Proton accumulation accelerated by heavy chemical nitrogen fertilization and its long-term impact on

Cropland productivity has been signiifcantly impacted by soil acidiifcation resulted from nitrogen (N) fertilization, especialy as a result of excess ammoniacal N input. With decades’ intensive agricultural cultivation and heavy chemical N input in the Huang-Huai-Hai Plain, the impact extent of induced proton input on soil pH in the long term was not yet clear. In this study, acidiifcation rates of different soil layers in the soil proifle (0–120 cm) were calculated by pH buffer capacity (pHBC) and net input of protons due to chemical N incorporation. Topsoil (0–20 cm) pH changes of a long-term fertilization ifeld (from 1989) were determined to validate the predicted values. The results showed that the acid and alkali buffer capacities varied signiifcantly in the soil proifle, averaged 692 and 39.8 mmolc kg–1 pH–1, respectively. A signiifcant (P