Pyroligneous Acid Boosts Greenhouse Tomato Yield and Nutritional Quality

Introduction

Pyroligneous acid (PA), also known as wood vinegar, has gained attention as a natural biostimulant with the potential to improve crop yields and fruit quality. A recent study published in Plants investigated the impact of different PA concentrations on the growth, yield, and biochemical composition of greenhouse-grown tomatoes (Solanum lycopersicum 'Scotia'). The study aimed to determine optimal PA application rates that enhance productivity while maintaining fruit quality.

Experimental Design and Application

To evaluate the effects of PA, researchers applied 0%, 0.25%, 0.5%, 1%, and 2% PA (v/v with distilled water) as a soil drench biweekly to tomato plants grown in a greenhouse. A 20-20-20 NPK fertilizer was applied every 20 days to all treatments. The study measured plant morphological traits, physiological responses, fruit yield, and biochemical composition.

Key Findings

1. PA Treatment Increased Fruit Number and Yield

  • The 0.5% PA treatment increased total fruit weight by 26%, although this was not statistically different from the control.
  • Fruit number increased by 65.6% with 0.5% PA and 34.4% with 0.25% PA, compared to the control.
  • Higher PA concentrations (1% and 2%) negatively affected fruit yield, likely due to stress-related responses.

2. PA Had Minimal Effect on Plant Growth Metrics

  • Plant height, stem diameter, branch number, and flower count were not significantly different between treatments.
  • The above-ground fresh weight increased with 0.25% PA, while 0.5% and 1% PA slightly reduced it.

3. Influence on Photosynthesis and Stomatal Activity

  • Photosynthetic rate was not significantly affected by PA application.
  • Leaf transpiration and stomatal conductance decreased with increasing PA concentration, particularly at 1% and 2% PA, possibly as an adaptive response to stress.
  • Interestingly, 0.25% PA increased sub-stomatal CO₂ levels by 3%, suggesting improved internal CO₂ concentration.

4. Effects on Tomato Fruit Quality

  • The 2% PA treatment increased Brix content by 13%, suggesting an improvement in fruit sweetness.
  • Higher PA concentrations elevated titratable acidity, total dissolved solids, and electrical conductivity, which could impact flavor profile.
  • 0.5% and 1% PA significantly increased carotenoid content by 20-22%, improving the nutritional value.
  • 2% PA significantly enhanced total phenolic and flavonoid content, indicating higher antioxidant levels.

5. Impact on Fruit Nutritional Composition

  • 0.25% PA increased nitrogen (N), magnesium (Mg), phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and copper (Cu) content.
  • 1% PA increased calcium (Ca) and sodium (Na) levels but reduced other nutrients.
  • 0.5% PA slightly reduced overall nutrient content, indicating a possible dilution effect due to increased fruit size.

Optimal PA Concentrations for Tomato Production

The findings suggest that 0.5% PA is the best concentration for enhancing tomato yield, while 2% PA is better suited for improving antioxidant content and fruit quality parameters. However, high PA concentrations may induce stress responses, reducing overall yield.

Implications for Greenhouse Tomato Cultivation

  • PA has biostimulant properties that can improve tomato yield and quality, but the application rate is crucial.
  • Low to moderate PA concentrations (0.25–0.5%) enhance fruit production, while higher doses (1–2%) are more beneficial for increasing nutritional compounds.
  • Further studies should explore long-term effects, cost-effectiveness, and interactions with different soil types.
  • This study adds to the growing body of evidence supporting the use of pyroligneous acid in sustainable agriculture.

Article based on: Effect of Pyroligneous Acid on the Productivity and Nutritional Quality of Greenhouse Tomato