Growing-medium effects and limited responses to short-fermented banana stem liquid organic fertilizer in grafted ‘Alligator’ avocado seedlings (Persea americana Mill.)

Abstract

Growing medium and liquid organic fertilizer (LOF) quality influence seedling performance, although their combined effects remain unclear. This study evaluated seedlings treated with short-fermented banana stem LOF in different media. A factorial randomized complete block design comprised five LOF concentrations (0, 225, 450, 675, and 900 mL L⁻¹) and three media compositions: cocopeat + soil (1:2, v/v), rice husk + soil (1:2, v/v), and cocopeat + rice husk + soil (1:1:2, v/v/v). The LOF was fermented for 14 days and contained low total N (0.014%), P₂O₅ (0.01%), and K₂O (0.05%). Seedling height, cumulative stem diameter increment, leaf number, leaf dimensions, leaf length-to-width ratio, and SPAD index were evaluated for 16 weeks. Growing-medium composition significantly affected seedling height at all observation times. Cocopeat + soil produced the greatest height, reaching 75.93 cm at 16 weeks, whereas rice husk + soil produced 70.60 cm and the three-component medium was intermediate. LOF concentration significantly affected leaf number at 4, 12, and 16 weeks, but 225 mL L⁻¹ did not differ from the control. The effect was associated with lower leaf numbers at higher concentrations, particularly 900 mL L⁻¹. No interaction or effects on other variables were detected; growing medium influenced growth more consistently than LOF, which is not yet recommended for nursery use.