ABSTRACT 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.

ABSTRACT Eggplant is a vegetable considered as moderately sensitive to salinity, and its production is affected by water deficit in the soil, mainly in the reproductive phase of the crop. The objective of this study was to evaluate the use of irrigation with brackish water using continuous drip and pulse in production, water consumption, water use efficiency, and soil salinization. The experimental design was in randomized blocks, in a 4 × 4 factorial scheme, with five replicates, totaling 80 plots. The treatments consisted of four forms of water application, continuous drip, and pulse throughout the cycle; continuous drip in the vegetative phase and pulse in the reproductive phase, and pulse in the vegetative phase and drip in the reproductive phase and four levels of irrigation water salinity - ECw (0.3; 1.5; 3.0; 4.5 dS m−1). The inversion of irrigation treatments occurred 65 days after transplanting. Increase in water salinity from 0.3 to 4.5 dS m−1, the total production (-11.96%), fruit length (-5.05%), and water use efficiency (-7.01%) reduced while there was no significant effect for the forms of water application and interaction between the studied factors. Pulse irrigation provided greater water savings and resulted in higher electrical conductivity in the soil saturation extract. The efficiency of water use did not show statistical difference when continuous drip or pulse irrigation was used throughout the cycle.

ABSTRACT Water scarcity is one of the main problems in the Semiarid region of Brazil, which can be mitigated by water resource management strategies. The objective of this work was to classify waters of a watershed in the Semiarid region of Brazil and select the water attributes that most affect the quality of waters used for irrigation (QWI), using multivariate statistics. The study area was the Riacho da Bica watershed, which is between the municipalities of Portalegre and Viçosa, Rio Grande do Norte, Brazil. The QWI was determined using water samples from 15 collections carried out from 2016 to 2018, in five specific points of the watershed, starting in the spring and following the water course. The water attributes evaluated were: electrical conductivity (EC), potential hydrogen (pH), and sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), carbonate (CO32-), chloride (Cl-), and bicarbonate (HCO3-) contents. The water quality data were subjected to multivariate statistics through factorial analysis (FA) and principal component analysis (PCA). The application of multivariate statistics through FA-PCA generated four principal components. The attributes that most explained the QWI variation were potassium, calcium, and pH for Factor 01, and sodium and RAS for Factor 02. The watershed waters were classified as low risk of salinity and medium risk of sodicity (C1S2) for irrigation purposes.

ABSTRACT The use of organo-mineral fertilizer is an alternative measure to mitigate salt stress in semiarid regions. Thus, the objective of this work was to evaluate the physiological indexes of peanut crops under irrigations with fresh and brackish waters and applications of organo-mineral fertilizers. The experiment was conducted from June to September, 2019, at the Universidade da Integração Internacional da Lusofonia Afro-Brasileira (UNILAB), in Redenção, state of Ceará, Brazil, using a completely randomized experimental design in a 5 × 2 factorial arrangement, with four replications. The treatments consisted of five soil fertilizers (F1= 100% NPK mineral fertilizer at the recommended rate; F2= 100% bovine manure-based biofertilizer; F3= 100% plant ash; F4= 50% mineral fertilizer and 50% bovine manure-based biofertilizer; and F5= 50% mineral fertilizer and 50% plant ash); and two salinity levels (electrical conductivities) of the irrigation water (1.0 and 5.0 dS m-1). Photosynthetic rate, transpiration, stomatal conductance, leaf temperature, internal CO2 concentration, water use efficiency, and chlorophyll index of the plants were evaluated at 40 and 54 days after sowing (DAS). Plants irrigated with fresh water presented higher stomatal conductance, photosynthetic rate, and transpiration, regardless of the fertilizer used. The use of 100% bovine manure-based biofertilizer resulted in decreases in salt stress and increases in water use efficiency at 40 DAS, and decreases in leaf temperature and increases in relative chlorophyll content at 54 DAS.

ABSTRACT Cactus seeds in seasonal dry tropical forests are subject to several stressors, such as salt stress which limits imbibition and therefore germination. Thus, this study aimed to compare germination performance of Cereus jamacaru subsp. jamacaru and Pilosocereus pachycladus subsp. pernambucoensis seeds under salinity conditions. To this end, NaCl and KCl solutions were used in the following osmotic potentials: 0.0 (control),-0.2,-0.4,-0.6,-0.8,-1.0, and-1.2 MPa. Seeds were placed to germinate at 25 °C and 12-hour photoperiod. The number of germinated seeds was counted daily for 21 days after root protrusion. The variables analyzed were: water content, germination, normal seedlings, germination speed index, and average germination time. The experimental design was completely randomized, following a 2 × 7 factorial scheme (species × osmotic potential) for each saline source. Water restriction and ionic effect caused by salts favored seed germination and vigor in both species at-0.2 and-0.4 MPa. However, from-0.8 MPa onwards, germination decreased significantly for both salts. Seeds of C. jamacaru subsp. jamacaru and P. pachycladus subsp. pernambucoensis were tolerant to salt stress since they germinated up to-0.8 MPa (NaCl) and-1.2 MPa (KCl). The latter occurred only for P. pachycladus subsp. pernambucoensis.

ABSTRACT In semiarid regions with greater climatic variability, including prolonged droughts and delayed rainy seasons, supplemental irrigation is critical to ensuring yields of forage cactus pear. The objective was to evaluate root distribution and nutrient concentration and accumulation in ‘Gigante’ forage cactus pear subjected to different irrigation regimes. Seven irrigation regimes were tested: no irrigation (rainfed); five liters of medium-salinity water, with an electrical conductivity (EC) of 0.75 dS m−1, applied per linear meter every 15 days; 7% reference evapotranspiration (ETo) with a 15-d irrigation interval (II); 15% ETo with a 7-d II; 33% ETo with a 3-d II; 50% ETo with a 2-d II; and 100% ETo, irrigated daily - high-salinity water, EC of 3.6 dS m−1, was used in the last five treatments. The treatments were laid out in a randomized block design with four replicates. Roots developed best in plants irrigated at 50% ETo with a 7-d II. Applying high-salinity water at 15% ETo with a 7-d irrigation interval promotes higher concentrations of P, Ca, Mg and S in cladodes of cactus pear. Applying high-salinity water at 33% ETo with a 3-d II promotes higher uptake/accumulation of P, Ca, Mg, S and Zn in cladodes of ‘Gigante’ forage cactus pear.

ABSTRACT Macrophomina (Botryosphaeriaceae) is one of the main genera of soilborne phytopathogenic fungi, which causes root and seed rot in more than 800 host plants worldwide. Recent phylogenetic studies identified the species M. phaseolina and M. pseudophaseolina in Trianthema portulacastrum and Boerhavia diffusa in melon and watermelon production areas in northeastern Brazil. Therefore, the objective of this study was: i) to verify the effect of temperature and salinity on the mycelial growth of M. phaseolina, M. pseudophaseolina and M. euphorbiicola, ii) to assess their pathogenicity on melon and watermelon seedlings, and iii) to determine their sensitivity to the fungicide carbendazim. The optimal temperature for mycelial growth rate (MGR) for Macrophomina spp. ranged from 27.18 ºC (CMM4771 – M. pseudophaseolina) to 31.80 ºC (CMM4763 – M. phaseolina). For the effect of salinity on mycelial growth of Macrophomina isolates, the EC50 ranged from 103.76 (CMM4868 – M. euphorbiicola) to 315.25 mM (CMM4801 – M. pseudophaseolina). The pathogenicity test demonstrated that M. phaseolina, M. pseudophaseolina and M. euphorbiicola are pathogenic on melon with M. phaseolina exhibiting a higher level of virulence. Macrophomina euphorbiicola isolates did not cause disease in watermelon. The most sensitive isolates to the fungicide carbendazim were CMM4868, CMM4867 (M. euphorbiicola) and CMM1531 (M. phaseolina) with EC50 of 0.003, 0.012 and 0.012 mg.L-1 a.i., respectively. All Macrophomina spp. used in these experiments were pathogenic to the tested melon and watermelon cultivars with the exception of the M. euphorbiicola isolate that did not cause damage to watermelon.

ABSTRACT Plant parasitic nematodes cause severe agricultural damage in Northeast Brazil. Additionally, soil salinization, especially in the semiarid region of the Northeast, is another factor that limits crop yield. The study evaluated the motility of Meloidogyne enterolobii and Pratylenchus coffeae, and the vertical migration of P. coffeae under saline conditions. Motility was assessed by submitting juveniles of the second stage of M. enterolobii and juveniles and adults of P. coffeae to saline solutions of NaCl, CaCl2, and MgCl2 at concentrations of 0.00, 0.25, 0.50, 0.75, and 1.00 M, and in a mixed solution (combination of the three salts in a 7:2:1 ratio) at 2, 4, 6, and 8 days of exposure. The migration of P. coffeae was studied in segmented columns of 10 cm in length and 4.40 cm in internal diameter, filled with saline soil (mixture of NaCl, CaCl2, and MgCl2) and non-saline, whose evaluations were carried out at 2, 4, and 6 days after soil infestation. The motility and number of active juveniles of both nematodes reduced with increasing saline concentration. From 0.50 M, M. enterolobii activity was not observed in any of the exposure periods to NaCl and CaCl2. The increase in the concentrations of NaCl, CaCl2, and MgCl2 exponentially reduced the number of active P. coffeae, decreasing its activity from 0.75 M. The vertical migration of P. coffeae in the soil was negatively affected by salinity, presenting a more uniform distribution in the non-saline soil.

ABSTRACT Yellow passion fruit is a fruit species widely cultivated throughout the Brazilian semi-arid territory, but its yield is affected by the quality of the waters of this region. In this context, the objective was to evaluate the gas exchange and production of passion fruit cv. BRS Rubi do Cerrado irrigated with waters of different cationic natures. The study was conducted in drainage lysimeters under greenhouse conditions in Campina Grande, PB, Brazil, in a randomized block design, and the treatments were eight cationic natures of irrigation water (S1 - Control; S2 - Na+; S3 - Ca2+; S4 - Mg2+; S5 - Na+ + Ca2+; S6 - Na+ + Mg2+; S7 - Ca2+ + Mg2+ and S8 - Na+ + Ca2+ + Mg2+) with three replicates. Plants in the control treatment were irrigated with water of low electrical conductivity (ECw = 0.4 dS m-1), while those of the other treatments were irrigated using water with ECw of 3.5 dS m-1. The treatments Na+ + Ca2+, Na+ + Mg2+ and Ca2+ + Mg2+ were prepared in the equivalent ratio of 1:1, and Na++Ca2++Mg2+ in the ratio 7:2:1, respectively. Water salinity of 3.5 dS m-1 reduced gas exchange, and stomatal conductance and transpiration were the most sensitive variables of passion fruit. The number of fruits of passion fruit cv. BRS Rubi do Cerrado decreased with water salinity, regardless of the cationic nature. The waters of calcic and calcic+magnesian nature caused the greatest deleterious effects on the production variables of passion fruit, at 259 days after transplanting.

ABSTRACT The Brazilian Northeast region suffers from some abiotic stresses that are responsible for the loss of agricultural production, such as long drought periods and high evapotranspiration, associated with the quality of the water, which induces the use of saline water as an alternative for the expansion of irrigated areas, and silicate fertilization contributes to reduce the effects of salinity under the Northeastern semi -arid conditions. The objective of this study was to evaluate the osmotic potential and physiological indices of yellow passion fruit seedlings under irrigation water salinity and silicate fertilization. The experiment was carried out under greenhouse conditions at the Federal University of Campina Grande, Pombal -PB, Brazil, in a randomized block design in a 5 x 5 factorial scheme, relative to five levels of electrical conductivity of irrigation water - ECw (0.3; 1.0; 1.7; 2.4 and 3.1 dS m-1) and five doses of silicate fertilization (0; 25; 50; 75 and 100 g silicon per plant) in four replicates and two plants per plot. The application of 50, 75 and 100 g silicon per plant reduced the osmotic potential in the leaf tissues of ‘Gigante Amarelo’ passion fruit plants. Water salinity lower than 1.3 dS m-1 resulted in an increase in chlorophyll b content; increase in carotenoid content was observed in plants subjected to silicon doses of 25 and 100 g per plant. Salinity levels above 1.1 dS m-1 compromised the performance of photosystem II of passion fruit plants when subjected to silicon doses. | RESUMO O Nordeste brasileiro sofre com alguns estresses abióticos que são responsáveis pela perda de produção agrícola, como os longos períodos de estiagem e elevada evapotranspiração, associado à qualidade das águas que induz ao uso de águas salinas como alternativa para expansão das áreas irrigadas, com isto a adubação silicatada contribui para redução dos efeitos da salinidade nas condições de semiárido nordestino. Objetivou-se avaliar o potencial osmótico e os índices fisiológicos de mudas de maracujazeiro amarelo sob salinidade da água de irrigação e adubação silicatada. O experimento foi desenvolvido em condições de casa de vegetação na Universidade Federal de Campina Grande, Pombal-PB, em delineamento de blocos ao acaso em esquema fatorial 5 x 5, relativo a cinco níveis de condutividade elétrica da água de irrigação - CEa (0,3; 1,0; 1,7; 2,4 e 3,1 dS m-1) e cinco doses de adubação silicatada (0; 25; 50; 75 e 100 g de silício por planta) em quatro repetições e duas plantas por parcela. A aplicação de 50, 75 e 100 g por planta de silício reduziu o potencial osmótico nos tecidos foliares das plantas de maracujazeiro ‘Gigante Amarelo’. A salinidade da água menor que 1,3 dS m-1 resultou em incremento no conteúdo de clorofila b; aumento nos teores de carotenoides foi verificado nas plantas submetidas as doses de 25 e 100 g de silício. Níveis salinos acima de 1,1 dS m-1 comprometeram o desempenho do fotossistema II das plantas de maracujazeiro quando submetidas as doses de silício.