A Novel Organic Substrate Based on Hemp (Cannabis sativa) or Flax (Linum usitatissimum) Fibre for Hydroponic Systems

New consumer considerations regarding mining impacts and waste disposal issues have highlighted the need to innovate alternative horticultural media. The goal of this study is to determine whether a novel hydroponic substrate based on the bast fibres of hemp (Cannabis sativa) or flax (Linum usitatissimum) could perform comparable with popular existing media. First, physical and chemical properties of hemp- and flax bast fibre were characterized in the laboratory, including effective pore volume, moisture content, moisture holding capacity, saturated hydraulic conductivity, cation exchange capacity, electrical conductivity, and pH. These properties were evaluated as useful indicators of the media's ability to exchange and store both oxygen and water, as well as to provide information about its chemical nature. In the second part of the study a plant growth trial was conducted to compare the effect of 9 hydroponic media on plant growth parameters. Lettuce (Lactuca sativa var. Buttercrunch) was cultivated for 28 days in a greenhouse for two weeks in a grow chamber, followed by another two weeks in the Plant Research Facility Greenhouse (McGill University, Macdonald campus) using a nutrient film technique (NFT) hydroponic system. Plants were analyzed at two points in time: at germination (days 2-7), and post-harvest. At germination we will measure total germination frequency and mean germination time. Following harvest, we will determine shoot biomass (fresh and dry), root biomass (fresh and dry), shoot: root biomass ratio (fresh and dry), moisture content and levels of various nutrients and metabolites were evaluated. Results from this study may potentially lead to a novel hydroponic substrate that is biodegradable, harvested sustainably, and produced from local resources that are frequently (un/under)utilized.