Abstract: Clarifying the yield and environmental effects of optimized fertilization in summer maize production in Hebei Province, and analyzing the influencing factors, are critical for providing data support for regional green agricultural development. Based on field trials conducted in Hebei Province from 2006 to 2022, we used farmer practice fertilization (FP) and no fertilization (CK) as control groups for optimized fertilization (OPT) to quantify the yield increase and greenhouse gas (GHG) emission reduction effects of optimized fertilization by meta-analysis. We analyzed the impacts of region identity (Baoding, Cangzhou, Langfang, Hengshui, Shijiazhuang, Handan and Xingtai), growing time (≤100, 101-110, 111-120, and >120 d), soil type (fluvo-aquic, meadow cinnamon, cinnamon and other), and soil fertility (high, medium, low) with random forest model. The results showed that compared to CK and FP, OPT significantly increased maize yields by 45.3% and 8.3%, respectively. Compared to FP, optimized fertilization significantly reduced fertilization-induced global warming potential (GWP_F) and greenhouse gas emission intensity (GHGI_F) by 8.7% and 16.0%, respectively. Among different regions, Cangzhou and Handan exhibited the highest yield increases in OPT treatment, while Langfang and Handan achieved the highest emission reductions, corresponding to GWP_F and GHGI_F. Among the soil types, calcareous cinnamon soil demonstrated the best performance in both yield increase and emission reduction. Across different growing periods, when it was ≤100 days, optimized fertilization achieved the highest yield and emission reduction benefits. Under basic soil productivity below 5.5 t·hm^-2, OPT showed greater potential for yield improvement and emission mitigation. For different soil fertility factors, when soil organic matter 10.0-15.0 g·kg^-1 and >25.0 g·kg^-1, pH 8.0-8.5 and 8.5-9.0, available nitrogen 50.0-80.0 mg·kg^-1 and ≤50.0 mg·kg^-1, Olsen phosphorus 10.0-15.0 mg·kg^-1 and ≤10.0 mg·kg^-1, and available potassium 100-115 mg·kg^-1 and >130 mg·kg^-1, the OPT had the greatest yield-increasing effect compared with the CK and FP, respectively. For emission reduction, when soil organic matter 10.0-15.0 g·kg^-1, pH 6.5-7.5, Olsen phosphorus >30.0 mg·kg^-1, and available potassium 100-115 mg·kg^-1, the OPT treatment had the greatest reduction effect of GWP_F and GHGI_F. When available nitrogen 110-140 and >140.0 mg·kg^-1, the OPT treatment had the greatest reduction effect of GWP_F and GHGI_F, respectively. The random forest model revealed that region identity and fertilization management were the most influential factor on yield and GHG mitigation, respectively. In summary, optimized fertilization could significantly increase the yield of summer maize in Hebei Province and reduce greenhouse gas emissions.

Key words: summer maize, optimized fertilization, meta-analysis, environmental effect