High yields of hybrid rice do not require more nitrogen fertilizer than inbred rice: A meta-analysis

Hybrid rice has been planted throughout China to ensure food security owing to its higher yield potential than inbred rice. Meanwhile, substantial nitrogen (N) fertilizer has been applied to feed hybrid varieties for maximizing grain yield. However, to what extent the higher yield of hybrid than inbred rice depends on N fertilizer input remains unclear. A meta-analysis was conducted in this study to (1) quantify the difference in N uptake and utilization between hybrid and inbred rice; (2) determine whether hybrid rice requires more N than inbred rice for producing per unit grain yield; and (3) evaluate the impact of the difference in crop growth duration between hybrid and inbred rice on their yield performance. The results showed that, overall, hybrid rice achieved a 10.1% higher grain yield, and 9.7% higher daily grain yield than inbred rice. This grain yield advantage increased from 6.1% to 11.9% depending on whether hybrids have longer crop growth duration than inbred rice. The yield advantage of hybrid rice was explained by higher total N uptake and internal N use efficiency, but not explained by N fertilizer input. Moreover, the yield advantage of hybrid rice with N fertilizer was driven by higher yield without N fertilizer instead of yield response to N fertilizer. These results suggest that hybrid rice does not necessarily require more N fertilizer to achieve higher yield than inbred rice. Therefore, hybrid rice could be planted with fewer external N to ensure food security and reduce environmental costs.

Automated summary

The study found that the higher grain yield of hybrid rice is mainly attributed to higher total nitrogen uptake and internal nitrogen use efficiency, rather than nitrogen fertilizer input. Hybrid rice does not necessarily require more nitrogen fertilizer than inbred rice to achieve higher yield, suggesting that it can be planted with less external nitrogen input to ensure food security and reduce environmental costs.