Growth and yield responses of maize, beetroot, and quinoa to salinity and straw mulching

Vietnam’s Mekong River Delta (MRD), where rice is the dominant crop, is increasingly impacted by salinity intrusion, highlighting the need for alternative cropping options. This study evaluated the growth and yield performance of quinoa, beetroot, and maize under three irrigation salinity levels (0, 2 and 4 g/L), with and without rice straw mulch (7 t/ha), in greenhouse conditions representative of the MRD dry season. Agronomic traits, physiological parameters, and changes in soil, including electrical conductivity (ECe), soluble sodium (Sol-Na⁺), and exchangeable sodium percentage (ESP), were assessed. Results showed that quinoa demonstrated the greatest salinity tolerance, maintaining stable growth and yield under 4 g/L saline irrigation and soil ECe exceeding 15 dS/m. Beetroot’s yield was not significantly different under 2 g/L saline irrigation with straw mulching. Maize was highly sensitive to salinity and environmental stress, failing to complete its growth cycle under high heat and humidity, even in non-saline conditions. Across treatments, rice straw mulching significantly reduced soil ECe, Sol-Na⁺, and ESP, and improved crop performance under saline irrigation. Overall, quinoa and beetroot, especially when combined with mulching, offer promising alternatives for dry-season cropping in saline-prone areas of the MRD. In contrast, maize cultivation requires improved soil and environmental management under such conditions.