The effects of birch (Betula spp.) biochar and pyrolysis temperature on soil properties and plant growth

• All tested biochar types had equal effects on soil properties and plant growth.
• Biochar produced at 300 °C had initial negative effect on the germination of lettuce.
• Biochar improved the yield of radish and ryegrass regardless of pyrolysis temperature.
• None of the biochar types affected the survival of nematodes and earthworms.

The addition of biochar to agricultural soils is recommended to improve soil functions and plant growth. However, due to high variability in the quality of biochar, its effects on soils and plants are likely to differ. We explored the impacts of pyrolysis temperature on the quality and usability of birch wood biochar as a soil amendment. The impact of three biochar types – pyrolysed at 300, 375 or 475 °C – on soil characteristics and the growth of lettuce (Lactuca sativa), radish (Raphanus sativus), barley (Hordeum vulgare) and ryegrass (Lolium perenne) was investigated in a greenhouse experiment. In addition, the potential adverse effects of biochar on soil organisms (nematodes, earthworms, microbial biomass and activity) were studied.Biochar produced at the lowest temperature had initial transient negative effect on the germination and biomass of lettuce, while biochar produced at higher temperatures had no such effect. After five weeks, pyrolysis temperature had only a marginal influence on biochar-induced effects on soil pH, WHC, soil organisms and plant growth. Our results suggest that birch biochar, irrespective of pyrolysis temperature, has a parallel effect on plant biomass production and soil characteristics but the effect depends on plant type and biochar application rate.