Abstract

Calcareous soils in coastal lowland regions are typically deficient in nitrogen (N) and available phosphorus (P). Moreover, these agro-ecosystems are regularly affected by tidal activities. Therefore, this study evaluated the effect of bio-organic fertilizer application without inorganic phosphorus and with a 30% reduction in nitrogen on the yield and yield attributes of rice in a coastal area of Bangladesh. A field experiment was conducted during the Rabi season using a randomized complete block design (RCBD) with five treatments and three replications. Each plot measured 20 m² with a spacing of 20 cm × 20 cm. The treatments included: T1 = 100% chemical fertilizer (control); T2 = 70% N without inorganic P + recommended fertilizers; T3 = 70% N without inorganic P + K and S + bio-organic fertilizer at 500 kg ha⁻¹; T4 = similar to T3 with bio-organic fertilizer at 750 kg ha⁻¹; and T5 = similar to T3 with bio-organic fertilizer at 1000 kg ha⁻¹. Results demonstrated that bio-organic fertilizer significantly improved growth and yield attributes. Treatment T4 produced the highest effective yield (6.66 MT ha⁻¹), representing an 11.09% increase over the control. Although T5 showed the highest numerical yield, T4 was identified as the optimal treatment due to its comparable productivity at a lower input cost and the highest benefit-cost ratio. The findings suggest that integrating bio-organic fertilizer at 750 kg ha⁻¹ can effectively replace inorganic phosphorus and reduce nitrogen use by 30% without compromising yield. This strategy improves soil biological activity and supports sustainable nutrient management. Overall, the approach offers a cost-effective and environmental solution for rice cultivation in Bangladesh and similar agroecological systems.

Key words: Bio-organic, Soil organic matter, Microorganisms, Sustainable agriculture, Save Phosphorus & Nitrogen, Yield and Productivity, Cost effective;