Best 16-10-13 Fertilizer: High Nitrogen with Polymer-Coated Slow Release, Sulfur & Magnesium Buy on Old Cobblers Farm
Heavy feeders like asparagus, corn, and brassicas demand more nitrogen than a standard 10-10-10 can deliver. This 16-10-13 provides it with polymer-coated slow release plus sulfur and magnesium from langbeinite — a professional 6-ingredient blend.
Old Cobblers Farm™ Wicked Growth 16-10-13 Fertilizer – Balanced Nutrition
by Conventional Fertilizer — Littleton, NH
16% Nitrogen for Heavy Feeders
The highest nitrogen in the slow-release lineup. Powers dense fern growth in asparagus, vigorous leaf canopy in brassicas, and strong vegetative push in heavy-feeding crops.
Polymer-Coated Slow Release
Purkote technology releases nitrogen gradually over weeks. No flush-and-fade cycle — steady nutrition through the entire growing period with reduced burn risk.
Sulfur & Magnesium Included
Potassium magnesium sulphate (langbeinite) delivers sulfur and magnesium in every granule — two critical secondary nutrients that most fertilizers leave out entirely.
330+ sq ft Per Bag
At 1.5 lbs per 100 sq ft, one 5 lb bag covers over 330 sq ft of garden. Higher analysis means more coverage per dollar compared to 10-10-10.
39% Total NPK
High-analysis formula at 39% total nutrients means less filler per bag. More nutrition per pound applied, less product to haul and store.
6-Ingredient Professional Blend
Six precision ingredients: two nitrogen sources (instant + slow-release), phosphorus, potassium, sulfur, and magnesium. Professional-grade complexity in a single bag.
Multi-Use Beyond Asparagus
Also excellent for corn, brassicas, established perennial beds, lawns, and any crop where high nitrogen with K support and secondary nutrients are needed.
Trusted by 20,000+ Growers
Developed in Littleton, New Hampshire. Sold nationwide on Amazon, Walmart, eBay, and theoldcobblersfarm.com.
| NPK Ratio | 16-10-13 |
| Item Form | Slow-release granular (polymer coated) |
| Coverage | 250–333 sq ft (garden) | 1,000–1,667 sq ft (lawn) per 5 lb bag |
| Category | Conventional Fertilizer |
| Type | All-Purpose NPK Blends |
| Sizes | 5 lb | 10 lb | 15 lb | 20 lb |
| NPK | 16-10-13 |
| Nitrogen | 16% (polymer coated) |
| Phosphorus | 10% available phosphate |
| Potassium | 13% soluble potash |
| Secondary | Sulfur, Magnesium |
| Form | Slow-release granular |
| Rate | 1.5–2 lbs / 100 sq ft |
| Method | Broadcast or side-dress |
| Sizes | 5, 10, 15, 20 lb bags |
| Best For | Asparagus, heavy-feeding crops, brassicas, established beds |
| Feature | Old Cobblers Farm™ Wicked Growth 16-10-13 Fertilizer – Balanced Nutrition Old Cobblers Farm | Super 16-16-16 All-Purpose Schultz | All Purpose Plant Food 16-16-16 Expert Gardener | 16-16-16 Fertilizer GroundWork | Smart-Release Flower & Vegetable Osmocote | Multi-Purpose Fertilizer 14-14-14 GreenView | Lawn & Garden Food 16-16-16 Lilly Miller (Pennington) | Triple 16 Fertilizer Hi-Yield (VPG) |
|---|---|---|---|---|---|---|---|---|
| NPK | 16-10-13 | 16-16-16 | 16-16-16 | 16-16-16 | 14-14-14 | 14-14-14 | 16-16-16 | 16-16-16 |
| Form | Slow-release granular (polymer coated) | — | — | — | — | — | — | — |
| Coverage | 250–333 sq ft (garden) | 1,000–1,667 sq ft (lawn) per 5 lb bag | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed |
| Price / Size | 5 lb | 10 lb | 15 lb | 20 lb | $26.97 | $16.97 | $39.99 | $12–$34 | $29–$37 | $18–$25 | $20–$35 |
| Our Take | The highest-nitrogen slow-release formula in the Wicked Growth line... | — | — | — | — | — | — | — |
Super 16-16-16 All-Purpose
All Purpose Plant Food 16-16-16
16-16-16 Fertilizer
Smart-Release Flower & Vegetable
Multi-Purpose Fertilizer 14-14-14
Lawn & Garden Food 16-16-16
Triple 16 Fertilizer
16% Nitrogen for Heavy Feeders
The highest nitrogen in the slow-release lineup. Powers dense fern growth in asparagus, vigorous leaf canopy in brassicas, and strong vegetative push in heavy-feeding crops.
Polymer-Coated Slow Release
Purkote technology releases nitrogen gradually over weeks. No flush-and-fade cycle — steady nutrition through the entire growing period with reduced burn risk.
Sulfur & Magnesium Included
Potassium magnesium sulphate (langbeinite) delivers sulfur and magnesium in every granule — two critical secondary nutrients that most fertilizers leave out entirely.
330+ sq ft Per Bag
At 1.5 lbs per 100 sq ft, one 5 lb bag covers over 330 sq ft of garden. Higher analysis means more coverage per dollar compared to 10-10-10.
