Molecular Soil Biology 2025, Vol.16, No.2, 63-72 http://bioscipublisher.com/index.php/msb 69 more sustainable. This "combination management" approach can not only amplify the effect of soil improvement, but also promote the long-term stable development of agriculture. 7 Challenges and Limitations 7.1 The costs, technical implementation difficulties, and economic feasibility of soil improvement Although improving soil structure has many benefits for planting, it is not easy to actually implement it. Some new improvement technologies, such as the use of plant growth-promoting bacteria (PGPB) or nanomaterials, although they can indeed help plants detoxify and stimulate growth, their raw materials and equipment prices are usually not low (Sun et al., 2022). These techniques also involve rather complex reaction processes between soil and crops, and they are not easy for everyone to master. Farmers may need to learn some basic knowledge first before they can use them correctly. In addition to the input cost, the final economic return also needs to be considered in the actual planting process. If an improvement measure costs a lot of money but does not significantly increase production or fails to fetch a good price, it is actually not very cost-effective. For instance, the addition of plant hormones (such as indoleacetic acid IAA) can indeed promote crop growth and reduce the accumulation of heavy metals in plants. However, if the benefits do not cover the inputs, this method loses its significance (He et al., 2021). So before deciding whether to carry out soil improvement or not, it is best to conduct a detailed income and expenditure analysis. Only when the returns can exceed the investment in the long term are these measures worth continuing to promote and apply. 7.2 Regional differences leading to variations in soil improvement effectiveness The soil conditions vary greatly in different regions, which can result in different effects of the same improvement methods in different places. In the arid Pilbara region of Australia, scientists tried using inorganic amendments such as gypsum and urea, and found that although seedlings grew faster, the rate of dead seedlings also increased (Bateman et al., 2019). This indicates that not all places can use the same method, and it depends on the local climate, soil type, and agricultural habits. In some places, the available resources are also relatively limited. Lack of topsoil or suitable organic materials poses difficulties for soil improvement. In this case, some people began to try soilless seedling cultivation methods, although this approach also has problems, such as slower greening after transplantation and changes in plant hormone levels (Lei et al., 2017). So in practical operation, it is necessary to find a more suitable solution based on local conditions, and not blindly apply the experience of other places. 7.3 Potential environmental impacts and risks associated with certain soil improvement measures Although most soil improvement methods are beneficial to crop growth and can reduce some harmful components, in some cases, they may also bring considerable environmental risks. Therefore, when using these materials, one should not only focus on the immediate benefits but also take into account the long-term ecological impact. Take nanomaterials for example. If the usage methods are not appropriate, they may bring some unexpected problems to the environment. For example, although iron oxide nanoparticles can reduce the toxicity of arsenic in plants, it is still unclear whether they will have side effects in the ecosystem in the long term (Sun et al., 2022). Special attention should be paid to the application of such materials. Regular monitoring should be carried out to avoid causing damage to the microbial community in the soil or water. Inorganic improvers are not 100% safe either. If used in excessive amounts, it may alter the chemical state of the soil and interfere with the normal activities of beneficial microorganisms in the soil. Some studies have pointed out that when conducting mine land restoration, if the dosage of gypsum and urea is too large, although the soil quality in some areas has improved, the problem of increased seedling mortality rate has also emerged (Bateman et al., 2019). Therefore, when applying these substances, it is necessary to control the dosage well to avoid "good intentions leading to bad results". 8 Future Directions and Research Needs 8.1 The need for research on promoting soil improvement techniques in different regions Soil and climate conditions vary in different regions, so the implementation of soil improvement technologies needs to be adapted to local conditions and cannot be applied universally. Lei et al. (2019) conducted a study in the gully areas of the Loess Plateau in China. They used organic fertilizers and fly ash, effectively improving the local soil conditions and increasing the crop yield. But if this method is applied to other regions, it won't work
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