Influences of Nitrogen Application Levels on Properties of Humic Acids in Chernozem Amended with Different Types of Organic Materials

Wang Wang,Zhang Zhang,Yin Yin,Chen Chen

doi:10.3390/su11195405

Abstract

The objective of this study was to examine the structure changes in humic acids (HAs) in Chernozem after the application of different types of organic materials (OMs) under an indoor simulation condition for plastic mulched drip irrigation, measured with Fourier transform infrared (FTIR) spectroscopy. The biotechnological extract of fulvic acid (BFA), decomposed sheep manure (M), corn straw pellets (Ps) and corn straw powder (Pr) were used as the four OMs for testing, and they were applied to Chernozem at the same amount of actual material; three nitrogen (N) levels (no N, low N, and high N supply) were applied to each type of (OMs), separately. The total culture period was set to 90 days and soil sampling was taken at 0, 30, 60 and 90 days, respectively. The results showed that different types of OMs exerted different effects on Chernozem based on the FTIR spectra of HAs. The application of M combined with high N supply was the best way to fertilize Chernozem, under which the H-bonded OH groups and aromatic compounds were enhanced, resulting in increased soil carbon (C) sequestration; while the carbohydrates in HAs was easily consumed as microbial energy substance. The HAs from the Chernozem amended with BFA became more aliphatic, simpler and younger. High N supply was beneficial for increasing the complexity of HAs from Chernozem amended with Ps, but was not conducive to soil cation retention. Within a short time of incubation, the application of Pr combined with high N was detrimental to the C sequestration in Chernozem, and inhibited the consumption of carbohydrates by microorganisms.

Highlights

Maintaining food security was a major challenge in China
All the Fourier transform infrared (FTIR) spectra showed the predominance of hydroxyl groups, aromatic compounds [4], and carbohydrates in the humic acids (HAs) extracted from Chernozem amended with these four types of organic materials (OMs)
It was feasible to evaluate the effects of different types of OMs on Chernozem fertility and health according to the spectral characteristics of HAs using the FTIR spectroscopy technique

Summary

Introduction

Maintaining food security was a major challenge in China. The deterioration in soil quality is a very severe problem. The decline in soil fertility and productivity due to excessive soil erosion, nutrient run-off, and loss of soil organic matter (SOM) has stimulated the interest in improving soil quality with the addition of organic materials (OMs) from different sources [1]. To maintain or improve the fertility and productivity of arable soils, several types of OMs can be considered, such as crop straw, animal manure and other organic wastes from agricultural processing, as a source of SOM. The HAs function in various ways in maintaining and improving soil fertility and health, the quality of HAs is considered as a key indicator for evaluating the effects of different types of OMs on soil fertility and health [4]

Objectives

Methods

Results

Conclusion