Wortelmilieu: rol van substraat, additieven en micro-organismen in een weerbaar substraat: Eindrapport TKI/Cv100/KIJK-project wortelmilieu

In the years 2019-2022 the findings of the project ‘Root environment’, financed by TKI, KIJK and Cv100, have generated much insight in the role of microbial functions in the disease resistance and nutrient dynamics of greenhouse slabs. In this report the results of greenhouse experiment in 2021 and the validation experiment in practice in 2023 are presented. A cucumber crop was tested on the effect of additives on resistance to Pythium and Fusarium. Champost and champost tea were shown to slow down Fusarium infection as well as the disease symptoms and loss of cucumber plants. In addition, higher activity of the fungal-degrading chitinase was demonstrated through both enzyme determination and gene expression. Pythium symptoms were only visible at the roots, as in the trial in 2020 on rockwool slabs, without being related to the type and level of additive. A metabarcoding analysis was performed on samples from all three trials carried out in the project (years 2019-2021) and showed that the microbial composition differed significantly between the substrate types, by addition of the additives biochar, champost and chitin, and by presence or absence of plants in the substrate. With the measured substrate conditions and organic matter dynamics, calculation rules have been drawn up in a calculation tool to predict nitrogen and organic matter dynamics. The calculation tool offers growers and substrate suppliers insight into the nitrogen availability from fertilizers and substrate, but is not yet ready for practical use. Calculation rules on disease suppression were not formulated due to the complex processes involved, but some general recommendations could be given.