Frontiers in Environmental Science (Apr 2022)
Characteristics of Fluorescent Dissolved Organic Matter in Paddy Soil Amended With Crop Residues After Column (0–40 cm) Leaching
Abstract
Dissolved organic matter (DOM) has a critical impact on various processes in the ecological environment, especially in soil and surface water due to its mobility and reactivity. In the present study, a column experiment simulating a paddy field was conducted to evaluate the feasible application of inorganic fertilizer incorporated with three types of organic materials (wheat straw, rapeseed shell, and astragalus smicus). Researchers investigated the vertical distinctions of soil (combined with different organic materials in 0–10 cm) DOM in 0–40 cm profiles after long-term leaching. Excitation–emission matrices coupled with parallel factor analyses (EEM-PARAFAC) and UV-visible techniques were employed to diagnose the spectral characteristics of soil DOM at four depths in different treatments, qualitatively and quantitatively. The results showed that the DOM content of CF (conventional fertilizer) (0.14 g kg−1) was the highest at the 10–20 cm layer and the CK (no fertilizer) (0.05 g kg−1) at 30–40 cm was the lowest, and the mean DOC concentration decreased with the increase in soil depth. Four fluorescent components, protein and tryptophan-like, humic acid-like, fulvic acid-like, and solubility-like microbial metabolite product materials, were identified by the PARAFAC model. Relative distributions of calculated components suggested that DOM mainly contained more aromatic humic materials and litter fulvic acid with the increase in soil depth. However, the SUVA254 showed a maximum in 20–30 cm layers, indicating strong aromatic and abundant hydrophobic fractions. Fluorescent index (FI) values of soil DOM from various treatments have a similar terrestrial and allochthonous source in topsoil and microbial source in deeper soil. In short, the findings obtained in our work could commendably provide some valuable optical information of DOM released from soil column and offer technical guidance when applying organic or green fertilizer to paddy soil during rice production.
Keywords
