Effect of exogenous proline application on maize yield and the optimum rate of mineral nitrogen under salinity stress

Salinity is a negative abiotic stress that produces drastic disorders on soils and plants causing a critical reduction in plant growth and yield parameters, particularly maize plant, which considers a moderately sensitive plant to soil and water salinity. Although proline and nitrogen are well known to protect plants and improve their tolerance against various abiotic stresses including salinity, the interaction between proline and nitrogen fertilizer under saline conditions remained unclear. Two field experiments were conducted, on a clay saline soil in a split-plot design with four replicates. The main plots were arranged to study the effect of exogenous of proline applications at 0, 50 and 100?mM during seedling and vegetative stages, and mineral of nitrogen fertilization rates were 0, 140, 280, and 420?kg N ha(?1) occupied the subplots. A significant response to fertilizer N was observed at 420?kg ha(?1), while the optimum N rate of 50?mM of proline was 410.3?kg ha(?1) and the economic optimum dose was 403.43?kg ha(?1). Therefore, we recommend using 403.43?kg N ha(?1) to get an optimum economic yield of maize, especially in saline soil, when used 50?mM exogenous of proline at seedling and vegetative stages.