Microbially managed growing media for a decreased environmental footprint

Over the past century, enormous progress has been achieved worldwide in increasing global agricultural and horticultural production. Agricultural and horticultural production relies among others on plant growing media that provide a proper physicochemical and biological environment. It needs no discussion that the continuing demand for more agricultural production cannot be driven simply by using more peat, synthetic fertilizers and pesticides. The path forward can only be one toward more sustainability to preserve nature and future human generations. As a consequence, the use of peat, a major growing medium constituent, will be reduced and synthetic fertilizers, a major additive, will be replaced by organic fertilizers. The urgent need for more sustainability prompted a renewed attention to the development of biological solutions in soilless culture systems. The challenge of the next decade will be to develop strategies to compose and manage microbiomes. Scientists together with growing media producers want to steer in a safe and reproducible way the microbial black box in engineered soilless culture systems, rather than only describe them. Various opportunities for improving plant nutrition and as a consequence plant yield and quality are relevant, such as improving the nutrient use efficiency of conventional and organic fertilizers, disease suppression, nitrogen mineralization and subsequent nitrification, phosphorous solubilization, alleviation of abiotic stresses, such as water and temperature stress and salinity stresses, thereby optimizing the beneficial interplay between plants rhizosphere organisms and the growing medium. Interactions between microorganisms, organic matter of which peat is an important and safe source, clay minerals and the plant are complex and play pivotal roles as they provide nutrients, habitats for microorganisms and inhibiting or promoting microorganism growth, adsorb and hold nutrients in a plant available form and give structure. Peat and clay minerals, an essential safe backbone of growing media, and also alternatives, such as wood and grass fibers, and green compost are under investigation, however more and more attention is given to the microbial properties of these products and the desired activity in growing media.