Effects of long-term fertilization on soil humic acid composition and structure in Black Soil

Jiuming Zhang; Jingkuan Wang; Tingting An; Dan Wei; Fengqin Chi; Baoku Zhou

doi:10.1371/journal.pone.0186918

Effects of long-term fertilization on soil humic acid composition and structure in Black Soil

PLoS One. 2017 Nov 2;12(11):e0186918. doi: 10.1371/journal.pone.0186918. eCollection 2017.

Authors

Jiuming Zhang^{1

2}, Jingkuan Wang¹, Tingting An¹, Dan Wei², Fengqin Chi², Baoku Zhou²

Affiliations

¹ College of Land and Environment, Shenyang Agricultural University, Shenyang, China.
² Soil Fertilizer and Environment Resources Institute, Heilongjiang Academy of Agricultural Sciences, Key Laboratory of Soil Environment and Plant Nutrition of Harbin, Heilongjiang Province, China.

Abstract

The composition and structure of humic acid (HA) can be affected by fertilization, but the short-term effects are difficult to detect using traditional analysis methods. Using a 35-year long-term experiment in Black Soil, the molecular structure of HA was analyzed with Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance spectroscopy (NMR), and fluorescence spectroscopy. Variation in HA was analyzed after long-term fertilization, including fertilization with manure (M), inorganic N, P and K fertilizer (NPK), manure combined with inorganic N, P, and K fertilizer (MNPK), and a no-fertilizer control (CK). The application of each fertilizer treatment increased crop yields compared with the CK treatment, and the MNPK treatment increased crop yield the most. The ratio of main IR absorption peak of HA at 2,920 cm-1 compared with the peak at 2,850 cm-1 (2920/2850) was higher in the NPK and MNPK treatments compared with the CK treatment. The application of manure (MNPK and M treatments) increased the ratio of hydrogen to carbon (H/C) in HA, and raised the ratio of the main IR absorption peak of HA at 2920 cm-1 to that at 1720 cm-1 (2920/1720). Manure treatments also raised the ratio of aliphatic carbon (C) to aromatic C, alkyl C to alkoxy C and hydrophobic C to hydrophilic C and the fluorescence index (f 450/500), but decreased the degree of aromatization of HA, when compared with the CK treatment. The ratio between each type of C in HA was similar among all the fertilizer treatments, but NPK had a lower ratio of H/C and a lower content of aliphatic C compared with the CK treatment. These results indicated that the molecular structure of HA in Black Soil tends to be aliphatic, simpler, and younger after the application of manure. While the application of inorganic fertilizers increased in the degree of condensation of HA and made HA structure complicated. The application of manure alone or combined with inorganic fertilizers may be an effective way to increase crop yield and improve the structure of soil organic matter.

MeSH terms

Carbon-13 Magnetic Resonance Spectroscopy
Crops, Agricultural
Fertilizers*
Humic Substances*
Soil / chemistry*
Spectrometry, Fluorescence
Spectroscopy, Fourier Transform Infrared

Substances

Fertilizers
Humic Substances
Soil

Grants and funding

The study was supported by the Youth Fund of Heilongjiang Province (Grant No. QC2014C042), National Science and Technology Support Program (Grant No. 2013BAD07B01), National Natural Science Foundation of China (41771284), and the Public Welfare Industry (agriculture) Research Project (Grant No. 201303126) supported this study.