Evaluation of different feeding schedules on morphological traits, economical yield and photosynthetic pigments of roselle (Hibiscus sabdariffa L.)

.Roselle from the Malvaceae family, which specialized in warm climates (Copley, 1975), is considered a medicinal plant (Aziz et al., 2007). The growing trend towards the consumption of medicinal plants without proper planting methods, proper management and planning will have alarming consequences such as environmental degradation. The evaluation of plant nutrition systems is one of the most important crop planning needs in order to achieve high yield and optimum quality. Soil fertility and plant nutrition can improve input efficiency while preserving the environment, water quality, and reducing erosion. The results of numerous studies indicate the significant effect of combined fertilizers along with organic and biofertilizers on plant height, leaf protein percentage, anthocyanin content and dry weight of roselle (Mohammadpour Vashvaei et al., 2017; Ahmad et al., 2011). Due to the importance and role of medicinal plants in various industries and the need for their production in agricultural systems and the need to manage plant nutrition to increase production and environmental protection, it is necessary to conduct this type of research.
Materials and Methods: Experiment was conducted in a completely randomized block design with four replications in Ghale Ganj city in 2017-18. Treatments comprised NPK fertilizer, humic acid, Nano Biozar, 50% NPK + 50% humic acid, 50% NPK + 50% Nano Biozar, 50% humic acid + 50% Nano Biozar and control. The measured traits include characteristics plant height, stem diameter, dry weight of sepals, number of boll per plant, weight of boll, weight of fresh shoot, percentage of leaf protein, chlorophyll, relative leaf water content and anthocyanin. Finally, data was analyzed using SAS9.1 and means were compared by Duncan’s multiple range test at 5% level of probability.
Results and Discussion: Results of analysis of variance showed that plant height, stem diameter, dry weight of sepals, number of boll per plant, weight of boll, weight of fresh shoot, leaf protein percentage, leaf chlorophyll, relative water content were affected by different feeding schedules. The highest amount of mentioned traits belonged to the application of 50% NPK and 50% humic acid and the lowest values belonged to the control treatment. So that dry weight of sepals increased about 47% in 50% humic acid + 50% NPK fertilizer compared to control. The lowest amount of dry weight of sepals was obtained from the control treatment and the highest amount from the use of 50% NPK + 50% humic acid and the use of humic acid and Nano-biozar had 27.0% and 21.2% higher dry weight of sepals compared to the control, respectively. The results showed that the highest amount of anthocyanin were obtained from the use of 50% NPK + 50% humic acid, although the difference with NPK treatment was not statistically significant.
Conclusion: Results showed that the combined application of humic acid + chemical fertilizer improved the physiological and morphological traits and increased roselle growth by accelerating root nutrient uptake and this resulted in rapid establishment of plants.