Blood Meal vs. Bone Meal: Which Organic Amendment Does Your Garden Need?

Blood meal and bone meal are sold side by side at every garden center, both marketed as "organic fertilizers" for general garden use. The problem with treating them interchangeably is that they supply almost entirely different nutrients and are appropriate for almost entirely different.

—- title: "Blood Meal vs. Bone Meal: Which Organic Amendment Does Your Garden Need?" slug: blood-meal-vs-bone-meal hub: care category: "Comparison" description: "Blood meal and bone meal are both organic fertilizers but supply completely different nutrients. Confusing them leads to deficiencies or imbalances. Here's the breakdown." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 7 —-

Blood meal and bone meal are sold side by side at every garden center, both marketed as "organic fertilizers" for general garden use. The problem with treating them interchangeably is that they supply almost entirely different nutrients and are appropriate for almost entirely different situations.

Using blood meal when your soil needs phosphorus — or bone meal when your plants need nitrogen — does nothing useful and in some cases causes harm. The confusion is common enough that it is worth laying out exactly what each product is, what it contains, and when to use it.

What Each Product Is

Blood Meal

Blood meal is dried and powdered blood, typically from cattle or pigs, collected at slaughterhouses. Per Penn State Extension, it typically contains 12–13% nitrogen by weight, with trace amounts of phosphorus (1%) and potassium (0%). All of that nitrogen is protein-bound and must be broken down by soil microbes into ammonium and then nitrate before plants can absorb it.

The breakdown is relatively fast for an organic material — in warm, moist soil, blood meal becomes plant-available within 1–3 weeks. It acidifies soil slightly as nitrification converts ammonium to nitrate, releasing hydrogen ions in the process.

Bone Meal

Bone meal is ground animal bones — also typically from cattle — that has been steamed and dried. Per Clemson HGIC, standard bone meal contains:

• 3–6% nitrogen (as protein in bone collagen)
• 12–20% phosphorus (as calcium phosphate, the mineral component of bone)
• 0% potassium

Steamed bone meal releases phosphorus more slowly than the raw product; raw bone meal also exists but is less common in retail. The calcium content (24–30%) is significant and can raise soil pH if applied repeatedly.

Nutrient Content Comparison

When to Use Blood Meal

Blood meal is appropriate when:

• Soil test shows nitrogen deficiency
• Leafy crops (spinach, lettuce, kale, Swiss chard) need a nitrogen boost mid-season
• A vegetable bed planted with a high-nitrogen-demand crop needs supplemental fertility
• You want an organic nitrogen source that works faster than compost

Per Cornell Cooperative Extension, blood meal at 2–3 lbs per 100 sq ft supplies approximately 0.3–0.4 lbs of actual nitrogen — equivalent to about 3 lbs of a 10-0-0 synthetic fertilizer. This is a meaningful amount and should not be applied without considering current soil nitrogen levels.

Do not apply blood meal when growing flowering perennials mid-season, on plants approaching dormancy, or in fall when nitrogen uptake is winding down. Late-season nitrogen from blood meal stimulates soft growth vulnerable to frost damage.

When to Use Bone Meal

Bone meal is appropriate when:

• Soil test confirms phosphorus deficiency
• Establishing new perennial beds where root development is a priority
• Planting bulbs (bone meal is traditionally worked into the planting hole for fall bulbs)
• Growing fruiting and flowering crops in genuinely phosphorus-deficient soil

Per Penn State Extension, the standard application for bone meal at bulb planting is 1–2 tablespoons worked into the bottom of each planting hole.

Critical caveat: Per UMN Extension, most established garden soils in the US are not phosphorus-deficient. Repeated bone meal applications in already-adequate-phosphorus soil lead to phosphorus excess, which interferes with zinc and iron uptake (causing micronutrient deficiency despite adequate soil levels) and contributes to runoff pollution in water bodies. Do not apply bone meal annually as a routine amendment without a soil test confirming deficiency.

The Phosphorus Accumulation Problem

This is an important issue that bone meal marketing material does not address.

Per UMN Extension, garden soils routinely tested at University Extension labs show phosphorus levels from 2x to 10x the crop requirement, particularly in gardens that have received regular compost, manure, or bone meal applications. Plants cannot absorb excess phosphorus and it binds tightly to soil particles, accumulating season after season.

Excess soil phosphorus causes two problems:

1. It blocks uptake of zinc and iron, causing deficiency symptoms even when those elements are present
2. It runs off in stormwater, contributing to algal blooms in nearby water bodies

The practical implication: bone meal should be applied only when a soil test indicates phosphorus at or below the adequate range. If your soil test shows "high" or "excessive" phosphorus, skip the bone meal entirely and do not add any other phosphorus source.

Handling and Safety

Both products have handling considerations.

Per Clemson HGIC, blood meal has a strong odor that attracts dogs and other animals. Keep dogs away from freshly applied areas. Blood meal is a protein source that some animals will dig for, potentially disturbing a bed.

Bone meal also attracts dogs and may attract other vertebrate pests. In areas with significant wildlife pressure, both products should be incorporated into soil rather than broadcast on the surface.

Deer and Pest Deterrence

Blood meal is sometimes promoted as a deer repellent. Per Rutgers NJAES, the evidence for blood meal as a reliable deer deterrent is mixed. It may deter deer initially due to the predator scent association, but effectiveness degrades quickly after rain or decomposition and deer in high-pressure areas habituate to the scent within a season. It is not a reliable long-term deer management tool.

I use fencing for deer management at my Long Island property — chemical repellents and blood meal are not consistent enough to protect high-value plants.

Combined Use

Blood meal and bone meal can be used together to supply both nitrogen and phosphorus, but this combination should only be considered when a soil test confirms deficiency of both nutrients. Per Penn State Extension, neither product supplies potassium, so any complete fertility program also requires a potassium source (greensand, kelp meal, wood ash, or a potassium fertilizer).

For gardens where compost is applied regularly at 2 inches per season, additional nitrogen and phosphorus amendments may not be needed at all. Mature compost supplies both nutrients at modest rates sufficient for most vegetables.

Common Mistakes

Frequently Asked Questions

Is blood meal good for tomatoes?

Per Penn State Extension, blood meal is useful for tomatoes at transplant time and in early vegetative growth when nitrogen demand is highest. Once plants are flowering and setting fruit, excess nitrogen from blood meal can cause the plant to put energy into foliage at the expense of fruit set. At that point, a balanced fertilizer or no additional nitrogen is appropriate.

Can blood meal burn plants?

Yes. Per Cornell Cooperative Extension, blood meal applied at high rates or in contact with roots or seed can cause nitrogen burn. The protein breakdown products include ammonium at relatively high concentrations. Apply at recommended rates (1–2 lbs per 100 sq ft), incorporate into the top 2 inches of soil, and water in immediately.

Does bone meal work in alkaline soil?

Less effectively. Per Clemson HGIC, phosphorus availability from bone meal decreases as soil pH rises above 7.5. In alkaline soils (pH 7.5+), much of the phosphate bonds to calcium and becomes unavailable to plants. If you have alkaline soil with phosphorus deficiency, a more soluble phosphorus source and pH correction (with elemental sulfur) are better approaches than bone meal alone.

Is blood meal suitable for vegetables grown organically?

Per USDA National Organic Program, blood meal derived from animals not treated with prohibited substances is allowed in certified organic production. Most commercially available blood meal meets this standard but verify with the supplier for certified operations.

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Sources

1. Penn State Extension — Organic Fertilizers
2. Clemson HGIC — Organic Soil Amendments
3. Cornell Cooperative Extension — Soil Fertility
4. UMN Extension — Phosphorus and Water Quality
5. Rutgers NJAES — Deer-Resistant Plants
6. USDA National Organic Program — Organic Regulations