Nitrogen and Sulfur Fertility Practices: Influences on Hop Chemistry, Aroma, and Nitrate Accumulation

Abstract

Multiphasic studies were conducted to quantify how sulfur fertilization influences nitrate levels in hops, and how nitrogen and sulfur fertilizer dose jointly affect hop yield, brewing chemistry, and aroma of hops and beer. In an observational study of commercial lots of Simcoe® hops, a weak positive correlation was found between sulfur and nitrate concentrations. In field studies with Simcoe® in Washington, factorial combinations of representative low and high rates of nitrogen and sulfur fertilizer revealed that nitrate content of cones increased 13 to 22% with increasing nitrogen dose yet declined 8 to 8.7% with an increasing sulfur dose. Yield was unaffected by the lower dose of nitrogen when sulfur dose was high; effects on α-acids, total oil, and hop and beer aroma were not detected. Cysteine-3SH and cysteinylglycine-3SH were reduced 19% and 23%, in cones that received the higher sulfur dose in one year; other thiols and precursors were unaffected. In cultivar Willamette in Oregon, increasing sulfur dose over an 11-fold range by varying nitrogen fertilizer form from urea to ammonium sulfate had small to non-detectable effects on yield, α-acids, or nitrate concentrations. Hop aroma and brewing characteristics appear largely invariant to sulfur fertilization; increased sulfur fertilization may reduce hop nitrate levels modestly in certain situations.

Keywords:

• Humulus lupulus L.
• nitrate
• nitrogen
• sulfur
• thiol

Acknowledgements

We thank Perrault Farms for hosting and supporting the experiments in Washington and Yakima Chief Hops for providing cone samples.

Disclosure statement

No potential conflict of interest was reported by the authors.

Disclaimer

The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the United States Department of Agriculture or the Agricultural Research Service of any product or service to the exclusion of others that may be suitable.

Additional information

Funding

Funding for these studies was provided from the USDA-ARS CRIS 5358-21000-040-00D, the Hop Research Council, and the Brewers Association.