Genotypic variation in nitrogen use efficiency and yield stability of 28 indica hybrid rice cultivars under tropical...

Excessive nitrogen (N) application is a prevalent issue in tropical rice production, often leading to environmental degradation without guaranteeing yield gains. Exploiting genotypic potential for low-N tolerance is essential for sustainable intensification.

This study investigated the N response of 28 indica hybrid rice cultivars under a gradient of N rates (60-240 kg N ha^-¹) in the tropical climate of Hainan, China.

We identified significant genotypic divergence in yield sensitivity to N, categorizing the varieties into four functional groups: High-efficiency/High response, Low-efficiency/High-response, High-efficiency/Low-response, and High-N inhibited. The differentiation in yield potential was mechanistically linked to plasticity in effective panicle number and sink size (spikelet number per panicle). Crucially, this study highlights a pathway for N reduction: 10 identified cultivars maintained yields exceeding 8.0 t ha^-¹ at a medium-low N rate (120 kg N ha^-¹), achieving a 33% reduction in N fertilizer usage compared to the local standard (180 kg N ha^-¹) without yield compromise.

These "N-efficient and stable-yielding" varieties demonstrated superior N agronomic efficiency, suggesting that optimizing variety selection can reduce rice productivity's dependence on high N inputs. These results provide scientific support for N reduction and efficiency-enhancement strategies in tropical agroecosystems.