Manganese

What it does

Manganese sits right at the start of photosynthesis. Inside the leaf, a tiny cluster of manganese is where the plant splits water, and that’s what gets the whole engine going. Sunlight powers the split. The water gives up its electrons, and the oxygen is let go. The leaf uses those electrons, with carbon dioxide from the air, to build sugar. Everything else the crop does, it pays for with that sugar.

It has other jobs, and Steve has his own names for two of them. “It’s a potassium thermostat,” he says. “It’s a barometer.” Ask him what he means by each at the live Q&A.

Two more are well known. It helps the plant build lignin, the tough stuff in its walls that’s part of how it defends itself, and it helps the plant handle its nitrogen.

A broad, heart-shaped green leaf on its stalk, tilted up to the right, in soft sunlight. — Manganese is where the leaf splits water: the first turn of the engine that makes the crop’s sugar. An illustration, simplified.

One thing to take home

Steve doesn’t ask growers to learn the chemistry of photosynthesis. Farmers get bored with it, he thinks, and he doesn’t put that down to their intellect. He gives them one thing to take home instead: the number one thing for photosynthetic efficiency is making sure the plant’s manganese is where it should be. That gives you a reason to check it, and getting it right can drive better yield. His slide calls manganese the hidden engine of crop performance.

Where a shortage shows

Manganese doesn’t move much once it’s in the plant, so a shortage usually shows on the younger leaves first: pale between the veins while the veins stay green, a fine mottle, sometimes small dead spots. But the engine often runs rough before the leaves show a thing. That’s the hidden part, and it’s why testing earns its keep here: a sap or leaf test can pick up the shortage while there’s still time to act.

A young bean plant, cut away below the ground: trifoliate leaves, all an even green, with a few small white flowers, and its roots in red-brown soil. — Short of manganese, the leaf’s engine often runs rough before the leaves show a thing. A sap or leaf test can find it while there’s still time to act. An illustration, simplified.

Short of manganese, the leaf’s engine often runs rough before the leaves show a thing. A sap or leaf test can find it while there’s still time to act. An illustration, simplified.

Manganese and magnesium are easy to mix up. Magnesium moves around the plant, so its shortage shows on the old leaves. Manganese doesn’t move much, so its shortage mostly shows on the new ones.

What locks it up

Plenty of manganese in the soil isn’t the same as plenty in the plant. It gets tied up by:

High pH, and lime. The higher the pH, the less the plant can get.
Dry, loose, airy soils. Waterlogged soils do the opposite, and can release more than the plant wants.
Nitrate pushing up the pH right around the root. As Steve says, all nitrogen is not equal.

A young bean plant in dry, loose, pale soil with gaps between its crumbs, its youngest leaves pale between green veins. — Plenty of manganese in the soil isn’t the same as plenty in the plant. Dry, loose, airy soil ties it up, and so do lime, a high pH and nitrate at the root. Waterlogged soil does the opposite, and can release more than the plant wants. An illustration, simplified.

Plenty of manganese in the soil isn’t the same as plenty in the plant. Dry, loose, airy soil ties it up, and so do lime, a high pH and nitrate at the root. Waterlogged soil does the opposite, and can release more than the plant wants. An illustration, simplified.

And in potatoes, when Steve sees scab, manganese is where he looks.

When it matters most, crop by crop

The stages where manganese is one of the minerals that matter most, in the program builder’s seasons. Each bar is a whole season, from sowing or planting to harvest, or a tree’s year. Build yours in the program builder.

Potatoes about 120 days

Stolon development · Vegetative growth · Tuber initiation (hooking) · Tuber bulking
Beans about 70 days

Bud development · Flowering · Cell division
Carrots about 120 days

Leaf growth
Onions about 180 days

Canopy development · Bulb initiation and cell division
Poppies about 140 days

Rosette · Stem elongation · Capsule fill
Sweet corn about 90 days

Early leaf growth
Cotton about 180 days

Early growth to first square
Wheat about 170 days

Tillering
Avocados a year

Autumn flush and oil
Apples a year

Silver tip and bud swell · Tight cluster to first pink · Fruit set, 6 to 10 mm · Bulking to early ripening

Where it fits in a program

Check it. Look for manganese on your next sap test, in the new leaves as well as the old.
Check it ahead of each critical stage of influence, where you can.
If it’s short, find out why before you add more. The pH, a dry spell or nitrate at the root may be locking up what’s already there.
Where the soil’s locking it up, a foliar spray gets it into the leaf faster. Rates come from your tests and the label.

“The number one thing for photosynthetic efficiency is making sure your manganese levels are optimal in your plant.”

— Steve, on the hidden engine

Manga­nese