Do I need to add nitrogen for beans?

Southern peas, English peas, and beans are all legumes and will form symbiotic relationships with bacteria in the soil. The bacteria will fix nitrogen for the plant to use. With the exception of green beans grown at high populations for mechanical harvest, peas and beans generally require no more than 20 pounds of nitrogen per acre to obtain good yields. The green beans are generally harvested before the plant-bacteria relationship has time to develop.