Wood Vinegar Enhances Blueberry Yield and Quality Better Than Biochar

Introduction

Soil degradation is a major challenge for sustainable fruit production, particularly for crops like blueberries (*Vaccinium corymbosum*), which have specific soil requirements. A recent study published in *Chemosphere* investigated the effects of individual and co-applied biochar and wood vinegar on blueberry tree growth, fruit yield, nutritional quality, and soil properties.

Why Biochar and Wood Vinegar?

Biochar is a carbon-rich material that improves soil structure, water retention, and nutrient availability, but its alkaline nature can be unsuitable for acid-loving crops like blueberries. Wood vinegar (WV), a byproduct of biochar production, is known to have biostimulant effects that enhance plant growth and nutrient uptake. Some studies suggest that WV can lower soil pH, but its effectiveness depends on concentration, soil buffering capacity, and application frequency. In this study, WV had little effect on soil pH, indicating that its benefits to blueberries were likely due to biostimulant activity rather than pH modification. The study aimed to determine whether these amendments, alone or in combination, could enhance blueberry production.

Experimental Design and Application Methods

A field trial was conducted in Qingdao, China, on a blueberry plantation with weakly acidic soil (pH 5.55). The following treatments were tested:

  • CK: Control, no amendments
  • 1.5%BC: Biochar applied at 1.5% (w/w), equivalent to 213 g/tree
  • 3%BC: Biochar applied at 3% (w/w), equivalent to 426 g/tree
  • 0.2%WV: Wood vinegar applied via soil irrigation at 1 L/tree, four times at 30-day intervals
  • 1.5%BC-WV: Combined application of 1.5% biochar and 0.2% wood vinegar

The amendments were applied by incorporating biochar into the soil around the trees, while wood vinegar was fertigated at regular intervals.

Key Findings

Effects on Blueberry Growth and Yield

  • No Significant Effect on Tree Growth: None of the treatments had a significant impact on tree height or canopy expansion.
  • Fruit Yield Improvements: The 1.5%BC treatment increased total fruit yield by 4.82%, while the 3%BC treatment increased fruit count by 8.27% compared to the control. The WV treatment increased total yield and fruit count by 18.4% and 16.4%, respectively, whereas the co-application of biochar and WV resulted in a 4.76% increase in total yield and 15.4% increase in fruit count.
  • No Significant Differences Between Treatments: While all amendments improved yield metrics, the differences between them were not statistically significant.

Effects on Fruit Quality

  • Apparent Quality Unchanged: Fruit weight, volume, density, and moisture content remained similar across treatments.
  • Improved Nutritional Quality:
    • Vitamin C content: increased significantly with 3%BC (+30.4%) and 1.5%BC-WV (+26.6%).
    • Titratable acidity: decreased by 17.7% in the 1.5%BC-WV treatment, making the fruit less acidic.
    • Total soluble sugar, flavonoid, phenolic, and anthocyanin contents: showed minimal changes.

Effects on Soil Properties

  • Slight pH Increase: Biochar slightly increased soil pH, but WV had little effect on reducing it.
  • Higher Soil Organic Matter (SOM): Biochar significantly increased SOM content, enhancing soil fertility.
  • Inconsistent Nutrient Availability Changes:
    • NH₄⁺-N and NO₃⁻-N: increased across all amended treatments, with the highest increase in WV-treated soil (+51.5% NH₄⁺-N, +12.2% NO₃⁻-N).
    • Olsen-P (available phosphorus) content: increased in WV-treated soil but decreased slightly with biochar alone.
    • Available potassium (AK) and magnesium (Mg): increased slightly in WV and biochar treatments.
    • No Significant Effect on Other Micronutrients: such as calcium, copper, and zinc.

Implications for Blueberry Cultivation

The study did not examine the underlying mechanisms behind the observed increases in blueberry productivity, but the results align with prior research suggesting that wood vinegar acts as a biostimulant, enhancing plant growth and fruit yield. Since foliar application of wood vinegar has been widely reported to increase productivity, its effects are likely not primarily due to soil pH changes but rather due to improved nutrient uptake, stress tolerance, or plant hormone modulation. Further research is needed to determine whether these specific factors contributed to the observed yield and quality improvements in this study.

This study suggests that while biochar and wood vinegar can improve fruit yield and nutritional quality, their co-application did not produce significantly better results than individual applications. More research is needed to optimize application methods, particularly for adjusting soil pH to better suit blueberry requirements. The findings indicate that wood vinegar alone may be a more effective amendment for blueberries than biochar, but further trials across different soil conditions are necessary.

Article based on: Comparative Study of Individual and Co-Application of Biochar and Wood Vinegar on Blueberry Fruit Yield and Nutritional Quality