The main disadvantages of blood meal are five. You get nitrogen burn, low phosphorus, soil acidification, a strong smell, and a draw for dogs and raccoons.
Knowing each one helps you use it with care or skip it for a safer feed. The choice depends on your plants and your soil.
I learned the burn risk the hard way one spring. I dumped a heavy scoop on a row of young lettuce seedlings, and within 48 hours the leaves curled brown at the edges and the plants drooped flat.
Nitrogen burn happens because blood meal carries so much salt and ammonium that it pulls water out of root cells. The roots dry up before they can take in the feed, and the plant wilts fast.
Soil acidification is the slow problem. As soil microbes turn the nitrogen into nitrate, they release hydrogen ions that drop the soil pH over time.
Plant Root Burn
- Salt damage: High ammonium and salt content pulls water out of roots, leading to wilting in 24 to 48 hours.
- Vulnerable plants: Seedlings under 6 weeks old, young transplants, and small herbs with short roots suffer the worst.
- Prevention: Keep granules 4 to 6 inches (10 to 15 cm) from stems and water in right after spreading.
Soil pH Drop
- Acid release: Each round of blood meal pushes the soil pH down by a small but real amount each year.
- Crop impact: Beets, brassicas, and asparagus all suffer in low-pH soil, with weaker growth and pale leaves.
- Easy fix: Test pH each year and add a bit of garden lime to keep the level near 6.5 for most veggies.
Strong Smell and Pest Draw
- Ammonia odor: Wet blood meal gives off a sharp, rich smell as the proteins break down in warm soil.
- Animal magnet: Dogs, raccoons, foxes, and skunks dig in beds to find the source, ruining your rows.
- Storage tip: Keep dry blood meal in a sealed bin to cut the smell and stop pests from finding the bag.
Blood meal also has near-zero phosphorus and potassium. If you use it alone, your plants get plenty of leaves but few flowers or fruit, which is bad news for tomatoes and peppers.
Never spread more than 3 pounds (1.4 kg) per 100 square feet (9.3 square meters) in one go. Two heavy years in a row without lime will swing your pH below the safe zone for most crops.
The other blood meal side effects show up when storage goes wrong. A torn bag in a garage can pull in mice or attract a neighbor's dog, both of which I have seen happen on my own street.
To stay safe, keep granules a hand's width from stems and water in right after spreading. Check soil pH each year, and store the bag in a sealed bin to stop the smell from drawing pests.
Read the full article: Blood Meal Fertilizer: NPK and Best Crops
