Denitrification Potential of Paddy and Upland Soils Derived From the Same Parent Material Respond Differently to Long-Term Fertilization

Haicui Wang,Dandan Li,Qinghai Huang,Lei Ma,Jiabao Zhang,Kailou Liu,Zhaodong Liu,Bingzi Zhao

doi:10.3389/fenvs.2020.00105

Abstract

To investigate the effect of land use and fertilization regimes on soil denitrification potential (SDP), two more than 30-year long-term fertilization experiments derived from same parent material (paddy soil and upland soil) were selected. Generally, the SDP in paddy soil was 6.82 times higher than the upland soil, which was due to the higher abundances of narG, nirS, and nirK genes and nirS-denitrifying bacteria (Bradyrhizobium, Cupriavidus, and Herbaspirillum) in paddy soil. Inorganic fertilization regimes in upland soil did not significantly affect the SDP over Control, while the SDP in NPK and 2NPK of paddy soil decreased by 26.48% and 75.65%, respectively. Compared with Control, NPKOM consistently yielded the highest SDP in both two soils, with 2.47 times and 2.86 times higher for paddy soil and upland soil. The SDP of paddy soil showed correlation with narG and nirS genes mainly regulated by Alo, while the difference in the SDP of upland soil largely depended on the change of nirS-denitrifying bacteria at genus level (Herbaspirillum, Sulfuritalea, and Cupriavidus) and species level, which was mainly controlled by soil pH. PLS path modeling further demonstrated that direct effect of functional genes on the SDP was the greatest for paddy soil, while nirS-denitrifying bacterial communities for upland soil. The results presented herein represent a key step toward understanding the mechanisms that govern SDP under land use and long-term fertilization.

Highlights

Soil denitrification is an alternative respiratory microbial process under oxygen-limited conditions (Philippot and Hallin, 2005), which is an important process of the nitrogen cycle in upland and paddy fields (Galloway et al, 2004; Butterbach-Bahl et al, 2013; Yin et al, 2015)
Both paddy and upland soils developed from the Quaternary red clay, different land uses have led to significant differences in Soil organic matter (SOM), Total N (TN), NO3−, NH4+, Available P (AP), Free iron oxide (Fed), Feo, and aluminum oxide (Ald) for the control sites (Supplementary Table S4)
NPKOM application significantly increased contents of SOM, TN, and NH4+-N compared with the control, but no obvious differences among control, NPK, and 2NPK were found

Summary

Introduction

Soil denitrification is an alternative respiratory microbial process under oxygen-limited conditions (Philippot and Hallin, 2005), which is an important process of the nitrogen cycle in upland and paddy fields (Galloway et al, 2004; Butterbach-Bahl et al, 2013; Yin et al, 2015). Key functional genes, such as narG, nirS, nirK, and nosZ, involved in the denitrification process, have been commonly used to detect the abundance or diversity of denitrifying bacterial flora (Wolsing and Prieme, 2004; Sun et al, 2015). During this process, the nitrogen oxides (NO3− and NO2−) were reduced stepwise to gaseous oxides (NO, N2O, and/or N2) by particular groups of ubiquitous microorganisms under limiting oxygen (Henry et al, 2004; Philippot et al, 2007). A better understanding of the mechanisms by which denitrifying bacterial communities drive soil denitrification will be essential for developing management practices to regulate the soil N cycle

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