Glycyrrhizic residues substrates as component of growing media for the growth of pepper (Capsicum annuum) plug seedling

An experiment was conducted to study the possible utilization of glycyrrhizic residues (GR) as a substitution for widely using expensive peat in growth media for plug seedlings production of pepper (Capsicum annuum). The research was arranged in a completely randomized design with seven treatments and four replications. These treatments were T1-GR: vermiculite=1:1 (v/v), T2-GR: pearlite=1:1, T3-GR: vermiculite:pearlite=1:1:1, T4-GR: pearlite=2:1:1, T5-GR:vermiculite:pearlite= 3:1:1, T6-glycyrrhizic alone. A mixed substrate of peat with perlite (1:1; v:v) was used as the control (CK). The results showed that the physicochemical characteristics of all mixed GR-based media were better than glycyrrhizic residues-only (T6) medium and satisfied for the general requirements of growing media. The medium of T5 (GR:vermiculite:pearlite=3:1:1; v/v/v) gave higher leaf chlorophyll content and root activity of the pepper seedlings than the other GR-based media. This medium was also the best medium for the growth of pepper seedling as it gave the highest parameters in terms of plant height, roots-top ratio and healthy seedling index and the lowest root plum collapse rate. This result suggested that GR:vermiculite:pearlite (v/v/v)=3:1:1 is an appropriate media for pepper seedlings with suitable physicochemical properties, availability and low cost, following by the media of T1 (GR:vermiculite=1:1; v/v) and T5 (GR:vermiculite:pearlite=2:1:1; v/v/v). Therefore, glycyrrhizic residues should be considered as an alternative for the widely used but expensive and resource-limited peat in plug seedlings production of vegetables and soilless cultivation.