Soil and greenhouse gas responses to biochar additions in a temperate hardwood forest

Abstract

Biochar additions can improve soil fertility and sequester carbon, but biochar effects have been investigated primarily in agricultural systems. Biochar from spruce and maple sawdust feedstocks (with and without inorganic phosphorus in a factorial design) were added to plots in a commercially managed temperate hardwood forest stand in central Ontario, Canada; treatments were applied as a top-dressing immediately prior to fall leaf abscission in September 2011. Forests in this region have acidic, sandy soils, and due to nitrogen deposition may exhibit phosphorus, calcium, and magnesium limitation. To investigate short-term impacts of biochar application on soil nutrient supply and greenhouse gas fluxes as compared to phosphorus fertilization, data were collected over the first year after treatment application; linear mixed models were used to analyze data. Two to six weeks after treatment application, there were higher concentrations of potassium in spruce and maple biochar plots, and phosphorus in spruce biochar plots, as compared to the control treatment. There were higher concentrations of calcium, magnesium, and phosphorus in the phosphorus plots. In the following spring and summer (9-12 months after treatment application), there were higher soil calcium concentrations in maple biochar plots, and phosphorus plots still had higher soil phosphorus concentrations than control plots. No treatment effects on fluxes of carbon dioxide, methane, or nitrous oxide were detected in the field; however, laboratory incubations after 12 months showed higher microbial respiration in soils from maple biochar plots as compared to spruce biochar, despite no effect on microbial biomass. The results suggest that the most important short-term impact of biochar additions in this system is the increased supply of the limiting plant nutrients phosphorus and calcium. We expect that larger changes in mineral soil physical and chemical properties will occur when the surface-applied biochar becomes incorporated into the soil after a few years.

Charcoal in Organic Horizon and Surface Mineral Soil in a Boreal Forest Fire Chronosequence of Western Quebec: Stocks, Depth Distribution, Chemical Properties and a Synthesis of Related Studies

“…They also tend to be higher in elements such as Ca, Fe, Al and heavy metals, due to factors such as soil contamination of logging waste, mixing of sand or soil in fluidized bed combustion and presumably contact with heated metal surfaces. Three biochar preparations (primarily from softwood; Robertson et al, 2012;Sackett et al, 2015;Criscuoli et al, 2017) had Ca, Mg, P, and S concentrations comparable to our median values, but our K concentrations were much higher (Table 3B). Additional expectation of the composition of wildfire chars may be found by comparison of fresh biomass, and of element recoveries (2015) plus pers comm., Hatton et al (2016), and Pingree et al (2016).…”

Is There a Positive Synergistic Effect of Biochar and Compost Soil Amendments on Plant Growth and Physiological Performance?

“…As an organic fertilizer, compost (including SMS) provides plants with important nutrients and facilitates subsequent uptake. Similarly, unweathered BC also provides a short-term pulse of certain important nutrients, in particular K and P [18,62]. If growth responses to BC and SMS treatments are mainly due to nutrient provision, then a saturation of plant nutrient demands will often result in a non-additive positive effect on plant growth (e.g., [63]), and may lead to a decline in plant growth at high levels [28] (p. 46).…”

“…), the pyrolysis process (e.g., fast, slow, and gasification), and the temperature during pyrolysis [3,14]. BCs derived from woody feedstock demonstrate particularly important ameliorative properties that include high ability to sorb soil contaminants [15], retain nutrients and water [16][17][18], increase soil pH, and provide pulses of nutrients that are potentially limiting in certain systems (e.g., phosphorus in Pluchon et al [19]). …”

Soil microbial responses over 2 years following biochar addition to a north temperate forest

“…This study focuses on the effects of hardwoodand softwood-derived biochar and P addition on soil microbial community composition and functioning 1 and 2 years after addition in a temperate hardwood forest in Central Ontario. We build upon the work of Sackett et al (2014), who characterized soil properties at this site up to 12 months after biochar addition and found that biochar increased availability of limiting plant nutrients. In addition, Mitchell et al (2015) documented changes in soil microbial flora in a 24-week incubation experiment of these soils, most notably finding an increase in the ratio of bacteria to fungi and a decrease in the ratio of Gram-negative to Gram-positive bacteria with biochar addition.…”