Pyroligneous Acid Increases Rice Yield by 60% with 50% Fertilization Rate
Introduction
Rice (Oryza sativa L.) is a staple food for over half of the world’s population, providing daily sustenance and crucial livelihoods across Asia and beyond. In Bangladesh, it occupies a dominant position in agriculture, with Aman rice grown extensively during the wet season. Although advances in fertilizer use have propelled rice yields in many regions, maintaining soil health and maximizing crop productivity remain ongoing challenges. Against this backdrop, plant extracted pyroligneous acid (often referred to as wood vinegar or PA) has emerged as a potential tool to enhance rice yields. This organic product, derived from the condensation of smoke produced during biomass pyrolysis, contains diverse bioactive compounds. Its reported benefits include improved soil quality, stimulation of beneficial microbes, and enhanced plant growth.
Experimental Design and Application
Researchers at Sher-e-Bangla Agricultural University conducted a field experiment during the Aman rice season (August–December) using BRRI dhan34, a popular transplant Aman variety. The soil was fertilized according to recommended doses for T. Aman: Urea (120 kg/ha), TSP (90 kg/ha), MoP (40 kg/ha), Gypsum (60 kg/ha), and Zinc Sulphate (10 kg/ha). Urea was applied in three equal splits at 7, 30, and 50 days after transplanting (DAT).
Pyroligneous acid was prepared by diluting the raw material in water. A “100% PA” solution (approximately 1% v/v) was obtained by mixing 200 ml of PA in 20 liters of water, whereas a “50% PA” solution (approximately 0.5% v/v) required 100 ml in 20 liters. The PA solutions were foliar-sprayed at 7, 30, and 50 DAT using a knapsack sprayer. The experiment followed a randomized complete block design with six treatments:
- T1 – Control (no fertilizer, no PA)
- T2 – 100% recommended dose of fertilizer (no PA)
- T3 – 100% recommended dose of fertilizer + 100% PA
- T4 – 50% recommended dose of fertilizer + 50% PA
- T5 – 50% recommended dose of fertilizer + 100% PA
- T6 – 100% PA only (no fertilizer)
Thirty-day-old seedlings (three per hill) were transplanted at a 25 cm × 15 cm spacing, and standard crop management practices (weeding, irrigation, pest control) were performed uniformly.
Key Findings
- Plant Growth Parameters: The tallest rice plants (150.2 cm) appeared in T2 (full fertilizer, no PA). Interestingly, T4 (50% fertilizer, 50% PA) produced the highest number of total tillers per hill (24.20), while the control (T1) recorded the fewest. Effective tillers – the productive ones that lead to grain formation – were highest under T2, but T4 and T5 were close behind.
- Panicle Features: Panicle length was not significantly affected by PA application, indicating that genetic factors and base fertilizer levels may have had a stronger role in determining panicle size.
- Grain Yield: Treatment T4 (50% recommended fertilizer + 50% PA) significantly outperformed all other treatments, producing 5.05 t/ha of rice grain. By comparison, T2 (full fertilizer, no PA) yielded 3.15 t/ha, and the control (T1) lagged at 2.55 t/ha. The notable yield gains in T4 were linked to a higher number of effective tillers, more filled grains per panicle, and heavier grain weight.
- Straw Yield and Biological Yield: Straw yield was highest under T2 (6.68 t/ha). Meanwhile, T3 (full fertilizer + 100% PA) recorded the highest total biological yield (10.52 t/ha). However, T4 distinguished itself with the highest harvest index (48.32%), meaning a greater proportion of total biomass was transformed into grain.
- Potential Mechanisms: Foliar spraying with PA may stimulate soil microbes, enhance nutrient assimilation, and modulate plant growth hormones. By pairing half the recommended fertilizer rate with half-strength PA, researchers observed an optimal balance of nutrient supply and growth stimulation.
Implications
This study underscores the potential of plant extracted pyroligneous acid to complement fertilizer inputs in transplanted Aman rice. Interestingly, halving fertilizer and PA application (both at 50%) consistently outperformed other treatments, possibly due to improved plant vigor, reduced input costs, and minimized environmental load from excessive fertilizer use. Additionally, PA’s organic constituents might help boost soil fertility and beneficial microbial activity.
For farmers and agricultural practitioners, these findings support the partial replacement of chemical fertilizers with PA-based organic inputs. Future large-scale trials could refine the best application rates under diverse soil conditions and test the broader economic feasibility for smallholder farmers. As sustainable agriculture practices become increasingly critical, the strategic use of pyroligneous acid could help stabilize yields, reduce costs, and preserve soil health over the long term.