Silicon is known to be an effective salt stress attenuator for crops, and evaluating its application effectiveness in combination with other salt stress attenuators is essential for crops and soils. This work aimed to assess whether applying organic matter (OM) and Trichoderma (T) potentiates silicon (Si) in mitigating soil salinization and promoting quinoa growth under salt stress. Quinoa plants were grown in pots under saline irrigation (3.12 dS m⁻¹) and subjected to the following treatments: quinoa only; quinoa + Si; quinoa + Si + OM; quinoa + Si + T; and quinoa + Si + OM + T, at two levels of soil moisture—30 and 80% of the available water content (AWC). Sixty days after transplanting, soil and quinoa plants were collected from the pots. At 80% AWC, Si + OM and Si + OM + T promoted the highest fresh mass for quinoa—301.54 and 247.26 g, respectively. Si + OM + T significantly mitigated saline parameters (EC = 9.82 dS m⁻¹; ESP = 32.27%). Si combined with OM and T was the most effective way to attenuate salt stress in quinoa and soil salinization and promote a more sustainable way to manage saline irrigation in semiarid regions.

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.