The effect of foliar application of Sequential2-Omax on growth and physiological indices of tomato seedlings (Solanum lycopersicum)

Introduction
As the population increases, most research conducted by scientists has aimed at increasing yield per unit area by creating optimal growth conditions and enhancing plant access to nutrients (Tehrani et al., 2012). One of the strategies to increase yield per unit area is the use of external inputs in the form of chemical fertilizers (Malakouti, 2018). The advantages of chemical fertilizers include rapid absorption, significant effects, reasonable prices, and ease of use (Nasiri et al., 2016). Tomato is one of the most important and widely consumed vegetables, usable both fresh and processed (Bibi et al., 2012). Due to its various vitamins, lycopene, phenolic compounds, carotene, and mineral salts, this plant plays a significant role in improving human health (Nosoohi et al., 2012). Based on the conducted research, it appears that foliar spraying can positively affect the growth rate of tomato seedlings at the tray stage and subsequently accelerate vegetative and reproductive growth stages in the greenhouse phase. Therefore, in this study, the effect of Sequential 2 Omex liquid fertilizer (one of the widely used imported fertilizers as a foliar spray) on improving the growth parameters of tomato seedlings was evaluated.
Materials and Methods
To evaluate the effect of foliar application of Sequential 2 Omex fertilizer, a product of Omex Agriculture Ltd., UK, on the growth parameters of tomato seedlings under laboratory conditions, a factorial experiment was designed and executed based on a completely randomized design with 5 replicates. The first factor included 5 levels of optimized liquid fertilizer from the Iranian Academic Centre for Education, Culture and Research (ACECR) (control (distilled water), 0.5x, 1x, 2x, and 3x) applied as irrigation fertilizer. The second factor was the use of Sequential 2 Omex fertilizer at a concentration of 1 per thousand as a foliar spray in two levels (use and non-use). Greenhouse tomato seeds of the Newton variety were used for this experiment.
Results and discussion
The study of plant height showed that foliar application with Sequential2 Omex had a significant impact on plant height. In the control treatment (no irrigation fertilizer), treatments 0.5x, 1x, and 3x with foliar application of Sequential2 Omex significantly increased plant height compared to non-use. In the control treatment (no irrigation fertilizer), plant height increased by 59.4% with foliar application of Sequential2 Omex. In the 0.5x, 1x, and 3x irrigation fertilizer treatments, plant height with foliar application of Sequential2 Omex increased by 11.7%, 19.7%, and 21.9% respectively (Table 3). Foliar application of tomato plants with Sequential2 Omex in different irrigation fertilizer treatments increased the average number of leaves in the plant. The average number of leaves in the control treatment (no irrigation fertilizer) increased by 50% with foliar application of Sequential 2 Omex compared to non-application (Table 2). The study of stem diameter changes in tomato seedlings showed that foliar application with Sequential 2 Omex in the control treatment (foliar application with water, no irrigation fertilizer) increased stem diameter by 33.4%. In the 1x irrigation fertilizer treatment, the leaf area in plants treated with Sequential 2 Omex (129.07 square centimeters) significantly increased compared to untreated plants (94.37 square centimeters) (Table 2). Results related to leaf chlorophyll content showed that applying irrigation fertilizer treatments at different concentrations increased chlorophyll content in the plant. Examination of chlorophyll b content also revealed that different irrigation fertilizer treatments and foliar application with Sequential2 Omex increased chlorophyll b content in the plant. In the control treatment (no irrigation fertilizer), foliar application with Sequential2 Omex significantly increased chlorophyll b content in the leaf compared to non-application (Table 6). One effective and compatible method is foliar application of micronutrients in plants (Rios et al., 2020). Foliar application is effective in increasing plant yield (Mondal et al., 2011). Addressing nutritional needs in plants with major and minor elements through foliar application is highly efficient. Moreover, this method is economically viable. Due to direct contact of nutrients with the leaf, nutrient absorption efficiency is increased. Therefore, plant access to nutrients is facilitated (Ali et al., 2014). Micronutrients in Sequential2 Omex fertilizer are in chelated form. As a result, improved absorption of micronutrients enhances photosynthesis speed, leading to increased carbohydrate accumulation and its transfer from leaves to fruits and consumption sites (Uchida, 2000; Jadhav et al., 2014; Sidhu et al., 2019).
Conclusion
The results of the study indicated that foliar application of Sequential 2 Omex fertilizer at low concentrations of irrigation fertilizer led to improved growth indices in tomato seedlings. At higher concentrations of irrigation fertilizer, given that the nutritional needs of the plant were met by the irrigation fertilizer, foliar application with Sequential 2 Omex did not have a significant impact on improving growth parameters. Therefore, foliar application of tomato seedlings with Sequential2 Omex fertilizer, in conjunction with the use of irrigation fertilizer at a concentration of 1x, is recommended for producing strong seedlings with high growth potential.