Production and water relations of peanut irrigated with brackish water under pulse and continuous drip /Produção e relações hídricas do amendoim irrigado com águas salobras sob gotejamento pulso e contínuo

HIGHLIGHTS: Under brackish water irrigation, pulse drip irrigation favored water use efficiency and grain production of peanut. The form of drip irrigation - continuous or pulse - did not influence the osmotic adjustment of the peanut plants. Pulse drip irrigation did not influence transpiration, but the increasing salinity in the water resulted in its lower rate. An efficient water management in irrigation is essential to optimize water efficiency, especially when using brackish water. Thus, the present study was carried out aiming to analyze gas exchanges, pod production, and the water status of peanut plants under increasing levels of salinity (electrical conductivity of 0.12, 1.6, 2.8, 4.0, and 5.2 dS [m.sup.-1]) and the application of the irrigation depth via pulses. A randomized block design in a 5 * 2 factorial scheme was used with four replications, adding up to forty experimental units. The experiment was carried out in drainage lysimeters, at the Federal Rural University of Pernambuco, in open fields from September to November 2019. It was concluded that the use of pulse drip irrigation did not mitigate the deleterious effect of salinity but promoted higher grain and pod production compared to continuous drip irrigation. It was also found that the use of brackish water via pulse drip irrigation promotes greater water use efficiency compared to continuous drip irrigation, and that the increase in the electrical conductivity of the water reduced the water, pressure, and osmotic potentials, along with the osmotic adjustment. Key words: Arachis hypogaea, salt tolerance, salinity stress Um eficiente manejo da água na irrigação é fundamental para a otimização da eficiência hídrica, especialmente quando se utiliza águas salobras. Neste sentido, o presente estudo foi desenvolvido com o objetivo de avaliar as trocas gasosas, produção de vagens e grãos e o estado hídrico de plantas de amendoim sob níveis crescentes de salinidade (condutividade elétrica de 0,12; 1,6; 2,8; 4,0 e 5,2 dS [m.sup.-1]) e a aplicação da lâmina de irrigação via pulsos. O delineamento experimental adotado foi em blocos ao acaso, analisado em esquema fatorial 5 * 2 com quatro repetições, totalizando quarenta unidades experimentais. O experimento foi realizado em lisímetros de drenagem, na Universidade Federal Rural de Pernambuco, em campo aberto, entre os meses de setembro a novembro de 2019. O uso de pulsos de irrigação não mitigou o efeito deletério da salinidade, mas proporcionou