Research on the trade-off relationship between soil nutrients and heavy metals based on exploratory factor analysis

Deciphering the dynamic interactions between soil nutrients and heavy metals is a key step to ensuring the sustainable and safe use of agricultural soils. Current studies mainly focus on soil organic matter or a single heavy metal pollutant, which makes it difficult to effectively quantify the risk of heavy metal accumulation during soil fertility improvement, and lack methods to evaluate the long-term sustainability of different farmland management practices. In this study, a typical black soil region in China was taken as an example. An exploratory factor analysis method (EFAM) was applied to integrate 21 soil physicochemical indicators, and scenario simulations were employed to quantitatively analyze the dynamic interactions between soil nutrients and heavy metals. Results showed that soil nutrients can be characterized based on three soil factors: soil organic matter, soil available nutrients, and soil nutrient buffering structure. By classifying agricultural intensity scenarios using the enrichment factor, it was found that fertilization enhanced the level of available nutrients and significantly increased soil organic matter and available phosphorus by 13.1% and 38.3%, respectively. However, the soil Cd concentration in the high-intensity agricultural scenario (HS) significantly increased by 74.8% compared to the traditional agricultural area (TS). Further long-term simulations indicated that under high-intensity farming scenarios, soil Cd concentrations would increase from 0.17 mg·kg^-1 to 0.40 mg·kg^-1 over the next 50 years. The study demonstrated that long-term excessive application of phosphate fertilizers leads to nutrient surpluses and continuous Cd accumulation, whereas maintaining appropriate levels of soil available phosphorus is a key to balancing nutrient utilization and pollution risk. The combined application of EFAM and scenario simulation provides a scientific basis for enhancing the long-term protection and sustainable management of agricultural soils.