Mitigating the trade-off between grain yield and vegetative biomass with orthosilicic acid towards enhancing lodging resistance in upland rice

Achieving a balance between high yield and strong lodging resistance (LR) remains a major challenge in rice improvement, as shifts in biomass accumulation and allocation can enhance yield but weaken plant architecture. This study examined how biomass allocation under varying soil volume and growth conditions affects LR-grain yield (GY) trade-offs in upland New Rice for Africa (NERICA) cultivars and mitigating role of orthosilicic acid (OSA) fertilizer. Ten upland cultivars, including NERICAs 1–8, Moroberekan, and Ofada, were grown under 500 mL ha−1 OSA in 10 kg and 23 kg soils, while selected cultivars were tested in the field. Larger soil volume increased aboveground vegetative biomass (AVB), total dry biomass (TDB), GY, and stem lodging traits but reduced bending stress and LR. OSA application enhanced plant height, cross-sectional modulus, and breaking strength, and shifted biomass allocation toward GY at the expense of AVB. Lodging traits correlated more with absolute biomass than with partitioning in pots, and with GY and root:shoot ratio in the field. Without OSA, a 33% increase in TDB from larger soil volume raised GY and lodging index (LI) by 36% and 30%, respectively, compared to smaller gains of 20%, 13%, and 16% under OSA. Only TDB under OSA exceeded averages under field condition. NERICAs in 10 kg soil with OSA traded 20% biomass and 13% GY for a 16% improvement in LR. OSA moderates biomass–yield–lodging trade-offs, though soil volume and conditions obscure its effects. OSA thus offers a promising strategy for stabilizing the yield–lodging relationship in upland NERICAs, but its effectiveness ultimately depends on validation under diverse field environments.