Summarizing results of 45 trials across the 2 years, 62% of the sites had a statistically significant yield increase to applied S fertilizer.  The across-site yield increase averaged 13 bu/acre for all sites.  Analyzed across S rates, the economic optimum S rate was 16 lb S/acre for fine-textured soils and 23 lb S/acre for coarse-textured soils. The research indicates that S application is an economically viable fertilization practice on many soils.  However, the research also shows that corn does not respond to S application in all fields or field areas.  The best way to determine this is to conduct 1 or more sulfur fertilizer strips trial on your own farm.
 
The research confirms that (1) The S soil test is no help in determining need for S fertilizer; (2) Plant analysis of %S in ear leaves sampled at VT is not accurate enough to determine S need either; (3) While organic matter is an important source of S, it is not a clear deciding factor either for S fertilization.  (4) The only absolute has been the need for S on a sand or loamy sand soil lacking a recent manure application.  In addition, this work indicates that more research is needed regarding plant and soil S tests, plant canopy S stress sensing, site characteristics, and S deposition in order to develop better predictive indices of S deficiency and need for S fertilization.  Hopefully one of these tools conducted that right way could provide better decision making and enhance positive economic return to S fertilization for producers.
 
I Need a Few Serious Cooperators for 2009

ISU wants to establish 6 on-farm field scale replicated strip-trial in northeast Iowa in 2009.  I am looking for the following:
1)  Fields with no manure or sulfur fertilizer applications for at least the last 5 years.
2)  A farmer &/or ag supplier willing to take the time to make sure that the field gets spread properly.
     a)  The product must be calcium sulfate (gypsum).
     b)  Application most likely done with a spinner spreader as a separate application from other fertilizer applications, alternating strips the entire length of the field with a minimum of 4 strips with sulfur and 4 strips without sulfur.
     c)  Application best done early April (or late March if field conditions are okay), before other spring field operations pick up speed.  It could be applied before or after any secondary tillage passes, or also surface applied on no-till.
     d)  The strips are properly flagged.
3)  Harvest could be done with a yield monitor (preferred) or weigh wagon.  If by yield monitor, we would like a copy of the harvest data file.
 
Please email me if you are interested.  As usual, I have no money to put towards this project.  Any interested individual should be interested because they want to know if sulfur fertilizer can help their operation.  Currently we do not have any analytical tool (soil test, plant analysis, etc.) that helps us determine if the corn crop needs sulfur.  So this trial will help you on your farm, but you would have to afford the sulfur fertilizer and the extra time to harvest the trial.  ISU would be 100% responsible for conducting some additional tasks in these trials, including:  soil test, plant analysis, plant sensor readings, and a small plot multiple-rate sulfur trial overlaid in an untreated check strip.

Brian J Lang
ISU Extension Agronomist
911 S. Mill Street, Decorah, IA 52101
Ph 563-382-2949
Fax 563-382-2940
Email bjlang@iastate.edu