Assessment of Environmental Impacts of Some Plants in Crop Rotation with Soybeans Using SimaPro Software (Vr 9.5)

Introduction
Soybean, as one of the most important plant-based protein sources in the world, plays a vital role in human nutrition, animal feed, and various industries. This oilseed crop is recognized as a functional food due to its high protein content, essential amino acids, isoflavones, and bioactive compounds. Soybean is crucial for both human and animal nutrition, accounting for 28% of global oil production and approximately 60% (ranked first) of the world's animal feed protein supply. This highlights the impossibility of eliminating soybean from the livestock industry. Monocropping (cultivating the same crop on a piece of land over consecutive years) is a major constraint in soybean production. For instance, four-year monocropping can reduce soybean grain yield by up to 18.7%. Therefore, implementing a proper crop rotation system is essential to mitigate the drawbacks of monocropping and ensure sustainable production. However, previous studies on rotational crops with soybean have primarily focused on yield enhancement, neglecting their environmental impacts. Management strategies should be designed to ensure sustainability from economic, agronomic, and environmental perspectives. A valuable tool for assessing the environmental impacts of crop production processes is Life Cycle Assessment (LCA), which provides a comprehensive approach to evaluating the environmental footprint of agricultural products across all production stages. Accordingly, this study aimed to evaluate the environmental effects of seven proposed rotational crops to identify the most suitable plants for soybean rotation systems. The assessment considered their influence on key environmental health categories, including human health, natural resources, and ecosystems.
 
Materials and Methods
Impact analysis of crops on human health, ecosystems and resources was carried out using SimaPro vr 9.5.0. Method used for comparison was ReCiPe 2016 endpoint (H) V1.08/world (2010) H/A/characterization. The environmental damage data of plants was calculated based on the production of one kg of plants.
 
Results and Discussion
The studied crops (corn, alfalfa, rye, wheat, barley, rapeseed, and chickpea) influenced 22 impact categories across ecosystems, human health, and environmental resources. With the exception of rye's water consumption and terrestrial ecosystem impacts, all crops demonstrated negative environmental effects, indicating detrimental consequences for ecological health categories. Notably, rye exhibited positive environmental effects regarding water use and terrestrial ecosystems. The results showed that wheat and rye caused the most environmental damage in all three environmental categories (human health, ecosystems, and resources). While the least environmental damage belonged to alfalfa. The percentage of damage that wheat and rye cultivation inflicted on the human health category was obtained as 83% and 80% higher than alfalfa, respectively. After wheat and rye, the most damage to this category belonged to barley, which was about 60% higher than alfalfa. The results showed that all studied crops (corn, alfalfa, rye, wheat, barley, rapeseed, and chickpea) had their greatest environmental impact on human health, as the majority of environmental effects across all crops were associated with the human health category. Following human health, ecosystems were the second most affected category. The crops' impact on the resources category was negligible. Therefore, it can be concluded that when evaluating the environmental effects of these crops for soybean rotation systems, particular attention should be paid to their impacts on human health. Based on these findings, wheat and rye showed the most negative environmental impacts and are therefore not recommended for soybean rotation systems from an environmental perspective. In contrast, alfalfa and rapeseed, which demonstrated fewer negative environmental effects, can be utilized in rotation with soybeans. This approach would allow for both satisfactory grain yield and significant prevention of environmental degradation. However, considering wheat's economic importance and its crucial role in global food security, economic factors must be incorporated into final decision-making. Additional research is needed to determine whether wheat's environmental impacts in soybean rotation systems outweigh its economic benefits and the costs required to mitigate its negative environmental effects.
 
 
Conclusion
According to the findings of this research, among the crops proposed for rotation with soybeans, wheat and rye had the most negative impact on all three environmental categories: natural resources, ecosystems, and human health. In contrast, alfalfa production showed the lowest environmental impact. Based on the environmental effects of the evaluated crops, alfalfa and rapeseed are recommended as the most suitable options for rotation with soybeans to increase grain yield of soybean and reducing negative impacts of environment.