Enhancing Nutrient Uptake and Growth Quality of Lowland Rice through the Application of AMF and Nutrient-Enriched Biochar

Abstract Rice cultivation in acidic soils is limited by low nutrient availability and poor soil quality. Arbuscular mycorrhizal fungi (AMF) and nutrient-enriched biochar offer potential solutions to enhance nutrient uptake and soil health. This study evaluated the individual and combined effects of AMF inoculation (0, 5, and 10%) and nutrient-enriched biochar (0, 2.5, and 5.0 t ha −1 ) on rice growth and herbage productivity under flooded conditions. AMF colonization increased with inoculation, from 26.67% (0% AMF) to 55.56% (10% AMF), and reached 62.22% with 2.5 t ha⁻¹ biochar, showing synergistic effects. However, plants without AMF produced higher early biomass, suggesting an initial energy cost for symbiosis. The highest root dry weight (1.05 g) occurred with 2.5 t ha −1 biochar, while maximum herbage productivity (1.73 t ha −1 ) was achieved with 5.0 t ha −1 biochar without AMF at 45 DAT. Overall, nutrient-enriched biochar had a stronger and more consistent positive effect than AMF under flooded conditions. Moderate AMF inoculation with biochar (2.5–5 t ha −1 ) improved physiological traits, tiller number, and assimilation efficiency, while excessive AMF reduced yield. Thus, combining moderate AMF inoculation with biochar application is recommended for optimizing rice growth and biomass production in acidic soils.