These are some of my shelling peas. I'm growing both shelling and sweet snap peas this year. I really love shelling peas, especially fresh off the vine and raw. Peas are legumes, so they can't take nitrogen out of the soil in the form it's in. They attract beneficial bacteria, which form nodes on the pea plants roots. These nods take up the nitrogen from the soil and convert it to a form the plant can take up and use. The off shoot of this is the plant puts nitrogen back into the soil in a form most other plants can take up and use. This is why legumes are known as natural nitrogen fixers. Most green manure mixes will contain some sort of legume. Most soil has enough beneficial bacteria that you don't need to use an inoculant. Inoculants are the beneficial bacteria that all legumes need. I do use an inoculant for my peas and dried beans, more because it increases the productivity, who doesn't want the most food from the plants you are growing? Inoculants are only good for the year you buy them in. So if you don't use all of it this year, throw the rest away, it will not be viable next year. Remember the inoculant is a living beneficial bacteria, there is only so long it will survive in your fridge.