Amending hardwood biochar with compost tea improves soil quality

Compost tea — compost steeped in water — has been used as an amendment for biochar, charcoal that’s used in agriculture as a soil amendment. Evidence of the practice’s positive effects is scarce, prompting researchers to investigate the matter in a study published in Biological Agriculture & Horticulture.

  • The researchers investigated the effects of combining hardwood biochar and different types of compost teas and microbial enhancement prepared from vermicompost on the growth of eggplants (Solanum melongena) and the severity of damage caused by the flea beetle (Epitrix fuscula), an insect pest. They also looked into the effects of these combinations on microbial activity and functional diversity in two types of temperate soil.
  • The researchers recorded no short-term positive effects of biochar amended with compost teas prepared from mushroom compost, horse manure, and vermicompost on both eggplant growth and insect pest damage.
  • A second experiment revealed that amending biochar with microbial enhancements prepared using vermicompost tea may have a positive effect. Community Level Physiological Profiling (CLPP) also showed that the effects of this practice on both microbial activity and functional diversity were different from those that resulted from amending with just biochar. These changes were observed to correspond with both plant growth and insect damage.

The researchers found that the biochar and microbial enhancement combination had a positive effect on plant growth when matched with the physical and chemical properties of the soil used.

Learn how to amend soil for organic gardening and farming at

Journal Reference:

Edenborn SL, Johnson LMK, Edenborn HM, Albarran-Jack MR, Demetrion LD. AMENDMENT OF A HARDWOOD BIOCHAR WITH COMPOST TEA: EFFECTS ON PLANT GROWTH, INSECT DAMAGE AND THE FUNCTIONAL DIVERSITY OF SOIL MICROBIAL COMMUNITIES. Biological Agriculture & Horticulture. 2017;34(2):88–106. DOI: 10.1080/01448765.2017.1388847

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