Since the mid-'90s, potassium (K) deficiency in corn has become
more noticeable in major production states in the Corn Belt,
says Antonio Mallarino, Iowa State University (ISU) agronomist.
If left unchecked, extreme cases of the problem can easily cut
yields by as much as 50% or more per acre and affect grain
quality. A recent survey by the Potash & Phosphate Institute
(PPI) reports that nationally about 43% of soils were potassium
deficient. The survey found that a higher percentage of lower-
testing soils occurred in the Midwest, as well as in the East
and South. Soils in the Great Plains and the West tended to
exhibit naturally higher potassium levels. But putting your
finger on the root cause of this deficiency problem isn't always
easy since it may involve several factors — individually or in
combination. “In some cases you may face a fertility issue where
there simply isn't enough available K in the soil in most areas
of a field or its availability may be low only in a few select
areas within the field,”