CHANGES IN ROOT GROWTH AND PHYSICAL PROPERTIES IN SUBSTRATES CONTAINING CHARRED OR UNCHARRED WOOD AGGREGATES^©

In recent years, biochar (BC) has attracted attention for use as a horticultural substrate amendment due to its potential benefits, such as promoting substrate/rootzone biology and nutrient holding/exchanging capacity. Biochar also has the potential to be a local and renewable substrate component produced from waste products and regionally available material (Peterson, 2013). The potential for horticultural use of BC in soilless substrates with greenhouse crops is clouded, however, because initial reports of BC in substrates do not show consistent results or benefits. There is a need to explore the impact of the vast range of BC properties on their potential use in greenhouse and nursery container production (Altland and Locke, 2012).
Biochar has been shown to be a potential use as a replacement for perlite in greenhouse mixes (Northup, 2013), because it is lightweight, porous, and it is thought to have potential economic benefit (cost savings) over perlite. Increased root growth has also been reported when BC was amended to a peat-based substrate (O’Hara, 2013); however quantification of increased root growth in biochar amended substrates has not been published.
To investigate the potential of using BC in greenhouse substrates, BC was produced with known/measurable parameters so that a definable and repeatable product was used in these studies. Mini-horhizotrons and rhizometers were used to quantify and observe root growth and changes in substrate physical properties amended with BC (Judd, 2013). The objectives of this study were: 1) to test the effects of BC and root growth on substrate physical properties over time, and 2) test the effects of BC amended substrate on plant root growth.