The effect of different peat-free growing media and fertilization levels on the plant nutrition of Leucanthemum vulgare (lam.) and (Dianthus barbatus L.)

Research on peat-free substrates is increasing due to the environmental concerns associated with peat extraction and with the aim of promoting sustainable horticultural practices. Previous research has shown that green compost mixed with coconut coir dust and stabilized wood fiber can be a valuable peat-free alternative for growing media. This study extends this knowledge by exploring the possibility of reducing fertilization levels by exploiting the nutrient content of green compost. In this paper we tested two ornamental herbaceous perennial plants, Leucanthemum vulgare Lam. and Dianthus barbatus L. For each species, we carried out five different substrate mixtures: 1) peat:pumice 70:30 v v−1; 2) coconut coir dust:pumice 70:30 v v−1; 3) coconut coir dust:green compost 55:45 v v−1; 4) green compost:stabilized wood fiber 60:40 v v−1; and 5) coconut coir dust:green compost:stabilized wood fiber 40:30:30 v v−1. For each mixture, we explored three different levels of fertilization: i) no fertilizer application; ii) low dosage of a controlled-release fertilizer at 2 g L−1; and iii) high dosage of the same controlled-release fertilizer at 4 g L−1. Plant biomass, biometric parameters, eco-physiological parameters, and plant mineral content were measured as performance indicators. The results showed that the nutrient surplus provided by the peat-free substrate, particularly when it contains green compost, can enhance the growth potential of the plants. Adding green compost to non-peat substrates can be an opportunity to optimize plant nutrition while reducing the presence of peat in plant nurseries and the use of chemical fertilizers.