Towards organic farming in roselle (Hibiscus sabdariffa L.) cultivation- feasibility of changing its nutrition management from chemical to bio-organic.

The high dependence on chemical fertilizers in the farming systems especially in the arid regions has become a serious challenge that threatens the stability and sustainability of crop production. Therefore, determining alternative nutrition systems based on the organic and biological sources is a critical issue of crops management. The objective of this study is to assess the response of the roselle (Hibiscus sabdariffa L.) to chemical, organic and biological nutrient systems. A two-year field experiment was conducted with a split-plot based on randomized complete blocks design with three replications. The main plots consisted of control (CL), vermicompost (VP), poultry manure (PM), and chemical fertilizer (NPK) (CF), while the sub-plots involved control (AM0), application of Glomus mosseae (AM1), and Rhizophagus intraradices arbuscular mycorrhiza (AM2). The results showed that PM and CF treatments led to the highest increase in fresh calyx yield (58.6%) compared to the control. While PM treatment showed the highest increase in dry calyx yield (23.9%) and seed yield (32.0%). AM inoculation resulted in a 27.3, 26.8, and 22.3% increase in mentioned traits, respectively compared to the control. PM treatment showed the highest values of dry calyx and seed water productivity (13.5 and 15.5 kg m−3, respectively). Also, AM2 treatment showed the highest values for these indices (13.5 and 14.5 kg m−3, respectively). The highest increase in calyx ascorbic acid (20.1%) was obtained from PM treatment, while the highest value of calyx anthocyanin content (0.307 and 0.292 µmol g−1) in the first and the second year was found in PM and CF treatment, respectively. VC treatment resulted in the highest increase in seed oil content (12.8%), while the highest increase in seed protein content (22.8%) belonged to the CF treatment. The average improvements in the calyx ascorbic acid, calyx anthocyanin content, seed oil content, and seed protein content due to AM inoculation were 11.2, 5.0, 9.2, and 7.8%, respectively. According to our findings, the use of mycorrhiza (especially Rhizophagus intraradices) in combination with poultry manure is recommended to achieve proper economic yields and improve water productivity and quality indices of the roselle in order to replace the chemical fertilizers in the cultivation of this plant in the study area. [ABSTRACT FROM AUTHOR]