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| Over the 2007-8 winter I read all I could find in the ISU library and on line about micros for beans. I found that soil tests rarely correlate with needs shown by tissue tests. For some micros that comes from the available chemical extraction methods being far more effective at getting the nutrients than plants.
And in that time period, ISU reports were saying, "no response to sulfur." In the two years since, ISU reports finding some fields that respond to S (as much as 25 or 30 bushels per acre) yet the soil tests showing shortage didn't match the fields that responded. Or the fields that responded didn't show a different S need than those that didn't respond. I suppose that could be difference in soil chemistry, difference in S extraction efficiency by the soil tests, or differences in corn extraction or corn need for S. They report S won't hurt and sometimes it may help the yield. But a shortage of S on a soil test isn't proof of need. I don't know of experiments looking for response to S when the soil tests showed an "adequate" level. Now I question that soil test saying adequate when ISU fields showed no response to S in the past. While ISU reports are saying no correlation when soil tests show low S, I'm wondering if that also applies when the soil tests show what's been considered adequate S.
Without being able to prove a response to or need for sulfur, my tenant has applied AMS this year and allowed me to help pay for it.
Gerald J. | |
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Sulfur deficiency in corn on corn
