Microbially managed organic growing media for greenhouse horticulture

The production of vegetables in growing media is an efficient way to produce vegetables in soilless culture systems. The management of the microbial community associated with growing media may serve as potential sustainable pathway to increase eco-efficiency. Consequently, it is important to find out how biotic and abiotic factors affect the composition and diversity of microbial communities associated with growing media. The aim of this PhD thesis was to study the ecology of the microbial community in soilless culture systems. First, the microbial community of a mineral and an organic growing medium was examined and it was found that both growing media have a distinct, microbial community structure. Second, key functionalities of growing media and their individual constituents were quantified. Particularly, the nitrogen dynamics were studied in relation to the microbial community associated with plant and growing medium. Third, the valorization of recycled nutrients as a high-value microalgae fertilizer and struvite was investigated. In addition, an adapted fertigation strategy in combination with organic fertilizers was developed to narrow the yield gap with a pure mineral growing medium when cultivating tomatoes. Afterwards, the microbial community structure of four contrasting soil and soilless tomato cultivating systems were studied. Finally, the effect of fertilizers and plant type on the microbial community structure of the rhizosphere and the bulk zone were investigated. Overall, organic growing media show a potential for developing novel cultivating systems fitting into a more sustainable horticulture.

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