Degradation of the Urease Inhibitor NBPT as Affected by Soil pH

Soil Science Society of America JournalVolume 79, Issue 6 p. 1674-1683 Soil Fertility & Plant Nutrition Degradation of the Urease Inhibitor NBPT as Affected by Soil pH Richard E. Engel, Corresponding Author Richard E. Engel [email protected] Dep. of Land Resources and Environ. Sci., Montana State Univ., 334 Leon Johnson Hall P.O. Box 173120, Bozeman, MT, 59717-3120Corresponding author ([email protected]).Search for more papers by this authorBrad D. Towey, Brad D. Towey Dep. of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717Search for more papers by this authorEmily Gravens, Emily Gravens Dep. of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717Search for more papers by this author Richard E. Engel, Corresponding Author Richard E. Engel [email protected] Dep. of Land Resources and Environ. Sci., Montana State Univ., 334 Leon Johnson Hall P.O. Box 173120, Bozeman, MT, 59717-3120Corresponding author ([email protected]).Search for more papers by this authorBrad D. Towey, Brad D. Towey Dep. of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717Search for more papers by this authorEmily Gravens, Emily Gravens Dep. of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717Search for more papers by this author First published: 06 November 2015 https://doi.org/10.2136/sssaj2015.05.0169Citations: 61 This article has supplemental material available online. All Rights reserved. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract Soil pH is an important property affecting N-(n-butyl) thiophosphoric triamide (NBPT) inhibition of urease. Only a few studies have followed NBPT decay kinetics by making direct measurements of this molecule, and its oxygen analog (NBPTo) in soil or buffer mediums. This study characterized NBPT metabolism under biotic and abiotic conditions including the appearance of NBPTo and decay products under a pH gradient. Chemical buffer incubations were conducted at pH 4.0, 5.0, 6.0, and 7.2, and degradation was quantified using 1H-NMR. Soil incubations were conducted at pH 5.1, 6.1, 7.6, and 8.2 with sterilized (autoclaved) and non-sterilized soil collected from an agricultural field; and NBPT degradation and metabolism products were measured with high-preformance liquid chromatography (HPLC)-mass spectroscopy (MS). We found NBPT and NBPTo followed pseudo first-order decay kinetics in chemical buffers, and NBPT exhibited exponential decay patterns in soil with n-butylamine being a primary reaction product. The NBPT decay constants in buffers and soil were larger under acidic conditions and became progressively smaller as pH rose. Calculated NBPT half-life in non-sterilized soil was 0.07, 0.59, 2.70, and 3.43 d at pH 5.1, 6.1, 7.6, and 8.2, respectively. Soil sterilization increased these half-lives by 0.13, 0.55, 1.03, and 4.07 d, respectively. We found NBPTo to be more sensitive than NBPT to hydrolysis as result of the greater electrophilicity of the P atom. Chemical hydrolysis will likely be a large contributing factor to NBPT and NBPTo degradation in acidic to slightly alkaline soils (pH 5.1–7.6), while microbial degradation will likely become more important under more strongly alkaline conditions (pH 8.2). Citing Literature Supporting Information Filename Description saj2sssaj2015050169-sup-0001.pdfPDF document, 284.3 KB Supplemental Material Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume79, Issue6November-December 2015Pages 1674-1683 RelatedInformation