Abstract Soil carbonates (inorganic C mainly as CaCO3) account for about 750 Gt C in the top 1 m and more than 2300 Gt in the top 2 m (nearly equal to organic C stocks). These inorganic C stocks have millennial to million-year turnover times and protect natural soils from degradation. Under croplands, however, these inorganic C stocks are continuously lost as CO2 by neutralization of N-fertilization-induced soil acidification. We estimated that over the last 50 years, at least 0.41 Gt C have been released irrecoverably as CO2 to the atmosphere from agricultural soils, and an additional 0.72 Gt C will be released until 2050. These inorganic C losses make our soils vulnerable to physical, chemical and biological degradation. Liming – a common agricultural practice to neutralize soil acidification – is the 2nd enormous source of irrecoverable C, accounting annually for 0.27 Gt C losses as CO2. In conclusion, soil carbonate loss due to N-fertilization-induced acidification is a huge source of unaccounted CO2 from C stock, which is irrecoverable over the mankind lifetime.

中文翻译：

---

土壤碳酸盐：无法计算的、不可恢复的碳源

摘要 土壤碳酸盐（无机碳主要为CaCO3）在顶部1 m 中约占750 Gt C，在顶部2 m 中占2300 Gt 以上（几乎等于有机碳储量）。这些无机碳储量具有千年到百万年的周转时间，并保护天然土壤免于退化。然而，在农田下，通过中和施氮引起的土壤酸化，这些无机碳库作为 CO2 不断流失。我们估计，在过去的 50 年中，至少 0.41 Gt C 已从农业土壤中以 CO2 的形式不可恢复地释放到大气中，另外 0.72 Gt C 将在 2050 年之前释放。这些无机碳损失使我们的土壤容易受到物理、化学和生物降解。石灰——一种中和土壤酸化的常见农业实践——是不可恢复的 C 的第二大来源，每年将 0.27 Gt C 损失计为 CO2。总之，施氮引起的酸化造成的土壤碳酸盐损失是 C 库中未计算的 CO2 的一个巨大来源，在人类的一生中是无法恢复的。