Interveinal chlorosis in corn: causes and what it means

You're walking a field in late June, the stand looks decent from the truck, and then a patch of plants shows that striped look: veins staying dark green while the tissue between them washes out to yellow or almost white. That's interveinal chlorosis, and it's one of those symptoms that tells you something's wrong without telling you what. Three different deficiencies can produce it, and they call for three different answers in the recommendation.

What interveinal chlorosis looks like in the field

The vein stays green because it's still getting whatever's short in supply, usually because the plant moves mobile nutrients toward active tissue and leaves the older leaf behind. With immobile micronutrients, the pattern shows up on new growth first, the top leaves, because the plant can't shuttle what little it has from older leaves to younger ones. That's the first thing to check: is it the newest leaves showing the stripe, or the oldest? New-leaf chlorosis points to iron or manganese. Old-leaf yellowing without the sharp vein contrast usually means something else entirely, like nitrogen.

Sulfur is the odd one. It behaves like a mobile-ish nutrient in corn under some conditions, so sulfur deficiency often shows up as an overall pale yellow-green across the whole plant, sometimes with faint interveinal striping on upper leaves, rather than the crisp white-between-green-veins look you get with iron.

Iron, manganese, or sulfur: how to sort it out

Iron deficiency hits hardest on high-pH, calcareous soils, the kind with visible lime chunks or a soil test pH north of 7.5. It shows up in strips or spots that follow soil texture changes, eroded knobs, old terrace cuts, places where topsoil is thin and subsoil lime is closer to the surface. The newest leaves can go almost white in severe cases, with the veins staying a thin green thread. Cold, wet springs make it worse because root uptake of iron slows down even more in cold soil.

Manganese deficiency likes the same high-pH ground but also shows up on sandy soils with low organic matter, and on soils that have been overlimed. It looks similar to iron: interveinal yellowing on new leaves, but usually with a mottled or spotted look rather than iron's clean stripe, and it tends to be patchier across a field rather than following one obvious soil feature.

Sulfur deficiency is the one that's crept up over the past decade as atmospheric sulfur deposition has dropped. It's worse on sandy, low-organic-matter soils, especially after a cold, wet start that slows mineralization. Because it's less immobile than iron or manganese, the yellowing is more general across the whole plant rather than sharply confined to new growth, and it can look a lot like early nitrogen stress from a distance, which is exactly why it gets misdiagnosed from the truck.

A tissue test settles it when the field pattern isn't obvious, but tissue sampling takes time you don't always have mid-season, and by the time results come back you've already walked past the next client's gate.

What it means for your scouting list

None of these three show up as a clean uniform band across a field the way a nitrogen-rate strip does. They follow soil variability: knobs, sandy stringers, old filled-in waterways, spots where lime was applied unevenly. That's the pattern worth flagging before you even get out of the truck: it separates a management call, sidedress or a foliar feed, from a soil-chemistry problem that isn't getting fixed this season no matter what goes in the tank.

If you're trying to catch that pattern before a client calls you about a yellow patch they noticed on the way to town, a weekly red-edge read of the field does a lot of that sorting for you. Crop Stress Map flags the stressed zones and tags them by likely cause so you're walking into the field already knowing roughly what you're looking for, instead of guessing from the fence line.

Next time a yellow patch shows up on the weekly read, you'll already have a shortlist of the three usual suspects to check against the soil map before you get your boots dirty.