This research was carried out aiming at evaluating the effects of nitrate and ammonium ions on nutrient accumulation, biochemical components and yield of Italian zucchini (cv. Caserta) grown in a hydroponic system under salt stress conditions. The experiment was carried out in a greenhouse utilizing an experimental design in randomized blocks, arranged in a 2 x 5 factorial scheme, with 4 replications. The treatments consisted of two forms of nitrogen (nitrate - NO3- and ammonium - NH4+) and 5 electrical conductivity levels of irrigation water (ECw) (0.5, 2.0, 3.5, 5.0 and 6.5 dS m-1). The analysis of the results indicated that supply of N exclusively in NH4+ form promotes greater damage to the leaf membrane and reduction in accumulation of macronutrients and higher Na+/K+, Na+/Ca++ and Na+/Mg++ ratios in the shoots of zucchini plants. Electrical conductivity of irrigation water above 2.0 dS m-1 reduces the accumulation of nutrients in shoot and yield of Italian zucchini plant. The toxicity of NH4+ under Italian zucchini plants overlap the toxicity of the salinity, since its fertilization exclusively with this form of nitrogen inhibits its production, being the NO3- form the most suitable for the cultivation of the species.

Cowpea is an important source of protein, being the main subsistence crop in the northeast region of Brazil, where water restriction and salinity are limiting factors. Identification of saline stress tolerant varieties can aid crop expansion and improve crop yields. The objective was to study the tolerance of traditional varieties of cowpea to the salinity of irrigation water in the emergency and initial growth phase. The experiment was carried out in a greenhouse using a completely randomized design (DIC), in a 23 x 2 factorial scheme, composed of 23 cowpea varieties (Canapu Vermelho, Boquinha, Pingo de Ouro, Sempre Verde, Ceará, Baeta, Manteiga, Roxão, Costela de Vaca, Feijão Branco, Coruja, Rabo de Peba Branco, Sopinha, Canapu Branco, Lisão, Canapu Miúdo, Sempre Verde Ligeiro, Vagem Roxa, Ovo de Peru, Rabo de Peba Miúdo, Feijão Azul, Canário, and Paulistinha) and two levels of salinity of irrigation water (S1 = 0.5 and S2 = 5.5 dS m-1), with four repetitions of 50 seeds. The seedlings were evaluated for emergence, vigor, salinity tolerance index, and dissimilarity. Increased salinity of irrigation water reduced emergence, vigor and dry matter accumulation of cowpea varieties. The cowpea varieties ‘Lisão’, ‘Costela de Vaca’, ‘Canário’, ‘Feijão Branco’, ‘Ceará’, and ‘Boquinha’ are the most tolerant to salinity, while the varieties ‘Sempre Verde’ and ‘Manteiga’ are the most sensitive to salinity in the emergency and initial growth phase.

Water scarcity in Brazil’s semi-arid region necessitates the agricultural reuse of aquaculture effluents, although emitter clogging remains a challenge. This study evaluated clogging mitigation in drip irrigation systems using liquid anti-clogging fertilizer. The experiment employed a split–split–plot scheme with three water treatments (supply water, aquaculture effluent, and effluent with liquid fertilizer) and three emitter types (ST, SL, and GA), assessing performance over 360 h. A water quality analysis at 0, 160, and 360 h complemented hydraulic evaluations of the average flow rate variation and Christiansen uniformity coefficient measured every 40 h. Energy-dispersive X-ray spectroscopy, X-ray diffractometry, and scanning electron microscopy were used to characterize biofouling. The results showed that the liquid fertilizer mitigated the clogging by biofouling in the three types of emitters, but only the ST emitter presented acceptable hydraulic performance rates. There are relationships between the anti-clogging effect of the liquid fertilizer, the structural characteristics of the emitters, and the flow velocity inside the labyrinths. The SL dripper applying only aquaculture effluent presented the highest clogging rate due to biofouling. Agricultural reuse is a strategy for the rational use of water resources that is of great relevance for arid and semi-arid regions and can insert aquaculture into the circular economy.

Clogging is a major constraint to the agricultural reuse of produced water; however, ultra-low-frequency dynamic electronic pulses (EPs) can help control biofouling in drip emitters. This study aimed to evaluate the reduction in clogging in non-self-compensating emitters applying onshore oil-and-gas-produced water treated with EP. Three experimental benches were assembled using drip irrigation units supplied with different water sources: water supply (WS), produced water with EP (OPW + EP), and produced water without treatment (OPW). Hydraulic performance was monitored every 40 h for 400 h using average flow rate variation (AFVR), flow variation coefficient (FVC), and distribution uniformity (UD) indices. Data were analyzed using RT-1 analysis with Bonferroni post hoc tests. Results showed that the interaction between water sources and evaluation times significantly (p ≤ 0.01) affected the hydraulic indices. After 400 h, the indices ranked as UD and FVC: WS > OPW + EP > OPW, and AFVR: OPW + EP = WS > OPW. Although OPW presented a low risk of clogging, the application of EP mitigated the obstruction and maintained higher uniformity by reducing clogging. These findings demonstrate that ultra-low-frequency electronic pulses are an innovative anti-clogging technology and provide insights for the sustainable application of produced water.

Water scarcity and the search for alternative water reuse are challenges faced in the Brazilian semi-arid region. The objective of this study was to predict the risk of clogging of drippers based on water quality attributes and to analyze the effects of industrial residual water and supply water on their hydraulic performance. Two experimental benches were set up in a completely randomized design, in split-split plots, with three replicates. Plots contained the types of water (supply water and reverse osmosis reject), subplots contained the types of non-pressure-compensating drippers (NST - 1.6 L h^-1, NSL - 1.6 L h^-1 and NDT - 1.7 L h^-1) and sub-subplots contained the evaluation times of the distribution uniformity coefficient and relative flow rate (0, 20, 40, 60, 80, 100, 120, 140 and 160 hours). At times 0, 80 and 160 hours, the attributes pH, electrical conductivity, total suspended solids, total dissolved solids, calcium, magnesium, iron and manganese were characterized in both types of water. The data were subjected to descriptive analysis, ANOVA and Tukey test at 5% probability level. In residual water, the attributes that represented a risk of clogging for drippers were pH, electrical conductivity, magnesium and total dissolved solids, while in supply water only pH represented risk. The interaction between types of water and operating time significantly affected both hydraulic performance indicators, but there was no significant effect of the dripper type factor.