Management for grain sorghum cultivation under saline water irrigation /Manejo da irrigação para o cultivo de sorgo granífero com água salina

HIGHLIGHTS: Application of leaching fractions promotes better distribution of electrical conductivity in soil. Leaching fractions of up 15% with saline water increase production of sorghum grains. Applying leaching fractions up to 12% increases water use efficiency in sorghum. In order to obtain an efficient cultivation of grain sorghum in production systems that use saline water, an adequate management becomes necessary for maximizing its production. The present study aimed to evaluate the effect of the application of leaching fractions in the saline water irrigation management on the production of sorghum varieties and on the distribution of water and salts in the soil profile, under semiarid conditions. The study was carried out in the municipality of Petrolina, semiarid region of Brazil. The experimental design was randomized blocks, with four replicates, in split-split plots; four leaching fractions (LF): 0, 5, 10, and 15% with saline water from artesian well in the plots, three varieties of grain sorghum: 1011-IPA, 2502-IPA and Ponta Negra in the subplots, and two crop cycles (1st and 2nd cut) in the sub-subplots. The evaluated variables were distribution of water and salts in the soil profile, biometric variables, fresh biomass, dry biomass, and grain yield. Application of leaching fractions of up 15% in saline water irrigation promotes better distribution of salts in the soil profile, with increments of up to 60% in the grain yield of the sorghum varieties evaluated. The production of the varieties 1011-IPA and Ponta Negra is a feasible alternative in systems irrigated with saline water with average electrical conductivity of 4.19 dS [m.sup.-1], in Ultisol, under semiarid conditions. Key words: Sorghum bicolor (L.) Moench, leaching fraction, salt distribution Para se obter um cultivo eficiente de sorgo granífero em sistemas de produção que utilizam água salina, torna-se necessário um manejo hídrico adequado para maximizar sua produção. Com isto, o presente estudo teve como objetivo avaliar o efeito da aplicação de frações de lixiviação no manejo da irrigação com água salina na produção de variedades de sorgo granífero e na distribuição de água e sais no perfil do solo, em condições semiáridas. O estudo foi realizado no município de Petrolina, região semiárida do Brasil. Foi utilizado o delineamento experimental em blocos casualizados, com quatro repetições, em parcelas subdivididas; sendo as parcelas quatro frações de lixiviação (FL): 0; 5; 10 e 15