Wood ash application increases pH but does not harm the soil mesofauna.

Area of Science:

• Ecotoxicology
• Soil Science
• Environmental Chemistry

Background:

• Bioash application in soil aids nutrient recycling but poses ecotoxicological risks.
• Wood ash is a complex mixture affecting soil invertebrates via direct toxicity or habitat alteration.

Purpose of the Study:

• To evaluate the ecotoxicological effects of wood ash on key soil invertebrates.
• To compare wood ash effects with calcium hydroxide (Ca(OH)2) due to pH changes.

Main Methods:

• Laboratory toxicity studies using agricultural and coniferous plantation soils.
• Tested effects on collembolans (Folsomia candida, Onychiurus yodai), mites (Hypoaspis aculeifer), and worms (Enchytraeus crypticus).
• Applied wood ash at concentrations from 0-75 g kg-1 soil.

Main Results:

• Significant negative effects on collembolans observed only at high wood ash concentrations (≥15 g kg-1 agricultural soil).
• Hypoaspis aculeifer and Enchytraeus crypticus were not affected by wood ash.
• Osmolality, not high pH or heavy metals, was identified as the likely cause of toxicity.

Conclusions:

• Short-term chronic effects of wood ash vary across soil types.
• Osmotic stress is the probable mechanism of wood ash toxicity to soil invertebrates.
• High pH and heavy metals play a minor role in wood ash ecotoxicity.