BACKGROUND Saharan dryland systems in southern Tunisia are characterized by severe environmental constraints, including saline and waterlogged soils due to poor drainage and compacted textures. Agroecological practices such as intercropping and crop rotation offer sustainable alternatives to intensive monoculture for improving soil health and productivity. This study, conducted in southern Tunisia, evaluated the agroecological performance of different quinoa genotypes under varying planting densities, comparing monocropping, intercropping with oat, and rotation with traditional cereals such as wheat and oat. Seed rate (sowing density) significantly influenced growth, yield, and seed quality.RESULTS A 6 kg ha-1 seed rate produced the highest stem diameter, plant height, and biomass. A 12 kg ha-1 seed rate reduced growth and yield, with harvest index (HI) and seed yield declining by up to 76%, depending on genotype. Saponin content increased by up to 25% with a high seed rate, whereas protein content decreased. Quinoa-oat intercropping enhanced plant height, stem diameter, and dry weight, but reduced quinoa HI by up to 53%. In contrast, oat HI, seed yield, and thousand-kernel weight (TKW) increased under the intercropping system. Land equivalent ratio values ranged from 1.5 to 2.14, indicating improved system productivity, whereas competitive ratio (CRq) values confirmed that quinoa was less competitive than oat. Rotation with quinoa increased oat harvest index by 95% but reduced wheat harvest index by 22%. Both intercropping and rotation improved soil organic matter, nitrogen, and phosphorus availability while reducing salinity, enhancing soil fertility.CONCLUSION These results highlight the potential of quinoa-based cropping systems for sustainable production and soil management in arid and saline environments.