[header] How to use blood meal [title] Test your soil to see if it needs nitrogen. [step] Buy a simple soil test from your local nursery or garden center and use a sample of soil from your garden or plant container. Follow the test kit instructions to get accurate results. 
The test will tell you the levels of nitrogen, phosphorus, and potassium. [substeps] For example, the test will tell you if there's a surplus of nitrogen, sufficient levels, a deficiency of nitrogen, or if it's completely depleted.