The canonical correlation is used to correlate groups of distinct variables. The objective of this study was to use canonical correlation analysis to evaluate the interaction between water quality attributes clogging-causing and the hydraulic performance of non-pressure compensating drippers operating with dilutions of aquaculture effluent in well water. The experiment was in a completely randomized design in a split-split-plot scheme with three replicates, with five dilutions in the plots (Dilution 1: 100% aquaculture effluent; Dilution 2: 75% aquaculture effluent + 25% well water; Dilution 3: 50% aquaculture effluent + 50% well water; Dilution 4: 25% aquaculture effluent + 75% well water; and Dilution 5: 100% well water), three emitters in the sub-plots (ST (1.6 L h^-1), SL (1.6 L h^-1) and NJ (1.7 L h^-1)), and three operating times in the sub-subplots (0, 80 and 160 hours, in which 0 hours operating time means the start of evaluations). The statistical analyses performed were correlation matrix and canonical analysis. The canonical correlation analysis indicated that when the concentrations of attributes increase, the hydraulic performance of the drippers decreases. The interaction of this group of attributes indicates that the clogging of drippers operating with the five dilutions of aquaculture effluent in well water occurs by the combined action of physical, chemical, and biological agents. The ST dripper was the least sensitive to the group of quality attributes of the dilutions, whereas the most sensitive was the SL dripper.

Cowpea (Vigna unguiculata) is a crop widely grown in semi-arid regions but faces challenges due to high salinity levels in irrigation water. Management strategies, such as hydrogen peroxide (H2O2) application, promise to mitigate salt stress. This research aimed to evaluate hydrogen peroxide as an attenuator of salt stress in cowpea. The experiment was performed in a randomized block design, in a 3 × 3 factorial scheme, with four replicates. The treatments consisted of three v alues of electrical conductivity of the irrigation water (0.5, 3.5, and 6.5 dS m-1) and three concentrations of H2O2 (0, 100, and 200 μM). Growth variables, number and weight of nodules, gas exchange, chlorophyll indices, chlorophyll a fluorescence, electrolyte leakage, and water relations were evaluated. The application of 200 μM of H2O2 is the most recommended to mitigate the effects of salt stress up to 3.5 dS m-1. Applying 200 μM of H2O2 mitigated these effects, improving the net CO2 assimilation rate, and cell integrity, resulting in higher biomass and development of cowpea plants. The use of H2O2 enables the development of management strategies aimed at optimizing cowpea growth and tolerance under salinity conditions, possibly by enhancing cellular integrity and mitigating oxidative stress.

Bell peppers (Capsicum annuum L.) are of great importance and have high productive potential in Brazil, especially in the Northeast region; however, their production is limited due to salinity problems in water and soil. The objective of this study was to evaluate sources and methods of calcium application for mitigating salt stress in bell pepper plants grown in a substrate-based hydroponic system. The experiment was conducted using a split-plot design in a 2 × 2 × 3 layout with four replicates, consisting of two application methods (substrate and spray), two ECiw levels (0.5 and 5.0 dS m⁻¹), and three calcium sources (no calcium—NCa; calcium nitrate—Ca(NO₃)₂; calcium complexed with amino acids—Ca-AA). Forty-two days after transplanting, gas exchange analysis, chlorophyll a, b, and total chlorophyll indices, chlorophyll fluorescence, fruit number and weight, and yield per plant were measured. Ca-AA showed higher photosystem II efficiency when applied via the substrate and higher stomatal conductance (28.10%), resulted in higher fruit yield compared to the other treatments, and contributed to a reduction in apical rot. Meanwhile, the application of Ca(NO₃)₂ improved electron transport in photosystem II by 5.46%, gas exchange, and increased chlorophyll b and total chlorophyll indices by 29.62% and 10.93%, respectively. It is concluded that the application of Ca sources, especially Ca-AA, has the potential to mitigate the effects of salt stress on bell pepper plants in a substrate-based hydroponic system, improving their photosynthetic and productive performance.