In situ visualization of soil profile acidification and processes following nitrogen fertilization and liming

authored by

Jingjing Tao, Lichao Fan, Tao Jiang, Xiaona Song, Mengzhen Zhao, Jianbin Zhou, Yakov Kuzyakov, Kazem Zamanian

Abstract

Soil pH is the master variable of soil properties and understanding its spatiotemporal changes in situ is key to unveiling numerous biogeochemical processes. The development of non-invasive imaging techniques provides the possibility to visualize and localize soil pH changes depending on various factors, e.g. fertilization and climate. Herein, the optodes pH mapping system was used to study the effects of eight fertilizer types including chicken manure, Ca(NO₃)₂, Mg(NO₃)₂, KNO₃, NH₄NO₃, (NH₄)₂SO₄, NH₄H₂PO₄, and urea on the spatiotemporal distribution of soil pH with and without liming at 10 °C and 25 °C. Ammonium-based fertilizers, especially NH₄NO₃, (NH₄)₂SO₄, and NH₄H₂PO₄ strongly decreased soil pH by a maximum of 1.4 ± 0.16 units at both temperatures. The 0–2 cm, where fertilizers were applied, had the highest pH decreases, from where the acidity rapidly diffused to depth. The acidified depth extended down to 4.5 ± 0.14 cm over 60 d. Chicken manure increased the pH within 5 d, but the pH decreased again after 60 d. Soil temperature was a strong controller of acidity generation and transport to depth after fertilization: pH decreased by 0.1 ± 0.07–0.3 ± 0.07 units more at 25 °C than 10 °C due to increased activity of nitrifying microorganisms, and higher temperature accelerated the spatiotemporal dynamics of soil acidity. Although pH increased shortly after liming compared to unlimed soils, it decreased after adding ammonium-based fertilizers. Therefore, N fertilizer types and temperature should be considered for having a more efficient fertilization management with less consequences for soil acidification. The planar optode is a powerful non-invasive imaging technique that enables in situ visualization of the spatiotemporal changes of soil pH profile after fertilization.

Organisation(s)

Institute of Earth System Sciences

External Organisation(s)

Northwest Agriculture and Forestry University
University of Göttingen
Peoples' Friendship University of Russia (RUDN)
Kazan Volga Region Federal University

Type

Article

Journal

GEODERMA

Volume

456

ISSN

0016-7061

Publication date

04.2025

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Soil Science

Sustainable Development Goals

SDG 2 - Zero Hunger

Electronic version(s)

https://doi.org/10.1016/j.geoderma.2025.117243 (Access: Open)