Field Crop 2025, Vol.8, No.6, 258-264 http://cropscipublisher.com/index.php/fc 262 6.2 Quality improvements in Huang-Huai-Hai Plain with moderate substitution In the Huanghuaihai Plain, planting soybeans in rotation or intercropping systems has a good effect. Yields have increased, soil organic carbon has increased, and overall carbon emissions have decreased. For example, when wheat and corn are planted together with soybeans, annual grain production has increased by 3.6% and energy production has increased by 6.7%. Moreover, more money can be made and planting is more sustainable (Yang et al., 2025). Field trials have also been conducted in this area, combining straw mulch with fertilization, which has increased soybean yields by an average of 17.2%. The structure of roots and leaves has improved, which has also improved seed quality and protein content. Compared with the old wheat-corn rotation system, wheat-soybean rotation produces more protein, higher returns, and is more environmentally friendly. 6.3 Soil improvement and fertilizer efficiency enhancement in southern hilly regions In the southern hilly areas and similar southwestern mountainous areas, planting soybeans and corn together (intercropping) is more effective than planting only one crop, and the total yield can be increased by about 12%. By adjusting the planting method, such as wider strips and appropriate row spacing, soybean yields and fertilizer use can be more effective. Studies in these regions also show that soybeans have many benefits when used in rotation or intercropping: they can make the soil structure softer, increase organic matter, and improve nutrient cycling. These changes make the land more fertile and more conducive to long-term planting in the future (Yang et al., 2024b). 7 Concluding Remarks In many planting methods, replacing part of chemical fertilizers with organic fertilizers can continuously improve crop yields, soil fertility and the quality of agricultural products. Generally speaking, the replacement ratio is between 30% and 50%. This practice can not only improve yields and water use efficiency, but also bring better economic benefits. It can also increase organic carbon in the soil, making nutrients more easily absorbed by plants and increasing the number of microbial species in the soil. These changes are all related to a more reasonable nutrient supply time, that is, fertilizers can better meet the growth needs of crops, thereby improving yields and quality. This "partial replacement" method has many other benefits. It can prevent soil acidification, reduce nitrous oxide emissions and nutrient loss, and is more environmentally friendly. Moreover, it can help farmers make more money, and the income per unit area can be increased by up to 46%. This method is suitable for different regions and various crops, so it is a very practical and popular green planting method. At the same time, the use of organic fertilizers can also better recycle and utilize organic waste such as farmyard manure and straw, which also makes it more supported in policy and more popular in practice. Looking ahead, partially replacing chemical fertilizers with organic fertilizers may become an important direction for achieving sustainable agricultural development. It can take into account both environmental protection and farmers' benefits without sacrificing yields. However, future research needs to continue to improve, such as finding the most suitable replacement ratio, controlling greenhouse gas emissions (such as carbon dioxide and methane), and making more specific plans for different regions, soils and crops. As soil management and microbial utilization technologies become more mature, combining organic fertilizers with chemical fertilizers will be a key step in achieving a high-yield, environmentally friendly and risk-resistant agricultural system. Acknowledgments We appreciate Dr Huang from the Hainan Institution of Biotechnology for his assistance in references collection and discussion for this work completion. Conflict of Interest Disclosure The authors affirm that this research was conducted without any commercial or financial relationships that could be construed as a potential conflict of interest.
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