AP BIOLOGY

Detailed explanation-1: -Alfalfa fixes more nitrogen than any legume crop. In fact, a stand can fix as much as 300 pounds of N per acre per year. It uses much of this nitrogen to produce protein in the plant, which growers can harvest and feed to livestock.

Detailed explanation-2: -Biological nitrogen (N) fixation is the most relevant process in soybeans (Glycine max L.) to satisfy plant N demand and sustain seed protein formation.

Detailed explanation-3: -Legumes are able to form a symbiotic relationship with nitrogen-fixing soil bacteria called rhizobia. The result of this symbiosis is to form nodules on the plant root, within which the bacteria can convert atmospheric nitrogen into ammonia that can be used by the plant.

Detailed explanation-4: -Grain legumes such as soybean and peanut use most of their fixed nitrogen for themselves. Forage legumes, such as alfalfa and clovers, are the best crops for companion planting as they can fix substantial amounts of surplus nitrogen under the right conditions.