Peas take nitrogen from the atmosphere and ‘fix’ it in the soil. Adding beneficial bacteria to the soil through an inoculant helps the peas do this extra efficiently. Here’s a good system for inoculating peas (and beans for that matter) with a commercially available bacteria (total natural and approved for organic farming, btw)
1. Place peas in a glass of water
2. Remove the peas and place the peas in a second glass
3. Sprinkle pea inoculant in the glass and shake up the peas till they are coated
4. Plant peas

You don’t need to add additional nitrogen to the soil when you plant inoculated peas, and you can till in the peas when they are done and enrich the soil in your garden bed.

We get our inoculant from Johnny’s Selected Seeds in Maine:Inoculant for peas and beans