Effect of foliar Salicylic acid application on growth and nitrogen fixation in Chickpeas (Cicer arietinum) grown under water stress using ¹⁵N

A pot experiment was conducted to determine the impact of foliar spraying of salicylic acid (SA) (0, and 10^-5 Mol L^-1) on dry matter production (DM), nitrogen uptake (NY), and N₂-fixation by chickpea (Cicer arietinum L.) plants subjected to three soil moisture regimes (FC1 high stress 45-50%, mild stress FC2 60-65% and well watered FC3 75-80% of field capacities). The ¹⁵N-isotope dilution method was employed to evaluate N₂ fixation by chickpeas using barley as a reference crop. Water restriction drastically affected DM, NY, and N₂ fixation in chickpea. However, chickpea responded positively to SA as a means of enhancing growth and overcoming the stress conditions. SA increased DM by 13, 17, and 6% and total NY by 14, 20, and 10% in FC1, FC2, and FC3, respectively. Percentages of nitrogen derived from atmosphere (%Ndfa) increased with increasing soil moisture. SA significantly enhanced amounts of fixed N₂ by 32, 30 and 18% in FC1, FC2 and FC3, respectively. Our results indicated that the positive effect of SA in enhancing plant performance (growth and N-uptake from available sources) was affected by soil water content. The beneficial effect of SA on mild water-stressed chickpea resulted from stimulating the growth and improving soil and fertilizer N uptake as well as fixed N₂. Under high stress conditions, the main effect of SA was on growth and N₂ fixation. In well watered chickpeas, SA was beneficial to enhance N₂ fixation. In conclusion, SA application may be considered as an important agricultural practice for the symbiotic performance (i.e., N₂ fixation) in water stressed as well as in well watered chickpeas plants (author).