Effect of combined feeding system on N, P and K concentration, biochemical characteristics and calyxes yield of roselle (Hibiscus sabdariffa L.)

To evaluate the effect of chemical and bio-fertilizer on nitrogen, phosphorus and potash concentration, biochemical traits and calyxes yield of roselle, an experiment was conducted in the split plot based on randomized coplete block design with three replications, at the Research Station in Zabol University, during 2013 and 2014. The main plot consisted of three levels: phosphorus, nitrogen and NPK fertilizer and the subplot involved five levels: Nitroxin, supernitroplus, superbiosulphate, mycorrhizal and non-bio-fertilizer. The results of combined analysis of variance showed that the effects of chemical and biological fertilizers were significant (P≤0.01) for all studied traits. Interaction of chemical and biological fertilizer was significant for all traits except for percentag of leaves nitrogen, phosphorus and protein. The highest values for the percentage of leaves and sepals nitrogen, leaves and sepals protein, percentage of sepals potash, sepals anthocyanin content, sepals vitamin C content, sepals acidity and calyxes yield belong to the NPK fertilizer in combination with nitroxin bio-fertilizer treatment. The highest values for the percentage of leaves and sepals phosphorus triates belong to the NPK fertilizer in combination with superbiophosphate bio-fertilizer treatment.Thus, with respect to the production of medicinal plants in cropping systems, the use of chemical fertilizers with bio-fertilizers to improve the efficiency of chemical fertilizers in order to achieve sustainable agriculture and environmental protection are recommended.