Coconut Shell Pyroligneous Acid Revives Depleted Filipino Soil

Introduction

Soil degradation has become a pressing issue worldwide, particularly in regions with intensive agricultural activity. One potential solution to improve soil health is the use of pyroligneous acid, a by-product of biomass pyrolysis. This study examines the impact of coconut shell pyroligneous acid (CSPA) on the biological and chemical properties of depleted soil in Bohol, Philippines, assessing its potential as a soil amendment.

Experimental Design and Application

The study was conducted at the Oikos Garden in Bilar, Bohol, using soil samples from a degraded upland farm in Carmen, Bohol. The experiment was divided into two major sections: one focused on soil fauna and the other on soil chemical properties.

Three concentrations of CSPA were tested: 10%, 20%, and 30%, mixed with rainwater and applied to the soil. The control group received no CSPA treatment. Soil samples were analyzed for pH, organic matter, phosphorus, and potassium levels before and after treatment.

For the biological study, polyethylene terephthalate (PET) bottles were used as observation chambers to assess soil arthropod populations. The fauna were collected using an improvised Berlese funnel system and identified under a microscope. Observations were made at 7, 14, 28, and 42 days post-treatment.

Key Findings

Changes in Soil Chemistry

  • pH Alteration: The baseline soil pH was 4.1 (classified as 'extremely acid'). The application of 10% and 20% CSPA raised the pH to the 'strongly acid' category, while the 30% treatment resulted in a 'very strongly acid' classification.
  • Organic Matter Content: Organic matter increased in soils treated with 10% and 30% CSPA by 1%, and by 0.5% in soils receiving 20% CSPA.
  • Phosphorus Levels: No significant change was observed in phosphorus levels for 10% and 20% CSPA applications, but a slight decrease (3 ppm) was noted in the 30% treatment.
  • Potassium Deficiency: There was no improvement in potassium levels across all treatments, indicating that CSPA does not contribute to potassium enrichment.

Effects on Soil Fauna

  • The study identified seven groups of arthropods, including Acarina (mites) and several insect orders such as Coleoptera, Collembola, Dermaptera, Diptera, Hemiptera, and Hymenoptera.
  • The population of soil fauna increased with higher CSPA concentrations. The control group had the lowest arthropod count (8), while the 10% and 20% CSPA treatments showed moderate increases (8 and 33 individuals, respectively). The highest concentration (30%) resulted in a significant boost in arthropod population (55 individuals).
  • The Simpson’s dominance index indicated moderate biodiversity across all treatments, with higher concentrations of CSPA supporting a greater number of soil organisms.

Implications

The findings suggest that coconut shell pyroligneous acid has a measurable impact on soil health, particularly in improving organic matter content and promoting soil fauna diversity. However, its effect on pH is concentration-dependent, with higher levels potentially exacerbating soil acidity rather than neutralizing it. Additionally, while phosphorus levels remained stable in lower concentrations, a decline in the 30% treatment suggests that excessive application could lead to nutrient depletion.

The increased arthropod population in higher CSPA treatments indicates a potential benefit to soil biodiversity, which can enhance nutrient cycling and soil structure. However, the lack of improvement in potassium levels suggests that supplementary amendments may be required for a balanced soil nutrient profile.

Conclusion

Coconut shell pyroligneous acid shows promise as a biostimulant for soil rehabilitation, improving organic matter content and supporting soil biodiversity. Future research should explore optimal application rates to balance soil pH effects while maintaining nutrient availability. These findings contribute to the growing body of knowledge on sustainable soil management practices, particularly for regions facing severe soil degradation.

Article based on: Impacts of Pyroligneous Acid to Biological and Chemical Properties of Depleted Soil in Bohol, Philippines by Jose T. Travero and Machito Mihara, published in the International Journal of Environmental and Rural Development, Volume 6, Issue 1, 2015.