Higher yields of hybrid rice do not depend on nitrogen fertilization under moderate to high soil fertility conditions.

BACKGROUND: Increasing rice yield with fewer external inputs is critical to ensuring food security, reducing environmental costs, and improving returns. Use of hybrid rice has expanded greatly in China due to its higher yield potential. Meanwhile, large and increasing amounts of nitrogen (N) fertilizers have been used for expanding rice production in China. It is not clear to what extent the success of hybrid rice in China is associated with N fertilizer inputs. FINDINGS: We observed that the higher grain yield with N fertilizer in hybrid rice was driven more by a higher yield without N fertilizer than by increases in grain yield with N fertilizer under moderate to high soil fertility conditions. CONCLUSIONS: Our results suggest that greater application of N fertilizers is not needed to benefit from hybrid rice production under moderate to high soil fertility conditions, and that improving and maintaining soil fertility should be a focus for sustaining hybrid rice production. Moreover, our study also indicates that zero-N testing may be a potentially useful tool to develop hybrid rice with high yield and without requirement of greater external N inputs under moderate to high soil fertility conditions.