Irrigation Scheduling and Organic Manure Application for Quinoa Production Under Saline Water in the Brazilian Semiarid

Freshwater scarcity and soil salinization are major constraints to agricultural production in semiarid regions, requiring irrigation strategies that enable the use of saline water while maintaining crop performance. This study evaluated the interactive effects of irrigation scheduling and organic manure application on soil salinity, physiological responses, biomass accumulation, and quinoa (Chenopodium quinoa Willd.) production under saline irrigation in the Brazilian semiarid region. A field experiment was conducted using three irrigation shifts-(IS) (48, 72, and 120 h) and four organic matter–cattle manure (OM) rates (0, 15, 30, and 60 t ha−1), arranged in a 3 × 4 factorial scheme with four replications. Plant growth, leaf area index (LAI), stomatal conductance (gs), transpiration (E), fresh and dry biomass, harvest index (HI), and soil electrical conductivity (EC) were evaluated. Quinoa responses to organic manure depended on irrigation scheduling. The 120 h interval promoted greater phytomass accumulation, while intermediate manure rates (15–30 t ha−1) improved plant growth and leaf area index (LAI) under longer irrigation intervals. The treatments did not result in soil salinization at the end of the crop cycle. These findings indicate that combining irrigation scheduling with organic manure management can support quinoa production under saline irrigation in semiarid environments.