The only form of nitrogen that nonlegume plants can take in and use is nitrate ions (NO3−). Nonlegume plants lack the symbiotic nitrogen-fixing bacteria found in legumes, so they rely on absorbing nitrogen from the soil primarily in the form of nitrate
. Nitrogen gas (N2) from the atmosphere is not directly usable by most plants; it must first be fixed into ammonia or nitrate by nitrogen-fixing bacteria or through industrial processes before plants can absorb it
. Nonlegumes depend on soil nitrogen in forms such as nitrate for their nitrogen nutrition.
