Subsurface soil inorganic carbon gains offset half of surface losses in China's upland croplands over the last four decades.
Cai A, Han T, Zhou Z, Liu K, Xu X
Soil Health
The dirt beneath your food crops holds as much carbon as all Earth's living plants combined, and this study shows that modern farming is quietly moving that carbon deeper underground, changing soil fertility and the planet's ability to buffer climate change in ways we're only beginning to measure.
Soil stores an enormous amount of carbon in mineral form — not just in dead leaves and roots, but locked in rocks and salts. Scientists compared thousands of farm soil samples from across China taken in the 1980s versus 2023 and found that the topsoil has been steadily losing this stored carbon, likely due to plowing, irrigation, and fertilizers. But surprisingly, deeper soil layers have been gaining carbon at the same time, cushioning about half of the loss — meaning the full picture is more complicated than simply 'farming depletes soil carbon.'
Key Findings
Surface soil (0–40 cm) in China's upland croplands lost an average of 0.68 kg of inorganic carbon per square meter over the past four decades.
Subsurface soil gains offset approximately half of the surface inorganic carbon losses, revealing significant downward redistribution of carbon through the soil profile.
The study is among the most comprehensive of its kind, comparing 4,305 soil profiles across 204 matched sites sampled in the 1980s and re-verified in 2023.
chevron_right Technical Summary
A large-scale study of China's farmland soils found that four decades of intensive agriculture have depleted inorganic carbon in the top 40 cm of soil, but deeper layers have gained enough carbon to offset roughly half the surface losses. This challenges the long-held assumption that soil inorganic carbon is stable over human timescales and reveals that farming reshuffles — not just destroys — this vast underground carbon reservoir.
Abstract Preview
Soil inorganic carbon (SIC) constitutes half of the terrestrial carbon pool and exerts a profound influence on global carbon cycling and ecosystem multifunctionality. Contrary to the view of millen...
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