Short-term effects of nitrapyrin, rice straw and its biochar application on N transformation in soils of humid subtropical China

ABSTRACT

The features of N transformations in humid subtropical soils vary greatly due to the wide variations of soil properties, particularly soil pH. Purpose: To understand whether the effects of countermeasures regulating N transformation varied with the prevailing soil N transformation characteristics. Materials and methods: The effects of nitrapyrin, rice straw and its biochar applications on N dynamics at the beginning stage (first 24 h) of a zonal acid soil (JX soil, pH 5.26) and a non-zonal alkaline soil (SC soil, pH 7.62) from the humid subtropics in China were investigated via a ¹⁵N tracing laboratory incubation. Results and conclusions: Rice straw incorporation affected almost all processes involved in and production and consumption, and decreased the net mineralisation and nitrification rates in both soils significantly. Nitrapyrin decreased the net nitrification rates in both studied soils by affecting different N transformation processes. In the SC soil, nitrapyrin reduced the net nitrification rate by inhibiting the gross autotrophic nitrification rate while the gross autotrophic nitrification in the JX soil was negligible and nitrapyrin decreased its net nitrification via a stimulation of the gross rate of dissimilatory nitrate reduction to ammonium (DNRA). Biochar stimulated the gross rates of mineralisation, immobilisation, autotrophic nitrification and DNRA significantly, but did not affect the net mineralisation and nitrification rates in both soils. Countermeasures to regulate N transformations are tightly linked to the prevailing soil N transformation characteristics and should be taken into account for the recommendation of suitable management options.

KEYWORDS:

• N regulation
• N dynamics
• gross rate
• net rate
• ¹⁵N tracing

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Ying Zhao is a Ph.D. candidate at the School of Geography Sciences, Nanjing Normal University. Her research is about soil nitrogen transformation.

Jing Wang is employed at the College of Forestry, Nanjing Forestry University. Her research is about soil nitrogen transformation.

Zucong Cai is a professor at the School of Geography Sciences, Nanjing Normal University. His main research topic is about the relationship between soil nitrogen cycling and global change, including the relationship between nitrification/denitrification and nitrogen oxides emissions, and agricultural non-point source pollution.

Christoph Müller is a professor at Justus-Liebig University Giessen. His main research areas are: effect of climate change on ecological processes, elemental cycles in terrestrial ecosystems, and production processes of climate-relevant trace gases.

Jinbo Zhang is a professor at the School of Geography Sciences, Nanjing Normal University. He is mainly engaged in the study of soil carbon and nitrogen biogeochemistry cycle, focusing on soil nitrogen transformation processes and the relationship with environmental changes.

Additional information

Funding

This work was financially supported by grants from the National Natural Science Foundation of China [grant number 41330744], the National Basic Research Program of China (973 Program) [grant number 2015CB954201], and the Priority Academic Program Development of Jiangsu Higher Education Institutions [grant number PAPD, 164320H116]. This study is also in line and was carried out under the Consolidated Research Project (CRP) of the International Atomic Energy Agency (IAEA) [grant number D15016].