Calcium Nitrate Fertilizer 15.5-0-0 (Ammonia Calcium Nitrate 15.5-0-0)
- Regular Price
- $ 24.99
- Sale Price
- $ 24.99
- Regular Price
- $ 19.99
Sold Out
- Unit Price
- per
Greenway Biotech · Made in California since 1989
Calcium Nitrate Fertilizer 15.5-0-0.
Calcium and nitrogen, fully dissolved.
A 100% water-soluble source of 15.5% nitrogen and 19% calcium — built for growers who need both nutrients available immediately. The nitrogen is almost entirely in fast-acting nitrate form, the calcium supports cell-wall development where fruit and leaf tissue expands fastest. CDFA registered and independently lab tested for heavy metals, with results consistently well below required limits.
Find your size → Calculate how much I need15.5%
Nitrogen — mostly fast-acting nitrate
19%
Calcium for cell-wall structure
100%
Water soluble — no residue
0P-K
No phosphate or potash to manage
01 / Choose your size
Right-sized for the job.
Coverage figures below assume a general garden rate of about 2 lb per 100 sq ft per application. Your actual need depends on crop, growth stage, and how often you reapply — use the calculator further down for an exact figure.
| Bag Size | Garden Coverage (per application) | Hydroponic Reservoir (single fill) | Best For |
|---|---|---|---|
| 5 lb | ~250 sq ft | ~300 gal at 1.5 tsp/gal | Home gardens, container growers |
| 10 lb | ~500 sq ft | ~600 gal at 1.5 tsp/gal | Larger raised-bed gardens |
| 25 lb | ~1,250 sq ft | ~1,500 gal at 1.5 tsp/gal | Most popular |
| 50 lb | ~2,500 sq ft | ~3,000 gal at 1.5 tsp/gal | Best value |
02 / Ideal applications
One bag.
Six different jobs.
Calcium nitrate works wherever a fast, clean source of nitrogen and calcium is needed — in soil, in solution, or on the leaf. A few uses come with honest caveats, noted below.
Tomatoes & Peppers
A standard sidedress for fruiting nightshades. Supplying calcium during fruit expansion may support fruit calcium nutrition, which research links to lower blossom end rot incidence.
Hydroponics & Fertigation
A clean, phosphate-free calcium and nitrate source for recirculating systems. Always kept in a separate stock tank from phosphates and sulfates.
Cucurbits & Melons
Sidedress nitrogen for cucumbers, squash, and melons, with calcium supplied alongside during the rapid fruit-sizing window.
Fruit Trees
A soil nitrogen source for bearing trees, and a foliar calcium option for pome fruit — though calcium chloride is the more common orchard choice and some apple cultivars are sensitive (see Application Rates).
Leafy Greens
A useful nitrate-nitrogen source for lettuce, brassicas, and other greens. Note that calcium sprays have limited effect on head-lettuce tipburn — airflow and even moisture matter more.
Foliar Correction
A low-rate foliar spray for short-term calcium support during rapid growth. Most effective as a supplement to root uptake, not a replacement for it.
03 / Why calcium nitrate
Two nutrients.
One dissolving step.
The case for calcium nitrate is speed and simplicity — immediately available nutrients, a near-neutral pH effect, and no phosphate or potash to balance.
14.5%
Nitrate nitrogen, ready on contact.
Of the 15.5% total nitrogen, 14.5% is nitrate (NO₃⁻) — the form plants take up directly with no conversion step. The remaining 1% is ammoniacal nitrogen. Nitrate is also the preferred nitrogen form for calcium-sensitive crops, since ammonium competes with calcium for uptake at the root.
19%
Calcium where tissue expands fastest.
Calcium builds cell walls and the middle lamella that holds cells together. It is largely immobile once deposited, so a steady supply during rapid fruit and leaf growth matters. Adequate fruit calcium nutrition is linked in research to lower blossom end rot incidence, though even soil moisture is an equally important factor.
100%
Dissolves completely, no residue.
Calcium nitrate goes fully into solution, leaving nothing behind to clog drip emitters, injectors, or foliar sprayers. That makes one product workable across watering cans, fertigation lines, and hydroponic reservoirs alike.
pH
Near-neutral effect on most soils.
Unlike ammonium sulfate, which acidifies soil, or lime, which raises pH, calcium nitrate has a near-neutral pH effect under normal use. That allows routine applications without constant pH correction in most buffered soils. If you specifically need to acidify, consider Ammonium Sulfate 21-0-0 instead.
0P
No phosphate to manage or lose.
With zero available phosphate (P₂O₅) and zero soluble potash (K₂O), calcium nitrate adds nothing to phosphorus runoff load — useful near waterways or in regions with phosphorus application limits. Pair it with MKP 0-52-34 or Potassium Sulfate 0-0-53 when P and K are also needed.
04 / The science
Why calcium delivery is a transport problem.
Ca(NO₃)₂
Ammonium Calcium Nitrate Double Salt — 15.5% N, 19% Ca
Calcium nitrate supplies two of the most in-demand plant nutrients in a single soluble salt. The nitrogen drives chlorophyll production, protein synthesis, and vegetative growth — and because it is almost entirely nitrate, it is plant-available the moment it dissolves, with no microbial conversion step. The calcium serves a structural role: it cross-links pectin in cell walls and the middle lamella, the layer that cements adjacent cells together.
The reason calcium gets so much attention in fruiting crops is not usually a shortage in the soil — it is a transport limitation. Calcium moves through the plant almost exclusively in the xylem, pulled upward by transpiration. It cannot be redirected through the phloem to tissues that need it later. Rapidly expanding fruit transpires very little, so it can run short of calcium even when soil levels test adequate. Inconsistent watering, humidity swings, and fast growth spurts all disrupt that delivery.
This is why supplying calcium through fertigation or a foliar spray during fruit development can help — it offers a more direct route during the window when demand peaks. It is also why no calcium product should be treated as a guaranteed fix: maintaining even soil moisture is just as important as the calcium supply itself. Foliar calcium in particular is a supportive measure, since fruit surfaces absorb little of it and calcium will not migrate from a sprayed leaf into the fruit.
For deeper background, see our guides to the function of calcium in plants and choosing the right calcium fertilizer.
05 / Application rates
Pick your use.
Get your rate.
Rates below are drawn from university extension publications. Every table cites its sources. Calcium nitrate is 15.5% N, so a nitrogen target in lb/acre converts to product by dividing by 0.155.
Tomatoes & Fruiting Vegetables — Sidedress
Quick answer: Sidedress at roughly 2 lb per 100 ft of row, applied monthly, beginning once the first fruits have set.
| Use | Rate | Source | Notes |
|---|---|---|---|
| Tomato sidedress (home garden) | 2 lb per 100 ft of row, monthly | UGA Extension | Usually the best single choice for tomato sidedressing |
| General vegetable side-dressing | 1 lb per 100 ft of row (about 1 level tbsp per plant) | UGA Extension | Keep at least 2 in. from the stalk; avoid contact with wet foliage |
| Commercial root-zone rate | ~3.5 lb per 100 ft of plants (~12 oz per plant) | Extension producer guidance | Applied to the root zone during flowering |
| Small-plot nitrogen sidedress | ~0.25 lb per 100 sq ft | Oregon State University Extension | Calcium nitrate or ammonium sulfate as the N source |
Note: As a general rule, do not sidedress tomato vines until their first fruits have set — over-fertilizing early drives leafy growth that competes with fruit for calcium. Maintain even soil moisture alongside any calcium program.
Sources: University of Georgia Extension; Oregon State University Extension; North Dakota State University Extension.
Field Vegetables — Nitrogen Sidedress
Quick answer: Extension nitrogen targets are listed per acre; divide the N target by 0.155 to get the calcium nitrate rate.
| Crop | N Target (lb/acre) | Calcium Nitrate Equivalent | Source |
|---|---|---|---|
| Cucumbers, squash, beans | 20 | ~129 lb/acre | Extension vegetable handbooks |
| Eggplant | 30 | ~194 lb/acre | Extension vegetable handbooks |
| Cole crops, greens | 30–40 | ~194–258 lb/acre | Extension vegetable handbooks |
| Watermelon, melons, potato | 40 | ~258 lb/acre | Extension vegetable handbooks |
| Tomatoes, peppers | 40–60 | ~258–387 lb/acre | Extension vegetable handbooks |
| Sweet corn | 40–80 | ~258–516 lb/acre | Extension vegetable handbooks |
📋 Soil Test First: Field crop application rates above are general guidelines based on typical soil test levels and crop removal estimates. Actual rates should be confirmed by a current soil test and consultation with your local cooperative extension service, as needs vary significantly by soil type, crop variety, and regional conditions. For calcium-sensitive crops such as tomato and pepper, non-acidic nitrogen forms like calcium or potassium nitrate are generally recommended.
Sources: University extension vegetable crop handbooks; Alabama Cooperative Extension System (fertigation conversion guidance); Clemson University Extension.
Hydroponic & Greenhouse Systems
Quick answer: Maintain calcium between 150–200 ppm for fruiting crops; always keep calcium nitrate in a separate stock tank from phosphates and sulfates.
| System / Crop | Rate or Target | Source | Notes |
|---|---|---|---|
| Fruiting crops (tomato, pepper, cucumber) | 150–200 ppm Ca in solution | UMass Amherst | Monitor potassium to avoid antagonism |
| Leafy greens & herbs | ~100–150 ppm Ca in solution | UMass Amherst | Manage airflow for tipburn-prone greens |
| Greenhouse tomato stock solution | 10 oz per gallon, injected 1:100 | UMass Amherst | Yields ~200 ppm N; keep in a tank separate from other macronutrients |
| Home-scale reservoir mixing | 1–2 tsp per gallon | Greenway Biotech product label | EC contribution roughly 0.5–1.0 mS/cm |
Compatibility: Use separate stock tanks for calcium fertilizers and other concentrated fertilizer salts. Always dilute each independently before combining in the main tank, and jar-test unfamiliar combinations before injecting. Mixing concentrated calcium nitrate directly with phosphate or sulfate sources causes insoluble precipitates that clog irrigation lines.
Sources: University of Massachusetts Amherst (greenhouse stock-solution guidance); Greenway Biotech product label.
Fruit Trees — Soil & Foliar
Quick answer: For bearing trees, the product label rate is 1–2 lb per inch of trunk diameter, applied beneath the dripline.
| Use | Rate | Source | Notes |
|---|---|---|---|
| Bearing fruit trees (soil) | 1–2 lb per inch of trunk diameter | Greenway Biotech product label | Apply beneath the dripline, well away from the trunk |
| Bearing trees, trunk-diameter method | 2/3 lb per inch of trunk diameter; do not exceed 1.75 lb/yr | UNH Extension | Fertilize in spring, before June 1 |
| Apples, by tree age | 0.5 lb per year of tree growth, to a maximum of 8 lb per tree | Commercial label guidance | Broadcast under the tree |
| Apple foliar calcium | No more than 5 lb per 100 gal, plus a surfactant | Oregon State / PNW guidance | Not advised on Delicious or York cultivars; trial a single branch first |
Cultivar caution: Foliar calcium nitrate is not advised on Delicious and York apple cultivars, where it can induce cork-spot-like symptoms. In orchards already well supplied with nitrogen, calcium nitrate sprays may also reduce fruit color. Calcium chloride is the more common orchard choice; use calcium nitrate where you also want the nitrogen and the cultivar is not sensitive. Trial a single branch on unfamiliar cultivars.
Sources: University of New Hampshire Extension; Oregon State University Extension / Pacific Northwest guidance; Greenway Biotech product label.
Foliar Spray
Quick answer: For home gardens, dilute 1–2 tablespoons per gallon of water and spray in cool conditions.
| Use | Rate | Source | Notes |
|---|---|---|---|
| Home garden foliar | 1–2 tbsp per gallon of water | Greenway Biotech product label | About 15–30 g per gallon |
| Fruiting vegetables (field) | 10–15 lb per 100 gal per acre | University of Delaware / Iowa State Extension | Targets 2–4 lb Ca per acre for tomato, pepper, eggplant |
| Apple foliar (orchard) | No more than 5 lb per 100 gal, plus a surfactant | Oregon State / PNW guidance | Higher rates can burn foliage and fruit |
Foliar safety check: Foliar rates should be well below soil rates — typically 1–4 g/gallon (or 2–6 g/liter) of elemental calcium delivery depending on crop sensitivity. Always test on a small area first, spray in early morning or late afternoon, and avoid spraying in temperatures above 85°F. Foliar calcium is a supportive measure: fruit absorbs little of it, and it will not move from a sprayed leaf into the fruit. Root uptake with even moisture remains the primary control.
Sources: University of Delaware Cooperative Extension; Iowa State University Extension; Oregon State University Extension; Greenway Biotech product label.
06 / How to use & calculate
Dissolve.
Apply.
Water in.
Calcium nitrate is simple to apply — the details that matter are timing, keeping it away from phosphates in concentrate, and watering in dry applications.
-
01
Soil & garden beds
Scatter the rate for your crop evenly around the dripline of plants, work it lightly into the top 2–3 inches of soil, and water thoroughly to move the calcium into the root zone. Reapply every 2–3 weeks during active growth.
-
02
Containers & hydroponics
Dissolve in water before applying. In hydroponic systems, add calcium nitrate to the reservoir first, stir until fully dissolved, then add other nutrients separately. Adjust pH last, to 5.5–6.5 for most crops.
-
03
Foliar spray
Dissolve 1–2 tbsp per gallon, spray both leaf surfaces until lightly dripping, and apply in early morning or evening below 85°F. Test on a small area and wait 24 hours before treating a full crop.
-
04
Never mix directly with phosphates
Calcium nitrate reacts with concentrated phosphate and sulfate fertilizers to form insoluble precipitates. Keep it in a separate stock tank, dilute each fertilizer independently, and jar-test unfamiliar combinations before injecting.
07 / Compare
Four calcium &
nitrogen sources.
Calcium nitrate is the fast, dual-nutrient option. Other sources win on different jobs — here is where each fits.
| Product | Nitrogen | Calcium | Speed / pH Effect | Best For |
|---|---|---|---|---|
| Calcium Nitrate 15.5-0-0 (this product) | 15.5% | 19% | Immediate / near-neutral | Fast N + Ca for soil, hydroponics, and foliar feeding |
| Cal-Mag Plus 2-0-0 | 2% | 3.2% (plus Mg + Fe) | Immediate / near-neutral | RO water and coco coir, where Mg and Fe are also short |
| Ammonium Sulfate 21-0-0 | 21% | 0% | Immediate / acidifying | Nitrogen plus sulfur where lowering soil pH is desired |
| Gypsum (Calcium Sulfate) | 0% | ~23% | Slow / near-neutral | Long-term calcium and soil-structure improvement in clay |
08 / Decision
Is this the right
source for you?
Calcium nitrate is a strong fit for most fast-feeding situations — but a few needs are better served by another product.
Best Choice For
- Supplying fast-acting nitrogen and calcium in a single application
- Supporting fruit calcium nutrition in tomatoes, peppers, and cucurbits
- Hydroponic and fertigation systems needing a clean, phosphate-free calcium source
- Short-term foliar calcium support during rapid growth
- Routine feeding where a near-neutral pH effect is wanted
- Properties with phosphorus runoff restrictions (0% P formula)
Consider Another Product If
- You also need magnesium and iron — try Cal-Mag Plus 2-0-0 instead or alongside
- You want long-term calcium building without nitrogen — use Gypsum (Calcium Sulfate)
- Your goal is raising pH in acidic soil — use Dolomite Lime
- You need nitrogen but not calcium — use Ammonium Sulfate 21-0-0
- You are correcting iron chlorosis in alkaline soil — use Chelated Iron DTPA 11%
09 / Build the program
Calcium nitrate is N + Ca.
These complete the program.
Calcium nitrate covers nitrogen and calcium. Add phosphorus, potassium, magnesium, and iron as your crop and growing system require — keeping phosphates in a separate tank.
Potassium
Potassium Sulfate 0-0-53
Adds soluble potash (K₂O) and sulfur for fruit quality and water regulation — the K that calcium nitrate does not provide.
Phosphate + PotassiumMKP 0-52-34
Available phosphate and potash for flowering and fruiting. Always add to the reservoir in a separate step from calcium nitrate.
MagnesiumEpsom Salt (Magnesium Sulfate)
Supplies magnesium for chlorophyll production — complementing calcium for complete secondary-nutrient coverage.
MicronutrientChelated Iron DTPA 11%
Keeps iron plant-available in alkaline soils and hydroponic solutions up to pH 7.5 — a useful partner in intensive feeding programs.
10 / Safety & handling
Read this before
you mix.
Calcium nitrate is straightforward to handle with basic precautions. The one rule that protects your equipment is keeping it away from phosphates in concentrate.
- Wear chemical-resistant gloves (nitrile recommended) and safety glasses when handling dry product or concentrated solutions; use a dust mask in enclosed spaces.
- Store in a cool, dry place in the original sealed container. Calcium nitrate is hygroscopic — it absorbs moisture from the air, so reseal bags tightly after each use.
- Water soil thoroughly after any dry application to move calcium into the root zone and prevent salt buildup on roots. Do not apply to wilted or drought-stressed plants — water first.
- Never mix calcium nitrate directly with phosphate or sulfate fertilizers in concentrate. Use separate stock tanks, dilute each independently, and jar-test unfamiliar combinations.
- First aid — eyes: flush with water 15 minutes; skin: wash with soap and water; ingestion: do not induce vomiting, rinse mouth, contact Poison Control (1-800-222-1222); inhalation: move to fresh air. Refer to the SDS for complete information.
11 / FAQ
Common questions.
Honest answers.
If your question isn't here, contact our team at questions@greenwaybiotech.com.
What is calcium nitrate and what does it do?
Calcium nitrate (15.5-0-0) is a water-soluble fertilizer that supplies 15.5% nitrogen — almost entirely as fast-acting nitrate — plus 19% calcium. It dissolves completely for immediate plant availability and is widely used to support cell-wall development and fruit calcium nutrition. Learn more in our guide to choosing the right calcium fertilizer.
Does calcium nitrate help with blossom end rot?
Supplying calcium during fruit development may support fruit calcium nutrition, which research links to lower blossom end rot incidence in tomatoes, peppers, and cucurbits. It is not a guaranteed fix, however. Blossom end rot is largely a calcium transport problem rather than a soil shortage — calcium moves only through the xylem and cannot be redirected to expanding fruit. Consistent soil moisture is just as important as the calcium supply. Apply when fruits are walnut-sized and continue every 2 weeks through fruit development.
When should I apply calcium nitrate?
For fruiting vegetables, begin once the first fruits have set — the critical window is when fruits are walnut-sized and calcium demand peaks — then continue every 2 to 3 weeks. Also consider an application after heavy rain, which leaches calcium, or during drought stress, which impairs uptake. For a complete guide on nitrogen timing and sources, see our article on the best nitrogen fertilizers.
Can I use calcium nitrate in hydroponics?
Yes. At home scale, use 1 to 2 teaspoons per gallon for an EC contribution of roughly 0.5 to 1.0 mS/cm. For fruiting crops, university guidance targets 150 to 200 ppm calcium in solution. The one critical rule: always add calcium nitrate to the reservoir first, in a separate step from phosphate and sulfate sources — mixing them in concentrate causes precipitation. See our complete guide to hydroponic fertilizers.
Why can't I mix calcium nitrate with phosphate fertilizers?
When concentrated calcium nitrate contacts concentrated phosphate sources such as MAP or MKP — or sulfate sources such as potassium sulfate — calcium reacts to form insoluble precipitates that settle out and clog irrigation lines and injectors. Use separate stock tanks for calcium fertilizers and other concentrated salts, dilute each independently before combining in the main tank, and jar-test unfamiliar combinations before injecting. At normal soil-application dilution this is not a concern; the reaction happens in concentrated stock solutions.
How does calcium nitrate compare to gypsum or lime?
Calcium nitrate supplies immediately available calcium and nitrogen, dissolves completely, and has a near-neutral pH effect — making it the practical choice for fast feeding. Gypsum is slow-releasing and better suited to long-term calcium building and clay-soil structure without adding nitrogen. Lime raises soil pH and releases calcium slowly. If raising pH is your goal, Dolomite Lime is the better fit.
Does calcium nitrate help with tip burn in lettuce?
It can serve as a useful nitrate-nitrogen source for lettuce and leafy greens, but expectations should be realistic for tip burn specifically. In head lettuce, soil and foliar calcium are generally not effective, because calcium cannot reach the enclosed inner leaves where tip burn develops. For tip burn, even moisture, good airflow, and resistant cultivars matter most. For broader lettuce nutrition, see our article on the best fertilizer for lettuce.
Can I use calcium nitrate as a foliar spray on fruit trees?
For most fruit trees, dilute 1 to 2 tablespoons per gallon and spray in cool conditions. In apple orchards, calcium chloride is the more common choice; calcium nitrate is used where the extra nitrogen is also wanted. Note that foliar calcium nitrate is not advised on Delicious and York apple cultivars, where it can induce cork-spot-like symptoms, and PNW guidance caps orchard sprays at no more than 5 lb per 100 gallons plus a surfactant. Trial a single branch first on unfamiliar cultivars. For a broader look at fruiting nutrition, see our guide to the best fertilizer for apple trees.
Will calcium nitrate change my soil pH?
Calcium nitrate has a near-neutral pH effect under normal use — it will not acidify soil like ammonium sulfate or raise pH like lime. That makes it well-suited to repeated applications without requiring pH correction in most soils. In hydroponic systems, monitor pH as usual and target 5.5 to 6.5 for most crops. For a deeper look at how it compares with other soluble feeds, see our guide to the best water-soluble fertilizers.
Ready to feed?
Pick your bag. We'll ship it.
Calcium nitrate 15.5-0-0 ships in 5, 10, 25, and 50 lb bags, with free shipping on orders over $100. Every order is backed by our 90-day money-back guarantee — if it isn't right for your garden, contact us for a full refund.
Choose your size →
