Biochar used as a peat substitute for nursery plants reduces negative salinity effects in sensitive ornamentals

Biochar is a fine-grained material with a high porosity (10-15 times higher than soil), primarily composed of organic carbon. As reported by many studies, its water and nutrient retention capacity could make it a good amendment for plants. Therefore, few data are reported in the literature for biochar addition to ornamental sector substrates. The utilization of biochar could open up interesting possibilities for the ornamental sector by reducing peat volumes used in the substrates and amounts of good water for irrigation. An experiment was done on potted cherry laurel (Prunus laurocerasus L.), a salinity sensitive species, and phillyrea (Phillyrea latifolia L.), a resistant one, using substrates with different percentages of biochar to replace peat. Irrigation waters at two different salinity concentrations were applied and the results showed that the addition of biochar to the medium had no effect on plant growth but limited the damage due to salinity in cherry laurel, the sensitive species. The observed tolerance was related to lower Na+ retention in the substrates with biochar. Consequently biochar could allow not only the reduction of peat percentage in the substrates commonly used for ornamental species cultivation but also the utilization of low quality water for irrigation reducing also the leaching of nutrients such as K+ and N-NH4+.