Biochar-based nursery substrates: The effect of peat substitution on reduced salinity

The growing of ornamental plants for urban greening has significant environmental and economic implications. In particular, the intensive use of peat and high-quality water at the nursery stage is sensitive due to the problems of soil depletion and water salinization even in urban areas. In these contexts, a preference for salinity-resistant species and cultivation techniques based on the substitution of low-impact materials could be beneficial. Here, an experiment has been carried out with two ornamental plant species - cherry laurel [Prunus laurocerasus L.] which is salinity-sensitive, and phillyrea [Phillyrea latifolia L.] which is salinity-resistant - using substrates containing different amounts of biochar in place of peat. Moreover, using irrigation water at two different salinity concentrations, we assess the extent to which the biochar can mitigate salinity damage in these plant species. The results of this study showed that the addition of biochar to the potting medium had no effect on plant growth but crucially limited cherry laurel salinity damage. Tolerance to salinity was attributed to lower Na+ retention in the biochar-containing substrates. Based on these findings, we conclude that the application of biochar not only reduces the amount of peat required in growth substrates, but can also permit the utilization of low-quality irrigation water - thereby also reducing the leaching of nutrients such as K+ and N-NH4+.