Physiological responses and antioxidant enzyme activities of chickpeas and barley under row intercropping with foliar application of plant growth regulators in saline soil conditions

Soil salinity, a major environmental stressor, impairs agricultural productivity across over one billion hectares globally. This study evaluated the effects of row intercropping of chickpeas (Cicer arietinum L.) and barley (Hordeum vulgare L.) with foliar application of plant growth regulators (PGRs) on nutrient uptake, physiological responses, and yield in saline soils (electrical conductivity 4.5 dS m−1). A split-plot experiment with three replications was conducted in Fasa, Iran, during 2021–2022, using a randomized complete block design. Planting arrangements included sole cropping and intercropping ratios of 75% chickpea + 25% barley, 50% chickpea + 50% barley, and 25% chickpea + 75% barley, with foliar treatments of distilled water (control), 1 mM salicylic acid (SA), 100 μM jasmonic acid (JA), and 1 μM brassinosteroids (BR) applied at growth stages. Salicylic acid and JA reduced leaf sodium by 3.0–3.8% in chickpeas and 2.3–3.5% in barley, while increasing nitrogen by 7.5–11.3%, phosphorus by 5.0–7.9%, and potassium by 4.8–12.4% compared to controls. The 50% chickpea + 50% barley treatment enhanced phosphorus uptake by 8.0% in chickpeas and 7.9% in barley, decreased malondialdehyde by 5.8% in chickpeas and 2.7% in barley, and improved relative water content by 6.0% in chickpeas and 2.8% in barley. In 2022, this treatment with SA increased chickpea seed yield by 12.5% to 916 kg ha−1, and with JA, boosted barley biological yield by 21.2% to 5365 kg ha−1 compared to sole cropping. This approach enhances crop resilience and productivity, offering a sustainable solution for saline agriculture.