Nitrogen fixing plants (NFPs) accumulate their own fertilizer, grow extremely quickly, tolerate harsh climatic conditions, and are prolific. NFPs utilize atmospheric nitrogen. Through an association with Rhizobium, a bacteria which is hosted in the root system of NFPs, these plants biologically accumulate nitrogen, pulling this essential nutrient out of the air for their own use, and, if managed, making it available to other crops as well.
Nitrogen fixing trees (NFTs) are used for windbreaks, shade, fodder, organic matter production, mulch, fuel, timber and food. NFTs fulfill many of their own needs in infertile, harsh conditions, and therefore have the ability to quickly "pioneer" bare or degraded lands. NFT species can be pruned back frequently, and their nutrient-rich leaves used as a high-fertility mulch, or for animal fodder. In this way, NFTs support many other life forms on the farm.
Inga is a large genus of leguminous trees native to the American humid tropics. Inga edulis, the best known of the Inga species, is popular with agroforesters for its rapid growth, tolerance of acid soils and high production of leafy biomass to control weeds and erosion. Prosopis alba, P. chilensis, P. flexuosa, and P. nigra are collectively known as 'algarrobo' and are deep-rooted, nitrogen-fixing trees that produce sweet pods that are still eaten by humans and rapidly eaten by livestock in the semiarid regions of Argentina. These trees are the essential component of the agroforestry land use system in these parts of Argentina.