Proper management of brackish water can increase plant production in the Brazilian semi-arid region. The objective of this study was to evaluate the production performance and water use efficiency of two peanut genotypes irrigated with brackish water during the reproductive stage, in soil with and without soil cover. The study was conducted in a greenhouse. The experimental design used was randomized blocks, with four replicates, in a 2 x 2 x 2 factorial scheme (two electrical conductivities of irrigation water -ECw 0.9 and 5.0 dS m -1 , two peanut genotypes -AC 130 and cv. BR1, and the presence or absence of soil cover). At 72 days after sowing, harvest was performed and the following variables were evaluated: number of marketable pods, number of non-marketable pods, pod mass, diameter and length, production and water use efficiency. Salinity impacted production more than the water use efficiency in the two peanut genotypes, with the relative reduction in production being higher in cv. BR-1. Soil cover with dead plant material mitigated the effects of salinity on production and increased water use efficiency, only in genotype AC 130.

Hydrogels favor moisture retention in the substrate and can attenuate the effects of salt stress on the production of potted plants. In this context, this research sought to evaluate the use of hydrogel to mitigate the damage caused by the salinity of irrigation water on the emergence, growth, and thermal index of Tagetes patula L. seedlings. The research was carried out in a greenhouse, in September 2020, in the municipality of Fortaleza, Ceará State, Brazil. The design used was randomized blocks in a split plot. The plots corresponded to seven levels of electrical conductivity of the irrigation water - ECw (0.5, 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 dS m-1) and the subplots corresponded to four hydrogel concentrations (0, 1.0, 2.0, and 3.0 g L-1), with five replicates and each subplot consisted of 27 seeds. The application of 3.0 g hydrogel L-1 of substrate favored the production of leaves and reduced the thermal index in plants associated with the increase in the salinity of the substrate up to 6.0 dS m-1. The use of 3.0 g L-1 hydrogel increases seedling height, leaf dry mass, and total dry mass compared to treatments without water-retaining polymer, even at moderate (2.0 to 3.0 dS m-1) and high (4.0 to 6.0 dS m-1) salinity levels, thus indicating a possible effect of mitigation of damage caused by the salinity of the irrigation water. However, the intensity of this mitigating effect decreases at higher levels of salt stress.

INFLUÊNCIA DA IRRIGAÇÃO SUPLEMENTAR COM ÁGUAS RESIDUÁRIAS SOBRE AS TROCAS GASOSAS FOLIARES DO ALGODOEIRO   ADRIANA CRUZ DE OLIVEIRA1; ANTONIO FLAVIO BATISTA DE ARAUJO2; CLAUDIVAN FEITOSA DE LACERDA3; JUVENALDO FLORENTINO CANJÁ4; LUCIANA LUZIA PINHO5 E NAARA IORRANA GOMES SOUSA6     1 Mestranda no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: drica_fj@hotmail.com.br 2 Doutorando no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: antonioflaviobatistadearaujo@gmail.com 3 Professor Titular do Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: cfeitosa@ufc.br 4Mestrando no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: batchijuve@gmail.com 5 Mestranda no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: englucianaufc@gmail.com 6 Mestranda no Programa de Pós-Graduação em Engenharia Agrícola, Departamento de Engenharia Agrícola, Universidade Federal do Ceará-UFC, Av. Mister Hull, s/n -Pici, Centro de Ciências Agrárias, Bloco 804, CEP: 60455-760, Fortaleza-CE, Brasil. E-mail: naara_iorrana@hotmail.com     1 RESUMO   O uso de águas residuárias na irrigação tem crescido como suplementação para driblar a escassez hídrica. Contudo, pouco se sabe sobre as respostas das culturas sobre sua aplicação. Assim, objetivou-se avaliar os impactos da irrigação suplementar com águas residuárias tratadas sobre as trocas gasosas do algodoeiro (Gossypium hirsutum L), simulando-se cenários hídricos considerados normais, seca e seca severa, na presença e ausência de NPK. O experimento foi conduzido no município de Russas – CE, em área vizinha à lagoa de estabilização da CAGECE – Companhia de Água e Esgoto do Estado do Ceará, em DBC, no esquema de parcelas subsubdivididas, com quatro blocos. As parcelas foram cenários hídricos (normal, seca e seca severa); a subparcela foi a suplementação ou não com água residuária tratada nos veranicos simulados; a subsubparcela foi a aplicação ou não de NPK. A cultivar utilizada foi BR 433. Aos 25 dias após a semeadura foram analisadas fotossíntese, transpiração, concentração interna de CO2 e temperatura foliar. Os cenários de seca e seca severa apresentaram pequeno impacto sobre as trocas gasosas foliares do algodoeiro. Entretanto, a irrigação suplementar reduziu a temperatura foliar e atenuou os efeitos do cenário de seca sobre a fotossíntese, independente da aplicação ou não de NPK.   Palavras-chave: Gossypium hirsutum L, Reúso de água, Seca.         OLIVEIRA, A. C. de; ARAUJO, A. F. B. de; LACERDA, C. F. de; CANJÁ, J. F.; PINHO, L. L.; SOUSA, N. I. G. INFLUENCE OF SUPPLEMENTAL IRRIGATION WITH WASTEWATER ON COTTON LEAF GAS EXCHANGE     2 ABSTRACT   The use of wastewater in irrigation has grown as a supplement to circumvent water scarcity. However, little is known about the responses of cultures to its application. Thus, the objective was to evaluate the impacts of supplementary irrigation with treated wastewater on gas exchange of cotton (Gossypium hirsutum L), simulating water scenarios considered normal, drought and severe drought, in the presence and absence of NPK. The experiment was conducted in the municipality of Russas - CE, in an area next to the stabilization pond of CAGECE - Companhia de Agua e Esgoto do Estado do Ceará, in DBC, in the subdivided plot scheme, with four blocks. The plots were water scenarios (normal, drought and severe drought); the subplot was supplemented or not with wastewater treated in the simulated summer days; the sub-installment was the application or not of NPK. The cultivar used was BR 433. At 25 days after sowing, photosynthesis, transpiration, internal CO2 concentration and leaf temperature were analyzed. The drought and severe drought scenarios had little impact on the cotton leaf gas exchange. However, supplementary irrigation reduced leaf temperature and attenuated the effects of drought scenario on photosynthesis, whether or not NPK was applied.   Keywords: Gossypium hirsutum L, Water reuse, Drought.