Effects of organic amendment with licorice (Glycyrrhiza glabra) root residue and humic acid on the vegetative growth, fruit yield, and mineral absorption of bell pepper (Capsicum annum)

During industrial licorice production, considerable amounts of licorice root residues (LRR) are produced. The use of these residues as an agricultural production input could be beneficial to sustainable economic growth and the environment. Therefore, we evaluated the application of LRR to some growth media at (v/v) [100% soil (S), 100% LRR (L), 50% soil + 50% LRR (SL), 50% perlite + 50% LRR (PL), 50% cocopeat + 50% LRR (CL), and 25% soil + 25% perlite + 25% cocopeat + 25% LRR (SPCL)] plus humic acid (HA) (0, 5, 10, or 15 gl(-1)) during bell pepper production. Results showed that LRR application plus HA fertigation significantly improved the vegetative and reproductive growth and mineral content of pepper. The highest fresh weight (shoot and root), plant height, root length, leaf number, and chlorophyll content were observed for plants treated with SPCL + 15 gl(-1) HA. The highest number of flowers (18.08), fruits per plant, fruit length and diameter, fruit fresh weight, and yield were associated with the peppers grown under SPCL. Deformed fruits significantly increased in the S treatment whereas no deformed fruits were observed under the SPCL treatment. The highest leaf K, Ca, Fe, and Zn contents were observed in the medium culture containing 25% LRR (SPCL) + 15 gl(-1) HA. The findings revealed that the use of SPCL + 15 gl(-1) HA fertigation could provide the best conditions for fruit production by bell pepper.