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Northern Idaho | I am located in northern Idaho and grow mostly wheat, both winter and spring planted, along with legumes. Our soil tests always show about 2 ppm sulfur and we typically apply a fair amount of ammonium sulfate blended with the urea. What we used to do and what most people still do is to take the 39-0-0-7 blend and use it for all crops (except legumes) adjusting the rates up for high yielding wheat, and down for spring wheat and canola. This would give sulfate at the same proportion as the nitrogen. However the last couple years with the CSP program we are required to follow the University of Idaho fertilizer guidelines which have a good recommendation for nitrogen but the sulfur part seems to be lacking. For all crops and regardless of expected yields it calls for 0lbs of sulfur for soils above 10ppm and 25lbs S for soils below 10ppm. This means we now have our fertilizer blended differently for each field and for spring wheat we do a 50-50 urea AMS blend and winter wheat can sometimes get a 80-20 mix. To me this does not seem right that we would need 25lb S regardless of yield and amount of Nitrogen being applied. Our applied N rates range from 50lbs an acre to well over 100 so I would think the S rates should vary as well, I just want some data to back this up.
I have tried looking for other fertilizer guidelines and cant seem to find anything good out there. Anybody know of any university data about sulfur rates in wheat?
Edited by NIF 4/23/2010 20:36
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Sulfur question
