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Sulfur Species Formed in the Seed Row of Sulfur‐Fertilized Soils as Revealed by K‐Edge X‐ray Absorption Near‐Edge Structure Spectroscopy
Author(s) -
Kar Gourango,
Schoenau Jeff J.,
Gillespie Adam W.,
Dhillon Gurbir Singh,
Peak Derek
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2019.01.0008
Subject(s) - sulfur , chemistry , fertilizer , ammonium sulfate , gypsum , soil water , thiosulfate , sulfate , chernozem , xanes , ammonium , agronomy , inorganic chemistry , environmental chemistry , spectroscopy , soil science , materials science , environmental science , metallurgy , organic chemistry , physics , quantum mechanics , biology
Core Ideas Knowledge of the S fertilizer reaction products is important for understanding the behavior and efficacy of S fertilizers in soils. Sulfur K‐edge X‐ray absorption near‐edge structure spectroscopy is a useful tool for identifying the soil S species formed following application of different fertilizer forms under field conditions. Knowledge of S fertilizer reaction products following application is needed to predict the ability of different fertilizer forms to provide sufficient plant‐available S to crops. K‐edge X‐ray absorption near‐edge structure (XANES) spectroscopy and wet chemical analysis techniques were used to identify the soil S species formed week to months after fertilization in the field on Brown Chernozem and Black Chernozem soils in Saskatchewan, Canada. The S fertilizer forms were ammonium sulfate, liquid ammonium thiosulfate, gypsum, elemental S, and a zero‐S control treatment. Treatments were applied at seeding at 20 kg S ha −1 . Sulfur as ammonium sulfate, ammonium thiosulfate, and gypsum increased the extractable SO 4 –S in the seed row 1 wk after application; thereafter, it decreased through plant uptake and runoff. For all fertilizers, total S concentration in the seed row increased after application and decreased over time. The XANES results showed that the highly oxidized sulfate form of S was dominant (45–55%) in ammonium sulfate‐ and gypsum‐treated soils 1 wk following application. Thereafter, the proportion as sulfate decreased over time while the reduced and intermediate S forms increased. The proportion of reduced S was highest in the elemental S and ammonium thiosulfate treatments and the proportion in oxidized forms increased from Week 1 to Week 8. Overall, the highly oxidized fertilizer S forms applied (sulfates) transformed to intermediate and reduced S species via immobilization and reduction processes, whereas the highly reduced forms (e.g., elemental S) underwent some oxidation as reduced S decreased and highly oxidized sulfate increased.