Conventional transplanted rice (TPR) has been increasingly replaced by direct-seeded rice (DSR) because of its low water and labour requirements. Whether and how DSR can be as productive as TPR has received widespread attention. Here, a comprehensive meta-analysis was performed to quantify the effects of direct seeding on rice yield and identify the management and environmental factors that contribute to the yield gap between DSR and TPR. The results showed that, overall, the yield of DSR was 12% lower than that of TPR. However, the yield loss of DSR relative to TPR was highly variable depending on management practices, soil type, and climate conditions, ranging from −2% to −42%. Weed and water management and climatic stress had the largest impact on yield performance, resulting in over 15% yield variation. With respect to soil properties, the yield gap can be significantly reduced by planting in areas with high organic carbon content, such as clayed and acidic soils. Furthermore, the DSR yield penalty was only 4% in a high-yielding condition compared to 14% in a low-yielding condition. All these factors indicate that optimizing management practices is necessary to improve DSR yield performance and narrow the yield gap between DSR and TPR. In conclusion, DSR could produce comparable yields to TPR but is more prone to yield losses due to inappropriate management practices, unsuitable soil properties, and climatic stresses.

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.

The effects of global warming on crop production have received great attention in recent years. However, inconsistent results have been obtained with regard to major crops such as rice and wheat in rice–wheat rotation systems of China. Therefore, we undertook a comprehensive meta‐analysis of literature data. The yield response to warming differed for rice and wheat in the rice–wheat rotation system. Overall, warming significantly increased wheat yield (by 4.8%) but significantly reduced rice yield (by 14.8%). A number of factors were responsible for these observations. For example, rice yield responses varied with the temperature increase, variety and nitrogen (N) rate. Of these, N was the most important variable influencing yield responses to warming. The yield loss for rice was lower at temperature increases of 0.40–1.40°C and at a high N rate than that at temperature increases of 1.60–2.49°C and at a low N rate, respectively. The yield loss of indica rice was lower than that of japonica rice. For wheat, however, yield responses to warming varied with the warming regime, ambient temperature, temperature increases, and CO₂ concentrations. Of these factors, ambient temperature was the most important variable influencing yield in response to warming. Warming increased wheat yield at a mean growth season temperature ≤10°C, temperature increases of 0.80–1.50°C, and at ambient CO₂ concentrations. In addition, either daytime warming or nighttime warming significantly increased wheat yield. However, all‐day warming had no effect on wheat yields. We conclude that global warming will benefit wheat production but result in a serious loss of rice yield in rice–wheat rotations in China.