Multi-Year Organic Phosphorus
Best Organic Rock Phosphate (0-12-0): Multi-Year Slow-Release Phosphorus That Builds Permanent Soil Fertility Buy on Old Cobblers Farm
Rock phosphate doesn't feed this season — it feeds this decade. 12% phosphorus locked in mineral form releases over months to years as soil microbes and root acids slowly dissolve the rock. The ultimate long-term investment in permanent soil phosphorus reserves.
Old Cobblers Farm™ Wicked Organics 0-12-0 Fertilizer - Rock Phosphate
by Organic Fertilizer — Littleton, NH
0-12-0
N-P-K Ratio
"The slowest and longest-lasting organic phosphorus source available. 12% P₂O₅ from natural rock releases over years through biological and chemical weathering — building a permanent phosphorus bank in your soil that feeds crops season after season."
12%
Phosphorus (P₂O₅)
3–5+ yr
Release Duration
100 ft²
Max Coverage / bag
4 Sizes
5, 10, 15, 20 lbs
Multi-Year Phosphorus Release
Rock phosphate dissolves slowly through microbial activity and root exudates. A single heavy application can supply phosphorus for 3–5+ years in biologically active soils.
Builds Permanent Soil Fertility
Unlike water-soluble phosphorus that leaches, rock phosphate stays in the root zone. It becomes part of your soil's permanent mineral reserve — fertility that doesn't wash away.
20–33% Calcium
Rock phosphate is calcium phosphate — every application delivers significant calcium alongside phosphorus. Prevents blossom end rot and strengthens plant cell structure.
Mycorrhizae Activator
Mycorrhizal fungi specialize in dissolving rock phosphate and delivering it to plant roots. Rock phosphate applications actually stimulate mycorrhizal colonization — a biological feedback loop.
Heavy Application Rate
5–10 lbs per 100 sq ft worked into soil. Rock phosphate is used in volume because availability is low per unit — but the total reserve it builds is enormous.
Best for New Garden Prep
Apply heavily when establishing new garden beds, orchards, or perennial plantings. Build the phosphorus bank once and let biology meter it out for years.
100% Natural Mineral
Mined rock — no processing, no chemicals, no manufacturing. Approved for organic production. The most natural phosphorus source available.
Trusted by 20,000+ Growers
Developed in Littleton, New Hampshire. Sold nationwide on Amazon, Walmart, eBay, and theoldcobblersfarm.com.
| NPK Ratio | 0-12-0 |
| Item Form | Fine powder / granular |
| Coverage | 50–100 sq ft per 5 lb bag |
| Category | Organic Fertilizer |
| Type | Soil Amendments |
| Sizes | 5 lb | 10 lb | 15 lb | 20 lb |
| NPK | 0-12-0 |
| Nitrogen | 0% |
| Phosphorus | 12% (very slow-release) |
| Potassium | 0% |
| Calcium | 20–33% |
| Form | Fine powder / granular |
| Rate | 5–10 lbs / 100 sq ft |
| Method | Work into top 4–6" of soil |
| Sizes | 5, 10, 15, 20 lb bags |
| Best For | New garden establishment, long-term soil P building, orchards |
What We Love
✓ Multi-year phosphorus release — apply once, benefit for seasons
✓ Builds permanent soil phosphorus reserves that don't leach
✓ 20–33% calcium for cell structure and blossom end rot prevention
✓ Stimulates mycorrhizal fungi colonization
✓ 100% natural mined mineral — organic approved
Worth Noting
— Very slow availability — not for immediate phosphorus correction
— Heavy application rates — 5 lb bag covers only 50–100 sq ft
Buy on Old Cobblers Farm →
Available in 5 lb | 10 lb | 15 lb | 20 lb
| Feature | Old Cobblers Farm™ Wicked Organics 0-12-0 Fertilizer - Rock Phosphate Old Cobblers Farm | Down To Earth Organic Rock Phosphate 0-3-0 Down To Earth | Espoma Rock Phosphate (Pelletized) Espoma | Lancaster Agriculture Soft Rock Phosphate Lancaster Agriculture | PhoSul Granular Rock Phosphate with Sulphur 0-16-0 PhoSul | Ohio Earth Food Soft Rock Phosphate (Colloidal) Ohio Earth Food | Calphos Soft Rock Phosphate 0-3-0 Calphos / IMC Global | Gardener's Supply Rock Phosphate Gardener's Supply | Down To Earth Organic Rock Phosphate 0-3-0 Down To Earth | Espoma Rock Phosphate (Pelletized) Espoma | Lancaster Agriculture Soft Rock Phosphate Lancaster Agriculture | PhoSul Granular Rock Phosphate with Sulphur 0-16-0 PhoSul | Ohio Earth Food Soft Rock Phosphate (Colloidal) Ohio Earth Food | Calphos Soft Rock Phosphate 0-3-0 Calphos / IMC Global | Gardener's Supply Rock Phosphate Gardener's Supply | Organic Rock Phosphate Espoma | Rock Phosphate 0-3-0 Down to Earth | Soft Rock Phosphate 0-3-0 Calphos | Organic Bone Meal Espoma | Granular Bone Meal Jobe's Organics | Happy Frog Steamed Bone Meal FoxFarm | Natural & Organic Bone Meal Burpee | Rock Phosphate Down To Earth | Rock Phosphate Espoma | Soft Rock Phosphate Calphos | Soft Rock Phosphate Lancaster Ag | Seabird Guano True Organic | Organic P Phosul | Soft Rock Phos Dr. Earth | Bone Meal Jobe's Organics | Bone Meal Hi-Yield | Rock Dust Gaia Green |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NPK | 0-12-0 | 0-3-0 | Not listed | 0-3-0 | 0-16-0 | 0-3-0 | 0-3-0 | 0-3-0 | 0-3-0 | Not listed | 0-3-0 | 0-16-0 | 0-3-0 | 0-3-0 | 0-3-0 | 0-3-0 | 0-3-0 | 0-3-0 | 4-12-0 | 2-14-0 | 3-12-0 | 6-8-0 | 0-12-0 | 0-3-0 | 0-3-0 | 0-3-0 | 0-12-0 | 0-16-0 | 0-2-0 | 2-14-0 | 0-10-0 | 0-0-0 |
| Form | Fine powder / granular | Granular powder | Pelletized granular | Powder/granular | Granular | Fine powder (colloidal) | Fine powder (colloidal) | Granular | Granular powder | Pelletized granular | Powder/granular | Granular | Fine powder (colloidal) | Fine powder (colloidal) | Granular | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Coverage | 50–100 sq ft per 5 lb bag | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed |
| Price / Size | 5 lb | 10 lb | 15 lb | 20 lb | ~$14-17 (5 lb) / ~$40-50 (25 lb) | ~$15-18 (7.25 lb) / ~$30-40 (28 lb) | ~$15-18 (5 lb) / ~$25-32 (20 lb) | ~$35-45 (25 lb) | ~$35-50 (50 lb) | ~$30-40 (50 lb) | ~$12-16 (5 lb) | ~$14-17 (5 lb) / ~$40-50 (25 lb) | ~$15-18 (7.25 lb) / ~$30-40 (28 lb) | ~$15-18 (5 lb) / ~$25-32 (20 lb) | ~$35-45 (25 lb) | ~$35-50 (50 lb) | ~$30-40 (50 lb) | ~$12-16 (5 lb) | $18–$40 | $13–$30+ | $15–$50 | $11–$51 | $10–$12 | $16–$20 | $9–$10 | $13.00 | $45.91 | $9.99 | $34.95 | $19.99 | $42.75 | $15.99 | $10.50 | $29.62 | $14.99 |
| Our Take | The slowest and longest-lasting organic phosphorus source available... | Category leader. Strong certs. But only 3% P — OCF delivers 4x more phosphorus per pound at 0-12-0. | Widest retail distribution. Pelletized form. Good value on 28 lb bag. But no NPK listed. | Soft rock (colloidal) form may release faster than hard rock phosphate. Good 20 lb pricing. | Sulfur addition lowers soil pH, making P more available. Unique formulation. But limited reviews and availability. | Best bulk value. Colloidal form has higher P availability. But only available direct/dealer, not on Amazon. | Long-established farm product. Very low cost per lb in bulk. But not consumer-packaged or on Amazon. | Heritage brand. Vermont-based (near OCF market). But limited to own website, no Amazon presence. | Category leader. Strong certs. But only 3% P — OCF delivers 4x more phosphorus per pound at 0-12-0. | Widest retail distribution. Pelletized form. Good value on 28 lb bag. But no NPK listed. | Soft rock (colloidal) form may release faster than hard rock phosphate. Good 20 lb pricing. | Sulfur addition lowers soil pH, making P more available. Unique formulation. But limited reviews and availability. | Best bulk value. Colloidal form has higher P availability. But only available direct/dealer, not on Amazon. | Long-established farm product. Very low cost per lb in bulk. But not consumer-packaged or on Amazon. | Heritage brand. Vermont-based (near OCF market). But limited to own website, no Amazon presence. | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
The Competition
Down To Earth Organic Rock Phosphate 0-3-0
by Down To Earth
— Eugene, OR
0-3-0
N-P-K
FormGranular powder
Sizes5 lb | 25 lb | 50 lb
Price~$14-17 (5 lb) / ~$40-50 (25 lb)
Per Unit~$1.60-2.00/lb (25 lb)
IngredientsRock phosphate (mined mineral)
OrganicYes — OMRI + CDFA Listed
App. Rate1-10 lbs per 100 sq ft
CoverageNot listed
Best ForAll gardens, orchards, perennial beds
ClaimsOMRI + CDFA; calcium 24%+; slow-release phosphorus; used since 1700s
Category leader. Strong certs. But only 3% P — OCF delivers 4x more phosphorus per pound at 0-12-0.
Espoma Rock Phosphate (Pelletized)
by Espoma
— Millville, NJ
Not listed
N-P-K
FormPelletized granular
Sizes7.25 lb | 28 lb
Price~$15-18 (7.25 lb) / ~$30-40 (28 lb)
Per Unit~$1.07-1.43/lb (28 lb)
IngredientsRock phosphate
OrganicOMRI registered
App. Rate10 lbs per 100 sq ft
CoverageNot listed
Best ForGardens, flower beds, trees
ClaimsSince 1929; pelletized for easy spreading; available at Home Depot + Lowes
Widest retail distribution. Pelletized form. Good value on 28 lb bag. But no NPK listed.
Lancaster Agriculture Soft Rock Phosphate
by Lancaster Agriculture
— Lancaster, PA
0-3-0
N-P-K
FormPowder/granular
Sizes5 lb | 20 lb
Price~$15-18 (5 lb) / ~$25-32 (20 lb)
Per Unit~$1.25-1.60/lb (20 lb)
IngredientsSoft rock phosphate (colloidal)
OrganicNot confirmed
App. Rate5-10 lbs per 100 sq ft
CoverageNot listed
Best ForAll gardens, soil building
ClaimsSince 1988; soft rock phosphate variety; regenerative agriculture
Soft rock (colloidal) form may release faster than hard rock phosphate. Good 20 lb pricing.
PhoSul Granular Rock Phosphate with Sulphur 0-16-0
by PhoSul
— USA
0-16-0
N-P-K
FormGranular
Sizes25 lb
Price~$35-45 (25 lb)
Per Unit~$1.40-1.80/lb
IngredientsRock phosphate + elemental sulfur
OrganicNot confirmed
App. RatePer package directions
CoverageNot listed
Best ForGardens, orchards, sulfur-deficient soils
ClaimsHighest P (16%); sulfur-enhanced for faster P release and pH lowering
Sulfur addition lowers soil pH, making P more available. Unique formulation. But limited reviews and availability.
Ohio Earth Food Soft Rock Phosphate (Colloidal)
by Ohio Earth Food
— Hartville, OH
0-3-0
N-P-K
FormFine powder (colloidal)
Sizes50 lb
Price~$35-50 (50 lb)
Per Unit~$0.70-1.00/lb
IngredientsColloidal soft rock phosphate
OrganicOrganic-approved
App. Rate10-20 lbs per 100 sq ft
CoverageNot listed
Best ForFarms, large gardens, orchards
ClaimsColloidal form; higher availability than standard rock phosphate; 20%+ calcium; farm-scale pricing
Best bulk value. Colloidal form has higher P availability. But only available direct/dealer, not on Amazon.
Calphos Soft Rock Phosphate 0-3-0
by Calphos / IMC Global
— FL
0-3-0
N-P-K
FormFine powder (colloidal)
Sizes50 lb
Price~$30-40 (50 lb)
Per Unit~$0.60-0.80/lb
IngredientsColloidal soft rock phosphate (Florida deposits)
OrganicOrganic-approved
App. Rate10-15 lbs per 100 sq ft
CoverageNot listed
Best ForFarms, large gardens, soil building
ClaimsFlorida-mined colloidal phosphate; 20% calcium; established farm product
Long-established farm product. Very low cost per lb in bulk. But not consumer-packaged or on Amazon.
Gardener's Supply Rock Phosphate
by Gardener's Supply
— Burlington, VT
0-3-0
N-P-K
FormGranular
Sizes5 lb
Price~$12-16 (5 lb)
Per Unit~$2.40-3.20/lb
IngredientsRock phosphate
OrganicOrganic-approved
App. Rate5 lbs per 100 sq ft
CoverageNot listed
Best ForAll gardens
ClaimsTrusted Vermont garden brand; 100% satisfaction guarantee
Heritage brand. Vermont-based (near OCF market). But limited to own website, no Amazon presence.
Down To Earth Organic Rock Phosphate 0-3-0
by Down To Earth
— Eugene, OR
0-3-0
N-P-K
FormGranular powder
Sizes5 lb | 25 lb | 50 lb
Price~$14-17 (5 lb) / ~$40-50 (25 lb)
Per Unit~$1.60-2.00/lb (25 lb)
IngredientsRock phosphate (mined mineral)
OrganicYes — OMRI + CDFA Listed
App. Rate1-10 lbs per 100 sq ft
CoverageNot listed
Best ForAll gardens, orchards, perennial beds
ClaimsOMRI + CDFA; calcium 24%+; slow-release phosphorus; used since 1700s
Category leader. Strong certs. But only 3% P — OCF delivers 4x more phosphorus per pound at 0-12-0.
Espoma Rock Phosphate (Pelletized)
by Espoma
— Millville, NJ
Not listed
N-P-K
FormPelletized granular
Sizes7.25 lb | 28 lb
Price~$15-18 (7.25 lb) / ~$30-40 (28 lb)
Per Unit~$1.07-1.43/lb (28 lb)
IngredientsRock phosphate
OrganicOMRI registered
App. Rate10 lbs per 100 sq ft
CoverageNot listed
Best ForGardens, flower beds, trees
ClaimsSince 1929; pelletized for easy spreading; available at Home Depot + Lowes
Widest retail distribution. Pelletized form. Good value on 28 lb bag. But no NPK listed.
Lancaster Agriculture Soft Rock Phosphate
by Lancaster Agriculture
— Lancaster, PA
0-3-0
N-P-K
FormPowder/granular
Sizes5 lb | 20 lb
Price~$15-18 (5 lb) / ~$25-32 (20 lb)
Per Unit~$1.25-1.60/lb (20 lb)
IngredientsSoft rock phosphate (colloidal)
OrganicNot confirmed
App. Rate5-10 lbs per 100 sq ft
CoverageNot listed
Best ForAll gardens, soil building
ClaimsSince 1988; soft rock phosphate variety; regenerative agriculture
Soft rock (colloidal) form may release faster than hard rock phosphate. Good 20 lb pricing.
PhoSul Granular Rock Phosphate with Sulphur 0-16-0
by PhoSul
— USA
0-16-0
N-P-K
FormGranular
Sizes25 lb
Price~$35-45 (25 lb)
Per Unit~$1.40-1.80/lb
IngredientsRock phosphate + elemental sulfur
OrganicNot confirmed
App. RatePer package directions
CoverageNot listed
Best ForGardens, orchards, sulfur-deficient soils
ClaimsHighest P (16%); sulfur-enhanced for faster P release and pH lowering
Sulfur addition lowers soil pH, making P more available. Unique formulation. But limited reviews and availability.
Ohio Earth Food Soft Rock Phosphate (Colloidal)
by Ohio Earth Food
— Hartville, OH
0-3-0
N-P-K
FormFine powder (colloidal)
Sizes50 lb
Price~$35-50 (50 lb)
Per Unit~$0.70-1.00/lb
IngredientsColloidal soft rock phosphate
OrganicOrganic-approved
App. Rate10-20 lbs per 100 sq ft
CoverageNot listed
Best ForFarms, large gardens, orchards
ClaimsColloidal form; higher availability than standard rock phosphate; 20%+ calcium; farm-scale pricing
Best bulk value. Colloidal form has higher P availability. But only available direct/dealer, not on Amazon.
Calphos Soft Rock Phosphate 0-3-0
by Calphos / IMC Global
— FL
0-3-0
N-P-K
FormFine powder (colloidal)
Sizes50 lb
Price~$30-40 (50 lb)
Per Unit~$0.60-0.80/lb
IngredientsColloidal soft rock phosphate (Florida deposits)
OrganicOrganic-approved
App. Rate10-15 lbs per 100 sq ft
CoverageNot listed
Best ForFarms, large gardens, soil building
ClaimsFlorida-mined colloidal phosphate; 20% calcium; established farm product
Long-established farm product. Very low cost per lb in bulk. But not consumer-packaged or on Amazon.
Gardener's Supply Rock Phosphate
by Gardener's Supply
— Burlington, VT
0-3-0
N-P-K
FormGranular
Sizes5 lb
Price~$12-16 (5 lb)
Per Unit~$2.40-3.20/lb
IngredientsRock phosphate
OrganicOrganic-approved
App. Rate5 lbs per 100 sq ft
CoverageNot listed
Best ForAll gardens
ClaimsTrusted Vermont garden brand; 100% satisfaction guarantee
Heritage brand. Vermont-based (near OCF market). But limited to own website, no Amazon presence.
Organic Rock Phosphate
by Espoma
0-3-0
N-P-K
Sizes7.25 / 28 lb
Price$18–$40
Rock Phosphate 0-3-0
by Down to Earth
0-3-0
N-P-K
Sizes5 / 25 / 50 lb
Price$13–$30+
Soft Rock Phosphate 0-3-0
by Calphos
0-3-0
N-P-K
Sizes5 / 50 lb
Price$15–$50
Organic Bone Meal
by Espoma
4-12-0
N-P-K
Sizes4 / 8 / 24 lb
Price$11–$51
Granular Bone Meal
by Jobe's Organics
2-14-0
N-P-K
Sizes3 / 4 / 12 lb
Price$10–$12
Happy Frog Steamed Bone Meal
by FoxFarm
3-12-0
N-P-K
Sizes4 lb
Price$16–$20
Natural & Organic Bone Meal
by Burpee
6-8-0
N-P-K
Sizes3 lb
Price$9–$10
Rock Phosphate
by Down To Earth
0-12-0
N-P-K
Sizes5 lb, 25 lb
Price$13.00
OrganicOMRI, CDFA
Rock Phosphate
by Espoma
0-3-0
N-P-K
Sizes28 lb
Price$45.91
OrganicOMRI
Soft Rock Phosphate
by Calphos
0-3-0
N-P-K
Sizes5 lb, 25 lb
Price$9.99
OrganicOMRI
Soft Rock Phosphate
by Lancaster Ag
0-3-0
N-P-K
Sizes20 lb
Price$34.95
OrganicOrganic
Seabird Guano
by True Organic
0-12-0
N-P-K
Sizes4 lb
Price$19.99
OrganicOMRI
Organic P
by Phosul
0-16-0
N-P-K
Sizes25 lb
Price$42.75
OrganicOMRI
Soft Rock Phos
by Dr. Earth
0-2-0
N-P-K
Sizes4 lb
Price$15.99
OrganicNatural
Bone Meal
by Jobe's Organics
2-14-0
N-P-K
Sizes4 lb
Price$10.50
OrganicOMRI
Bone Meal
by Hi-Yield
0-10-0
N-P-K
Sizes20 lb
Price$29.62
OrganicNatural
Rock Dust
by Gaia Green
0-0-0
N-P-K
Sizes5 lb
Price$14.99
OrganicOMRI
Multi-Year Phosphorus Release
Rock phosphate dissolves slowly through microbial activity and root exudates. A single heavy application can supply phosphorus for 3–5+ years in biologically active soils.
Builds Permanent Soil Fertility
Unlike water-soluble phosphorus that leaches, rock phosphate stays in the root zone. It becomes part of your soil's permanent mineral reserve — fertility that doesn't wash away.
20–33% Calcium
Rock phosphate is calcium phosphate — every application delivers significant calcium alongside phosphorus. Prevents blossom end rot and strengthens plant cell structure.
Mycorrhizae Activator
Mycorrhizal fungi specialize in dissolving rock phosphate and delivering it to plant roots. Rock phosphate applications actually stimulate mycorrhizal colonization — a biological feedback loop.
Common Questions
