Wood Distillate and Biochar Improve Basil Yield and Soil Fertility.

Introduction

Sustainable agriculture aims to enhance crop productivity while maintaining soil health. A recent study by researchers at the University of Pisa explored how biochar (B) and wood distillate (WD), alone and in combination, influence soil properties, enzymatic activity, and basil (*Ocimum basilicum*) growth.

Why Biochar and Wood Distillate?

Biochar is a stable organic amendment that improves soil aeration, water retention, and nutrient availability. However, its alkaline nature can sometimes limit its benefits. Wood distillate (WD), also known as pyroligneous acid or wood vinegar, is a byproduct of biochar production that contains organic acids, phenols, and trace minerals. Its acidic nature can balance biochar's alkalinity, improve microbial activity, and enhance nutrient solubility.

Experimental Design and Application Methods

The study was conducted in a greenhouse using basil plants (*Ocimum basilicum var. Genovese*). The researchers tested four treatments:

  • Control (CTR): No amendments.
  • WD Treatment: 1% diluted wood distillate applied via fertigation once per week.
  • B Treatment: Biochar mixed into the soil at a rate of 2% (w/w), equivalent to 34 t/ha.
  • BWD Treatment: A combination of biochar and wood distillate, with biochar applied at 2% (w/w) and WD fertigated at 1% dilution once per week for the duration of the study.

The study ran for four weeks, with soil and plant samples collected at the end to assess biomass, nutrient content, microbial activity, and enzymatic function.

Key Findings

Soil Quality Improvements

  • Higher Organic Carbon Levels: The addition of biochar (B and BWD treatments) increased soil organic carbon (OC) by 18-20%, improving soil fertility.
  • Dissolved Organic Carbon (DOC) Retention: The B and BWD treatments enhanced DOC by 50% in bulk soil and rhizosphere, promoting microbial growth.
  • Improved Microbial Biomass: The BWD treatment showed a 52% increase in microbial biomass in bulk soil and 62% in the rhizosphere, indicating better soil biological quality.

Soil Enzymatic Activity

  • Phosphatase and Urease Activation: These key soil enzymes, involved in nitrogen and phosphorus cycling, were significantly higher in the BWD treatment.
  • Dehydrogenase Reduction in Biochar Treatments: Biochar alone decreased dehydrogenase activity, suggesting altered microbial respiration.
  • Overall Soil Health Indicator (AI3): The BWD treatment had the lowest alteration index three (AI3) score, suggesting enhanced biological stability in the soil.

Basil Growth and Nutrient Uptake

  • Increased Dry Biomass: The B and BWD treatments improved basil dry biomass by 36-43%, reflecting better growth conditions.
  • Enhanced Nitrogen and Phosphorus Uptake: BWD-treated plants had up to 40% more nitrogen and over twice the phosphorus content compared to the control.
  • Higher Nutrient Use Efficiency (NUE): The BWD treatment led to significant increases in nitrogen and phosphorus use efficiency, optimizing nutrient absorption.

How the BWD Combination Works

  • pH Balancing: WD's acidity counteracts biochar's alkalinity, stabilizing soil pH.
  • Nutrient Solubility: WD enhances phosphorus and nitrogen availability, supporting plant uptake.
  • Microbial Synergy: Biochar provides a habitat for microbes, while WD stimulates microbial activity, leading to improved soil processes.

Implications for Sustainable Agriculture

This study demonstrates that biochar and wood distillate can work together to enhance soil quality, improve plant growth, and increase nutrient efficiency. The findings support the co-application of these amendments as a sustainable strategy for improving horticultural crop production. Future studies should investigate field-scale applications and long-term effects to validate these greenhouse findings.

Article based on: Co-Application of Wood Distillate and Biochar Improves Soil Quality and Plant Growth in Basil (Ocimum basilicum)