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ISHS Acta Horticulturae 1137: International Symposium on Innovation in Integrated and Organic Horticulture (INNOHORT)

Assessing the potential of biochar as a growing media component for potted plants

Authors:   M. Dorais, C. Martinez, M. Diop, M. Thériault, C. Ménard, S. Pepin
Keywords:   biochar amendment, basil, geranium, sweet pepper, Pythium ultimum
DOI:   10.17660/ActaHortic.2016.1137.3
Adding biochar to growing media can be a promising avenue for increasing the productivity of potted organic plants. Indeed, there have been numerous reports that soil amendment with biochar increases the biological and physicochemical properties of different types of soil by promoting the development of microbial populations and soil mineralization rates, by improving porosity, particle aggregation and soil structure, by enhancing ion exchange capacity (cations and anions), by reducing nutrient losses to surface water and by minimizing the emission of greenhouse gases such as N2O and CH4. Thus, the goals of this study were (1) to evaluate the effect of soil biochar amendments for six types of organic soil (0 to 50% v/v; particle size: 0-150 mm) on tomato growth and root susceptibility to Pythium ultimum, and (2) to evaluate the effect of soil biochar amendment for a peat-based substrate (0 to 30% v/v; particle size: 2-4 mm) on plant growth and nutrient use efficiency of sweet pepper, geranium and ornamental basil. Two experiments were conducted in a greenhouse located at Laval University (46°49'N; 71°15'W) in a randomized complete block design with three to five replicates. Regardless of the types of soil, our results showed that soil amendments with a high percentage of biochar (50% v/v) decreased tomato plant height and total dry mass when tomato plants were grown on a peat mix growing medium and a sandy loam (p<0.05). However, there was no interaction between biochar amendment and soil P. ultimum inoculation, thereby suggesting that biochar did not suppress or promote tomato root colonization by P. ultimum. In addition, biochar amendment to the growing media of sweet pepper, geranium and basil had no significant effect on their root colonization by mycorrhizal fungi. No positive effect of biochar soil amendment on plant growth parameters was observed for any of the species studied or organic soils. However, we concluded that a proportion of up to 30% of biochar can be used in replacement of peat for organic potted plants without any significant negative effect on plant growth and disease sensitivity.

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