Development of alternative growing media with hydrochar from extensive grassland biomass and evaluation of their soil-chemical quality

F. Eulenstein, U. Schindler, E. Saljnikov, M. Klemm, T. Lühmann, M. Frerichs, M. Seiffert
Bog peat is a limited resource, but still forms the main component for the production of growth media. Due to the negative impact of peat use on the carbon footprint of ecosystems and the landscape, demand for peat substitutes is increasing. The objective of the substrate producers is to use regional, ecologically beneficial substrates that can be achieved through hydrothermal conversion by providing the process of converting biomass into peat-like properties. This method was investigated with materials originating from landscape conservation as starting material with the aim of using the generated peat substitute in culture experiments. The hydrothermal carbonization of the biomass from extensive grassland was first carried out in preliminary experiments on a laboratory scale by varying the temperature and holding time. Hydrothermally carbonized plant residues (hydrochar) were obtained on the basis of three different temperatures (150, 170, 190°C) and their chemical properties were analyzed. In the study, three different mixtures of a commercial growing medium with addition of 10, 20 and 30% v v‑1 of hydrochar were examined. The substrate chemical properties of the hydrochar mixtures differed only slightly. The hydrochar mixtures, a pure peat substrate and a peat substrate mixed with wood fibers, were used for substrate hydraulic, chemical and phytotoxic experiments. In addition, extensive cultivation and storage experiments of the described admixtures of the various varieties produced with Chinese cabbage, impatiens and daisies were carried out. Comparable plant growth could be observed for some of the tested qualities, but fungal and odor problems leave room for improvement, especially in terms of post-processing. The relationship between the growth of plants and soil chemical properties have been studied and presented. It was found that the chemical analyzes showed no dominant influence on the growth behavior. Presumably, the hydrothermally carbonized material fixed the added nitrogen.
Eulenstein, F., Schindler, U., Saljnikov, E., Klemm, M., Lühmann, T., Frerichs, M. and Seiffert, M. (2021). Development of alternative growing media with hydrochar from extensive grassland biomass and evaluation of their soil-chemical quality. Acta Hortic. 1305, 263-270
DOI: 10.17660/ActaHortic.2021.1305.36
growing medium, hydrothermal carbonization, peat substitute, cultivation trials, extensive grassland biomass, soil chemical properties, evaluation framework

Acta Horticulturae