RESUMO A região Nordeste brasileira apresenta condições climáticas favoráveis ao desenvolvimento da floricultura; contudo, a escassez hídrica e a salinização de parte de suas fontes hídricas atuam como entrave a essa atividade. Nesse contexto, objetivou-se testar os efeitos de níveis crescentes de salinidade da água de irrigação sobre as respostas quantitativas e qualitativas das espécies ornamentais Euphorbia milii e Zamioculcas zamiifolia, sob diferentes condições de luminosidade. A pesquisa foi realizada utilizando-se delineamento experimental em blocos casualizados, em esquema de parcelas subsubdivididas, com cinco repetições. As plantas foram cultivadas em vasos de 7 L, passando por um período inicial de aclimatação durante 15 dias com água não salina para que o seu estabelecimento não fosse comprometido; após esse período, as plantas foram submetidas a níveis crescentes de salinidade na água de irrigação (0,5; 2,0; 3,5; e 5,0 dS m-1) sob quatro intensidades luminosas (pleno sol, 30%, 50% e 70% de sombreamento), durante 60 dias. As variáveis analisadas foram altura da planta, diâmetro do caule, biomassa da parte subterrânea e das partes aéreas, tolerância à salinidade e análise qualitativa. O sombreamento teve maior impacto nas variáveis qualitativas das plantas do que na tolerância à salinidade baseada em variáveis quantitativas. O ambiente com 30% de sombreamento é o mais propício para o cultivo da E. milii quando se utiliza água de baixa a moderada salinidade. O sombreamento reduz os danos diretos da radiação nas folhas de Z. zamiifolia e melhora a qualidade visual dessa espécie sob elevada salinidade.

ABSTRACT The Brazilian Northeast region has favorable climatic conditions for the development of floriculture; however, water scarcity and salinization of part of its water sources act as an obstacle to this activity. In this context, the objective was to test the effects of increasing levels of salinity in irrigation water on the quantitative and qualitative responses of ornamental species Euphorbia milii and Zamioculcas zamiifolia, under different light conditions. The study was carried out using an experimental design in randomized blocks, in a split-split-plot scheme, with five replications. The plants were grown in 7 L pots, undergoing an initial period of acclimatization for 15 days with non-saline water so that their establishment would not be compromised; after this period, the plants were subjected to increasing levels of salinity in the irrigation water (0.5; 2.0; 3.5; and 5.0 dS m-1) under four light intensities (full sun, 30%, 50% and 70% shading) for 60 days. The variables analyzed were plant height, stem diameter, belowground and shoot biomass, salinity tolerance and qualitative analysis. Shading had a greater impact on the qualitative variables of the plants than on the salinity tolerance based on quantitative variables. The environment with 30% shading is the most favorable for the cultivation of E. milii when using water with low to moderate salinity. Shading reduces direct radiation damage to Z. zamiifolia leaves and improves the visual quality of this species under high salinity.

ABSTRACT: Supplemental irrigation during dry spells could reduce maize yield losses in tropical semi-arid regions, notably in small farms. However, good quality water reserves are not sufficient to meet the demands of farming communities. Consequently, our objective was to evaluate the productivity and profitability of maize under different simulated rainfall scenarios, with and without supplemental irrigation (SI) with brackish water. The field experiments were carried out during the cropping seasons of 2018 and 2019 on Ultisol. The experiment followed a randomized block design in the split-plot scheme with four replicates. The plots were formed by simulating the water supply in the soil corresponding to four water scenarios (rainy, normal, drought and severe drought), and the sub-plots with or without SI with brackish water (Electrical conductivity of 4.5 dS m−1). Mean yields of green maize ears were 13,083, 11,532, 10,358 and 9,609 kg ha−1 for rainy, normal, drought and severe drought scenarios, as supplemented with brackish water. For the same treatments without SI the values were 11,394, 7,896, 3,913 and 1,374 kg ha−1, respectively. Data on farmer's income showed that under normal, drought and severe drought supplementation with brackish water becomes economically advantageous from 0.9, 1.0 and 2.4 ha, respectively, while maize cultivation without SI is not advantageous under the last two scenarios. For severe drought conditions, however, SI using brackish water reduced commercial yield by 27 % with negative effects on the farmers’ profitability. In this case, it is necessary to use water with either lower salinity or select salt tolerant crops.

RESUMO A garantia do abastecimento de água para agricultura irrigada no semiárido deve passar necessariamente pelo uso de águas de qualidade inferior, como as águas salobras. O objetivo do presente trabalho foi avaliar a tolerância à salinidade para as espécies ornamentais Catharanthus roseus, Tagetes patula e Celosia argentea, utilizando-se diferentes métodos. O experimento foi conduzido em blocos ao acaso, arranjado em esquema fatorial 10 x 3, correspondendo a 10 concentrações salinas da água de irrigação (CEa 0,5; 1,0; 1,5; 2,0; 2,5; 3,0; 3,5; 4,0; 5,0 e 6,0 dS m-1) e 3 espécies de plantas ornamentais. Quatro métodos de avaliação da tolerância à salinidade foram testados, utilizando valores relativos ou percentuais de redução das análises quantitativas e qualitativas. Os diferentes métodos evidenciam maior sensibilidade à salinidade de C. roseus, na fase de produção de mudas, em relação às espécies T. patula e C. argentea. Os métodos da salinidade limiar e do índice ORN apresentaram resultados semelhantes, sendo C. roseus classificada como sensível e as espécies T. patula e C. argentea como moderadamente sensíveis à salinidade. O método de Fageria (1985) permitiu boa separação das espécies, com limites de tolerância de 1,5; 2,5 e 3,5 dS m-1, respectivamente para C. roseus, T. patula e C. argentea. Fica óbvio pela comparação com dados da literatura que a fase de produção de mudas é mais sensível ao estresse salino, sendo necessária a realização de novos estudos que visem atenuar os efeitos do estresse nessa fase, mediante o emprego de técnicas de manejo.

ABSTRACT The guarantee of water supply for irrigated agriculture in the semi-arid region must necessarily involve the use of lower quality water, such as brackish water. The objective of the present work was to evaluate the tolerance to salinity of the ornamental species Catharanthus roseus, Tagetes patula and Celosia argentea, using different methods. The experiment was conducted in a randomized block, arranged in a 10 x 3 factorial scheme, corresponding to 10 saline concentrations of irrigation water (ECw 0.5; 1.0; 1.5; 2.0; 2.5; 3.0; 3.5; 4.0; 5.0 and 6.0 dS m-1) and 3 ornamental species. Four salinity tolerance assessment methods were tested, using relative values or percentages of reduction in quantitative and qualitative analyses. The different methods show the highest sensitivity to salinity of C. roseus, in the seedling production stage, compared to T. patula and C. argentea species. The methods of threshold salinity and ORN index led to similar results in terms of classification of salt tolerance, with C. roseus classified as sensitive and T. patula and C. argentea as moderately sensitive. The method of Fageria (1985) allowed good separation of the species, with tolerance limits of 1.5, 2.5 and 3.5 dS m-1, respectively for C. roseus, T. patula and C. argentea. It is obvious from the comparison with literature data that the seedling production stage is more sensitive to salt stress, and it is necessary to carry out new studies aimed at attenuating the effects of stress at this stage, through the use of management techniques.