Growth characteristics and some secondary metabolism the effect of spraying with salicylic acid and NPK chemical fertilizer on vegetative compounds of Origanum majorana

The experiment is carried out in the horticultural facilities of the Department of Horticulture and Landscapes-College of Agriculture-Tikrit University for the agricultural season 2021 to detect the effect of spraying with salicylic acid at levels (0, 25, 50 mg L−1) and NPK chemical fertilizer at levels (0, 1.5 gm L−1) on the vegetative growth characteristics and some active compounds of Origanum majorana in an experiment designed with a randomized complete block design RCBD. The results show the superiority of plants sprayed with salicylic acid and NPK over untreated plants. The results of the bilateral interaction between salicylic acid and NPK chemical fertilizer show significant differences in the treatment S2F1 (1.5 gm l−1 NPK + 50 mg l−1 salicylic acid) in the vegetative growth characteristics (plant height 72.89 cm plant−1, number of branches 22.01 Plant branch−1, number of leaves 3080.80 leaf−1, leaf area 923.38 cm2 plant−1). The plants treated with salicylic acid and NPK also excelled in the leaves content of the active compounds. The binary interaction between the two factors salicylic acid and NPK chemical fertilizer at the level of S2F1 treatment (1.5 gm l−1 NPK + 50 mg l−1 salicylic acid) has given the highest average content of leaves for the active compounds reaching (Linalool 3.833 mg. gm plant−1, Limonene 3.245 mg.g. plant−1, Carvacrol 8.702 mg.g. plant−1, Terpinoid 38.661 mg.g. plant−1,-pineneα 2.375 mg.g. plant−1). Treatment S1F1 has given (1.5 gm l−1 NPK + 25 mg l−1 salicylic) values close to the superior treatments of terpinoid and α –pinene reaching (38.617 mg. gm plant−1, 2.368 mg. gm plant−1) respectively.