Long-Term Nitrogen Fertilization Impacts on Soil Bacteria, Grain Yield and Nitrogen Use Efficiency of Wheat in Semiarid Loess Plateau, China

Aixia Xu,Jeffrey A Coulter,Shahbaz Khan,Zhuzhu Luo,Lingling Li,Liqun Cai,Linlin Wang,Chang Liu,Junhong Xie,Subramaniam Gopalakrishnan,Renzhi Zhang

doi:10.3390/agronomy10081175

Abstract

Soil bacteria are key components of the soil microbial community contributing to soil health. Nitrogen (N) fertilization is an important factor that affects soil microbial community and cereal production. This study aims to explore the impact of long-term N fertilization on soil bacterial diversity, nitrogen use efficiency (NUE), and the grain yield of wheat in the semiarid region of Loess Plateau, China. The field experiment was conducted from 2003 to 2018 including five N treatments: 0 (N0), 52.5 (N52.5), 105 (N105), 157.5 (N157.5), and 210 (N210) kg N ha−1 yr−1. The soil pH was decreased by the N fertilization, while the soil ammonium, nitrate, and available phosphorus were increased. The N uptake and grain yield of wheat were significantly increased with N and the highest NUE (28%) and grain yield (44% higher than control) were observed at 105 kg N ha−1, but no significant increase in yield was observed by further increasing N rate. The bacterial diversity was significantly increased at N105. Soil bacteria community was strongly related to soil chemical properties and ammonium content was the most important contributor. The dominant soil bacterial phyla were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Gemmatimonadetes, Bacteroidetes, Nitrospirae, Verrucomicrobia, and Planctomycetes. The higher grain yield of wheat was related to the higher class Gammaproteobacteria and Sphingobacteriia abundance, and lower class Acidobacteria and Chloroflexia abundance. In summary, 105 kg ha−1 yr−1 was the optimum rate of N for diversified soil bacterial community and wheat yield for sustainable wheat production in semiarid Loess Plateau of China, whose higher N use efficiency was attributed to the higher phyla Verrucomicrobia and Planctomycetes, and lower Proteobacteria abundance.

Highlights

Nitrogen (N) is one of the most important elements in plant nutrition [1] and its deficiency can limit the productivity of crops [2,3]
There were no significant differences in soil total phosphorus (TP), total phosphorus (TN), and soil moisture (SM)
Results from this study showed that the soil NH4 concentration was correlated with most of the diversity indices, Simpson’s index was positively correlated with soil pH, and operational taxonomic units (OTUs) were positively correlated with grain yield and nitrogen use efficiency (NUE)

Summary

Introduction

Nitrogen (N) is one of the most important elements in plant nutrition [1] and its deficiency can limit the productivity of crops [2,3]. The global use of N fertilizer had increased dramatically, from 112.5 million tons in 2015 to 118.2 million tons in 2019 [8]. The use of N fertilizer in China exceeded 31 million tons in 2014, accounting for approximately 29% of global consumption [9], and the crop recovery rate of N fertilizer only accounts for 25–50% of the application rate [10,11]. Long-term application of high N affects soil properties [15,16], and leads to low nitrogen use efficiency (NUE), large amounts of nitrate in the soil profile [6], and subsequent soil acidification [15], groundwater pollution, eutrophication of surface water [17], and increased greenhouse gases emissions [18]

Objectives

Methods

Results

Conclusion