The excess of salts can affect several processes in the crops, and nitrogen (N) can attenuate the depressive effect of salinity. The objective was to evaluate the influence of nitrogen doses on the growth and gas exchange of corn crop irrigated with saline water. The experiment was conducted from June to September 2019 at the University of International Integration of Afro-Brazilian Lusophony, Redenção, CE, Brazil. The experimental design was completely randomized, in a 2 x 3 factorial scheme (supply water of 0.3 dS m-1 and saline solution of 3.0 dS m-1) and three nitrogen doses, 0, 80, and 160 kg ha-1, corresponding to 0, 50, and 100% of the recommended dose respectively, with six repetitions. At 30 and 45 days after sowing (DAS), plant height, leaf area, number of leaves, photosynthesis, transpiration, and stomatal conductance were evaluated. Saline stress affects plant height, leaf area, photosynthesis, transpiration, and conductance at 30 DAS. The doses of 80 and 160 kg ha-1 provide greater performance in plant height, leaf area, photosynthesis, transpiration, and conductance at 30 DAS. The use of low salinity water and doses of 80 and 160 kg ha-1 were more efficient in terms of plant height, leaf area, photosynthesis, transpiration, and conductance at 45 DAS. The dose of 160 kg ha-1 of N attenuates the harmful effects of salts in AG 1051 hybrid maize plants, providing higher values of photosynthesis, transpiration, and stomatal conductance at 45 DAS when irrigated with water of 3.0 dS m-1.

O objetivo deste trabalho foi avaliar o efeito da irrigação com água de alta e baixa salinidade em diferentes turnos de rega e cobertura morta, na cultura do sorgo. O experimento foi conduzido na área experimental da Unidade de Produção de Mudas Auroras (UPMA) da Universidade da Integração Internacional da Lusofonia Afro-Brasileira (UNILAB), com o delineamento inteiramente casualizado, em arranjo fatorial 2 x 2 x 2, sendo dois níveis de condutividade elétrica (A1 -água de abastecimento 0,8 dS m -1 e A2solução salina 4,0 dS m -1 ), dois turnos de rega (T1 -turno de rega diário e T2turno de rega a cada 4 dias) e, dois tipos de cobertura (Cccom cobertura morta e Scsem cobertura). Foram avaliadas as seguintes variáveis: área foliar (AF), diâmetro do caule (DC), altura da planta (AP), matéria seca da parte aérea (MSPA), potencial hidrogeniônico (pH) e Condutividade elétrica do extrato de saturação (CEes). A cobertura ajuda a minimizar os efeitos da irrigação com água de baixa e alta salinidade, para todas as variáveis analisadas. A água salina reduz o diâmetro do caule, mesmo na presença de cobertura morta. Os turnos de rega apresentam maiores valores de área foliar, altura de planta e diâmetro do caule, quando utilizados com cobertura morta.

ABSTRACT The objective of this study was to evaluate the production of watermelon seedlings irrigated with saline waters and cultivated in different types of environments and substrates. The experimental design was completely randomized with split-split plots, in which the plot corresponded to two growing environments (EN1 = full sun and EN2 = 50% shade black net), the subplot to two types of irrigation water (IW1 = 0.8 and IW2 = 2.5 dS m-1) and the sub-subplot to four types of substrates (SB1 = vermiculite + coconut fiber, SB2 = manure + soil, SB3 = carbonized rice husk + soil, SB4 = biochar + soil), with four replicates of twenty-five seeds. The variables analyzed were: emergence percentage (EP), emergence speed index (ESI), mean time of emergence (MTE), number of leaves (NL), stem diameter (SD), seedling height (SH) and root length (RL), shoot dry mass (SDM), root dry mass (RDM) and total dry mass (TDM). The EN2 treatment provided better conditions for emergence and initial growth, and EN1 was also favorable to the emergence and initial growth of watermelon seedlings, when the substrates SB1 and SB2 were used.

HIGHLIGHTS Saline stress did not affect the initial growth of the cowpea crop. The use of mulch provides better morphological results in the cowpea crop. Vegetal mulches as soil protection (sugarcane bagasse and bamboo straw) attenuated effect of salts on gas exchange of cowpea.

Absence of drainage associated with high evapotranspiration and irregular precipitations contributes to the accumulation of salts in the soil, reducing nutrient absorption and yield. Nutritional management is important for the crop to express its maximum production potential, and nitrogen is the macronutrient most required by the corn crop. The objective of this study was to evaluate yield and leaf contents in corn under different nitrogen fertilization recommendations and salt stress. The experiment was conducted from June to September 2019, at the University of International Integration of Afro-Brazilian Lusophony in Redenção-CE, Brazil. The experimental design used was completely randomized, in a 2 x 3 factorial arrangement, with 6 replicates, with two levels of electrical conductivity (0.3 dS m-1 and 3.0 dS m-1) and three nitrogen fertilization recommendations (0, 50 and 100% of the recommendation). The variables analyzed were unhusked ear weight, husked ear weight, yield and leaf contents of N, P, K, Ca, Mg and Na. Irrigation with saline water (3.0 dS m-1) reduces the unhusked ear weight, husked ear weight and yield. Nitrogen fertilization recommendations of 50% and 100% promoted higher values of unhusked ear weight, husked ear weight and leaf N contents, but reduced leaf P contents. The 50% and 100% recommendations promote higher yield values for the two levels of electrical conductivity studied (0.3 and 3.0 dS m-1). The 50% and 100% recommendations associated with saline water irrigation increased the leaf contents of K, Na, Mg and Ca.

The objective was to evaluate the initial growth and gas exchange of yellow passion fruit seedlings irrigated with saline water under different environments. The experiment was conducted of the University of International Integration of Afro-Brazilian Lusophony, Redenção-CE. The experimental design used was entirely randomized, in factor arrangement 4 x 2, referring to four environments with different shade screens (black screen; whitescreen; red screen; all with 50% shading; and full sun) and the values of electrical conductivity of irrigationwater (0.3 and 3.0 dS m-1), with five repetitions. The following variables were evaluated: number of leaves, plant height, leaf area, photosynthesis, transpiration, stomach conductance, instantaneous water use efficiency, electrical conductivity of the saturation extract and soil pH. The environment with black screen provides greater performance in leaf area, plant height and root length and was more efficient for the production of dry mass of the aerial part and the root of passion fruit seedlings in both irrigation waters. The red screen environment stimulates greater photosynthesis, transpiration, stomach conductance and chlorophyll in passion fruit seedlings irrigated with low salinity water, while the black screen mitigated saline stress for these variables. The full sun environment provided greater instantaneous water use efficiency in passion fruit seedlings for treatment with low salinity water and the black screen environment with high salinity water.

Irrigation water salinity can cause serious problems in crop production, while organic fertilizer sources potentially mitigate saline stress. Thus, this study aimed to evaluate the productivity of maize crops under irrigation with saline water and organic fertilization. The study was conducted in the field from August to November 2020 at the experimental farm of the Universidade da Integração Internacional da Lusofonia Afro-Brasileira (UNILAB), Redenção-CE. A randomized block design was used, in subdivided plots, in which the plots consisted of two levels of irrigation water salinity (0.8 and 3.0 dS m-1). Four combinations of organic fertilizer sources were applied in the subplots, composed of 10 plants each, with four replications: C1, cattle manure + poultry biofertilizer + goat biofertilizer; C2, cattle manure + goat biofertilizer; C3, cattle manure + poultry biofertilizer; and C4, control treatment. The combination of organic fertilizer sources did not influence the accumulation of assimilates and productivity of maize crops under the irrigation water salinity of 3.0 dS m-1, except for C3, which attenuated the saline effect.

Semi-arid regions present the inherent problem of accumulation of salts in the soil due to the use of brackish water for irrigation, and water deficit compromises the growth and physiological indices of crops. This study evaluated the effect of salt and water stress on growth and gas exchange in the zucchini cv. Caserta crop. The study was conducted at the University of International Integration of Afro-Brazilian Lusophony, Redenção, Ceará State, Brazil. The experimental design was completely randomized, in a 5 × 2 factorial scheme with five levels of electrical conductivity of the irrigation water - ECw (0.5, 1.0, 1.5, 2.0, and 2.5 dS m-1) and two water regimes (50 and 100% of the potential crop evapotranspiration - ETc), with five replicates. At 36 days after sowing, the following traits were evaluated: CO2 assimilation rate, transpiration, stomatal conductance, internal carbon concentration, leaf temperature, relative chlorophyll index, and water use efficiency. At 45 days after sowing, the plant height, stem diameter, number of leaves, and leaf area were also evaluated. The use of brackish water (1 to 2.5 dS m-1) reduced the growth parameters of zucchini cv. Caserta. The increase in ECw caused a decline in the physiological traits. Under 100% ETc, higher values of CO2 assimilation rate, transpiration, and instantaneous water use efficiency were recorded, and there was 50% ETc for internal carbon concentration, even with the increase in ECw.