Nutrient availability in peat-based growing media as affected by vermicompost, biochar and mycorrhizae inoculation for growing organic basil (Ocimum basilicum L.) and sweet pepper (Capsicum annuum L.)

The combination of vermicompost and biochar has the potential to supply sufficient nutrients to plants during their growth period. The objective of this study was to evaluate the nutrient availability in three vermicompost/peat ratios with or without biochar and/or mycorrhizal fungi inoculation for producing organic basil (Ocimum basilicum L.) and sweet pepper (Capsicum annuum L.). Treatments included mixture of biochar at two levels (0 and 10% weight basis), three levels of vermicompost/peat ratios (0, 15 and 30% volume basis) and mycorrhizal fungi inoculant (Glomus intraradices) at two levels (with and without application). Plants were grown under optimum growth chamber conditions in three replications. Plant dry aboveground biomass was measured at harvest. Nitrogen (N), phosphorous (P) and sulfur (S) content were measured in growing media and in plant tissue at harvest. The interaction among treatments was not significant both in basil and sweet pepper. Basil S uptake significantly increased by 68 and 44% in 15 and 30% vermicompost rates compared with control, respectively. Basil P uptake increased 2.4-fold in low rate and 2.1-fold in high rate of vermicompost compared with control (142 and 125 vs. 60 mg P pot^‑1). The measured nutrient parameters in basil were not affected by biochar treatment. Mycorrhizal inoculation only affected basil P uptake, where increased P uptake from 102 to 116 mg P pot^‑1. Among measured parameters in sweet pepper only total growing media P at harvest was affected by vermicompost/peat rate. Biochar treatment only affected sweet pepper tissue S concentration. Mycorrhiza inoculation did not affect measured parameters in sweet pepper. The treatment consisted of 15% (v/v) vermicompost/peat ratios with mycorrhiza inoculant was suitable for growing organic basil and provided a balanced nutrient level during basil life cycle. When this growing media composition used for sweet pepper, supplemental fertilization was required at reproductive stage.