Alternative substrates in the cultivation of ornamental and vegetable plants

Research objective: The aim of this research was to evaluate different types of innovative substrate mixtures as an alternative to traditional growing media with peat and pumice on vegetable and ornamental plants

Materials and Methods: The experiments, which began in November 2022, were conducted in the CREA-OF greenhouses in Pescia (Pt), Tuscany, Italy (43°54′N 10°41′E) on seedlings of Arbutus unedo, Photinia red robin, Fragaria vesca and Crassula sarcocaulis. The plants were placed in 14 diameter pots, 6 plants per 3 replications, for a total of 18 seedlings per experimental thesis. The test was divided into two parallel trials with different substrates. The first trial on Crassula sarcocaulis involved the following theses (irrigated and fertilised): peat 70% + pumice 30%; peat 65% + pumice 30% + biochar 5%; compost 60% + biochar 5% + insect humus 5% + pumice 30%; compost 60% + biochar 5% + earthworm humus 5% + pumice 30%. The second trial on Arbutus unedo, Photinia red robin and Fragaria vesca involved the following theses (irrigated and fertilised): peat 70% + pumice 30%; alternative soil 72% + biochar 5% + 3% humus + 20% pumice.

On 18 May 2023, plant height, vegetative weight, root volume and length, number of fruits (strawberry) and number of microorganisms were determined.

Results and Discussion: The experiment showed that the use of alternative substrates can effectively improve the vegetative and root growth of Crassula sarcocaulis, Fragaria vesca, Photinia red robin and Arbutus unedo.

In general, in the first experiment on Crassula sarcocaulis, a significant increase in plant height was observed with the biochar-only substrate, followed by the insect and earthworm humus-based theses. All the theses were significantly better than the control with peat and pumice. In the second trial on Fragaria vesca, Photinia red robin and Arbutus unedo, the thesis with altenative soil, biochar and humus was significantly better in all plant species for plant height, vegetative and root weight and root length. All alternative substrates showed a significant increase in microbial biomass compared to the control. Several materials have been evaluated as substitutes for or combination with peat in growing media formulation. They include coir dust, pine bark, and wood fiber as well as sand, tuff, and pumice processed materials (expanded clay, perlite, and vermiculite). Besides satisfying the relevant technical requirements, these alternatives have to be readily available at reasonable prices and be readily available in sufficient quantities. In addition to meeting specific plant requirements, these materials have been used to create tailored growing media that are environmentally friendly and reduce production costs.

Conclusions: The results of research on growing substrates must be translated into agricultural practice through various steps, in cooperation with horticultural companies. To ensure the best growing conditions for seedlings, nurseries should conduct a thorough analysis of the specific composts they use. As organic farming practitioners argue, greater involvement of compost producers and end-users could improve the quality of growing media by adding additional valuable characteristics and reducing the use of peat, which would allow for a more sustainable regime.