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.
Highlights
Organic matter plays important roles in soil fertility, environmental protection, and sustainable agricultural development
CK, no-fertilizer control treatment; NPK, inorganic nitrogen (N), phosphate (P), and potassium (K) fertilizers treatment; M, manure treatment; MNPK, treatment of manure combined with inorganic N, P, and K fertilizers
The application of manure (MNPK and M treatments) increased the ratio of hydrogen to carbon (H/C) whereas the NPK treatment decreased the ratio of H/C in soil Humic acid (HA), which indicates that soil HA tends to be aliphatic and be simplified after the application of manure, whereas it tends to be complicated after using inorganic fertilizers
Summary
Organic matter plays important roles in soil fertility, environmental protection, and sustainable agricultural development. Soil humic acid composition and structure variety of soil properties and forms. The quantity, composition and nature of humus reflect certain conditions and processes of pedogenesis, and these factors are important indicators of soil fertility [1]. Humic acid (HA) is an important component of soil humus, and its composition, structure and properties are directly related to soil fertility and crop yield [2]. The addition of organic materials increases the content of HA in soil and changed its chemical structure [3,4]. Other research found that the fertilization has little changes on the elemental composition of HA and increases the relative molecular mass [6]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
