Significant Acidification in Major Chinese Croplands

TLDR

Soil acidification is a major problem in intensive Chinese agricultural soils. The study used nationwide surveys, site‑level paired comparisons, and long‑term monitoring data to assess soil acidity changes. Soil pH fell sharply from the 1980s to the 2000s, driven mainly by nitrogen‑cycling and base‑cation uptake (20–221 kmol H⁺ ha⁻¹ yr⁻¹ and 15–20 kmol H⁺ ha⁻¹ yr⁻¹, respectively), while acid deposition contributed only 0.4–2.0 kmol H⁺ ha⁻¹ yr⁻¹.

Abstract

Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.