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Plant Nutrition – Corn in Focus

By Gary Zimmer & Charles Walters

The following tables give an idea of corn’s nutrient requirements. It is not practical to have companion plants in most field situations, but it is possible to read deficiencies and surpluses of plant nutrients even without the certainty of a petiole test, a refractometer readout, or a laboratory’s final audit.

black and white corn stalk
Evaluation your corn stalk color, look and feel can give you clues on its nutrition.

This is just a guide to help you determine the nutrients you have too much/little of, and how to tell.

Nutrient Deficiencies Guide

Nitrogen—lower leaves yellow at tip and center, later dying; rest of plant pale yellowish green; slow growth; stalks slender; ears small, not filled at tip.

Phosphorus—leaves dark green, turning reddish-purple be­ginning at tips of upper leaves (in young plant; purple leaves in older plant usually from other causes [drought, barren stalk]); slow growth; stalk size small; ears small, misshaped, often twisted from missing rows of kernels, not filled at tip.

Potassium—lower leaves yellow at tip and edges, later dying; stalk weak; ears small, poorly filled at tip, kernels loose.

Magnesium—lower leaves streaked by yellow between the veins, sometimes with rows of dead spots; upper leaves may be­come reddish-purple at tip and edges.

Calcium—in young plant, leaf tips stick together (do not un­fold), giving a ladder-like appearance.

Sulfur—yellow streaks between veins and stunted growth, es­pecially in young plant.

Iron—upper leaves pale green to nearly white between veins (along entire leaf).

Copper—young leaves yellow as they emerge, becoming pale streaked between veins, edges may later die; youngest leaves twisted and dried; stalk soft and limp.

Boron—leaves brittle with small dead spots or streaks; top of growing plant with bushy appearance because stalk does not lengthen; tassels and ears reduced or do not emerge.

Manganese—leaves olive green, may become streaked; stalk may be thin and limber.

Zinc—leaves with wide whitish bands between edge and midrib (edges remain green or turn purplish) which may later die, young­est leaves may be white; plant short because of little stalk growth.

Corn Nutrient Use Guide

corn nutrient guide
From How to Grow Top Quality Corn.

Nitrate (NO³ in ppm) — Nitrates in the sap represent future growth. Their effect is visible in 10-14 days. Too many nitrates too soon reduces fruit set. Changes in nitrates take effect fast.

Phosphate (PO4 in ppm) — Phosphates are in the sap for future growth. They show present root activity. Phosphates can be increased with humus, plant growth regulators and microbes.

Potassium (K %) — Potassium affects water uptake and efficiency, sugar production, enzyme formation and plant health. There is a high potassium requirement to form sugars.

Sodium (Na %) — Low amounts of sodium are best; just a trace is essential.

Calcium (Ca %) — Calcium is needed for cell walls, nitrate utilization, roots, leaves, pollination, and development fruit set.

Magnesium (Mg %) — Magnesium is needed for chlorophyll, photosynthesis, phosphorus metabolism and respiration.

Zinc (Zn in ppm) — Zinc is a plant growth stimulator. It affects enzymes, and metabolic reaction.

Iron (Fe in ppm) — Iron is needed for respiration, chlorophyll formation and energy. It is an oxygen carrier.

Manganese (Mn in ppm) — Manganese is needed for enzyme activation, photosynthesis, and maturity. It is connected with P and Ca.

Copper (Cu in ppm) — Copper is needed for chlorophyll formation and energy. It also catalyzes plant functions.

Boron (B in ppm) — Boron is needed for nitrate uptake, calcium utilization, pollination and sugar transport.


Nutrient: Nitrogen

Growing pattern: Throughout season

Leaf Translocation: Yes, during grain

Peak time of availability: Tassel to silk through with two peaks development grain fill

Nutrient: Phosphorus

Growing pattern: Steady accumulation

Leaf Translocation: Yes, during grain fill

Peak time of availability: Early tassel and early until maturity (more than N) dent

Nutrient: Potassium

Growing pattern: 86 percent accumulated

Leaf Translocation: Very little

Peak Time of Availability: Early tassel by silking

Nutrient: Calcium

Growing pattern: Vegetative growth 86%

Leaf Translocation: No

Peak Time of Availability: Early tassel before blister stage

Nutrient: Magnesium

Growing Pattern: Throughout growing

Leaf Translocation: Very little

Peak Time of Availability: All season

Nutrient: Sulfur

Growing Pattern: Throughout growing

Leaf Translocation: Very little

Peak Time of Availability: Steady supply all season

Nutrient: Boron

Growing Pattern: Throughout season

Leaf Translocation: Very little

Peak Time of Availability: Steady supply all with two peaks season (tassel to early grain fill)

Nutrient: Copper

Growing Pattern: Steady accumulation

Leaf Translocation: No

Peak Time of Availability: Steady supply all throughout season

Nutrient: Iron

Growing Pattern: Two distinct times, (70%)

Leaf Translocation: Very little

Peak Time of Availability: Early through blister accumulation by blister stage

Nutrient         Grain  Stover

Nitrogen         150     116

P2O5              87       27

K20                 57       209

Magnesium    18       47

Calcium          4          38

Sulfur             15       18

Zinc                 0.18    0.37

Manganese    0.12    1.75

Iron                 0.17    1.10

Copper           0.07    0.06

Boron              0.15    0.06

SOURCES: Gary Zimmer/The Biological Farmer; Charles Walters/Ask the Plant

Learn in the field with Gary Zimmer!

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The Acres U.S.A. On-Farm Intensive is held in partnership with experienced farm consultants Gary Zimmer and Leilani Zimmer-Durand at their famous Otter Creek Farm near Lone Rock, Wisconsin. This two-day educational experience will help farmers, growers and land owners maximize their land’s potential. Learn more here!