Role of (NH4) +, (NO3), K+ and (SO4) - to Tackle Salt Sensitivity of Allium Cepa L. under Saline Conditions

Abstract

Allium cepa L., an economically important bulbous crop, is a glycophytic plant species and is sensitive to mild concentrations of salt. A large area of Pakistan is affected by salinity, as it is in a semiarid and arid territory with a subtropical continental climate that is currently experiencing salinization. Therefore, this project was designed to explore the salinity tolerance in onions mediated by individual and combination of fertilizers (NH₄NO₃ and K₂SO₄) as source of (NH₄)⁺, (NO₃), K⁺ and (SO₄)^-  at two growth stages (vegetative, bulb maturation stage). For this purpose, three salt treatments (4.5, 8.5 and 12.5 dS m^-1 NaCl) were applied at vegetative and bulb maturation stages. The fertilizer treatments included T1) 250 mg/kg NH₄NO₃, T2) 250 mg/kg K₂SO₄, T3) 125mg/kg NH₄NO₃ + K₂SO₄, T4) 150 mg/kg NH₄NO₃ + 100 mg/kg K₂SO₄, T5) and 100 mg/kg NH₄NO₃ + 150 mg/kg K₂SO₄. It was observed that salinity affected onion’s growth and yield. Whereas combined and individual effect of fertilizers improved the growth and yield of onion by increasing the chlorophyll level, leaf and bulb relative water content, enzymatic antioxidant activities, proline and soluble sugar content. However, the combination of NH₄NO₃ +K₂SO₄ showed improvement in growth and osmolytes production even at 12.5 dS m^-1. Therefore, it was concluded that nitrogen fertilizer and combination of N+K can improve A. cepa production.