This study aimed to evaluate the effects of the nitrogen fertilizer optimization on the greenhouse gas emissions in the wheat/maize fields in the Huang-Huai-Hai Plain. There was the better balance in the crop yield and environmental sustainability. The conventional nitrogen application was set as the control group. The experimental groups included the reduced nitrogen application, organic fertilizer replacement, and inhibitors regulation. Meta analysis was finally implemented to clarify the impact of the nutrient fertilizer optimization on the greenhouse gas emissions in the wheat/maize fields. The results showed that nitrogen reduction could decrease the CO₂ emissions by 10.32% and N₂O emissions by 29.34% in the wheat/maize fields, compared with the conventional practices. There was the nonlinear positive correlation with the CO₂ reduction and nitrogen reduction ratios, indicating the greater efficacy in soils with pH > 6.5. N₂O reduction demonstrated the linear correlations with nitrogen reduction ratio. The optimal performance was achieved in soils with the organic matter content of ≤20 g/kg and nitrogen input >300 kg/hm². A nitrogen reduction of less than 20% was identified as the optimal threshold, in order to balance the yield stability and environmental benefits. There was the great contribution to the influencing factors on the greenhouse gas emissions under the reduced nitrogen fertilization. The soil pH shared the greatest impact on the CO₂ emissions, accounting for 30.5%. The contributions rates of the annual average precipitation and soil organic matter to the CO₂ emissions under reduced nitrogen fertilization were 19.8% and 17.8%, respectively. The soil SOM content had the greatest impact on the N₂O emissions, accounting for 24.5%. The nitrogen application rate was the second most important factor, contributing 20.8%. Organic replacement increased the CO₂ emissions by 14.26%, but reduced N₂O emissions by 15.97% in the wheat/maize fields. CO₂ emissions linearly increased with the replacement ratios, particularly under the conditions of the annual temperature ≤13 ℃, organic matter content of≤10 g/kg, and nitrogen input >300 kg/hm². Conversely, N₂O reduction was correlated positively with the substitution ratios. The maximum efficacy was achieved in loam soils with the annual precipitation ≤800 mm, temperature ≤13 ℃, and nitrogen input ≤200 kg/hm². A replacement ratio less than 30% was optimized from the emission reduction and yield enhancement. There was also the great contribution to the greenhouse gas emissions under the organic fertilizer replacement. The soil SOM content had the greatest impact on the CO₂ emissions, reaching 58.6%. The annual average temperature and crop type were contributed 24.4% and 22.6% to the N₂O emissions, respectively. Inhibitor regulation was significantly reduced the N₂O emissions by 42.84% in the wheat/maize fields. The N₂O emission reduction and production were ranked in the descending order of the nitrification inhibitor > combined application of urease/nitrification inhibitor > urease inhibitor. The best effect of 3,4-dimethylpyrazole phosphate was found among the nitrification inhibitors. There was the contribution rate of the influencing factors on the greenhouse gas emissions under the control of inhibitors. The type of the inhibitors had the highest contribution to the N₂O emissions, at 26.5%. While the contribution rates of the nitrogen fertilizer application rate and soil organic matter content were both above 15.0%. The finding can also provide a strong reference to optimize the nutrient measures in the grain fields, in order to balance the high crop yield, soil fertility, and greenhouse gas emission.

The objective of this study is to elucidate the nutrient accumulation and translocation, as well as the yield potential of the barren-tolerant and high-yielding maize varieties. The field experiments were conducted in N and P co-limited fields in 2022 and 2023. The 10 high-yielding maize varieties were taken as the tested materials. The treatments were set with fertilization and no fertilization. The results indicated that the varieties were classified into three types: barren-tolerant and high-yielding type (HB), barren-intolerant and high-yielding type (HNB), and barren-intolerant and sub-high-yielding type (SHNB), according to the average maize yield under fertilization and no fertilization. Under non-fertilized conditions, the yield of HB-type maize was significantly higher than that of the HNB and SHNB types by 16.23% and 19.66% in 2022, and 45.33% and 52.36% in 2023, respectively. Additionally, the total accumulation values of N, P, and K were all greater in the HB, compared with the HNB and SHNB varieties. The post-anthesis N accumulation of the HB varieties significantly increased by 38.22% to 54.99% and 57.34% to 82.00%, respectively, under no fertilization for two consecutive years; The post-anthesis P accumulation significantly increased by 76.19% to 106.31% and 105.56% to 317.60%, respectively; and the post-anthesis K accumulation significantly increased by 29.77% to 66.12% and 63.46% to 84.40%, respectively. However, there was no significant difference in the pre-anthesis N and P translocation among the three types of varieties. Under fertilization conditions, the indicators of the HB varieties shared no significant difference, compared with the HNB varieties, but they were significantly higher than those of the SHNB varieties. Their nutrient accumulation revealed that the HB varieties shared the outstanding advantage in the relative N, P, and K accumulation, indicating the strong capacity for nutrient acquisition. The maximum accumulation rates of N, P, and K were also significantly higher than before. These findings demonstrated that the HB varieties exhibited a pronounced superiority in the post-anthesis nutrient uptake and accumulation capacity in N- and P-deficient soils. The robust nutrient assimilation facilitated greater nutrient absorption and accumulation in the entire growth period, thereby enhancing the nutrient use efficiency. An ample supply of nutrients was realized during the critical grain-filling phase of maize, which was beneficial to the yield formation. In conclusion, HB maize shared an excellent capacity for tolerance and potential for fertilizer saving. The HB variety with its high yield and efficient nutrient utilization was suitable for the N and P co-limited fields. The finding can provide a scientific basis for the optimal selection of maize varieties and nutrient management.

No-tillage is one of the most important technologies in conservation agriculture. It is also crucial to understand the impact of no-tillage on grain crop yields, in order to promote the no-tillage application for food security. In this study, a meta-analysis was carried out to determine the regional yield and influencing factors of no-tillage on the three major crops in China. The data was collected from the published literature in Chinese (English) between 1995 and 2023. Conventional tillage (plowing, rotary tillage, or harrowing, depth < 18 cm) was taken as a control. Meta-analysis was employed to quantitatively investigate the overall and regional effects of no-tillage on the yield and yield components of three major grain crops (wheat, maize, and rice). Results showed that there was no significant effect of no-tillage on the regional yields of wheat, maize, and rice on the national scale. However, the regional analysis revealed that the no-tillage significantly increased the wheat yield by 4.1% and 2.2% in the Southwest and Northwest, respectively. There was a significant decrease in the maize yield by 2.4%, 2.6%, and 3.5% in the Northeast, Northwest, and Southeast, respectively. The rice yield was reduced by 1.0% in the Southeast. No significant effects were observed on the wheat and maize yields in North China, or on the wheat and rice yield in the rest regions. The yield components showed that the primary yield effect of no-tillage was attributed to the variation in the effective spikes. The influencing factors were examined on the regional crop yield. The mean annual precipitation was the main contributor to the wheat and maize yield, with the contribution rates of 12.7% and 13.6%, respectively. Soil organic carbon (SOC) content was the primary influencing factor (approximately 16.2%) on regional rice yield under no-tillage. The northwest region was characterized by mean annual temperatures <10 °C, annual precipitation <400 mm, and low soil nutrient content (SOC <10 g/kg, and total nitrogen <1 g/kg). Furthermore, no-tillage significantly increased the wheat yield under single and continuous cropping. Low annual precipitation (< 400 mm) promoted the maize yield in the Northwest, while the high soil pH (>8) and single or triple cropping in two years significantly reduced the crop yield. Specifically, the maize yield decreased in the Northeast and Southeast, which were influenced by the low (< 10 °C) and high (> 15 °C) temperatures, respectively. In the Southeast, the rice yield effects were influenced by the high annual precipitation (>800 mm), soil nutrient content (SOC >15 g/kg, and total nitrogen >1.5 g/kg), as well as the nitrogen and potassium fertilizer inputs. No-tillage was combined with the straw returning and scientific fertilization, in order to minimize the negative yield effect or even increase crop yield. The no-tillage technology was required to fully consider the crop types, regional climate, soil fertility, and cropping systems. These findings can provide a scientific basis to promote no-tillage technology in different agricultural regions in China.