Holt Modern Biology 1st Edition by John Postlethwait ,Janet Hopson

Exercise 51

Species of the symbiotic bacterial genus Rhizobium live within the root nodules of legumes, such as soybeans and peanuts. Some farmers take advantage of the nitrogen-fixing abilities of these species when they rotate their crops every few years and grow legumes instead of their normal food crops.
Part A Define nitrogen fixation.
Part B Explain the benefits of crop rotation on the soil.