam, India, Nigeria, Ivory Coast and Brazil (FAO, 2009). Brazil is considered as the largest cashew producer in the world but its yield is low, approximately 300 kg ha -1 (IBGE, 2013). The cashew ‘anão precoce’ is characterized by low plant size, mean height of 2.11 m and mean diameter of the crown of 4.52 m in the sixth year of age. These characteristics are peculiar to the type of cashew ‘anão precoce’. The agro-industrial indicators are weight of the nut of 6.4 g, degummed almond with average of 1.6 g with natural humidity, the ratio almond/bark of 25.5%. For the peduncle, the agro-industrial indicators are average weight of 76.5 g and yellow coloration (Paiva and Barros, 2004). According to Véras et al. (2014), cashew is native to Northeast Brazil and its cultivation is a source of income for farmers in the states of Ceará, Rio Grande do Norte and Piauí due to its adaptation to the edaphoclimatic conditions of this region. However, the producing states are located in areas subject to saline soils and water (Ferreira-Silva et al., 2009). According to Viégas et al. (2001), salinity can be aggravated by other environmental stress factors in semi- arid regions, including low water availability, high temperatures and high evapotranspiration. As an aggravating factor, the excess of salts may disturb plant