Revise the following abstract, noting that the abstract must be more than 800 words: low soil organic carbon level and large nitrogen fertilizer loss in the current season are urgent problems that need to be solved in the process of improving the quality of cultivated land in medium and low-yield fields in the Yellow River Gudao area, but their targeted improvement strategies still need to be further clarified. Therefore, meta-analysis was used to analyze the effects of natural factors, soil physicochemical indexes and nitrogen fertilizer application on the total nitrogen loss of fertilizers in the current season, and the main influencing factors of nitrogen fertilizer loss and their relationship with soil organic carbon (SOC) were clarified. Then, aiming at typical low- and medium-yield fields in the Gudao area of the Yellow River, field experiments were used to explore the effects of no-tillage, biochar application and polyacrylamide (PAM) application on SOC, soil aggregate, soil available nutrient content and crop yield, analyze the improvement effect of soil fertility under improvement measures, and explore effective measures to achieve rapid SOC improvement. Finally, the 15N in-situ tracing method was used to quantify the impact of each improvement measure on the destination and total loss of nitrogen fertilizer in the current season, analyze the reduction effect of nitrogen fertilizer loss in the current season under the improvement measures, and explore the best scheme to achieve SOC improvement and nitrogen loss reduction synergistically. The main results of this study are as follows: (1) Integrating the results at the global scale through meta-analysis, it was found that the SOC content of farmland in China was significantly lower than that in Europe and the United States (10.59 g/kg vs. 17.99 g/kg), but the total nitrogen loss in the current season was significantly higher than that in Europe and the United States. In terms of the effects of natural factors and soil physicochemical indexes on the proportion of nitrogen and fertilizer loss in the current season, the wheat season was mainly affected by the average annual precipitation (MAP) and soil pH, the rice season was mainly affected by pH and SOC content, and the corn season was mainly affected by SOC and rainfall. With the increase of nitrogen application, the total loss of soil nitrogen fertilizer increased significantly. By optimizing the nitrogen application rate and improving the SOC level, the nitrogen fertilizer loss can be reduced by 25.61 ~ 64.49 kg N/ha/season under the premise of ensuring crop yield. (2) The field test results showed that compared with conventional management, the application of biochar and the no-tillage measures increased the SOC content by 6.7%, 30.2%, 13.7% and 21.7%, respectively (P <0.05) in typical low- and medium-yield fields in the Gudao area of the Yellow River. The application of biochar and PAM significantly increased the content of large aggregates in soil aggregates, which increased by 0.9%, 13.9%, 1.8% and 14.5%, respectively (P < 0.05). The application of biochar significantly increased the average weight diameter of agglomerates by 4.3% and 18.0% (P <0.05). The SOC content increased significantly by 4.20 g/kg in two years, which was the highest among the treatments, and the yield increased by 6.3% and 12.9% compared with conventional crops, so biochar + PAM+ no-till could be used as a comprehensive optimization measure to improve grain yield and soil fertility. (3) Through 15N in-situ tracing, it was found that although the combined application of biochar and PAM under rotary tillage conditions could significantly increase the SOC content by 22.1% and reduce the total nitrogen loss of wheat season by 9.1%, it would lead to an increase of 10.2% in corn season fertilizer nitrogen loss. The nitrogen loss of fertilizer in the two crops under no-tillage combined with biochar and PAM application was significantly reduced by 11.3%~12.8%, and soil TN4.9%, available phosphorus 43.54% and soil available potassium content increased by 20.1%. Therefore, although the increase of SOC content can increase the nutrient storage capacity, the influence of the interaction between materials and tillage measures on the nitrogen loss in the current season should also be considered in the selection of improvement measures. No-tillage combined with biochar and PAM application can be used as a feasible scheme for SOC improvement and nitrogen loss reduction in the Yellow River Gudao area.
To improve the quality of low-yielding farmland in the Yellow River old channel area, it is important to address the issues of low soil organic carbon (SOC) levels and high nitrogen fertilizer loss during the growing season. This study used meta-analysis to identify the main factors affecting nitrogen loss and their relationship with SOC, and conducted field experiments to investigate the effects of no-till, biochar application, and polyacrylamide (PAM) application on SOC, soil aggregates, nutrient availability, and crop yields. The results showed that optimizing nitrogen fertilizer application while increasing SOC levels can reduce nitrogen loss by 25.61-64.49 kg N/ha/season while maintaining crop yields. Biochar and no-till practices were effective in increasing SOC levels, soil aggregate stability, and crop yields, and combining these practices with PAM application further improved the efficacy. However, the interaction between management practices and materials should be considered when selecting improvement strategies. From the results, it can be concluded that no-till in combination with biochar and PAM application could be integrated as a feasible solution to enhance SOC and reduce nitrogen loss in the Yellow River old channel area.
Published: 3 days ago