A review of the challenges facing horticultural researchers as they move toward sustainable growing media

Previous papers presented at ISHS symposia have looked in detail at the challenges presented to the horticultural industry in the quest for the replacement of peat as a dominant ingredient in substrate mixes. From the 1980s onwards the pressures in various European countries focused on the value of wetland habitats in terms of ecosystem services, especially in terms of storage of carbon, water purification and retention, and hence the reduction of flash flood risks. In countries such as Germany, Holland and the UK, considerable efforts have gone into investigating peat replacements or diluents. The UK Government department responsible for championing peat replacement, Department of Environment, Farming and Rural Affairs (Defra), have at various times established aspirational targets, such as 90% peat replacement across horticulture by 2010. All the targets were voluntary but failed to gain traction within the industry possibly due to there being no collective targets for the supply chain as a whole. In 2011 the UK Government passed a legislative bill establishing specific targets with regard to peat replacement in horticulture. These targets would be reviewed and monitored but were again considered voluntary and in order to support and encourage progress a Task Force was initiated which identified a series of projects against a number of specific challenges. The Task Force was composed of all individuals from across the supply chain, i.e., from substrate manufacturers, growers, retailers, NGO's and Government departments. The UK industry accepted the challenge by developing a responsible sourcing scheme which seeks to identify more sustainable practices through pragmatic assessments. From a horticultural researchers perspective and despite all the efforts and work undertaken by researchers around the world, at no point has there been any attempt to offer guidance on a unified approach to assessing and characterizing the use of new and novel substrate components. The ISHS has, over the last few years, become far more prescriptive of paper presentations and data records, but reviewing papers from the recent symposia reveals widely different methodology applied to the various trials of new and novel substrate materials. A great proportion of the research into new growing media mixes is driven by utilization/incorporation of waste stream materials and the researchers involved appear to have limited experience of commercial horticulture. This paper considers the needs of horticulturalists in relation to the essential characteristics of growing media and the selection of plant species and the criteria for performance evaluation of those plants in experimental work. These practices can be used to achieve a more consistent approach to the review of new and novel materials allowing for much greater transfer of knowledge in published work.