Using nitrogen (N) to increase plant tolerance to salinity has been tested in many species. However, in addition to controversial results, most studies are conducted with annual species and/or in the initial growth stage and there are almost no studies with perennial fruit crops in the production stage. Thus, this study aimed to evaluate the production components and post-harvest quality of 'Paluma' guava irrigated with water of increasing salinity in soil fertilized with N. The experiment was carried out for two years in drainage lysimeters in an experimental area of the Federal University of Campina Grande (UFCG), Pombal, PB, Brazil. The experimental design was in randomized blocks, in 5 x 4 factorial scheme, with of five levels of water salinity-ECw (NaCl) (0.3, 1.1, 1.9, 2.7 and 3.5 dS m-1) and four N doses (ureia) (70, 100, 130 and 160% of the recommended dose-541.1 mg of N dm-3 of soil per year), with three replicates. Number of fruits, mean fruit weight, production per plant, polar and equatorial diameters of fruit and contents of soluble solids and ascorbic acid (vitamin C) decreased linearly with the increase in irrigation water salinity from 0.3 dS m-1. The interaction between water salinity and N doses and the isolated action of N did not interfere statistically with the studied variables.

The low availability of water associated with high salt concentrations in irrigation water has become one of the leading challenges for agricultural production in the semiarid region of Northeastern Brazil. Thus, the study of strategies to enable the use of saline water in agriculture is essential. From this perspective, this study aimed to evaluate alterations in gas exchange, chloroplast pigments, and cell damage in soursop (Anonna muricata L.) irrigated with saline water and under exogenous application of hydrogen peroxide (H2O2) in the post-grafting phase. A study was conducted in Campina Grande, PB, under greenhouse conditions. The treatments were distributed in a randomized block design, in a 4 × 2 factorial arrangement, consisting of four levels of electrical conductivity of water (ECw; 1.6; 2.4; 3.2 and 4.0 dS m-1) and two concentrations of H2O2 (0 and 20 µM) with four replications. Irrigation water salinity from 1.6 dS m-1 caused changes in the stomatal conductance, respiration, and internal CO2 concentration of soursop plants. A 20 µM concentration of H2O2 reduced the effects of salinity on transpiration and CO2 assimilation values, in addition to promoting the biosynthesis of photosynthetic pigments and reducing cell damage in soursop plants, at 150 days after transplantation. The exogenous application of 20 µM H2O2 reduced the deleterious effects of salinity on the stem diameter of both rootstock and scion in soursop plants irrigated with ECw of 1.6 dS m-1. The exogenous application of 20 µM H2O2 was not efficient in mitigating the damage caused by salinity on the stem diameter of the soursop at grafting point.

The experiment was carried out in the greenhouse of the DEAg/UFCG, Campina Grande (PB), Brazil, to evaluate the growth and development of the bell pepper subjected to fertilization with biochar and nitrogen. The experiment was conducted in pots under greenhouse conditions. Treatments were arranged in a completely randomized design, in 4 × 4 factorial scheme, relative to four doses of biochar (0; 7; 14 and 21 m 3 •ha −1) and four doses of nitrogen (0; 40; 80 and 120 kg•ha −1), with three replicates. Considering the analysis of growth of bell pepper plants during the first 45 DAS, is recommended the average dose of biochar of 19 m 3 •ha −1 on vegetable behavior. Under the conditions of the experiment, nitrogen favored only the absolute growth rate of plant height and the stem diameter.

Potassium fertilization is one of the main techniques that has been studied to mitigateeffects of salt stress in plants, probably because potassium reduces the toxic effect of sodium by competitive inhibition and provides greater tolerance to genotypes of plants to salinity. Hence, this study aimed to evaluate the effect of different salinities of irrigation water in the formation of phytomass and quality of rootstocks of guava cv. Paluma, fertilized with increasing doses of potassium, in an experiment conducted using eutrophic Fluvic Neosol with sandy loam texture under greenhouse conditions, in the municipality of Pombal-PB, Brazil. The experimental design was randomized blocks in 5 × 4 factorial scheme, and the treatments resulted from the combination of five levels of irrigation water electrical conductivity (ECw = 0.3; 1.1; 1.9; 2.7 and 3.5 dS m-1) and four K doses (70, 100, 130 and 160% of K), in which the dose of 100% K corresponded to 726 mg of K dm-3 of substrate, with four replicates and two plants evaluated in each plot. Irrigation with water salinity from 0.3 dS m-1 compromises the total dry matter accumulation and the Dickson quality index of guava rootstocks cv. Paluma at 225 days after emergence (DAE), independent of potassium fertilization. Fertilization with different potassium doses did not promote differences in phytomasses and quality of rootstocks. There was no significant effect of interaction (salt × doses of K) on the studied variables.

Due to the reduced availability of good-quality water in the semi-arid region of Northeast Brazil, the utilization of saline waters in irrigation became an alternative for the expansion of agriculture in this region. Thus, it is necessary to develop techniques which can make viable the use of these waters in agriculture. Given the above, this study aimed to evaluate the morphophysiology of 'FAGA 11' cashew rootstock subjected to different levels of irrigation water salinity and exogenous proline application through the leaves. The experiment was carried out in a greenhouse of the Federal University of Campina Grande, at the Center of Sciences and Agri-Food Technology, Campus of Pombal, PB, Brazil, in a randomized block design, in 5 × 4 factorial scheme, with three replicates and two plants per plot. Treatments consisted of different levels of irrigation water electrical conductivity-ECw (0.3; 1.0; 1.7; 2.4 and 3.1 dS m -1 ) combined with proline concentrations applied through the leaves-PC (0; 4; 8 and 12 mM). Irrigations with water up to ECw of 1.37 dS m -1 may be used as it causes an acceptable 10% reduction in the variables of morphology of cashew FAGA 11 seedlings. The proline concentrations tested, with the exception of the Dickson's quality index of seedlings, did not attenuate the deleterious effects of irrigation water salinity on the cashew FAGA 11 rootstock seedlings.