Nitrogen is a necessary component in any garden for proper leaf growth. Plants that have pale-green leaves or are slow to grow are probably deficient in nitrogen. There are simple and natural ways to add nitrogen back into the soil. There are plants decompose and add nitrogen, while other actually add nitrogen while alive.
Beans release nitrogen back into the soil. Any type of bean; including bush, pole and wax; will work. Using crop rotation helps to grow better vegetables. Planting beans in one area of the garden one year and the following year planting nitrogen-hungry corn in that same spot. Each year, the corn should be planted where the beans were the previous year. Instead of removing the spent bean plants, allow them to decompose.
Leave the remnants of the pea plants and till them into the soil. Peas are nitrogen-rich plants. As the plant decomposes, the soil absorbs nitrogen, replacing what was lost in previous years. Tilling the pea plants into the soil works as a slow-release fertiliser.
Leaves are one of nature's great fertilisers, which will add just about everything the soil needs, including nitrogen, if allowed to decompose in the garden. Shred leaves first for faster decomposition. There are several ways to do this. Add a leaf bag to the lawnmower and simply mow them, rake them and send them through a wood chipper or spread them in the garden and till them directly into the soil. Do this in the fall so that they can have all winter to break down and add nitrogen and other much needed nutrients to the soil.
Many farmers plant alfalfa to return nitrogen to the soil. Each year, farmers plant alfalfa in one field, allow it to grow and then decompose at the end of the growing season by turning it back into the soil. Home gardeners can do this same method in their gardens. If there are separate garden patches, alternate where to grow the alfalfa from year to year. You can also just grow a few rows of alfalfa each year, moving them to different spots of the garden.