[Effects of Inorganic Fertilization on Soil Inorganic Carbon in Northern China's Croplands: A Meta-analysis]

Soil inorganic carbon (SIC) is a crucial carbon sink in terrestrial ecosystems. However, compared with soil organic carbon (SOC), SIC has received limited attention-particularly regarding its complex feedback mechanisms with human activities, which remain poorly understood. Based on 351 datasets from 24 domestic and international publications from 2000 to 2024, we conducted a Meta-analysis to investigate changes in SIC content in northern China's croplands under inorganic fertilization. Additionally, we combined multiple factors, such as climate, soil, and crop factors, to comprehensively explore the impact of inorganic fertilization on SIC content. The results showed that nitrogen addition significantly increased SIC content by 8%-28%, while combined nitrogen-phosphorus (NP) fertilization exerted significant negative effects on SIC. When fertilization duration exceeded 10 years or SOC content was high, inorganic fertilization could induce soil acidification, thereby promoting SIC dissolution and reducing its content. Surface soil exhibited stronger microbial activity, greater acidification, and higher moisture content compared to that in deeper soil layers, thereby enhancing SIC sensitivity to fertilization. During the initial establishment phase of fragrant pear orchards (<10 years), litter accumulation and improved soil pore structure facilitated carbonate accumulation, contributing to increased SIC content. As elevation decreased or the frost-free periods extended, rising temperatures promoted the accumulation of SIC under inorganic fertilization. Under high precipitation/low evaporation conditions, the increase of CO₂ partial pressure in soil pore water would promote the dissolution and migration of carbonates, which was not conducive to the storage of SIC. Agricultural strategies such as organic-inorganic fertilizer co-application, plastic mulching, and economic forest development could mitigate the negative effects of sole inorganic fertilization. This study provides a scientific basis for optimizing fertilization management in northern China's farmland, enhancing the carbon sink function of farmland soil, and responding to global climate change.