John Haarstad’s urea-sidedress bar can also be used as a deep bander by moving the row units 15 inches. Designed and built by Sheldon Stevermer, a Wells, Minn., farmer and B&D Metalworks engineer, the 30-ft. bar extends to 40 and 45 ft. and pulls a Montag 9-ton steerable cart. The openers are Dawn 6000s. This is Haarstad’s first year sidedressing. Based in Carlisle, Minn., he is skip-row sidedressing on 60-inch centers. Skip-row sidedressing is endorsed by the University of Illinois (pdf, page 15) because it avoids injecting N into a wheel track, where N losses can be greatest, and using a smaller tractor means less compaction.
Sulfur-supplementing decisions can be more challenging, says John Shanahan, DuPont Pioneer agronomy research manager. If you applied sulfur preplant, you may not need to sidedress it except on fields receiving elemental sulfur for the first time this year. Some striping may occur, even when sulfur was applied as elemental sulfur, he says. Sulfur-deficiency symptoms could be caused by rapid plant growth and possible limited sulfur uptake. The corn will grow out of this without affecting yields. If S was not applied this spring, research results indicate that early season applications (V3-V4) of S responded the same as those made at planting.
Surface-applying ammonium thiosulfate between the rows or coulter injected is best, according to University of Minnesota recommendations. Post-application with ammonium sulfate in 2009 and 2010 showed little effect on grain yields at 10 or 20 lbs. sulfur/acre or 42 or 84 lbs. of AMS/acre.
Sulfur can still be applied around the V5 growth stage, according to the University of Minnesota Extension. In most instances, 10 lbs. of sulfur per acre should be adequate for an in-season application. Some leaf burning may occur, but that generally has not been found to reduce yields. Spraying liquid sources containing thiosulfate over the top of growing corn can severely injure corn.
Gypsum (broadcast) is another sulfur source.