Biochar effects on the nursery propagation of 4 northern Rocky Mountain native plant species

Biochar has emerged as a promising potential amendment of soilless nursery media for plant propagation. With this greenhouse study we used biochar to displace standard soilless nursery media at 4 rates (0, 15, 30, and 45% [v:v]) and then examined media chemistry, irrigation frequency, and the growth of 4 northern Rocky Mountain native plant species: Clarkia pulchella Pursh (Onagraceae), Festuca idahoensis Elmer (Poaceae), Gaillardia aristata Pursh (Asteraceae), and Pinus ponderosa Lawson & C. Lawson (Pinaceae). For all 4 species, media electrical conductivity (EC) showed little variation and was unaffected by biochar treatment. Pinus and Gaillardia media pH was lowered by all biochar levels, but the magnitude of difference was minimal. For Pinus, Gaillardia, and Clarkia, final seedling shoot, root, and total biomass production for all biochar treatments were similar. Only Festuca experienced a negative biochar effect regardless of biochar rate; root biomass was reduced, which was also reflected in lower total biomass and lower root-to-shoot ratios. Notably, adding biochar reduced watering frequency for all 4 species, with the magnitude of reduction directly proportional to biochar content. In the most extreme case (Festuca), controls required 55% more frequent irrigation than the 45% biochar treatment. This research shows that for 3 of the 4 species studied, soilless nursery media can be amended by up to 45% biochar content with minimal costs to plant growth and a reduction in watering frequency.