Sugarcane bagasse (SCB), a byproduct from the refinement of sugar, is an abundantly available material in tropical and semi-tropical regions. The use of SCB as a component in soilless substrates and other horticulture applications has gained attention due to its regional availability, use as a peat alternative in floriculture production, and as a phosphorus-rich material. Phosphorus (P) is an essential element for the growth of plants; however, P leaching losses from excessive fertilizer applications can pose environmental concerns. This study evaluated using SCB as a soilless substrate amendment in the production of Petunia ‘E3 Easy Wave Coral’, where two particle sizes of SCB (hammermilled at 4 mm and 6 mm) were blended with a peat moss/perlite (7:3 by vol.) floriculture media at rates of 15% and 30% by volume. Two fertilizer rates were investigated, one applying P at 100 mg L-1 and one applying P at a reduced rate of 30 mg L-1. Plant growth and vigor was assessed through measuring growth index (average of plant height and two widths) and chlorophyll content (SPAD). Leachate collected from containers following the “Pour-Through” method was assessed for pH and electrical conductivity (EC), with subsamples collected and analyzed for nutrient content. Plants appeared to grow larger in the control (peat moss/perlite media only) and 15% SCB amended soilless substrates compared to the 30% SCB substrates, regardless of SCB size or fertilizer rate. Substrates amended with SCB at 30% resulted in less vigorous growth than either the control or the 15% SCB amended substrates; however, the differences were less visible in the 30% SCB media when provided the higher P fertilizer rate. Given the important role of P in plant growth and the environmental concerns associated with fertilizer applications, evaluating P availability in sugarcane bagasse and its potential contribution to plant nutrition could provide a more sustainable alternative for soilless substrate systems in floriculture production.
