Biochar as a Substitute for Vermiculite in Potting Mix for Hybrid Poplar

Abstract

The purpose of this study was to evaluate biochar as a substitute for vermiculite in potting mixes for unrooted vegetative cuttings of hybrid poplar as represented by the clone 'NM6' (Populus nigra L. × Populus suaveolens Fischer subsp. maximowiczii A. Henry). We compared three treatments (peat moss (control), peat moss mixed with vermiculite, and peat moss mixed with biochar) at three times (pre-experiment, pre-fertilizer, and post-fertilizer). The biochar and vermiculite mixes had significantly higher cation exchange capacity (CEC) and pre-experiment exchangeable K than the control. Trees grown in the biochar and vermiculite mixes had significantly higher shoot K than the control at pre-fertilizer and post-fertilizer and significantly higher shoot and total biomass at post-fertilizer. The biochar mix was also associated with lower root biomass and higher shoot/root biomass ratio than the vermiculite mix at postfertilizer. Vector analysis indicated that all treatments were deficient in N at pre-fertilizer, and the control was also deficient in K at pre-fertilizer and post-fertilizer. Linear regression confirmed that shoot biomass was strongly correlated (R 2 =0.97) with N and K uptake (in addition to initial cutting diameter), also, root biomass was strongly correlated (R 2 =0.96) with potting mix CEC (in addition to shoot biomass). Luxury consumption of K at pre-fertilizer indicates that the increases in shoot and total biomass observed with the biochar and vermiculite treatments arise from this nutrient being "pre-loaded" in both mixes. We conclude that biochar provides benefits equivalent to vermiculite in terms of key nutrient availability and total biomass productivity.

Evaluating On-demand Irrigation Systems for Container-grown Woody Plants Grown in Biochar-amended Pine Bark

“…Biochar (pH = 10.5) application has been reported to increase soilless substrate pH in tomato (Solanum lycopersicum L.) and geranium (Pelargonium ·hortorum) plants grown in a biocharamended peatmoss-based substrate (Altland and Locke, 2017). An increase in pH was also reported in biochar (pH = 10.7)-amended peat (Conversa et al, 2015) and biochar (pH = 7.5)-amended pine bark (Kaudal (Headlee et al, 2014;Tian et al, 2012), which is a result of the temperatures at which they were produced. Increasing pyrolysis temperatures is known to increase biochar cation exchange capacity and pH (Zhang et al, 2017).…”

“…Our results are consistent with other published studies that reported scheduling irrigation based on substrate water status or crop water requirements reduced water use without negative effects on plant growth and quality in comparison with conventional nursery irrigation systems (Basiri Jahromi et al, 2017;Grant et al, 2009;Incrocci et al, 2014;Stoochnoff et al, 2018;Warsaw et al, 2009). An increase or no changes in plant growth after biochar application was reported in different studies during container production (Dumroese et al, 2011;Graber et al, 2010;Headlee et al, 2014;Vaughn et al, 2013).…”

Substitution of peat moss with softwood biochar for soil-free marigold growth

“…At low amendment (1-5%) or substitution (< 25%) rates, BC has been found to maintain or improve plant growth as a result of increased nutrient availability (Headlee et al, 2014), reduced nutrient and water loss (Altland and Locke, 2013;Beck et al, 2011;Graber et al, 2010), and amelioration of peat acidity (Bedussi et al, 2015), though these effects may be BC-specific due to feedstock and pyrolysis influences on BC properties (McBeath et al, 2015;Zhao et al, 2013).…”

Agronomic and environmental effects of land application of residues in short-rotation tree plantations: A literature review

“…In eucalypts as well as in poplar plantations, biochar application was beneficial for stand yield, stimulating both aboveground biomass production [113] and the number of stems produced [114]. Soil C sequestration was greatly improved [115].…”