Mention 'nutrient deficiency' and you'll likely think of nitrogen in corn every time, especially this time of year. Areas that took too much water in June in pockets of low-lying fields later had yellow crops, unless water completely wiped out the field. Wet soils in May and June usually means nitrogen deficiency will be a possibility somewhere before the season ends.
Plants running short on N this time of year tend to fire, meaning lower leaves turn yellow, with the yellowing beginning down the leaf vein first. Ears on plants that run out of nitrogen will usually be inferior to those produced on plants with plenty of N. Presence of adequate fertilizer nutrients is one of the environmental triggers that determines whether corn plants go full speed ahead, or pull back their horns and attempt to salvage the kernels already in development.
Reports from across Indiana indicate nitrogen isn't the only nutrient that wound up short in some fields this year. Earlier in the season, before corn was waist high, agronomists fielded many calls about yellow striping in corn. In many cases, the corn 'grew out of it' as time passed. Tissue tests, if pulled at that time, would likely have revealed a sulfur deficiency, agronomists note.
Two decades ago farmers thought sulfur would never run short. If someone tried to sell them sulfur, many either ignored them or simply laughed. It was an element in the air, apparently free for the taking.
That was before utility plants were required to install scrubbing machines to pull more possible contaminants out of the air. Sulfur is one of the elements often removed from the atmosphere during this scrubbing process. As a result, sulfur is no longer as plentiful in Hoosier cornfields as it once was.
Some now add sulfur as part of their fertilization plan. Others test for it to make sure fields still have enough sulfur during the season. Since it's mobile in the soil, this is one that's best tested for in tissue samples during the season, rather than in soil samples.
Potassium deficiency symptoms have also been reported. If potassium runs short, leaves develop a brown, distinct discoloration, starting around the leaf edges. It can develop and turn into discoloration of a major portion of the leaf.
Agronomists have reported more cases of potassium deficiency in corn and soybeans over the past few seasons than in the past. Even black soils can develop potassium deficiency if soil tests aren't pulled and followed, or if too little potash is applied on areas testing low to moderate in potassium levels.