Sugarcane Bagasse Is an Effective Soilless Substrate Amendment in Quick-turn Osteospermum Production

Abstract

Many greenhouse growers rely on peat-based soilless substrates to produce salable crops in a relatively short period of time. Peat-based substrate suppliers often incorporate additional organic materials such as wood fiber to extend peat supplies. Given the relative success of wood-based substrates, growing interest in other fiber materials such as sugarcane bagasse may provide similar benefits for substrate processers. The objective of this research was to evaluate substrate properties and the productivity of a short-term floriculture crop, Osteospermum 'Bright Lights Purple', in a commercially available peat-based substrate (PL) that has been amended with either commercially available wood fiber [Hydrafiber (HF)] or an aged sugarcane bagasse fiber (SCB). Thus, substrates consisting of PL amended with 15% or 30% HF or SCB were developed. Plants were fertigated weekly at rates of 100, 200, or 300 ppm N, respectively. Crop growth and fertility dynamics were assessed. Substrate shrinkage was greatest in the 30% bagasse blend but had minimal impact given the 2-month crop cycle. The incorporation of 15% and 30% SCB and HF produced slight changes in pH over a 9-week growth period, with HF generally raising pH and SCB generally lowering pH compared with the 100% PL, showing promise for bagasse in managing substrate pH where irrigation water has high pH and/or alkalinity. Substrate EC was initially reduced by blending SCB and, to a lesser extent, HF, but differences ceased to exist by the end of the experiment. Chlorophyll and blooms were abundant in all substrates and fertigation rates. Regardless of fertigation rate, 30% HF had the lowest growth index and shoot dry mass, and 30% SCB had the lowest root dry mass, although differences were not visually apparent. Foliar N concentrations were greatest in plants grown in the PL and SCB substrates and lowest in HF blends. Overall, growth and dry mass differences were minimal across substrate treatment and fertigation rate, and all plants were marketable with statistically similar shelf life. In conclusion, this research indicates the potential of using SCB as a substrate amendment for short-term crop systems in a similar manner as wood fiber.