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Potassium Sulfate Fertilizer 0-0-53

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Weight: 2 Pounds

Greenway Biotech · Made in California since 1989

Potassium Sulfate 0-0-53.
Chloride-free potassium — with 17% sulfur on the side.

Solution-grade potassium sulfate (K₂SO₄) delivering 53% soluble potash (K₂O) and 17% sulfur in a single, fully water-soluble crystalline form. CDFA registered, independently lab tested for heavy metals, and built for the crops where chloride is a problem — tomatoes, peppers, berries, grapes, potatoes, citrus, and tobacco. Works in soil, foliar, fertigation, and hydroponic Tank B.

Find your size → Calculate how much I need

53%

Soluble potash (K₂O) per pound

17%

Sulfur — the secondary nutrient most often missed

0%

Chloride — safe for sensitive fruit and quality crops

35+yrs

Family-owned, California-made fertilizer manufacturing

01 / Choose your size

Right-sized for the job.

Coverage figures below assume a typical garden planning rate of 1.5 lbs per 100 sq ft (mid of the 1–2 lb range). For fruit trees, plan 1–3 lbs per tree per year. For field crops, base rates on a current soil test — the ranges in the Application section are general references only.

Potassium Sulfate 0-0-53 coverage by bag size at 1.5 lbs per 100 sq ft
Bag Size Garden Coverage Fruit Trees Best For
2 lb ~130 sq ft 1–2 trees Small gardens, trial use, foliar batches
5 lb ~330 sq ft 2–5 trees Most popular
10 lb ~660 sq ft 4–10 trees Backyard orchards, full-season hydro reservoir refills
25 lb ~1,650 sq ft 10–25 trees Market growers, greenhouse fertigation
55.1 lb ~3,650 sq ft 20–55 trees Best value
02 / Ideal applications

One bag.
Six different jobs.

Solution-grade crystalline form dissolves cleanly for soil, foliar, drip, and reservoir use — and the chloride-free chemistry is what makes it suitable for the most quality-sensitive crops in your rotation.

Tomatoes, Peppers & Eggplant

Side-dress at flowering and fruit set. Brix, color, and firmness all benefit from adequate K when fruit demand peaks — without the chloride that can shorten storage life.

Fruit Trees & Citrus

Apply under the drip line in split doses (early spring + during fruit development). Supports sugar accumulation, fruit size, and post-harvest shelf life across pome, stone, and citrus fruit.

Berries & Grapes

From bloom through veraison, K demand spikes. Sulfate-form K avoids the chloride that can flatten flavor and reduce sugar in strawberries, blueberries, raspberries, and wine grapes.

Hydroponics (Tank B)

Fully water-soluble and chloride-free — ideal for recirculating systems where chloride would otherwise accumulate. Keep in Tank B, separate from calcium nitrate.

Potatoes & Tobacco

Two crops where chloride is well known to lower specific gravity, processing quality, and leaf grade. Sulfate-form potassium is the long-standing preferred source.

Foliar & Fertigation

Quick correction during peak fruit fill. Foliar at low concentration (see Application section), or injected weekly through fertigation lines at standard dilution.

03 / Why potassium sulfate

High K.
No chloride.
Two nutrients in one.

Three reasons growers reach for sulfate-form potassium even when muriate of potash costs less per pound of K₂O.

53%

One of the most concentrated chloride-free potassium sources.

Potassium sulfate sits just below muriate of potash (0-0-60/62) in K₂O concentration — but it's the highest-K product available that avoids chloride entirely. That means fewer pounds applied, less salt loading on the soil, and lower freight per unit of K₂O than lower-grade sulfate alternatives like K-Mag.

0Cl

Chloride-free chemistry for quality-sensitive crops.

Crops such as tobacco, potatoes, many berries, grapes, tomatoes, and peppers may perform better with sulfate-based potassium sources. Sensitivity varies by crop, cultivar, irrigation water quality, and soil drainage. If you're running Potassium Chloride 0-0-62 on chloride-tolerant crops and need a separate source for the sensitive ones, K₂SO₄ is the standard companion.

17%S

Sulfur built in — no separate amendment needed.

Sulfur is a secondary macronutrient that's increasingly limiting as atmospheric sulfur deposition has declined. Each pound of K₂SO₄ carries 17% S as plant-available sulfate — supporting amino acid synthesis (cysteine, methionine), enzyme activity, and crop quality in sulfur-loving crops like alliums and brassicas. For deeper coverage, see What is the Function of Sulfur in Plants?

LowSI

Lower salt index than muriate of potash.

Salt index measures how much a fertilizer raises soil solution osmotic pressure relative to sodium nitrate. K₂SO₄ has a partial salt index near 0.85 per unit of K₂O, compared to roughly 1.94 for KCl. In practice, that means less risk of fertilizer burn on seedlings, in containers, and in low-rainfall regions where salts accumulate. Useful detail in our deeper comparison: What is the Best Potassium Fertilizer?

100%

100% water-soluble — solution grade.

Solution-grade K₂SO₄ dissolves completely in warm water with no insoluble residue, making it suitable for drip irrigation, foliar spray, fertigation injection, and hydroponic reservoirs. Maximum solubility is about 120 g per liter of water at 25°C — lower than KCl, so dissolve fully before injecting and avoid over-concentrating stock tanks.

CDFA 

CDFA registered & lab tested for heavy metals.

Registered with the California Department of Food and Agriculture and independently lab tested for heavy metal content — results consistently well below required limits. The current third-party analysis is published on our Heavy Metals Analysis page.

04 / The science

Why two nutrients in one matter.

K₂SO₄solution grade

Potassium sulfate — 53% K₂O, 17% S, chloride-free

Potassium is a regulator more than a builder — it doesn't end up structurally embedded in plant tissue the way nitrogen, phosphorus, or calcium do. Instead, it works as the dominant cellular cation, activating more than 60 enzymes, driving stomatal opening and closing, controlling water movement, loading sugars into fruit, and stabilizing pH inside the cell. When K runs short during fruit development, the consequences are visible: smaller fruit, lower Brix, softer texture, shorter shelf life, and reduced tolerance to drought, heat, and cold.

The chemistry choice — sulfate vs chloride — matters because the accompanying anion stays in the soil and the plant. Potassium chloride delivers more K₂O per pound and per dollar, but the chloride that comes with it can accumulate in salt-sensitive crops, suppress sugar accumulation in fruit, and shorten storage life. Sulfate-form potassium — K₂SO₄ — sidesteps that entirely while contributing 17% sulfur as plant-available SO₄²⁻, which supports amino acid synthesis and enzyme activity in its own right.

Practically, that means K₂SO₄ is the standard choice when crop quality is part of the equation: premium fruit, sweet vegetables, alliums, brassicas, processing potatoes, wine grapes, and tobacco. It's also the standard potassium source for recirculating hydroponic systems, where chloride buildup would otherwise become phytotoxic over time. For deeper coverage on potassium's role and why fruit crops in particular demand so much of it, see What's the Function of Potassium (K) in Plants? and Improving Fruit Quality and Yield with Fertilizers.

05 / Application rates

Pick your use.
Get your rate.

All rates are reference figures for medium-testing soils at typical yield goals. Actual rates should be based on a current soil test, crop removal estimates, and local extension guidance. The Calculator below the table converts these rates to total product needed for your garden, field, or reservoir.

Gardens & Vegetables — Soil Application

Quick answer: Broadcast 0.75–2 lbs per 100 sq ft (lower for maintenance, higher for K-deficient soils), worked into the top 4–6 inches, then water in deeply.

Garden & vegetable rates by application method
ApplicationRateTiming & Notes
Maintenance (medium-K soils)0.75–1 lb per 100 sq ftPre-plant; work into top 4–6 inches
Pre-plant build-up (deficient soils)1.5–2 lbs per 100 sq ftPer UConn Soil Lab recommendation for low-K soils
Side-dress at fruit set1 lb per 100 sq ftBand 6–8 inches from row, water in
Tomatoes & peppers1–1.5 lbs per 100 sq ft total seasonSplit: at planting + at flowering
Potatoes (chloride-sensitive)1.5–2 lbs per 100 sq ftPre-plant or at tuber initiation

Note: Garden rates assume soils testing in the medium range for K (about 100–200 ppm). If a soil test shows K below 100 ppm, rates may need to come up toward the high end; if it's already above 200 ppm, hold the rate down. Heavy clay soils tolerate higher single applications than sandy soils, where splitting the dose reduces leaching.

Fruit Trees, Citrus & Ornamentals

Quick answer: 1–5 lbs per tree per year depending on species and age, split into 2–3 applications, broadcast under the drip line.

Fruit tree and citrus annual application rates
Tree TypeAnnual RateTiming
Young trees (1–3 yrs)0.5–1 lb per treeEarly spring only
Mature stone & pome fruit1–3 lbs per treeSplit: early spring + during fruit development
Citrus (mature)2–5 lbs per tree2–3 split applications across the year
Almonds (backyard)3–7 lbs per treeFall maintenance band 4–5 ft from trunk; per UC research
Berries & grapes1–2 lbs per 100 sq ftPre-bud break + at veraison

Note: Apply under the outer canopy edge (drip line), not against the trunk. Rake lightly into the surface or cover with a thin mulch layer, then water in deeply. For container-grown citrus and small fruit, reduce the rate by 30–50% and split into more frequent feedings. Commercial almond orchards (per UC research) commonly band 285–500 lbs per acre annually in the same location 4–5 feet out from the trunk on both sides of the row.

Field & Row Crops

Quick answer: 200–500 lbs K₂SO₄ per acre, depending on crop, yield goal, and soil test. Field rates are not maintenance rates — soil test first.

Field crop reference rates per acre
CropReference RateNotes & Source
Tomatoes (processing/fresh)225–500 lbs per acreUC Davis: 220–330 lb K₂O removed at 45 ton yield; Auburn trial up to 340 lb/ac
Potatoes225–450 lbs per acreU. Maine Bull. #2251 (120–240 lb K₂O/ac); chloride-free essential
Almonds285–500 lbs per acreUC research: 150–250 lb K₂O/ac removed; fall maintenance band
Tobacco200–400 lbs per acreSulfate form preferred for leaf quality
Grapes & berries200–500 lbs per acreLodi/UCCE: high-rate (>1000 lb/ac) build-up on K-fixing soils; fertigated season total
Citrus orchards2–5 lbs per tree per yearConvert by tree density

📋 Field & Acreage Rates: The per-acre figures above are research-anchored references for medium-testing soils at typical yield goals. Actual rates should be based on a current soil test and local nutrient removal estimates. Even at the soil-test-recommended rate, peer-reviewed trials (e.g., Auburn tomato) have shown soil K can remain in the low-to-moderate range — recommended rates maximize yield, not always quality. Consult your local extension service for site-specific recommendations.

Foliar Spray

Quick answer: 1–4 tsp per gallon (1.3–5.3 g/L, 0.13–0.53% w/v) for home sprayers — well below the 1.2% K₂O burn ceiling. Apply early morning or late evening; never in direct sun above 85°F.

Foliar spray rates by crop, research-anchored
CropRate per GallonTiming & Source
Vegetables & fruiting crops1–3 tsp per gal (1.3–4 g/L)Every 2–3 weeks at fruit set; U. Delaware recommends 4 lb K/ac per pass on fruiting veg
Fruit trees & citrus2–4 tsp per gal (2.6–5.3 g/L)UF/IFAS: 8 lb K₂O/ac per pass on mature citrus; peer-reviewed citrus optimum 0.56% w/v
Peaches (fruit sizing)3–4 tsp per gal (4–5 g/L)Kasetsart 2024: 1.5% w/v (15 g/L) at 30/45/60 DAFB gave largest fruit size in pro sprayers
Grapes & berries1.5–3.5 tsp per gal (2–4.7 g/L)WVU: 6–10 lb per 100 gal carrier, 200 gal/ac at veraison
Potatoes (chloride-sensitive)1–2 tsp per gal (1.3–2.7 g/L)Keep below 1.2% K₂O to avoid leaf burn (Laughlin, Am. Potato J.)
Field crops (pro sprayer)9–19 lbs per acre per pass2–3 applications per season in 20–30 gal carrier

Foliar safety check: Peer-reviewed work places the leaf-burn ceiling at about 1.2% K₂O (~22 g/L) on chloride-sensitive crops; commercial optimums cluster at 0.56–2% w/v. The home-sprayer range above stays well below that. Always test on a small area first, spray in early morning or late afternoon, and avoid spraying in temperatures above 85°F. Do not foliar-spray K₂SO₄ together with calcium-containing tank-mix partners — sulfate and calcium can form insoluble gypsum on the leaf.

Hydroponics, Fertigation & Drip

Quick answer: 0.45–1.10 g per liter (about 1.5–4 tsp per gallon) in Tank B, targeting ~150–290 ppm K. Pre-dissolve in warm water; never combine with calcium nitrate in concentrate.

Hydroponic and fertigation dose rates, research-anchored
SystemConcentrationNotes
Recirculating hydroponics (low end)0.45 g per liter (~117 ppm K)U. Delaware strawberry trial baseline
Recirculating hydroponics (typical)0.75 g per liter (~196 ppm K)Common target for fruiting crops
Recirculating hydroponics (high end)1.10 g per liter (~288 ppm K)Upper end of U. Delaware tested range
Fertigation (injected weekly)1–2 lbs per 100 gal carrierInject Tank B alternately with Tank A
Stock solution (Tank B)up to 80 g per liter (cold) or 120 g/L (warm)Stay below max solubility; dilute 1:100 into main line
EC contribution (reference)~0.7–1.0 mS/cm at standard ratesVerify against your meter; salt index 46 (vs. 116 for MOP)

⚠️ Tank compatibility: Keep potassium sulfate in Tank B, separate from calcium-containing fertilizers like Calcium Nitrate 15.5-0-0 and Cal-Mag Plus. In concentrated form, sulfate and calcium react to form insoluble calcium sulfate (gypsum), which clogs drippers and locks up both nutrients. At normal dilution in soil application, this is not a concern. Solubility drops sharply in cold water (only ~85 g/L at 10°C/50°F) — always dissolve stock concentrates in warm water and flush lines after injection.

06 / How to use & calculate

Dissolve.
Apply.
Let the crop respond.

Four steps cover almost every use case. The calculator on the right turns your area, tree count, or reservoir size into product needed.

  1. 01

    Measure your area or volume.

    Square feet for gardens, tree count for orchards, gallons for hydroponics. Soil test results, if you have them, calibrate the rate — especially for field-scale applications.

  2. 02

    Pre-dissolve in warm water.

    K₂SO₄ dissolves cleanly in warm water (max ~120 g/L at 25°C). Stir until completely clear — no visible crystals — before adding to your hose-end sprayer, foliar tank, drip injector, or hydroponic reservoir.

  3. 03

    Apply, then water in (soil) or circulate (hydro).

    Broadcast applications need to be watered into the root zone within 24 hours. Foliar sprays go on in early morning or evening. Hydroponic adds should be circulated and the EC verified after dosing.

  4. 04

    Keep separate from calcium concentrates.

    In any concentrated mix — foliar tank, stock solution, drip injector — potassium sulfate goes in Tank B and calcium nitrate (or any soluble calcium source) goes in Tank A. They can combine downstream in the diluted main line, just not in concentrate.

07 / Compare

Four potassium sources.
Different jobs.

Potassium sulfate fits a specific slot in the lineup — chloride-free, high K, with sulfur. The table shows where each potassium source earns its keep. For deeper coverage see What is the Best Potassium Fertilizer?

Potassium Sulfate 0-0-53 compared with other potassium fertilizers
Product K₂O Co-nutrient Chloride Best For
Potassium Sulfate 0-0-53 (this product) 53% 17% S None Chloride-sensitive crops, hydroponics, premium fruit, foliar
Potassium Chloride 0-0-62 60–62% None ~47% Chloride-tolerant field crops where K cost matters most
K-Mag 0-0-22 (langbeinite) 22% 11% Mg, 22% S <2.5% K + Mg + S in one product; soil application
MKP 0-52-34 34% 52% P₂O₅ None Bloom-boost programs where P + K are both needed
08 / Decision

Is potassium sulfate
the right K source for you?

Use this list to confirm fit before buying. If two or three of the “consider another product” conditions apply, the alternative is probably a better starting point.

Best Choice For

  • Tomatoes, peppers, berries, grapes, potatoes, tobacco, or citrus where chloride can reduce quality
  • Recirculating hydroponics, where chloride buildup over time becomes phytotoxic
  • Soils already showing elevated chloride from prior KCl applications or saline irrigation water
  • Crops where sulfur is also limiting — alliums, brassicas, and high-yield row crops on sulfur-depleted soils
  • Late-season fruit-quality applications where extra nitrogen is unwanted
  • Foliar potassium sprays at the lower end of the dose range

Consider Another Product If

  • You're growing chloride-tolerant field crops at scale and unit-K₂O cost is the priority — try Potassium Chloride 0-0-62
  • You need potassium AND magnesium in one application — try K-Mag 0-0-22
  • You need potassium AND phosphorus during bloom — try MKP 0-52-34
  • Your soil pH is already on the acidic side and you don't want additional sulfate-driven acidification — K-Mag is gentler
  • You're correcting magnesium deficiency only — use Epsom Salt instead
10 / Safety & handling

Read this before
you dissolve.

K₂SO₄ is a low-toxicity crystalline fertilizer salt, but standard handling and tank-mix rules still apply.

  • Wear gloves, eye protection, and an N95 dust mask when handling dry product in enclosed spaces or when measuring large quantities — the fine crystalline form can become airborne.
  • Store sealed in a cool, dry place. K₂SO₄ is mildly hygroscopic — left exposed to humid air it will cake and absorb moisture, reducing solubility and flow.
  • Pre-dissolve completely in warm water before injecting into drip, fertigation, or hydroponic lines. Undissolved crystals can clog emitters and damage injectors.
  • Do not combine in concentrate with calcium-containing fertilizers (e.g. Calcium Nitrate, Cal-Mag Plus) — sulfate + calcium forms insoluble gypsum precipitate. Use separate Tank A / Tank B stock solutions and jar-test any unfamiliar combination before injecting.
  • First aid — eyes: flush with clean water 15 minutes, seek medical attention if irritation persists. Skin: wash with soap and water. Ingestion: do not induce vomiting; contact Poison Control (1-800-222-1222). Inhalation: move to fresh air. Refer to the Safety Data Sheet for complete safety information.
11 / FAQ

Common questions.
Honest answers.

If your question isn't here, contact our team at questions@greenwaybiotech.com or check the full FAQ page.

What's the practical difference between potassium sulfate and muriate of potash?

Potassium sulfate (0-0-53) and muriate of potash (potassium chloride, 0-0-60/62) both supply potassium, but the accompanying anion is different. K₂SO₄ carries sulfate (which contributes 17% S as plant-available sulfur), while KCl carries about 47% chloride. For chloride-tolerant field crops where unit-K₂O cost matters most, KCl is hard to beat. For chloride-sensitive or quality-sensitive crops — tomatoes, peppers, berries, grapes, potatoes, tobacco, citrus — sulfate-form K is the standard choice, and the cost premium is usually justified by improved fruit quality, sugar content, and storage life. For a deeper comparison see What is the Best Potassium Fertilizer?

When should I apply potassium sulfate for the best results?

Timing depends on the crop, but a few patterns hold consistently:

  • Fruit trees & citrus: split application — early spring + during fruit development.
  • Vegetables: at planting and again at flowering or fruit set.
  • Grapes: from veraison (color change) through pre-harvest.
  • Field crops: pre-plant or side-dress during rapid uptake.
  • Perennials & lawns: late summer or fall to support winter hardiness.

Because K₂SO₄ carries zero nitrogen, late-season applications can support fruit quality without triggering the unwanted vegetative growth that nitrogen-bearing K sources would.

Can I use potassium sulfate in my hydroponic system?

Yes — in fact, K₂SO₄ is the standard potassium source for recirculating hydroponics specifically because it adds no chloride. In closed systems, chloride accumulates over weeks and eventually becomes phytotoxic; sulfate-form K avoids that entirely. Typical reservoir rates are about 0.45–1.10 g per liter (roughly 1.5–4 tsp per gallon), targeting ~117–288 ppm K — the range used in University of Delaware strawberry trials. This contributes approximately 0.7–1.0 mS/cm to total EC. Pre-dissolve in warm water before adding to the reservoir, and keep K₂SO₄ in Tank B, separate from Calcium Nitrate in Tank A. After hydroponic disease events, K₂SO₄ is often part of the post-treatment nutrient solution — see How to Treat Root Rot in Hydroponic Plants.

How does potassium support plant health and stress tolerance?

Potassium acts as a regulator more than a structural element: it controls stomatal function (water use efficiency), activates 60+ enzymes, drives sugar loading into fruit, and stabilizes cellular osmotic balance. Plants with adequate K may show improved tolerance to drought, heat, cold, and salt stress, and research suggests that K-sufficient plants can be more resilient under disease pressure — though K is not a treatment for any specific disease. The full picture is in What's the Function of Potassium (K) in Plants?

What does the 17% sulfur actually do?

Sulfur is a secondary macronutrient required for amino acid synthesis (specifically cysteine and methionine), enzyme activation, and vitamin formation. Atmospheric sulfur deposition has declined over the last several decades, so sulfur deficiency is increasingly common on intensively cropped soils. The 17% S in potassium sulfate is delivered as plant-available sulfate (SO₄²⁻) — no separate amendment needed. Sulfate also has a mild soil-acidifying effect over time, which can help improve micronutrient availability in alkaline soils. For deeper coverage see What is the Function of Sulfur in Plants?

Why can't I mix potassium sulfate with calcium nitrate in the same tank?

In concentrated stock solutions, the sulfate ion (SO₄²⁻) and the calcium ion (Ca²⁺) combine to form calcium sulfate — gypsum — which has limited solubility and precipitates out. The result clogs drippers, lines, and injectors, and locks up both the calcium and the sulfate so plants can't use either. The fix is straightforward: keep K₂SO₄ in Tank B and put Calcium Nitrate in Tank A. The two tanks can be injected alternately, and at normal field dilution downstream the reaction does not occur. In soil applications at full dilution, this is also not a concern — the rule applies specifically to concentrated stock solutions and foliar tanks.

What does potassium deficiency look like?

K deficiency shows on older leaves first — marginal chlorosis (yellowing along leaf edges) progressing to necrotic scorching, weak or lodging-prone stems, poor fruit quality (small size, dull color, low sugar), and reduced tolerance to drought and cold. It is most common in sandy or leached soils, after heavy rainfall, and where high nitrogen rates have been applied without balanced K. A soil test result below about 100–120 ppm K typically indicates supplementation is needed. Plant tissue tests, where available, are more diagnostic than soil tests for confirming K status during the growing season.

Is this product certified organic?

No — Greenway Biotech's Potassium Sulfate 0-0-53 is a synthetic, solution-grade product and is not OMRI Listed. Growers in certified organic production should consult their certifier for approved potassium sources — K-Mag (langbeinite) is a naturally mined mineral that is allowed in organic production under many programs, depending on certifier and use.

Can I use potassium sulfate on my lawn?

Yes, particularly as a fall application to support winter hardiness, or where a soil test shows K is below the target range. A typical maintenance rate is about 2 lbs per 100 sq ft, watered in deeply. Because K₂SO₄ carries no nitrogen, it won't drive the flush of top growth that a complete lawn fertilizer would — useful when you want K without N. For nitrogen, pair it with a separate source like Urea 46-0-0 or an ammonium sulfate, applied at a different time.

12 / Documents

Lab-tested.
State-registered.

SDS, heavy-metal analysis, and product label — all linked below. Certificate of Analysis for a specific lot is available on request.

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