Effects of biochar and peat as potting soil amendments on water retention, seedling survival, and growth of eucalyptus clones from brooder to hardening off-stage.

Abstract

This study investigated the effects of peat moss and biochar amendments on the physical and chemical properties of potting soil, and their subsequent influence on the growth and survival of Eucalyptus clones (GC550 and GU7). Peat moss and biochar significantly (p<0.05) decreased Bulk Density and increased Water Holding Capacity (WHC) and porosity of the potting media compared to the control (100% soil). There was also a significant change in some soil properties especially the nutrient content (N, P, and K) and pH. For instance peat moss lowered soil pH, while biochar increased it. A combination of both amendments resulted in a more moderate pH level. All treatment groups displayed significantly (p<0.05) high survival rates of the plantlets of both GC550 and GU7 at the end of 30 days of the experiment in brooder and at the end of the 51 days of the entire experiment, with the peat moss and biochar combination achieving a perfect score by the 30th day of the experiment for the GC550. Growth rates were below 50%, but fertilizer application showed a positive influence. The improved water holding-capacity (WHC), potentially optimal nutrient uptake, and enhanced aeration likely contributed to the observed higher plantlets heights, positive effects on plant growth and survival rates in amended soils. These findings suggest that incorporating peat moss and biochar either individually or in combination, can be a viable strategy for improving potting soil properties and promoting plant survival and growth in nursery settings. Further research is needed to evaluate the economic feasibility and scalability of incorporating biochar and peat moss into nursery soil as amendment and also identify alternative and sustainable sources of biochar for wider applicability.