A Micrometeorological Study to Quantify Ammonia Volatilization Losses from Surface Applied Urea in the Semiarid Northern Great Plains

Montana winter wheat growers broadcast surface apply urea to their crops in late fall, or early spring to supply the crops with needed nitrogen. Urea is known to be susceptible to ammonia (NH3) volatilization losses, no studies have specifically targeted the measurement of these losses from cold soils ( 10°C). This study is being conducted to quantify NH3 emissions from surface applied urea to no till winter wheat; and to evaluate the efficacy of NBPT (N-(nbutyl) thiophosphoric triamide) to mitigate potential ammonia volatilization losses made during colder weather periods.

IPNI-2008-USA-MT17

Montana grain growers annually seed over 5 million acres of wheat with production averaging approximately 15 million bushels (1998-2007). Nitrogen is the primary nutrient that limits wheat production on this land. Hence N fertilization is essential for sustaining yields as well as ensuring production of high protein quality grain. To meet this challenge Montana wheat growers apply N fertilizer to their fields. Read more


Year of initiation:2008
Year of completion:2013
Map:

Interpretive Summary

Urea fertilizer hydrolyzes to release volatile ammonia gas when broadcast on the soil surface under certain moisture and temperature conditions. It had been generally accepted that such losses are accelerated under conditions of a moist soil surface under warmer temperatures in spring and summer, and when additional precipitation (e. g. 0. 5 to 1 in. of rain) was not received within a number of days following application.

In 2012, trials were conducted on a farm near Coffee Creek, Montana. The field site was under no-till management and was seeded to winter wheat. A mass-balance micrometeorological experiment was established to quantify ammonia (NH3) losses from urea and urea treated with NBPT [N-(n-Butyl)-thiophosphoric triamide]. Three application timings (fall, winter and spring) at 100 kg N/ha, with and without NBPT (1 g/kg), were made to circular plots (20 m radius) at this site.

Montana grain growers annually seed over 5 million acres of wheat, primarily winter wheat. Nitrogen is the primary nutrient that limits wheat production on this land. Hence N fertilization is essential for sustaining yields as well as ensuring production of high protein quality grain. To meet this challenge Montana wheat growers apply N fertilizer to their fields.

Ten field investigations [i. e. , ammonia (NH3) gas sampling campaigns] have been completed as part of this project over the past 3 years. The magnitude of N losses due to ammonia volatilization are quite variable and very much dependent on the soil moisture conditions, rainfall, and climatic conditions that are experienced following application of the fertilizer granules. The best example of this is provided by the contrast in results from Campaigns #2 and #5.

Ammonia (NH3) losses from urea have ranged from 3 to 40% of the application rate (19. 4% average) over eight gas sampling campaigns conducted to date in 2008 and 2009. In this semi-arid region, NH3 losses are sometimes delayed by 2 weeks or more until sufficient precipitation falls to dissolve urea granules. Significant NH3 losses may then occur over a three to six week period. Applying urea to frozen soils does not guarantee losses will be minimized.

Top-dress or surface application of urea is a common practice for Montana’s winter wheat producers. However, urea applied to the soil surface is susceptible to volatilization losses as ammonia (NH3-N). The objective of this study is to quantify the extent of ammonia loss from top-dress urea applications, applied in the early fall, late fall, and early spring to winter wheat using a mass-balance micrometeorological approach referred to as the integrated horizontal flux (IHF) method.

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Updates & Reports

2012

2012 Annual Report

2009

Published reports related to the research

2008

Project Description


Project Leader

Richard Engel, Montana State University


Project Cooperators

None


IPNI Staff

T. Jensen


Location

Americas \ Northern America \ USA \ Montana


Topics

4r place, 4r source, 4r time, nutrient management

wheat

Nitrogen (N)