Wheat Yield and Protein Response to Sulfur in North Dakota and Eastern Minnesota.

Amidst skepticism from some producers to justify the economic benefit of sulfur (S) application on hard red spring wheat (Triticum aestivum L), a 2014 study at the Carrington Research Extension Center (CREC) showed 11.2 kg S/ha increased grain yields by 670 kg/ha, and protein by 45 mg/kg (total soil N of 200 kg/ha), giving a net return of $25/ha. Because response to S is often not consistent, and nitrogen (N) is commonly the main determinant of HRSW performance, trials were set up in spring 2015 to assess HRSW yield and protein response to S (0, 11, 22 kg/ha) across 4 N levels (67, 135, 202, 269 kg/ha) plus a control, at three sites in eastern MN - Ada, East Grand Forks (EGF), and Thief River Falls (TRF), and in Carrington, ND. The setup was a split-plot arranged in an RCBD with N rates as the main plots and S rates as sub-plots. Results from Ada and EGF showed that there was S and N interaction (p<0.0007) for protein, but no significant yield response. Mean comparisons from Dunnett's t test at Ada showed no differences among N treatments across all levels of S, while S significantly increased protein (p<0.05) over the control. Mean yields increased significantly with S rates. At EGF mean protein differences were observed only between 22 kg S rate and the control. At CREC, protein was significantly affected by S (0.0425) and by N (p<0.0001). At 22 kg S/ha, grain protein was statistically different from the control. There was not a strong evidence that showed consistent trend in the crop response to a specific level of either S or N across any given level of the other. These preliminary results suggest differences in S response based on the location.