Evaluation of regenerative agriculture approaches integrating compost, biochar, and ash with reduced chemical fertilizers to enhance rice production and soil fertility

Rice production is fundamental to food security across Asia, yet excessive dependence on synthetic fertilizers has led to declining soil fertility and environmental degradation. Sustainable nutrient management approaches are needed to maintain productivity while restoring soil health. This study evaluated the potential of integrating organic amendments—compost, biochar, and ash—with reduced chemical fertilizer rates to enhance the growth, yield, and post-harvest soil nutrient status of BRRI dhan71 rice during the Aman (monsoon) season. A field experiment was conducted using a randomized complete block design with five treatments: control (T0), 100% recommended fertilizer dose (T1), ash at 1 t ha−1 + inorganic N: 180 kg ha−1, P: 12 kg ha−1 (50% of RFD), S: 18 kg ha−1 (T2), biochar at 1 t ha−1 + inorganic N: 180 kg ha−1, P: 12 kg ha−1, S: 18 kg ha−1 (T3), and compost at 5 t ha−1 + inorganic N: 180 kg ha−1, P: 12 kg ha−1, S: 18 kg ha−1 (T4). In these organic amendment treatments (T2–T4), potassium fertilizer was deliberately omitted from the chemical fertilizer component but remained supplied naturally through the organic materials themselves. Compost (T4) produced the highest plant height (107.9 cm), panicle length (26.2 cm), and effective tillers (14.9 hill−1), resulting in the greatest grain yield (5.99 t ha−1) and total biomass (12.87 t ha−1). Post-harvest soil analysis showed increased N (0.97%) and P (26.47 mg kg−1) under compost, while ash (T2) improved residual K (57.98 mg kg−1). Integrating organic amendments—especially compost—with reduced chemical fertilizers maintained high yield and improved post-harvest soil nutrient reserves, supporting regenerative agriculture practices that enhance soil fertility and nutrient-use efficiency.