Nitrogen Fertilization Methods for No-till Cropping of Winter Wheat in Central Montana

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). 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 no-till cropping systems in the Northern Great Plains (NGP). 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.


16 Feb 2013

2012 Annual Interpretive Summary

This experimental study was conducted on a no-till field at the Central Agricultural Research Center, Moccasin, MT, during the 2010-2011 and 2011-2012 crop years using winter wheat. Three N products (urea, Super-U® which contains urease and nitrification inhibitors, and ESN® which is a polymer coated urea) were applied at 80 lb N/A in the fall or spring using three methods (broadcast, sub-surface banded 2 in. deep between rows, and seed placed). Additional broadcast treatments included adding Agrotain® (urease inhibitor) or Agrotain® with N-Serve® (nitrification inhibitor) applied to regular urea. The experiment was a randomized complete block design with four replications.

In 2011, there was greater grain yield (36.5 bu/A) and grain protein (12.9%) from spring broadcasting of regular urea than fall application (27.7 bu/A and 8.9% grain protein). These results indicate possible N loss through leaching and/or denitrification from fall application of urea in 2010-2011. Annual crop-year rainfall from Oct 2010 through Sept 2011 was 21.6 in., significantly higher than the 2011-2012 crop year with 11 in. However, yield response to timing of urea application was reversed in 2012. The fall broadcast urea produced higher yield (31.9 bu/A) than spring broadcast urea (26.9 bu/A). In 2011, fall broadcast application of urea treated with a urease inhibitor [NBPT or N-(n-Butyl)-thiophosphoric triamide] plus a nitrification inhibitor (nitrapyrin) resulted in 20% more grain yield than regular urea broadcast in the fall. Yield in 2011 was not significantly different between fall application of ESN® and urea treated with the urease and nitrification inhibitors. When rainfall was low in 2012, regular urea broadcast in the fall resulted in similar grain yield compared to urea treated with the urease and nitrification inhibitors. Interestingly in 2012, the fall broadcast urea out-yielded ESN® applied with seed by 6.4 bu/A probably due to slow release of N from the ESN fertilizer due to droughty conditions. Therefore, the impact of inhibitors and controlled release polymer coating (ESN) on yield is affected by rainfall amounts received during the growing season. This study demonstrated that precipitation is a major factor determining optimal fertilizer placement, timing, and benefit of inhibitors or controlled release polymer coating for winter wheat production in central Montana. Final conclusions and recommendations will be made after the 2013 crop year data are available, and all three years of data are analyzed and interpreted. MT-18