Organic Fertilizers
Organic fertilizers that feed your plants and support healthier soil
Organic fertilizers do more than supply nutrients. They also help support soil biology, build organic matter, and improve soil structure over time — creating a growing environment that can improve season after season. Because nutrients are released gradually as materials break down, organic fertilizers often provide a steadier feeding pattern with less burn risk than fast-acting synthetic options.
Whether you're building a new organic vegetable garden or maintaining established beds, Greenway Biotech's collection of organic garden fertilizers includes natural sources of nitrogen, phosphorus, potassium, calcium, sulfur, and trace minerals. Choose a single amendment to address a specific nutrient need, or combine products based on your soil test results for a more complete seasonal fertility program.
Shop organic fertilizers by nutrient need
Every organic amendment has a specific role. Use this table to match your crop's needs to the right product — then combine amendments based on your soil test results. See individual product pages for full application rates.
| Product | Analysis | Primary Role | Release Speed | Best Use Case |
|---|---|---|---|---|
| Nitrogen Sources | ||||
| Blood Meal fertilizer | 13-0-0 | Fast nitrogen | 6–8 weeks | Leafy greens, corn, brassicas; correct nitrogen deficiency quickly; compost activation. Usually unnecessary for legumes unless a soil test shows nitrogen deficiency. |
| Feather Meal | 12-0-0 | Slow nitrogen | 3–4 months | Long-season crops (tomatoes, corn); one pre-season application feeds through harvest |
| Alfalfa Meal | 2.5-0-2.5 | N + K + growth-regulating compounds | 4–8 weeks | Roses, vegetables, compost activation; contains natural triacontanol growth-regulating compounds |
| Crustacean Meal | 4-0-0 | N + calcium + chitin | 3–4 months | Soil biology boost; one of few amendments providing both nitrogen and calcium without raising pH |
| Phosphorus Sources | ||||
| Bone Meal fertilizer | 3-15-0 | Phosphorus + calcium (+ some N) | 3–4 months | Root development, flowering, transplant establishment; bulbs and root crops |
| Fish Bone Meal | 4-17-0 | Phosphorus + N + marine trace minerals | 4–6 weeks | Faster-acting phosphorus than bovine bone meal; also provides nitrogen and marine amino acids |
| Potassium & Trace Minerals | ||||
| Kelp Meal fertilizer | 2-0-4 | K + 60+ trace minerals + growth-regulating compounds | 4–6 months | Transplant stress, frost prep, trace mineral baseline; pairs well with every other amendment |
| Azomite | 0-0-0.2 | 70+ trace minerals | Slow / residual | Remineralize depleted soils; support plant health in trace-mineral-deficient soils; OMRI listed |
| Soil Conditioning Amendments | ||||
| Dolomite Lime | 0-0-0 | Raise soil pH + calcium + magnesium | Months (slow) | Correct acidic soil; adds both calcium (~22%) and magnesium (~12%) without synthetic inputs |
| Gypsum | 0-0-0 | Calcium + sulfur; improve soil structure | Weeks–months | Break up clay soils, improve drainage, add calcium without changing pH; sodic soil reclamation |
| Sulfur Powder | 99% S | Lower soil pH + sulfur nutrition | Weeks (biological) | Acidify soil for blueberries, azaleas, and acid-loving plants; requires soil temps above 55°F to activate |
Choosing an organic nitrogen source
The organic nitrogen sources in this collection each have a distinct release speed and best use case. The right choice depends on how urgently your plants need nitrogen and how long you need it to last. Organic amendments require active soil microbial populations to release nutrients — for best results, apply when soil temperatures are consistently above 50°F.
Need nitrogen now — plants yellowing mid-season
→ Blood Meal 13-0-0. Fastest organic nitrogen (6–8 weeks in warm soil above 50°F). Work into soil and water in immediately.
Long-season crops that need sustained feeding all summer
→ Feather Meal 12-0-0. Slowest organic nitrogen (3–4 months). One pre-season application feeds corn, tomatoes, and brassicas through harvest.
Roses, vegetable beds, or compost piles needing a gentle lift
→ Alfalfa Meal 2.5-0-2.5. Balanced N + K with natural triacontanol growth-regulating compounds. Also accelerates compost decomposition.
Soil needs both nitrogen and calcium without affecting pH
→ Crustacean Meal 4-0-0. One of few amendments delivering both — plus chitin to feed beneficial soil microbes.
Building a complete organic soil amendment program
Most organic soil amendments are targeted single- or dual-nutrient sources. Blood Meal supplies nitrogen only; Bone Meal is primarily phosphorus (though it also contributes 3% nitrogen and calcium); Kelp Meal provides potassium and trace minerals but minimal nitrogen or phosphorus. A complete organic fertilizer program for vegetables typically combines amendments to cover all nutrient categories:
Work slow-release amendments (Bone Meal, Feather Meal, Azomite) into the top 4–6 inches of soil 2–4 weeks before planting. Apply faster-release sources (Blood Meal, Alfalfa Meal) closer to planting or as a side dressing during the growing season. Water in after application to activate microbial breakdown. Always follow individual product rate guidelines and account for all nitrogen sources across your full program.
Read: The Organic Gardener's Guide to Soil Preparation →
Read: Best Fertilizers for a Vegetable Garden →
Frequently asked questions about organic garden fertilizers
Do organic fertilizers actually work as well as synthetic?
It depends on what you're optimizing for. Synthetic fertilizers deliver nutrients faster — useful for correcting acute deficiencies mid-season. Organic fertilizers release more slowly but also help support soil biology, build organic matter, and improve soil structure over time — benefits synthetics typically don't provide. The tradeoff is planning: organic amendments work best when applied 2–4 weeks before peak plant demand, and they require warm soil (above 50°F) for microbial breakdown to proceed. For most home vegetable gardens, a combination approach works well: a foundation of organic amendments worked in before planting, with water-soluble fertilizers available during the growing season when fast response is needed.
Can I mix multiple organic amendments together?
Yes — combining organic soil amendments is standard practice and often necessary for a complete nutrient program. Blood Meal and Bone Meal together cover nitrogen and phosphorus. Adding Kelp Meal brings potassium and trace minerals. Crustacean Meal adds calcium and chitin. There are no compatibility concerns with dry organic amendments mixed into soil. Apply based on the recommended rate for each individual product and account for all nitrogen sources across your full amendment mix to avoid over-application.
How long do organic fertilizers take to work?
Release speed varies significantly by product and soil conditions. Blood Meal begins releasing within 1–2 weeks in warm soil (above 50°F) and finishes over 6–8 weeks. Feather Meal and Bone Meal start releasing in 2–4 weeks and continue for 3–4 months. Kelp Meal and Azomite are the slowest — residual trace mineral benefits build over a full season. Warm, moist soil with active microbial populations speeds up all organic amendment breakdown; cold or dry soil slows it significantly. Incorporate amendments into moist soil and water in after application for best results.
Are these fertilizers safe for edible crops?
Yes. All products in this collection are derived from natural plant, animal, or mineral sources and are suitable for organic gardening programs. Many are OMRI listed for certified organic production — check individual product pages for certification status. They are widely used on vegetables, herbs, fruit trees, and edible gardens. As with any fertilizer, follow recommended application rates and avoid direct contact between concentrated dry meal and plant roots or foliage at the time of application.
Do organic fertilizers attract animals or pests?
Blood Meal and Bone Meal have strong scents that can attract dogs and wildlife. To minimize this, work them thoroughly into the top 2–3 inches of soil and water in immediately after application — once incorporated and moistened, the scent dissipates quickly. Alfalfa Meal and Feather Meal have much milder odors and are far less likely to attract animals. Kelp Meal has a mild ocean scent. If animal access is a concern, incorporate all amendments into soil rather than leaving them on the surface.
Are Greenway Biotech organic fertilizers tested for heavy metals?
Yes. All products in this collection are third-party tested for heavy metal content. Results are available on our Heavy Metal Analysis page. We never make absolute heavy-metal-free claims — we show you the data. Products sourced from animal or marine materials are tested to ensure they meet safe use standards for edible crop production.
For more guidance on building a soil-health program with organic amendments:
