The NPK value of blood meal sits around 12-2-1 for most bags on the market. That means 12% nitrogen, 2% phosphorus, and 1% potassium by weight in each scoop you spread.
I checked three brands on my last trip to the garden store and saw the blood meal NPK ratio swing from 12-0-0 to 13-2-0 depending on the brand. The bags all said blood meal, but the numbers were not the same.
This swing comes from how the blood gets dried. Solar drying keeps more nitrogen in the powder, while flash drying or spray drying can shave a few points off the top.
The source animal also matters for blood meal nitrogen content. Beef and pork blood carry different protein levels. This changes the final nitrogen count in the dry powder you buy.
The headline 12-2-1 fertilizer number tells you that blood meal is a heavy nitrogen feed first. It only brings tiny amounts of phosphorus and potassium on the side.
That makes it a fine pick for leafy crops, but a weak choice for flowers and fruit. Plants that bloom need more P and K than blood meal alone can give them.
I learned this when I tried to feed my tomato bed with just blood meal one summer. The plants grew tall and bushy with deep green leaves, but I got only a handful of fruit by August.
The next year I added bone meal at planting time, and my tomato harvest tripled. The lesson stuck: blood meal alone is not a full plant feed for fruit crops.
I always tell new gardeners to read the label on each bag they buy. Two brands sitting side by side on a shelf can have very different numbers, and the price often does not match the NPK.
To cover the gaps in P and K, pair blood meal with bone meal or kelp meal. Bone meal brings phosphorus for strong roots, and kelp meal adds potassium plus trace minerals.
A simple home mix is 2 parts blood meal, 2 parts bone meal, and 1 part kelp meal. This blend gives a balanced organic feed that works for most beds without the need to buy a pre-made blend.
When you find a bag with a wild NPK number, treat it with care. A blood meal labeled 15-0-0 or higher may be processed in a way that burns roots faster, so cut your dose in half on the first try.
Read the full article: Blood Meal Fertilizer: NPK and Best Crops
