Micronutrients in Plants: List, Doses & Best Sources

The Complete List of Micronutrients in Plants

Boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and zinc (Zn) make up the standard list of plant micronutrients recognized by land-grant extension services, according to Mississippi State University Extension. That’s separate from the “big three” macronutrients — nitrogen, phosphorus, and potassium — which plants take up in far larger quantities.

How small is “micro”? NC State Extension’s Extension Gardener Handbook puts typical dry-tissue concentrations at iron 0.01%, chlorine 0.01%, manganese 0.005%, boron 0.002%, zinc 0.002%, copper 0.0006%, and molybdenum 0.00001% — a span of roughly 1,000-fold between the most- and least-abundant micronutrient. Nickel and cobalt are needed too, but NC State Extension lists their tissue concentrations as not established for general field crops.

Every one of the eight has a specific job. Iron, zinc, and manganese drive chlorophyll synthesis; molybdenum and manganese activate enzymes involved in nitrogen conversion; boron and copper are needed for hormone synthesis and transport; chlorine balances electrical charge in cells. Zinc alone is a cofactor in more than 200 enzyme systems, per Mississippi State University Extension. None of them substitutes for another — a zinc surplus doesn’t cover a boron shortfall.

Why Micronutrients Matter: Deficiency Signs

Because micronutrients are needed in such small amounts, deficiencies show up as subtle, easy-to-miss symptoms before they cost yield — what agronomists call “hidden hunger.”

• Boron: chlorosis of young leaves, bud death, and — in cotton — stunting with dark rings on leaf petioles. Over 90% of a plant’s boron stays locked in cell walls, so it can’t be remobilized from old tissue to new growth.
• Zinc: interveinal chlorosis (striping between the leaf margin and midrib), stunting, and rosetting; in pecans, pale green leaves and reduced nut fill.
• Molybdenum: stunting, pale green color, and scorched, cupped, or rolled leaves — most consequential in legumes, where molybdenum is a cofactor for the nitrogenase enzyme that fixes atmospheric nitrogen.
• Iron: interveinal chlorosis of young leaves progressing to whitish-yellow discoloration, most common on high-pH soils where iron becomes insoluble.
• Manganese: reduced photosynthesis and weaker disease defense at deficiency; the opposite problem — manganese toxicity — shows up on acidic soils below pH 5.3.
• Copper: stunting, chlorosis, bud dieback, and delayed maturity, though Mississippi State University Extension notes deficiencies are uncommon enough in its region that no blanket recommendation is issued.
• Nickel: poor seed germination and interveinal chlorosis progressing to tissue death, tied to nickel’s role in nitrogen-cycle enzymes.

Soil pH is the biggest lever on availability for most of these elements. Per Mississippi State University Extension, zinc, iron, manganese, copper, and boron all lose solubility as pH climbs above 7, while molybdenum solubility rises through the same range — availability for most micronutrients peaks between pH 6 and 6.5. That single number is the durable check here: pull a soil test, read the pH, and you already know which micronutrients are at risk before you look at a tissue sample.

Chelated vs. Mineral-Salt Micronutrients for Plants: What’s Actually in the Bag

Chelation binds a micronutrient ion — zinc, iron, manganese, copper — to an organic molecule such as EDTA, DTPA, or EDDHA. That bond keeps the ion soluble across a wider pH range and stops it from precipitating into an insoluble form in alkaline soil, which is why chelated products correct deficiencies faster on high-pH ground and in hydroponic nutrients systems where there’s no soil buffer at all. The trade-off buyers rarely see: chelation dilutes the guaranteed nutrient percentage on the label, because the organic carrier takes up part of the weight. Anyone who would rather avoid synthetic chelates can look at organic sources of zinc such as manures and composts.

Mississippi State University Extension’s fertilizer-materials guidance puts real numbers on that trade-off:

How Much Micronutrient to Apply, by Crop

Rates vary by crop because uptake demand and tolerance for excess both vary by crop. Mississippi State University Extension publishes these soil and foliar guidelines for boron and zinc:

• Boron — cotton: 0.3–0.5 lb/acre
• Boron — clover: 0.5–1 lb/acre
• Boron — peanuts: 0.5 lb/acre
• Boron — alfalfa: 1–3 lb/acre
• Boron — kale and other cole crops: 2–4 lb/acre
• Zinc — corn: 2–3 lb/acre
• Zinc — pecans: 1 lb of zinc sulfate per tree per inch of trunk diameter (soil application), or a 0.5 lb foliar spray
• Molybdenum — soybeans: 0.5 oz of sodium molybdate per bushel of seed, on Delta soils with pH 5.5 or below

Dry Hydroponic Mixes and Tower Garden Micronutrient Blends

In soilless systems, the nutrient solution is the entire root environment, so micronutrient dosing has to be exact rather than approximate. Dry hydroponic nutrients — concentrated powders mixed on-site rather than shipped as diluted liquid — dominate commercial greenhouses because they ship and store cheaper per unit of active nutrient and let growers build a fresh solution for each crop cycle rather than committing to one pre-mixed formula. The same logic that separates zinc oxide from zinc chelate above applies here: a dry mix’s label percentage tells you how much actual nutrient you’re buying per pound, and getting that ratio wrong is the single most common cause of an imbalance in a recirculating system.

Tower garden and other vertical setups add a second constraint: a compact substrate volume and high plant density mean there’s very little buffering capacity if the recirculating solution’s pH drifts, so tower garden nutrient blends lean on chelated forms specifically to avoid micronutrient lockout as pH swings through a shift cycle.

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Best High-Potassium Fertilizer: Comparing K₂O Sources

Potassium is a macronutrient, not a micronutrient, but it belongs next to this discussion because the same label-percentage logic decides which product actually delivers the most K₂O per acre. Four sources cover most of the U.S. and Canadian market, per Mississippi State University Extension:

By straight guaranteed analysis, muriate of potash is the highest-K₂O granular fertilizer in common use, at 60–62%. Penn State Extension notes that potassium hydroxide (KOH), used in liquid solution fertilizers, tests even higher at 70% K₂O — though the potassium a crop actually takes up from a KOH solution matches what it takes up from potassium chloride, so the higher lab number doesn’t translate into a real agronomic edge. Penn State Extension also flags a placement limit: keep total nitrogen plus K₂O under 70 lb/acre when starter fertilizer is banded 2 inches over and 2 inches down from the seed row, since potassium salts can injure roots at higher concentrations near the seed.

“Best” for your farm is a cost question as much as a concentration question. Retail muriate of potash averaged $487/ton for the week of March 16–20, 2026, $489/ton for the week of March 23–27, 2026, and $494/ton for the week ending around July 2, 2026, according to weekly surveys from DTN. That’s a fertilizer whose retail price moves week to week, so treat these three points as a snapshot of one season, not a forecast — check DTN’s current retail fertilizer trends page for this week’s number before you buy.

Calculator: Cost Per Pound of Actual Nutrient

Use your own product’s price and label percentage below to see what you’re really paying per pound of K₂O, zinc, boron, or any other nutrient — and how much it delivers across your acreage.

Monitoring Micronutrient Status With Satellite Data

Soil and tissue tests remain the only way to confirm a specific micronutrient deficiency, but satellite imagery can flag where to pull those samples before symptoms are visible to the eye. Farmonaut’s satellite-based crop health monitoring tracks vegetation indices and soil moisture across a field so uneven zones — often the first sign of a localized zinc or iron shortfall in high-pH patches — show up on a map rather than being discovered at harvest.

• Custom nutrient scheduling: pairing satellite vegetation data with soil test results narrows down where a foliar correction is worth the trip across the field.
• Remote guidance: the Farmonaut Satellite & Weather API lets farm management platforms pull the same vegetation and weather data into existing workflows.
• Traceability: logging micronutrient applications through Farmonaut’s product traceability tools documents input-to-output records for supply-chain audits.
• Environmental accounting: Farmonaut’s carbon footprinting tools factor fertilizer inputs, including potassium and micronutrient applications, into a farm’s overall emissions estimate.
• Logistics: Fleet management tools help coordinate delivery of micronutrient blends or potash shipments to multiple fields on schedule.

Farmonaut’s Role in Data-Driven Nutrient Management

Farmonaut’s platform serves individual growers managing a single plot up through agribusinesses and government programs coordinating region-wide input use. On the micronutrient side, that means multispectral imagery for vegetation and soil status, real-time deficiency flags with historical trend comparison, and AI-based advisory on when a correction is worth applying. On the operations side, the large-scale farm management platform lets a manager track inputs and satellite-derived data across every field or greenhouse from one dashboard, and developers can integrate the same data through the Farmonaut Satellite & Weather API developer docs.

FAQ: Micronutrients and Potassium Fertilizer

Conclusion: Match the Product to the Number, Not the Marketing

The eight-element list of plant micronutrients doesn’t change from one growing season to the next, and neither does the chemistry behind chelation or K₂O labeling. What does change is soil pH drift, crop-specific demand, and — as the potash price data above shows — the retail cost of correcting a deficiency. The durable habit that survives any given season: pull a soil or tissue test before diagnosing by eye, check the guaranteed-analysis percentage on the bag rather than assuming “chelated” or “highest K₂O” automatically means better value, and run the cost-per-pound-of-nutrient math above on your own numbers before buying.

• The eight plant micronutrients are boron, chlorine, copper, iron, manganese, molybdenum, nickel, and zinc.
• Chelated forms trade a lower guaranteed-analysis percentage for solubility across a wider pH range.
• Muriate of potash leads common granular sources at 60–62% K₂O; check current retail pricing before buying since it moves weekly.
• Soil pH between 6 and 6.5 is the range where most micronutrients stay available — test before you diagnose.