Hammermilled Sugarcane Bagasse Fibers Can Be Used to Reduce Peat and Phosphorus Applications in Petunia Production

For decades, the global horticultural industry has relied on peat-based soilless substrates to produce container-grown crops. While peat yields ideal physical properties for soilless culture, the industry has sought a sustainable alternative to provide greater flexibility in response to potential peat supply limitations, increasing costs, and regulations related to peat extraction and its use. Many agricultural by-products have gained attention as potential peat alternatives. Sugarcane bagasse (SCB), the fibrous residue from sugar production, has been identified as one such biomass because of abundant availability and favorable properties. This study aimed to evaluate the efficacy of SCB as a substrate amendment for ornamental production, specifically Petunia , and evaluate the physical properties of peat-based substrates amended with SCB of different particle sizes and incorporation rates. Furthermore, this study also aimed to determine the potential of SCB to reduce phosphorus (P) fertilizer applications. A standard peat-based soilless substrate was amended with SCB that was processed through a hammermill into two distinct particle sizes (4 mm and 6 mm screen) with two incorporation rates (15% and 30% by volume). These four experimental substrate treatments and a control with no SCB were used to grow Petunia ‘E3 Easy Wave Coral’ under two distinct P fertigation concentrations: a standard rate providing P at 100 mg·L −1 and a reduced fertilizer rate providing P of 30 mg·L −1 . The results showed that incorporation of SCB fibers resulted in minimal changes to substrate physical properties because the bagasse-amended treatments were similar to the control in air space ( P = 0.0334), container capacity ( P = 0.0214), and total porosity ( P = 0.5865). The addition of SCB improved plant growth in all treatments. At the reduced P fertigation rate, all SCB-amended substrates produced more flowers than the control ( P < 0.0001), but not significantly, at the standard P rate. A postharvest analysis confirmed that SCB-amended substrates retained greater levels of P. Although the 6-mm particle size with the 30% SCB incorporation rate resulted in lower shoot dry weight compared with the rest of the bagasse treatments, root dry mass was similar across treatments. This study validates the use of SCB as a viable amendment for peat-based substrates in petunia production, supporting plant growth and its potential to reduce fertilizer application rates. Overall, these results indicate the opportunity to use SCB in substrate materials with economical and environmental benefits.