Large Urea Granules for Broadcast Application in Perennial Forage Grasses

Earlier research in Alberta and North Dakota showed that using larger granules of urea compared to regular sized ag-grade urea was a means of increasing crop yield and reducing the potential for denitrification losses by slowing down nitrification of urea nitrogen (N) (Nyborg and Malhi 1979, and Goos and Johnson 1993). It is thought that a larger granule urea (up to 10 mm in diameter) that is used in helicopter applications to forestry replanting stands, and in agro-forestry plantations could be used as a broadcast application in forage grass cropping systems in the Northern Great Plains (NGP). The earlier research noted above was done largely by hand application to small field research plots. Standard spin-broadcast application equipment available earlier could not achieve an even spread of the larger urea granules. More recent pneumatic floater spreaders do have the capability to handle the larger granules and achieve a reasonably even spread of granules over the spreading width of the equipment. Goos and Johnson’s research investigated the addition of a nitrification inhibitor (DCD) with the urea in different sized granules; such treated granules were not commercially available at the time of this research. Recent developments of technology now allow the treatment of different sized granules of urea with both a urease and a nitrification inhibitor (i.e. Agrotain and DCD). This study will investigate the following factors in a factorial field experiment.


Justification

• This would be a potential way to more efficiently apply N fertilizer to forage grasses in the NGP.
• These forage stands were often fertilized with ammonium nitrate as the source of N. But with ammonium nitrate not being widely available since the year 2005 in the NGP, the only N fertilizer sources are either granular urea, or liquid urea ammonium nitrate solution (UAN). There is concern that there can be considerable ammonia volatilization losses of surface applications of granular urea, and the urea portion of the UAN. This concern has been recently documented under NGP winter wheat growing conditions (Engel 2008 and 2009), from both fall and early spring conditions, even when soil conditions are cold.
• There is potential to allow farmers to apply N in the fall at a time when urea N prices are usually less than the following spring prices, and spread out their work load by applying N in the fall and having less fertilizer to handle just before planting of other crops in the spring.
• This technology (fall broadcast applications of large granule urea treated with a urease and nitrification inhibitor) can be used in either the fall or spring for forage grasses, and this is why both fall and spring treatments are included.
• If this initial research shows an advantage for the large granule urea treated with urease and nitrification inhibitors this research might be expanded to multiple locations in Montana, North Dakota, Saskatchewan, and Manitoba for further evaluations and generation of research data under different agro-ecological zones, where tame forage grasses are grown for livestock by grazing or hay production.

Methodology

The study will be a four replicate, factorial design, with the inclusion of a no-N control treatment, a subsurface (2 inch depth) banding of regular urea, and a subsurface banding of urea plus Agrotain for comparison purposes. The last three treatments will not be part of the factorial design and statistical analysis, but are included to assess N response and how the technologies being evaluated compare to standard farm N applications for central Alberta. This forage study is meant to supplement research being done at three other sites: a winter wheat site experiment at Moccasin, MT conducted by Dr. Chengci Chen, MSU; a spring barley site experiment at Edmonton, AB conducted by Dick Puurveen, U of A, and a spring wheat site experiment at Acadia Valley, AB conducted by Audrey Bamber of the Chinook Applied Research Association (CARA). This forage site was added after discussion with the Chinook Applied Research Association manager, Dianne Westerlund. There was considerable interest in the research being done at the spring wheat site experiment, and because of the large acreage of tame forage grass grazing land in east-central Alberta, the CARA group suggested a related research experiment be conducted evaluating the large urea granules with and without urease and nitrification inhibitors under tame forage grasses.