CHALLENGES OF COMPOSTING FOR GROWING MEDIA PURPOSES IN SPAIN AND THE MEDITERRANEAN AREA

Growing media market is mainly based on natural resources like peat, and others that although derived from natural resources, involve high energy costs in production, including mineral wool perlite, and vermiculite. Thus, this implies the consideration of sustainability issues in any scenario. Recently, there is an increasing search for alternative materials to reduce the dependence of these traditional sub-strates related to their availability in the near future due to environmental constraints. Also, the EU research programmes are promoting and supporting these objectives to achieve an environmental friendlier agriculture in intensive production. In the Mediterranean countries, the horticultural sector has achieved a high relative importance, specifically Spain being one of the greatest horticultural producers, where curiously the natural resources for growing media are negligible. In this scenario, composting is a routine, efficient and sustainable treatment to obtain stabilized organic resources that can be used in extensive and intensive agriculture for amend¬ment and background fertilising purposes. However, in soilless cultivation conditions, the growing media must accomplish specific high standards of quality, environmental and safety issues, and moreover achieve specific properties depending on the type of cultivation requirements (seedling-propagation-growing). For this reason, much research has been done to establish the potential substitution of peat or perlite with routine-commercial compost, using in many cases around 20-30% in volume without any negative effect. The challenges to develop more efficient compost to substitute in higher proportion peat or perlite in the growing media are discussed, based on co-composting and additive strategies. In addition, the leading agricultural role of Spain in Mediterranean cropping give us the opportunity to reuse in these purposes associated waste fluxes coming from agricultural and agroindustrial production (wine, olive oil production, etc.), with specific properties that can increase compost value and quality.