Nitrogen fertilization raises CO₂ efflux from inorganic carbon

A global assessment

authored by

Kazem Zamanian, Mohsen Zarebanadkouki, Yakov Kuzyakov

Abstract

Nitrogen (N) fertilization is an indispensable agricultural practice worldwide, serving the survival of half of the global population. Nitrogen transformation (e.g., nitrification) in soil as well as plant N uptake releases protons and increases soil acidification. Neutralizing this acidity in carbonate-containing soils (7.49 × 10⁹ ha; ca. 54% of the global land surface area) leads to a CO₂ release corresponding to 0.21 kg C per kg of applied N. We here for the first time raise this problem of acidification of carbonate-containing soils and assess the global CO₂ release from pedogenic and geogenic carbonates in the upper 1 m soil depth. Based on a global N-fertilization map and the distribution of soils containing CaCO₃, we calculated the CO₂ amount released annually from the acidification of such soils to be 7.48 × 10¹² g C/year. This level of continuous CO₂ release will remain constant at least until soils are fertilized by N. Moreover, we estimated that about 273 × 10¹² g CO₂-C are released annually in the same process of CaCO₃ neutralization but involving liming of acid soils. These two CO₂ sources correspond to 3% of global CO₂ emissions by fossil fuel combustion or 30% of CO₂ by land-use changes. Importantly, the duration of CO₂ release after land-use changes usually lasts only 1–3 decades before a new C equilibrium is reached in soil. In contrast, the CO₂ released by CaCO₃ acidification cannot reach equilibrium, as long as N fertilizer is applied until it becomes completely neutralized. As the CaCO₃ amounts in soils, if present, are nearly unlimited, their complete dissolution and CO₂ release will take centuries or even millennia. This emphasizes the necessity of preventing soil acidification in N-fertilized soils as an effective strategy to inhibit millennia of CO₂ efflux to the atmosphere. Hence, N fertilization should be strictly calculated based on plant-demand, and overfertilization should be avoided not only because N is a source of local and regional eutrophication, but also because of the continuous CO₂ release by global acidification.

External Organisation(s)

University of Göttingen
University of Bayreuth
Kazan Volga Region Federal University

Type

Article

Journal

Global change biology

Volume

24

Pages

2810-2817

No. of pages

8

ISSN

1354-1013

Publication date

07.2018

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Global and Planetary Change, Environmental Chemistry, Ecology, Environmental Science(all)

Sustainable Development Goals

SDG 2 - Zero Hunger, SDG 15 - Life on Land

Electronic version(s)

https://doi.org/10.1111/gcb.14148 (Access: Closed)