Nitrogen Fertilizers
Nitrogen is the single most important nutrient for plant growth — it drives chlorophyll production, protein synthesis, and vigorous vegetative development. When nitrogen is deficient, plants yellow from the oldest leaves upward, growth stalls, and yields drop. The right nitrogen fertilizer, applied at the right time, is one of the fastest and most visible improvements you can make to any garden, lawn, or crop.
Greenway Biotech offers nitrogen fertilizers for every growing method and goal — from fast-acting synthetics for immediate green-up to slow-release organics that build soil health over the season. Use the guide below to find the best nitrogen fertilizer for your situation.
Best Nitrogen Fertilizer by Use Case
| Your Goal | Best Choice | N% | Speed |
|---|---|---|---|
| Highest nitrogen concentration | Urea 46-0-0 | 46% | Fast (7–14 days) |
| Fast lawn green-up + sulfur | Ammonium Sulfate 21-0-0 | 21% | Very fast (48–72 hrs) |
| Hydroponics & high-pH soils | Calcium Nitrate 15.5-0-0 | 15.5% | Immediate |
| Fastest organic nitrogen | Blood Meal 13-0-0 | 13% | Moderate (1–3 weeks) |
| Longest slow-release organic | Feather Meal 12-0-0 | 12% | Slow (3–4 months) |
| Gentle organic + soil builder | Alfalfa Meal 2.5-0-2.5 | 2.5% | Very slow (season-long) |
| Slow-release synthetic nitrogen | Nitroform 39-0-0 | 39% | Very slow (3–4 months) |
| Nitrogen + phosphorus together | MAP 12-61-0 (water-soluble) / MAP 11-52-0 (granular) | 12% / 11% | Fast / Moderate |
Fast-Release vs. Slow-Release Nitrogen Fertilizer
Fast-release (synthetic) nitrogen — Urea, Ammonium Sulfate, and Calcium Nitrate — dissolves in water and delivers nitrogen to plant roots within days. These are the right choice when you need quick green-up, are correcting a visible deficiency, or feeding crops with high immediate nitrogen demand like lawns, corn, and leafy vegetables. They require more precise application to avoid burn and need reapplication every 4–6 weeks.
Slow-release (organic) nitrogen — Blood Meal, Feather Meal, and Alfalfa Meal — releases nitrogen as soil microbes break down organic material. This steady release feeds plants over weeks or months, reduces burn risk, and improves long-term soil biology. Organic nitrogen is the right choice for certified organic programs, building soil health, and situations where consistent feeding matters more than speed.
Slow-release synthetic nitrogen — Nitroform 39-0-0 — bridges the gap between fast synthetics and organic slow-release. It contains 39% nitrogen in a ureaformaldehyde form that releases gradually over 3–4 months as soil microbes break it down. It has very low burn risk, minimal leaching, and works well for lawns, trees, and ornamentals where consistent long-term feeding is the priority. Unlike organic slow-release fertilizers, Nitroform is not approved for certified organic programs.
Water-Soluble Nitrogen Fertilizer
All three of our synthetic nitrogen fertilizers are 100% water-soluble — meaning they dissolve completely in water with no residue, making them ideal for drip irrigation, fertigation, foliar spray, and hydroponic systems. Urea 46-0-0 delivers the highest nitrogen concentration per gallon of solution. Ammonium Sulfate 21-0-0 adds 24% sulfur alongside nitrogen. Calcium Nitrate 15.5-0-0 pairs nitrogen with 19% calcium and is the preferred choice for hydroponic systems and blossom end rot prevention.
Best Nitrogen Fertilizer for Lawns
For lawns, the best nitrogen fertilizer depends on your soil pH and how fast you need results. Ammonium Sulfate 21-0-0 is the most popular lawn nitrogen source — it greens up turf within 48–72 hours and also lowers soil pH, making it ideal for high-pH lawns in alkaline regions. Apply at 5 lbs per 1,000 sq ft and water in immediately. Urea 46-0-0 delivers more nitrogen per pound and is more economical for large areas, but requires careful watering in to prevent volatilization losses. For organic lawn programs, Blood Meal 13-0-0 is the fastest-acting option.
Organic Nitrogen Fertilizer
All Greenway Biotech organic nitrogen fertilizers are derived from natural sources and are acceptable for certified organic production. Blood Meal 13-0-0 is OMRI listed and provides the highest nitrogen content of any organic source — releasing over 6–8 weeks as soil bacteria break down the protein. Feather Meal 12-0-0 is the longest-lasting organic nitrogen option, feeding plants steadily for 3–4 months with very low burn risk. Alfalfa Meal 2.5-0-2.5 is the gentlest option — it also contains triacontanol, a natural plant growth stimulant, and contributes to long-term soil structure.
Nitrogen Fertilizer for Hydroponics
In hydroponic systems, nitrate-form nitrogen is typically preferred because it is immediately plant-available without requiring soil microbial conversion. Calcium Nitrate 15.5-0-0 is the standard nitrogen source in most hydroponic nutrient programs — it fully dissolves, contains no phosphorus (preventing algae growth in recirculating systems), and pairs nitrogen with calcium to prevent blossom end rot. For systems also requiring magnesium, Magnesium Nitrate 11-0-0 is a complementary nitrate-form nitrogen source that adds 9.6% magnesium.
Nitrogen + Phosphorus Fertilizer: Monoammonium Phosphate (MAP)
When your plants need both nitrogen and phosphorus at the same time — common at transplanting, early season root establishment, and flowering — MAP 12-61-0 is the most efficient single-product solution. It delivers 12% nitrogen alongside 61% phosphate in a 100% water-soluble form, making it ideal for hydroponics, fertigation, and foliar feeding. For granular soil application, MAP 11-52-0 provides 11% nitrogen and 52% phosphate in a granular form suited for broadcast application and soil incorporation.
Frequently Asked Questions
What is the highest nitrogen fertilizer available?
Urea 46-0-0 is the highest-concentration solid nitrogen fertilizer commercially available, containing 46% nitrogen — nearly double ammonium nitrate (34%) and more than triple calcium nitrate (15.5%). Among organic sources, Blood Meal 13-0-0 has the highest nitrogen content.
What is the best water-soluble nitrogen fertilizer?
The best water-soluble nitrogen fertilizer depends on your goal. For maximum nitrogen concentration in solution, Urea 46-0-0. For nitrogen plus sulfur and pH management, Ammonium Sulfate 21-0-0. For hydroponics or when calcium is also needed, Calcium Nitrate 15.5-0-0. All three dissolve completely in water with no residue.
How do I know if my plants need nitrogen?
The clearest sign of nitrogen deficiency is yellowing that starts with the oldest (lowest) leaves and progresses upward. Plants also show slow or stunted growth and an overall pale green color. A soil test is the most reliable way to confirm nitrogen deficiency versus other causes. Our guide on nitrogen deficiency symptoms covers the full range of visual indicators.
What is the difference between organic and synthetic nitrogen fertilizer?
Synthetic nitrogen fertilizers (Urea, Ammonium Sulfate, Calcium Nitrate) deliver nitrogen in immediately plant-available chemical forms — they act fast but require precise application to avoid burn. Organic nitrogen fertilizers (Blood Meal, Feather Meal, Alfalfa Meal) release nitrogen slowly as soil microbes break down organic material — they're lower burn risk, improve soil biology, and are acceptable in certified organic programs, but cannot correct a severe deficiency as quickly.
Can I mix different nitrogen fertilizers together?
Generally yes, with some important exceptions. Never mix Urea and Ammonium Sulfate in storage — they form a cement-like substance when exposed to moisture. Calcium Nitrate should not be mixed in concentrated solution with sulfate-containing fertilizers as calcium sulfate can precipitate. Always dissolve fertilizers in water separately before combining solutions. Organic granular fertilizers can typically be blended and incorporated into soil together without issues.
Further reading: Best Nitrogen Fertilizer: Top 7 Options Compared · What's the Function of Nitrogen in Plants? · Ammonium Sulfate Uses: Complete Guide