Northeast China is a vital grain production region of China. By means of Meta analysis, we studied the synergistic effects of agricultural management practices and climatic factors on rice yield in cold regions, to provide a theoretical basis for high and stable rice production in this area.

Literature published from 2003 to 2024 was searched on Web of Science, PubMed, CNKI, WanFang, and VIP databases using the keywords “cold region” or “Northeast China” and “rice yield” or “straw return” or “nitrogen application” or “nitrogen cycle”. The studies were then screened based on the following criteria: 1) Field experiments conducted in the three northeastern provinces of China; 2) Included straw return or nitrogen fertilization treatments, with corresponding controls (no straw return or no nitrogen application); 3) Reported complete data with means, standard deviations (SD) or standard errors (SE), and had at least three replicates (n≥3); 4) Provided rice yield data and at least one indicator of soil properties and/or the abundance of a nitrogen - cycling gene. A total of 175 pieces of literature were acquired from 61 observation sites across the three northeastern provinces. Among these, 570 datasets were extracted from 154 publications, and the effects of straw return duration, nitrogen application rate, tillage, and irrigation methods on rice yield and soil physicochemical properties were quantified using a Random Forest model. Additionally, 73 datasets were obtained from the remaining 21 pieces of literature to examine the correlation between nitrogen-cycling functional genes and soil factors to elucidate the underlying microbially-mediated mechanisms.

The random forest model identified soil organic carbon (SOC) and nitrogen application rate as the dominant factors influencing rice yield, with contribution rates of 27.05% and 24.14%, respectively. Subgroup analysis revealed that the combination of deep tillage with film mulching and controlled irrigation (PFM-CI) increased SOC content and rice yield by 20.46% and 36.24%, respectively. Under conditions of nitrogen application at 90−180 kg/hm², straw return rates of 6000−9000 kg/hm², and a return duration of 5−10 years, medium -maturing rice varieties exhibited higher yield increases compared with early- and late-maturing varieties. The interaction between nitrification and denitrification processes regulated soil nitrogen forms and availability, thereby significantly affecting rice yield in cold regions. Correlation analysis showed that SOC was positively correlated with the abundance of the denitrification gene nosZ (r=0.84), and the abundance of nosZ was significantly positively correlated with total nitrogen (TN) content in the anaerobic paddy soils (r=0.85, P<0.001). SOC also showed a positive correlation with the abundance of the ammonia-oxidizing archaeal gene AOA-amoA (r=0.22).

Rice yield in cold regions is jointly regulated by soil carbon and nitrogen contents as well as microbial transformation processes. Adopting the deep tillage combined with film mulching and controlled irrigation (PFM-CI) mode, optimizing the nitrogen fertilizer-to-straw return ratio, and selecting medium-maturing varieties are key strategies for enhancing rice yield and nitrogen use efficiency in the cold regions of Northeast China.